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Furnace replacement - zoned system

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[OP]
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Nov 28, 2016
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Furnace replacement - zoned system

So this month, I have decided to replace my working single stage one speed furnace. Its a Keep Rite furnace, which seems to be rebadged of this model. Made Aug 2006, 1000 BTU, 92.1 efficiency. http://icpindexing.toddsit.com/document ... 111504.pdf

I have only had minor issues with it over the last 2 years. But as a single stage one speed, it should of never been zoned. Before I get a ton of messages of why replace something that works and wasting my money, I have 2 reasons.

1. My city has a rebate this year for certain HE furnaces for $350,
2. Im sticking with Lennox since they have extra Costco rebates in February, and a potential one more from Lennox themselves, which I am confirming. If thats the case, thats 2 extra rebates over others like Carrier, Trane, etc
3. My ac system was replaced in the fall with Lennox, with the same rebates, so got back almost $1500
4. I want to do a preemptive change, so Im not stuck replacing a furnace in an emergency, and miss out on rebates. My furnace could last another 10 years, or not.

I am including as many pictures that I can.

The models I jave been quoted are the EL296V, the SLP99V and the ML296V. I was actually all set to go forward with the SLP99V, until i read that it needs its own Lennox Thermostat to control all the features it boasts.

I have a 1350 sq. ft bungalow, finished basement and its a walk out . I have a dual zone setup, one zone per floor. For each zone I have the Ecobee 3 Lites, that have the option for dual stage furnace in their setting (currently set for single stage). My zone control board is a EWC
NCM-300 zone board I just had to replace Oct 2020. previous one was a Honeywell Tru Zone 4 zone panel.

I do not want to replace my Ecobees or my zone panel. And if the info above is correct about the SLP99V, then I would need 2 lennox thermostats, not one.

To throw some more fun into the mix, I also have a central exhaust system in the house, one vent per bathroom, and one for the kitchen. The kitchen one I have shut because we installed a downdraft vent when we did a kitchen reno, so I just turned the wall vent closed permantly.. When we did that, the suction increased for the bathrooms. As a venting system it works very well. But its also tied into the furnace fan. So if someone turns on the switch in the bathroom, not only does the Fantech fan in the furnace room start, it also starts the furnace fan itself for venting, and with that, draws air from outside into the cold air return of the furnace. I assume its not the best system for efficiency, it literally sucks out all the warm wet air and replaces it with whatever air is outside, whihc today, as an example, is -30 degree air. I have no idea if an HRV system can replace this, but thats down the line hopefully.

And another issue we have is airflow to the farthest parts of the house, basement or upstairs. And maybe that is why they tried to zone the system. I have done a few things to help out the issue over the two years, but its apparant that supply vents closer to the furnace just have better air flow. As well, the furnace is on the one end of the house, not the middle. So the rec room, laundry room, bathrooms and bedrooms get excellent airflow, the farther bedrooms in the basement, and the kitchen and living room, do not.

As an example, if I want to go from 17 degrees in the morning to 21.5 degrees for the day, before the house levels out, the closest bedrooms can hit 26 degrees before the kitchen and living room hit 21.5 And yes the kitchen and living room are bigger spaces, more to heat up, so I understand that, but its also the airflow from those far vents is probably half of the closest vents. if I leave the fan running, within a couple hours, the entire house can be within .5 degrees of any room.

The furnace is vented outside and as well takes air from outside to. Also have a flow through humidifier, but I dont think thats an issue. Its a manual dial one you set to whatever humidity you want. Its not automatic, but it works fine.

I have never had a setup like this before. Ive always just had the usual furnace, pipe out the roof, not zoned, no humidifier, and not HE


I am looking into if there are more HE furnaces for the rebate. Here is the website they make you go to https://www.ahridirectory.org/NewSearch ... chTypeId=4

But like I said I am sticking to Lennox because of the above reasons. I did get some other quotes for just to see, but nothing specular has come up to change my mind

I wanted the SLP99V because of the variable speed fan and modulating heat. But I think thats now out.

But I know I want minimum 2 stage furnace with a ECM fan. Unless there are reasons not to do ECM, etc.

Right now, if I run my fan constantly, like I usualy do during -30 cold snaps, the temp levels are pretty good all over. Sure the amount of air coming from the far vents doesnt change, but since its a constant flow, its better then off/on when just the furnace calls for heat,

The dual zone does work well, I can have ac just go off all summer upstairs, and the downstairs stays a nice temperature, not freezing like when its all one zone and you cool upstairs, and the basement is freezing.

