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Dual zone system - fan on or auto

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  • Feb 23rd, 2019 9:27 am
[OP]
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Nov 28, 2016
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Out west

Dual zone system - fan on or auto

So after two months, we have out dual zone system setup. I have a friend who runs an HVAC company and shortly after we moved in, the furnace was short cycling and taking forever to heat the house. His quick fix over Christmas was just to just disable the zoning, so we just manually opened all the zones, and I turned the downstairs thermostat off. So it was like a single zone again. He has been busy and I didn't want to bug him, and the house was still warm at least.

Anway, today we got the dual zone hooked back up, the short cycle is now gone, and its working as it should, We also added another vent to a downstairs bedroom that's hooked up to the upper zone. Since this room has terrible air flow, I wanted to add more heat for my daughter and this was the cheapest way since it was a T off a porch vent. Now her room has way better airflow since this isn't a in wall lower vent like her other one.

As well what I do like is that the basement now heats alone, and with that floats upstairs and just makes the house more comfortable it seems. When we had upstairs at 22, downstairs area was usually 20.5 or 21. Now the basement on its own zone is 22, and the upstairs is 22.5 with the thermostat set at 21

Anyway, with dual zone, is it better to run the system fan on Auto or On. Or should one zone be On and the other Auto. If I do both ON, then its like a single zone again, because then all the dampers are open. If I do the Basement ON then the basement vents get air flow, the upstairs doesn't, until its called for if I leave it on Auto

I also notice that when only one zone is open, the air flow for that zone is much better. Becauise my kids downstairs bedrooms have been a lot cooler because of terrible air flow, that's a good thing, so more air kicks around their rooms

Or is this a system that is basically run what works. Ive had the fan on ON for the last month basically with the cold weather

I know I will be grilling my friend on Tuesday when I see him, as he has to extend one more vent and do some more tweaking. Just so I know that I understand this completely. It seems that its not HEAT that calls for the damper operation, its the fan. Which I guess is the same sicne the fan would only operate when heat is called (in AUTO mode)
Last edited by WikkiWikki on Feb 27th, 2019 10:51 am, edited 1 time in total.
1 reply
[OP]
Deal Guru
User avatar
Nov 28, 2016
13952 posts
1602 upvotes
Out west
Actually I answered my own question this morning. If I both fans to ON, all zones open up and its like a single zone again. All zones open when nothing is being called for. When one zone ask for heat, the other zone closes, and then reopens with the other zone cycle is over.

I could have the downstairs zone to ON and the upstairs to auto to circulate air in the basement better, or vice versa. But for now Im going to try Auto on both and see how it works out. We have another cold snap coming so will be able to tell what works best

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