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Multi-Zone Furnace versus 2 Furnaces - need input

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  • Feb 21st, 2008 4:32 pm
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[OP]
Newbie
Jan 17, 2005
21 posts

Multi-Zone Furnace versus 2 Furnaces - need input

Hi,

I am building a 2500 sq ft, 2 story house and the builder is giving me 2 options for furnaces:

1) A Multi-Zone furnace, allowing me to control my basement, main, 2nd floor individually - each floor with its own thermostat
2) 2 Furnaces, one furnace for the basement and main, one furnace for the 2nd floor

Does anyone know the pro's and con's of 1 versus 2? There is not charge for either option.

Air Conditioning is also a concern - what will the above have on A/C?

Thanks.
12 replies
Deal Fanatic
User avatar
Feb 25, 2004
5653 posts
147 upvotes
New Westminster
Why ????

I have a 2000 sq ft 60 year old home that still leaks all over the place (despite ALL the renvoations I have done ... I only have R12 in the attic and can see light around all the doors) and I can still heat all 3 floors with a single 40K BTU furnace. This is about the smallest furnace you can buy.

With a new house properly insulated and the HVAC contractor doing a proper calculated heat loss and duct sizing calculations (spreadsheets and simulation) there is no reason why a single (smaller) furnace shouldn't do a proper job.

Save yourself $4k (or more) and the increased chance you will have to replace furnaces early.

edit ... the multi-zone furnace usually has computerized duct controls to direct heat to the required floors. Ask for a price quote for a "regular" furnace vs all this fancy stuff then ask for demonstrated gas savings and figure out if the pricing is worth it.
[OP]
Newbie
Jan 17, 2005
21 posts
CheapScotsman wrote:
Feb 15th, 2008 11:32 pm
Save yourself $4k (or more) and the increased chance you will have to replace furnaces early.

edit ... the multi-zone furnace usually has computerized duct controls to direct heat to the required floors. Ask for a price quote for a "regular" furnace vs all this fancy stuff then ask for demonstrated gas savings and figure out if the pricing is worth it.
Unfortunately, there isn't any savings to me - its already priced in as part of the home.
Deal Fanatic
User avatar
Feb 25, 2004
5653 posts
147 upvotes
New Westminster
Well, that is pretty sad

If I was looking to stay 15 years then ... I'd do it the way I suggested and let them walk with the profits. In that time frame there is possibility I may have to replace a furnace so do I want to replace two? ... along with dealing with failed switched ducting units forcing me to tear apart drywall, etc ???


Otherwise I would go with the single unit. A typical smaller furnace is around 40K BTU. A new house of your size should NOT required anywhere near 80K BTU to heat ... which means the furnaces will be UNDER utilized. Think of it as running your car for 5 minutes then turning it off for 20 then back on for 5 ... the car doesn't have a chance to warm up and that will shorten its lifespan.

I'd very reluctantly go with the single furnace / multi-zone approach.
Deal Addict
Jan 27, 2006
4887 posts
942 upvotes
Vancouver, BC
Besides, it will be cheaper to install the A/C.
Deal Addict
Jan 4, 2007
1341 posts
12 upvotes
markis wrote:
Feb 15th, 2008 11:04 pm
Hi,

I am building a 2500 sq ft, 2 story house and the builder is giving me 2 options for furnaces:

1) A Multi-Zone furnace, allowing me to control my basement, main, 2nd floor individually - each floor with its own thermostat
2) 2 Furnaces, one furnace for the basement and main, one furnace for the 2nd floor

Does anyone know the pro's and con's of 1 versus 2? There is not charge for either option.

Air Conditioning is also a concern - what will the above have on A/C?

Thanks.
Can you put your location in your profile?
[OP]
Newbie
Jan 17, 2005
21 posts
nornet wrote:
Feb 17th, 2008 7:29 pm
Can you put your location in your profile?