If I can provide any more info I will. I have tried the load calculation website, but it just asks a lot of questions on it I have no answer to. Any any tech so far giving mne quotes, just goes by sq. footage.

I want to solve as best as I can my air flow problem, and these drastic temp swings first call for heat. And yes, I know, if I want to do it correctly, I would need to redo my entire HVAC duct work. But thats not happening, due to cost of ripping apart an entire house. So I want to do the best as I can with a better furnace for a zoned system

If the pictures are wrong or you have questions please let me know. I need to have this done this month to be valid for 2 of the 3 rebates

Thank you
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89 replies
[OP]
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Nov 28, 2016
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Out west
Here is some more info as well if it will help

UPSTAIRS ZONE VENTS
• Master Bedroom – 4 vents (2 window, 1 deck door, 1 under sink / 1 return)
• Spare bedroom – 1 vent / 1 return
• Upstairs Bathroom – 1 vent
• Front Entrance – 1 vent
• Downstairs bedroom – Vent is t’ed off entrance vent - This I added after we moved because the room as very cold and had only one vent
• Living Room – 2 vents (behind tv/ north wall / 1 return)
• Kitchen – 3 vents
TOTAL VENTS = 13

DOWNSTAIRS ZONE VENTS
• Rec Room – 3 vents (2 lower wall, 1 roof / 1 return)
• Laundry Room – 1 roof vent
• Bathroom – 1 roof vent
• Bedroom – 1 wall vent / 1 return
• Bedroom – 3 vent (2 lower wall, 1 closet wall / 1 return)
TOTAL VENTS = 9

I also had to disconnect the btpass shortly after we moved because it was short cycling the furnace very bad. In the pictures you can see how short the run is, and that they are now capped off. It doesnt seem to cause an issue becase the DAT sensor doesnt kick in ever now thats its mounted in the correct spot, and its set to 160 Degrees, and the furnance high limit is 170 degress
Member
Oct 19, 2020
322 posts
189 upvotes
I haven't read this thread yet, but 3 quick tips in response to posts in other threads:

1. If your ducts are are small, one of the worst things to do is put a big furnace which needs more airflow. Small ducts can kill ecm motors as they try to ramp up to compensate

2. Poor distribution is not caused by undersized ducts alone - aka if the entire system was designed for a certain flow rate and it needs more, but everything was done properly. Poor distribution is caused by having undersized trunk lines relative to branches and generally a poor design.

3. You can size your furnace by monitoring on/off cycle lengths in extreme weather. This only works when the btu input is correct and it's not cycling on high temperature limit.

If you have an ecobee, you can actually download the history and zero in on an hour when it was -40 with strong winds, see how much it's been running. Data is not useful when zoning is involved, so dampers should be disconnected/in the open position and the furnace cycled off of the ecobee exclusively. for a bit to get accurate data.

Most dampers are in the open position when de-energized, not all!
[OP]
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Nov 28, 2016
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insertname2020 wrote: I haven't read this thread yet, but 3 quick tips in response to posts in other threads:

1. If your ducts are are small, one of the worst things to do is put a big furnace which needs more airflow. Small ducts can kill ecm motors as they try to ramp up to compensate

2. Poor distribution is not caused by undersized ducts alone - aka if the entire system was designed for a certain flow rate and it needs more, but everything was done properly. Poor distribution is caused by having undersized trunk lines relative to branches and generally a poor design.

3. You can size your furnace by monitoring on/off cycle lengths in extreme weather. This only works when the btu input is correct and it's not cycling on high temperature limit.

If you have an ecobee, you can actually download the history and zero in on an hour when it was -40 with strong winds, see how much it's been running. Data is not useful when zoning is involved, so dampers should be disconnected/in the open position and the furnace cycled off of the ecobee exclusively. for a bit to get accurate data.

Most dampers are in the open position when de-energized, not all!
Thanks for the tips.

1. Im not how undersized my ducts are, I can see some in the ceiling if I poke my head up, what would I measure. I took a picture of all the ducts in the furnace room, supply trunks, etc. Is my furnace to big for my current ducts, Im not sure. How would that be figured out.

2. If this is the case, its back to, it the setup I have, and cant afford 10K or more to redo my entire Hvac duct design. I want to do as best as I can with what I have. But I want to make sure I know what I have first,

3. Cycle lengths depends. Because I have my ecobees to go off .8 degrees from the tempertaure setting, so I have longer cycles. If its set for 21.5, it wont kick until its 20.7 degrees. You can adjust it almost 2 degrees. I tried 1.1 degrees, but even that .5 degree just made it cold enough to not be comfortable. I find the .8 degrees the sweet spot. For the first call in the morning from 15.5 to 21.5 can take about 2.5 hours for 6 degree rise. Is that good, is that bad, I dont know. Thats in the extreme cold. Less time when its nicer out. since the house doesnt cool down that much all the time. BTU input is correct, I dont know. The furnace turns on when needed, heats the house up like a furnace should, shuts down. Im not sure what you mean by cylcing on high temperature limit. If the furnace is calling for heat and its single stage, its on "Full blast" every time

Ive studied my Ecobee grpahs for both zones for 2 years now. In fact the web interface is usualy open at work on days like today, or hot day, just so I see if its doing whats its supposed to do. Ive tested over night with the fan running all the time, or the furnace running thr fan onlly when heat/cool is called for. Ive watched for window fog/frost, and to see whos room is cooler, etc, etc Thats how I know the temp diffences in each room, how pulling the shades helps in the summer to keep the house cool. or if someone forgot to draw the blinds when its +38 because I can see how hot that room is.

I have one more company coming over for a quote. Being from a small centre, businesses remember when you dont use them, so a lot of the places that I didnt get ac from, but got quotes, just gave me general information on price, and just used sq footage and what sicne furnace I have now for thier BTU output. Bad business practice or sour grapes, either or.

But this place has never been ehre before, Armstrong Air furnances. So this way I can get I hope some honest info, and they can see what I have, explain the low airflow problem, and see if they blow smoke up my ass or not



Here is the zoning info I printed up for my furnace room, so should explain if the dampers situation. Far as I know from looking, they are open by default, only close if the other zone is being used


Dual Zone Set-Up

1. Upper/back area grey & orange controller are for upstairs zone.

2. Lower gray is for downstairs zone.

3. Fan ON opens zone, other zone closes if fan is set AUTO

4. Both fans set to ON, both zones open.

5. Zone HEAT/COOL overrides any fan ON or AUTO setting.

6. When HEAT/COOL or fans not called for, zone dampers default open.

7. Zones ask for HEAT/COOL at same time both zones open.

8. When zone asks for HEAT/COOL, other zone damper close. When zone stops HEAT/COOL cycle dampers open back up on other zone.
[OP]
Deal Expert
User avatar
Nov 28, 2016
18791 posts
2421 upvotes
Out west
insertname2020 wrote: I haven't read this thread yet, but 3 quick tips in response to posts in other threads:

1. If your ducts are are small, one of the worst things to do is put a big furnace which needs more airflow. Small ducts can kill ecm motors as they try to ramp up to compensate

2. Poor distribution is not caused by undersized ducts alone - aka if the entire system was designed for a certain flow rate and it needs more, but everything was done properly. Poor distribution is caused by having undersized trunk lines relative to branches and generally a poor design.

3. You can size your furnace by monitoring on/off cycle lengths in extreme weather. This only works when the btu input is correct and it's not cycling on high temperature limit.

If you have an ecobee, you can actually download the history and zero in on an hour when it was -40 with strong winds, see how much it's been running. Data is not useful when zoning is involved, so dampers should be disconnected/in the open position and the furnace cycled off of the ecobee exclusively. for a bit to get accurate data.

Most dampers are in the open position when de-energized, not all!
So if an ECM motor wont work, what will. What different kinds of motors are there? Is it depending if they are one speed or two speed or multi speed?
[OP]
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Nov 28, 2016
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pootza wrote: You could possibly skim through this to show you how zoned system ductwork is sized and compare your system.

https://www.nrcan.gc.ca/sites/www.nrcan ... nglish.pdf
Ive read that, and multiple other manuals, watched videos, read things online.

And I know unless I rip out my entire system, which I cant afford to, and as well, I cant see things in walls either. I can get a general idea of ducting within the walls, but I dont have any any actual proof

Ive replaced a zone panel, adjusted the dampers from 100% closed to almost open to test, Ive removed a bypass duct, Ive added a new bypass damper, I removed that, didnt work. Ive even 3/4 blocked off an upstairs large return vent to make some of the other return vents in the basement suck more air across the room. Ive added a supply vent, and moved another supply vent out of a closet.