Hi - I am in Edmonton. We get +30 summers, and of course -30 winters.
Deal Addict
User avatar
Jan 28, 2008
1177 posts
29 upvotes
Sarnia
I guess I don't quite understand about this already being priced in? I'm with the other posters and would rather just have a single furnace and a/c and no thanks to any multi-zoning wizardry. Too chancey for my liking that something will go wrong with it sooner or later. Is there no way you can just get a decent mid or hi eff furnace/ac and have them apply the money not spent on an upgrade elsewhere such as a better dishwasher/stove/fridge or an extra window somewhere?
Deal Addict
Jan 4, 2007
1341 posts
12 upvotes
markis wrote:
Feb 17th, 2008 9:25 pm
Hi - I am in Edmonton. We get +30 summers, and of course -30 winters.
You can forget about a 40000 BTU furnace. Youll need closer to 100000 up there if not more. I've 2 houses much further south, one has 95 and the other 125. pkguy sums it up well. The only reason to go multi zone would be for the comfort of kids etc but I seen too many half a**ed HVAC installations. If later on you find there is an area that has considerably different heating/cooling requirements, you could get a split ductless unit. They can be had for $4000 installed and will heat/cool 1000 sq ft. Stick to the basics.
Out of curiosity, what is the builder recommending and what are his other clients
choosing?
Newbie
Feb 13, 2008
2 posts
sudbury
I have a dual zone furnace & AC installed, almost 4 years ago.

We have the 96.% efficiency furnace and the 4 ton AC. This house is 3300 sq ft; and includes a granny flat, for my elderly mother.

For obvious reasons, we need to keep my mother's side considerably warmer than we can stand it, and this furnace does that, beautifully; same thing with the A/C- it never goes on, in the granny flat.

I hesitate to provide the price, since it included first time duct work installation; the previous owner had electric heat.

The only "issue or complaint" with the system, is the electronic, programmable thermostat. We had many, many months of frustration with it, and the installer finally had to call the Bryant rep to come in and have a look at it. Turns out, it was news to us and the installer, that you have to program each zone, for 4 time periods per day, for 7 days; thus, you have to enter 56 separate programs.

My son was an HVAC guy; he states we have the state of the art furnace, being controlled by a 'piece of S--T thermostat". We've had many, many occasions where the thermostat says it's 19 degrees in here, although we've programmed it for 23 degrees; it's supposed to kick on, when there are 2 degrees difference, but, it doesn't always. They just changed a part on it, that they said was recalled, for just this reason;---no difference,,, same old, same old.

Would I go that way again,,absolutely!
[OP]
Newbie
Jan 17, 2005
21 posts
nornet wrote:
Feb 18th, 2008 3:56 pm
You can forget about a 40000 BTU furnace. Youll need closer to 100000 up there if not more. I've 2 houses much further south, one has 95 and the other 125. pkguy sums it up well. The only reason to go multi zone would be for the comfort of kids etc but I seen too many half a**ed HVAC installations. If later on you find there is an area that has considerably different heating/cooling requirements, you could get a split ductless unit. They can be had for $4000 installed and will heat/cool 1000 sq ft. Stick to the basics.
Out of curiosity, what is the builder recommending and what are his other clients
choosing?
Builder recommended 2 furnaces over the single with 3 zones. I opted for the single with 3 zones, 3 thermostats.
Newbie
Feb 13, 2008
2 posts
sudbury
As I sit here typing, the electronic, digital, programmable thermostat outside my office says it is 22 degrees, while the thermostat in my office says it is really 19 degrees; we've jacked it up to 26 degrees, but still, the furnace won't kick on,,,again! It'll start, when it pleases!

We just had the discussion that we are going to get this thermostat replaced by two separate, non digital ones, if possible.

Good choice going with the three thermostats for the three areas!
Deal Addict
Jan 4, 2007
1341 posts
12 upvotes
Aldama24 wrote:
Feb 21st, 2008 1:18 am
As I sit here typing, the electronic, digital, programmable thermostat outside my office says it is 22 degrees, while the thermostat in my office says it is really 19 degrees; we've jacked it up to 26 degrees, but still, the furnace won't kick on,,,again! It'll start, when it pleases!

We just had the discussion that we are going to get this thermostat replaced by two separate, non digital ones, if possible.

Good choice going with the three thermostats for the three areas!
Are you saying you have 2 zones with a thermostat each or that that is what you want? Digital thermostats are fine as long as they are not Noma or equivalent. Honeywell and Hunter are 2 manufacturers that have never let me down.
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