Ive vene tested running the fan all night compared to not running the fan all night. Which I have found out helps alot, but with a single speed fan, costs a lot in electricity. Ive taped over every seal I can find, Ive tried a ton of different filters as well

Ive even considered installing one of these, a good duct booster. But since its multiple branches off a main supply plenum in the ceiling, I would need to do this for every branch I have, which I dont have access to

https://www.amazon.ca/dp/B06ZXWN3BG/?co ... _lig_dp_it

As a non-Hvac tech, Ive done as much as I can to make my house more comfortable. So it comes down to, I want to replace the furnace to a more efficient and a proper one for a zoned system

I also learned when they put in the zone dampers for the upstairs, which I have two, but one zone. Is that they split them up wrong, so thats why I know this is a afetr the build install. On a zoned system, you usualy zone "like" rooms and areas together. So bedrooms have the option of one zone, and a kitchen, dining room and living room are another. All depends on layout. Mine however, arent like that. If that one zone was ever split into two, then one bedroom and the living room would be on one zone, and the master bedroom and kitchen would be on the other. Its because the ducts are zoned rifht in the furnace room, only place they had access, and used the main trunk branches,

But what I have learned from it all is you dont zone a single speed one stage furnace. Thats why I have decided to replace the furnace for something more proper. Do I expect it to magically erase every issue, no. But it sure has to be better than the situation I have going on now.
Member
Oct 19, 2020
322 posts
189 upvotes
I can't tell if the ducts are undersized based on the pictures.

Your heat imbalance could be caused by undersized trunk lines relative to branches and or excessive duct leakage.

The combo of balancing with dampers and the duct pressure compensating variable speed blower (I strongly recommend variable since you're dealing with zoning) could greatly improve the situation.

Also, one thing to keep in mind is that you don't have to re-do your entire system to fix undersized trunks -> may just need to open bulkheads. The entire trunk wouldn't have to be replaced, potentially only half the length of each.


I would need to know the size of each branch line listed - a vent usually has anywhere from 4" to 6".

Also need to know the sizes of the trunk lines and which branches are off of each trunk.
General length of longest run - how much distance between furnace and the furthest vent

Ditto for returns.

It may be easiest to post a diagram.

Do the zones have a dedicated trunk lines?

As far as furnace selection goes, the issue with the SLP is that a generic zoning panel can't directly control the output and airflow.
When wired as a 2-stage but set to modulating mode, the firing rate/percent total capacity and airflow is based on the length of previous cycles on low heat and when there's a call for high heat, it ramps up and stays high until the end of the cycle - which is horrible for zoning.
You can also have major issues on a modulator with far vents not getting proper airflow when it's running near 35 to 40%, which could make your balance problem worse.

The ML296V is absolutely unsuitable for zoning with a generic panel that does not have direct control over the blower, in fact the guide specifically says that:

"Units may be used with certain zoning systems
• Zone control panel must be able to interface and
communicate with the variable speed blower motor in
the unit

• Harmony III™ Zoning System has this capability"
https://tech.lennoxintl.com/C03e7o14l/V ... v_2009.pdf

It has to do with blower programming with there being barely being any difference between low and high heat airflow. (air temperature is higher on high heat instead)
Doesn't inspire confidence in the contractor who gave it as an option, doesn't seem to know basic stuff about the product and how to select the right furnace.

The elite, EL296V can be zoned with a generic panel, through the special lennox one is suggested.

EL296V is a 2-stage furnace with a variable speed blower.
When set up with extra relays, the zoning panel can hold it on low heat until both zones are on.

The 70/66k version would be my top pick if it's not too small for the house.
This furnace doesn't need as large ducts as the 90k.

Must verify that your heat loss is low enough for this furnace. 1300 sq ft newer contruction, I doubt needs more capacity even in an extreme climate. To give some perspective, a bungalow in the gta (which is milder) of that size and age would likely get a 45k btu.
The 90k may move too much air on low fire when one zone is on, which isn't great. Variable speed blowers can get very noisy and have a short lifespan when the duct pressure is too high.

(Too bad lennox doesn't have an 80k, since you're insisting on this brand)

*Is most of your basement under ground? Are your exterior walls 2x4 or 2x6?

90k is available in three different blower capacities and what makes the most sense depends on your duct system.
Blower programming - airflow on low vs high varies depending on the blower capacity, the ratio is actually more important than blower capacity. Variable speed can always be slowed down via settings on the board when the ratio is decent.


-----------
Runtime sizing method:

To verify that the furnace is running at 100 000 btu/hr input, you can clock the gas meter with all other appliances off.
You have to use the second smallest dial to be accurate, I've done it with the smallest dial and got a different result each time.

The btu content of the gas in your area needs to be known to do it accurately. 36 000 btu/m3 is the most common but it can vary by 5%-10%.

To verify it's not tripping on limit, run it with both zones on for 20 minutes and make sure the burners don't cut out during the cycle. Limit tripping is often not noticed until the cycles are long enough for it to trip like 3 times and the board locks it out.

To time the cycles, need to have the furnace cycling off of one thermostat and zoning inactive, go back the following day and download the data.

If you disconnect the zone dampers temporarily, they should stay open. Label wires before disconnecting.

From there, you turn the basement thermostat to off, turn the fan on and make sure both floors/all vents are getting airflow.
If they are, you can proceed to run the heat off of the upstairs thermostat only...

Leave the basement thermostat "off".

On the upstairs thermostat only:
Maintain a constant temperature for one day when doing this test, set it to 22c and do it in the coldest weather you get.

This is an excellent furnace sizing method.

You shouldn't have to do this sort of stuff and research, but the industry is what it is.
[OP]
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I will reply back with more info tomorrow. I am getting another quote by a Trane dealer as well, another one that hasnt been here before. See what info I can get from them, see if it matchs up, or just a your house is this much sq footage quote.

Maybe Ill be surprised and the quotes will be lower than the Lennox ones with the rebates. Just from my ac quote last fall, with the rebates from Costco, the Lennox ac just came ahead. Maybe with a furnace they wont, not sure until I get a couple. But I will get whatever HE is on the list for my cists $350 rebate for sure.
[OP]
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I can put different pictures if that helps, but inside the roof would be far away pics since I have barely any access to the ceiling for a good view. Im pretty sure its not duct leakage. Since it seems the entire east side of the house has this issue at multiple vents. Can I confirm, no. I wouldnt know how to. But from the parts I can see from cell phone pics I dont see any unhooked areas.

So with fans, what types are there? 1 speed, 2 speed and variable speed? Or are there more. I want to get the correct fan for this situation. I want to be able to run the fan on low 24/7 if I want and not cost me a small fortune like this week is, running my one speed fan for 72 hours straight so far.

I dont have any bulkheads. My entire ceiling is all the same height, each room. And I also found out my 8 foot ceiling is actuall 7' 10" So to make the ducting fit for the walk out and the height, maybe thats why I have undersized ducts, and maybe the same with the main trunk branchs.

As for size of each branch line, I cant measure those in the ceiling, I cant reach any of them. I can measure stuff in my furance room. I know I have 3 main branches off the furnace, 2 for upstairs, one for downstairs, but after they hit into the ceiling, I dont know after that

I have pictures in the post of each trunk line, each one has a zone damper on it. General length of longest run, I dont know, and hot to get that, I dont know the runs in the ceiling.

I will need to measure the length of the farthest runs, but its a 1350 sq foot house. So one side of the house to the other. And thats if its a straight run, which I know some arent. I have oe from the furnace room that goes up, then down underneath the stairs, and then across. That distance is double duct length than actual physical length

Returns I should be able to do, if they run they way they are supposed to. Some returns are literally right above the furnace room (bedrooms)

I could do a diagram, but I dont know what to draw that would make things explained better. I could do a general layout of the house

I have 3 zone dampers, 3 trunk lines off the main furnace supply plenum.

For furnace selection, you said a lot, almost to much for me to process, so know what I need.

When you say SLP, is that the model, or a type? What you say makes sense about a modulating fan, Right now if far vents have low air flow on full 1 speed fan, then with a low speed fan, I could get nothing.

I have a friend thats dropping a tool that measure CFM out each vent, so I can get actual numbers.


As for high limit tripping, my furnace doesnt do that. It did when the DAT sensor was installed in its original spot, which was right before an elbow in by a zone damper. I noticed it tripping when I was doing flooring there a few weeks ago. The zone panel has a trip light. But with help from EWC, it is now installed in the main supply plenum, as far up as I could. Ever since then, it hasnt tripped once. The DAT ssensor is set to 10 deggrees below the furnace high limit, so I never get a lock out.

I never have an issue with it tripping, with both zones open or just one zone. I check it enough lately expecially with the -30 we have now to know I have no short cycling

I dont need to disconnect any of my dampers to test. If both zones call for heat, both zones open. Its like having a no zoned furnace. Same as the fan, when the fan is runing on ON for both zones, both zones are open. Only heat overrides the fan

I dont understand by timing the cycles. The zones stay open until the heat is reach, weather it be 20 minutes for a small call for heat, for 2.5 hours from the first morning call.

My temp right now are a constant 21.5, and its cold out. The furnace is being used. So what am I measureing to know the BTU I need? How fast the house heats up? It takes 2.5 hours to go from 16.5 degrees to 21.5 degrees,

I will admit, Ill try some of this, but I dont have days and days of spare time to do it all in
Member
Oct 19, 2020
322 posts
189 upvotes
So, the SLP is the furnace model.

SLP98/99 is a modulator with a variable speed blower. Heat runs 35 to 100% capacity, like a dimmer switch and the blower adjusts itself on the fly to deliver airflow proportional to heat output.
The blower also compensates for the pressure in the air ducts, as it changes it adjusts the speed/rpm to get proper air volume/flow.

The problem is, the slp98/99 needs the lennox communicating zoning system to work to it's potential.
It's also a very complex, expensive to fix furnace, so best to stay away.

On a zoned setup, variable speed I would go for.
Variable speed is the type of motor that compensates for duct pressure. The other type is called constant torque/multi-speed.
The pressure on a zoned system varies depending on which combo of zones are on, constant airflow is beneficial because the furnace and ac get proper airflow at all times.

The cheaper motor has airflow drop as the duct pressure increases.

The EL296V is a 2-stage with the variable speed motor, and the stages can be controlled by thermostat or zoning panel input.
2-stage = two levels of heat output.
Airflow and heat output are lower on low heat than high, and when properly wired it can be held on low heat unless both zones are calling.
This way, the duct pressure stays in check.

The ML296V is also 2-stage with variable speed, but the airflow is basically the same on high as it is on low heat with a generic zoning panel - which is no good for zoning.

As far as limit tripping goes, the panel has a discharge air temperature limit, but the furnace itself has it's own limit.
The panel doesn't know when the furnace's own limit has tripped, so it has to be verified it's not.
Burners shut off during a heat cycle and the board flashes an error code. Burners come back on when limit resets.

As far as timing the furnace goes, it's simpler than I made it seem:

Say the furnace is burning the full 100 000 btu/hr - verified by meter clocking. (and not tripping the internal limit - more on that before)

If you time it over an hour when it's -45 and windy and it ran 40 minutes, (40/60) * 100 000 btu/hr = 67 000 btu/hr
At 92% efficiency, 40 minutes on/60 minutes off per hour indicates the house needs a furnace with a 62k btu minimum output.
You can compensate for temperature in the calculation and do testing in milder weather, but it's better to see what it actually does in extreme cold.

Now, ecobee thermostats have run-time logs which can make this a lot easier.
The problem is, when both zones are on at the same time, run time is counted on both, so the data is not useful to determine absolute run time.

So, the easiest thing to do is set only the main floor thermostat to heat and lower floor to off, make basement zone dampers open all the time (I think you would disconnect and tape off) hit hold for a full day at 21 to 22c, and go back after and download the logs.

If you can attach the csv file here after testing, I could take a look.

It's under home iq -> system log I believe, download data.

Clocking the meter: https://hvactechhangout.com/home/system ... gas-meter/
(have to get the metric values and do the math including btu per cubic meter)

Duct layout:

I have no idea what the layout is like - like if all the supply ducts are above the basement ceiling or what.

Need all the sizes too.

The CFM/velocity meter is useful, but only when total airflow furnace is moving is known.
The tool measures velocity and either you enter the vent area to get cfm or calculate cfm manually.

Duct evaluation is very important in your case, need to know the rough capacity of each zone.

Proper setup/commissioning is absolutely vital too - more so on your setup than typical single zone. There are different ways to wire/configure the zoning panel, control stages, different fan speed settings, etc. Because your zoning panel only supports timed staging (x minutes on low before switching to high), it will take extra creative wiring to get it to work optimally. (the stuff i mentioned with relays)
Last edited by insertname2020 on Feb 11th, 2021 8:29 pm, edited 1 time in total.
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Please cut power to the zoning panel if you decide to disconnect a damper and label/isolate disconnected wires before restoring power.
I don't not want you coming back here saying my advice fried your zoning panel. lol
Do everything at your own risk.
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So just had a quote, but it was actually more explaining, they were here for 45 minutes. So I never really got a furnace quote per say, but he explained the issue since he went to school for zoned systems and has been in Hvac for many years. He knew a lot it seemed, and from what I have learned over the years, none of it was baloney

Basically, its undersized ducts. Becaue of the walk out and no bulk heads, the basement zone has one trunk that goes in between the joists, north to south. Then off that, I I have 7 branches. The closest branchs of course have the best air movement

Same as upstairs, same scenario, bigger main trunks into multiple smaller ducts to fit.

HE suggested before trying a new furnace, to replace the fan with an ECW fan, to see if it helps. He said that on low, the system would always be charged, and having that constant air flow. That way, if it does work, then you know for when the furnace dies that you get one with a fan like that. And if it doesnt, or it does but only to a certain degree, you didnt waste 5000 on a furnace for nothing

He is going to price me out a fan replacement, and from a 14" to a 16" This model has both, but a 14". And a ECM with a variable speed. He said unless we redo the ducting system, we have to work with what we have. And he said how impressed he was with the amount of air sealing I did on the furnance ducts.

He also said, with an ECM motor, of course they cost less to run, but it would just have the system always charged and that would help with airflow to. And of course stop the noise of a one stage fan running air through the ducts. And to, when a one stage fan runs, and the heat isnt on, you do get the wind chill effect of sorts, since it just air blowing

As well he said shutting ducts that are closer and have a ton of airflow, will help with airflow to the others. Lot a lot, but at least some.

Better advice than just you need 100 BTU output and thats it

We never got into the new furnace sizing. But it might come down to that Im stuck with what I have, and just deal with it. Maybe a new furnace right now isnt worth it, and just upgrade when it dies. Not happy because since we moved there has been this massive air imbalance issue, but guess make the most of it. But he defintly provided more info than the Lennox guy did, in fact, he was fine just throwing in that one he said.

I havent gotten a reply back yet about it, expecially now that I read on here you need the special Lennox thermostat for it to run

At least now I wont bother trying duct boosters, I would need one for each branch, which would be expensive, have to rip out the ceiling and pull power and probably not the outcome I expect
Last edited by WikkiWikki on Feb 11th, 2021 10:00 pm, edited 2 times in total.
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insertname2020 wrote: Please cut power to the zoning panel if you decide to disconnect a damper and label/isolate disconnected wires before restoring power.
I don't not want you coming back here saying my advice fried your zoning panel. lol
Do everything at your own risk.
That I know :-) Ive had to remove a few of the dampers, and relocate the DAP. Any furnace work I always turn the switch off on the wall
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I will be answering as many questions to your post tomorrow. But quick question, how can you find the BTU output on furnaces. Does the same model come in differnt BTU? I cant find anything thats says the BTU out put
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When I was house hunting last year I came across a home I was considering that resembled yours. It also had the walkout basement, family room and bedroom or two in the basement, patio doors and windows in the basement looking out the back with an upstairs walkout onto a deck. The rear of the house had extra exposed basement walls on the sides to the environment vs a regular home as well. That home also had the furnace at the opposite end of the house furthest away from where it really ideally should have been - at the coldest end. I figured it would be chilly in the basement and tenant who gave me the tour did indicate after I asked that they used electric heat at times to supplement.
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WikkiWikki wrote: I will be answering as many questions to your post tomorrow. But quick question, how can you find the BTU output on furnaces. Does the same model come in differnt BTU? I cant find anything thats says the BTU out put
There's typically a few more digits tacked into the model number to designate if the furnace is an upflow or downflow, possibly the motor type if more than one is available etc.

It doesn't look like the Lennox site is very helpful in this respect but Google found this for you.

Lennox EL296V
Model number: BTU output per hour
UH045XV36B: 44,000
UH070XV36B: 66,000
UH090XV36C: 88,000
UH090XV48C: 88,000
UH090XV60C: 88,000
UH110XV48C: 110,000
UH110XV60C: 110,000
UH135XV60D: 132,000
DF045XV36B: 44,000
DF070XV48B: 66,000
DF090XV60C: 88,000
DF110XV60C: 110,000

The names EL296V and the EL296UHV used interchangeably. Basically, the “V” in the name refers to a variable speed blower motor. The “UH” refers to the unit’s ability to be configured in either an upflow or a horizontal position.

- DF would be a downflow model.
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WikkiWikki wrote: I will be answering as many questions to your post tomorrow. But quick question, how can you find the BTU output on furnaces. Does the same model come in differnt BTU? I cant find anything thats says the BTU out put
To find the BTU output, it's BTU input x efficiency. So a 80,000 btu furnace at 92% efficiency would have a max output of 73,600 btu.

You should look at the Mars Azure ECM motor retrofit for your current furnace. Myself and lots of other members have done the swap... See the RFD thread for info
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fergy wrote: When I was house hunting last year I came across a home I was considering that resembled yours. It also had the walkout basement, family room and bedroom or two in the basement, patio doors and windows in the basement looking out the back with an upstairs walkout onto a deck. The rear of the house had extra exposed basement walls on the sides to the environment vs a regular home as well. That home also had the furnace at the opposite end of the house furthest away from where it really ideally should have been - at the coldest end. I figured it would be chilly in the basement and tenant who gave me the tour did indicate after I asked that they used electric heat at times to supplement.
Did you look at my house :-) Thats exactly what ours is. On the cold snaps, is when we see the issue the most. And as well, we have no one around us, we are the wind block basically. It also bugs me some as well, that I am the dad, so its my job to make the people in my house comfortable. I always feel bad when I see the cold temps in my kids rooms compared to the rest of the house

I think its going to be what it will be. A new 2 stage furnace with a variable speed fan will probably help some, but not to the degree I want. I know I have ducting issues, so Ill just have to deal with what I have.

I have fixed and tweaked a lot over the 2 years, from ecobee thermostats/sensors, to sealing every pipe crack I could find, to even sealing the supply ducts where the metal might have spaces. Adding two new ducts helped some as well.

Surprisingly, although simple, what the tech suggested last night worked. I never adjusted anysupply vents in my house before. I assumed that since it was already zoned, I didnt want to screw up and air flow I already have.,

With that, on cold weeks like this, thats why our master bedroom and spare bedroom were always 26 degrees by the time the kitchen and the living room hit 21.5 degrees, because of the air flow difference

But last night, in those rooms, I adjusted each vent to 3/4 closed, and one by a deck door all the way closed. These vents had tremendous ariflow. So I had 4 in the MB, and one in the spare.

But this morning, as I look now, although its only been 2 hours on. Every room upstairs are basically the same temperature. This time yesterday, if the kitchen was 18.5 degrees, the MB would of been at least 22, or even 23. Right now, the MB is 19 degrees.. Ill know 100% when the far sensors reach the set limit.

I did the same for the basement, 3/4 turned off the laundry room supply, and one rec room supply 3/4. And as well, the far bedrooms seem to be heating up a lot faster, and keeping closer in temps than this time yesterday

So basically I turned down the vents that got great air flow, due to distance. I know it says if you close to much stuff off it damages the furnace due to pressure, but I already have a zoned system now, that basically cuts the ducting in half. What more harm can 3/4 shutting some vents do?

That why i want to get a CFM tester, just to confirm the difference in output. Today the test was "my hand" and I thought the far upstairs vents had better flow, or it could be my mind playing tricks "wanting" them to be.

Another thing I could try, is to change my current blower motor speed. Righty now it has 4 wires, Lo (REd wire), MLow (Blue wire) MHigh (Orange wire) High (Black wire) Red and blue are parked on the M1 and M2 spade connectors. Orange is plugged into the heat connector, balck into cool. If I swapped the orange and the Black, I could test what an increased speed would do for heat. Would that cause an issue if I tried that,? If it does do something for better airflow, just swap the wires back in the summer when ac is needed.

I wont try it until I confirm this vent adjustments works first over the next day or to. Ill watch tomorrow if any high limits hit in the morning, its still staying cold here the next few days
Last edited by WikkiWikki on Feb 12th, 2021 11:40 am, edited 4 times in total.
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schade wrote: To find the BTU output, it's BTU input x efficiency. So a 80,000 btu furnace at 92% efficiency would have a max output of 73,600 btu.

You should look at the Mars Azure ECM motor retrofit for your current furnace. Myself and lots of other members have done the swap... See the RFD thread for info
So this would just be the motor replaced, not the entire cage and blades. Ill see what the person from last night says.

I still want to figure out the BTU that insertname2020 suggested. But from what fergy posted, I have these choices for this model that seems to be the ones that winning my comparison race. 44,000 I know would be way to small, without even calculations. No way it would be made to keep up with -35. 110,000 way to much. Currently have 100,000 with 92.1 efficiency. So for age, probably a 90,000 output.

I think the 88,000 output might be the sweet spot. Ill still do the calculation best I can from his suggestions, but I think 66,000 BTU, even at 96% efficiency, will just be too low

UH045XV36B: 44,000

UH070XV36B: 66,000

UH090XV36C: 88,000

UH090XV48C: 88,000

UH090XV60C: 88,000

UH110XV48C: 110,000

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