2 stage furnace, 2nd stage doesn't run at low outside temperatures

tomns

I have a new American Standard 2 stage gas furnace and A/C. It ran fine all summer and has been heating through the winter until recently when the temperature began dropping below about 15 or 20 degrees. I have my thermostat set to 56 at night and 70 at 6 AM. Above 20 degrees everything is fine - stage 1 heat comes on at 6 AM and at 6:10, stage 2 kicks in until the house is 70. But when the outside temperature drops to 15 at night, stage 2 kicks in for just a couple of minutes at 6:10, then reverts back to stage 1 and it takes about 2 hours for the house to warm up. I have tried turning off power to the furnace but that did not change anything.

I have a zoned heating system with Honeywell (?) panel and 2 smart thermostats but I don't think they are zone-aware or 2-stage aware.

Any idea why stage 2 won't come on when it's cold outside? Is there an outside temperature gauge on the furnace that may be controlling something?

Jon_blaney

What actual inside temperatures have you observed under the two different ranges?

tomns

Eventually the house reaches the temperature set on the thermostat (70). With just the first stage working it takes about 2 hours to reach that temperature and just a trickle of air comes from the vents. When the 2nd stage is running the warm air blasts out of the vents and it takes only about 10 or 15 minutes to warm the house to 70. Again, if the outdoor temperature is above 20 then the 2nd stage operates as I would expect. It's only when its cold (15 or below) and I want the heat that the 2nd stage doesn't operate.

wmgeorge

First for a correctly sized unit for a calculated Manual J load thats way to much of a setback on a cold night. My 2 stage Trane with an ECM motor I only go back 2 or 3 degrees at the most. Do you have a true 2 stage thermostat and is it wired correctly?

I have extremely low heating cost compared to others.  Yes I did my Manual J on our school computers.I used to teach the HVAC Program. I took out a 80,000 Btu  92% and installed a  68,000 96%. 

tomns

The thermostats are wired to the zone control panel. I believe I wired them correctly but I'm open to considering they are not. When I replaced the thermostats I did not change the wiring between the zone panel and the furnace.

My understanding is that the furnace itself decides which stage is run - it starts with stage 1 and after 10 minutes switches to stage 2 if the thermostat has not reached its desired temperature. This is what I see happen when the temperature is above 20. It's just when its colder outside that only stage 1 runs.

The furnace is an 80,000 Btu 96% (Gold S9V2). The thermostats are Wyze.

Could the problem be the thermostat wiring?

HVACNUT

If your thermostats are wired for 2 stage, and the equipment side of the zone panel is wired for 2 stage to the furnace, then I would check the zone panel and furnace programming. Is SAT being used in the zone panel?
14° is too much setback. 
From what you describe, it seems the system is less than a year old (first winter). Why not call back the installer? 

GW

Good God heating people- the system has a zone panel, why ask what kind of thermostats are installed?

Anyway sorry I had to get that off my chest 😀

im not very familiar with the Honeywell zone panel. Some panels indicate which mode it’s on. I use the EWC, and it has indicators as to which stage it’s on. 

Last resort is getting a multi meter and seeing if there’s 24 volts on the W2 when you think it should be running second stage 

ratio

With the Honeywell TrueZONE® panels, W2-out is just all the W2-ins tied together & piped through a relay to allow it to stage down via DAT limit. (You will backfeed all the W2-in terminals when one is calling.) Regardless, it sounds like the furnace is staging up via a timer. Time to read through the manual. @tomns, how 'bout model numbers of the furnace, zone panel, & stats?

wmgeorge

Sounds as if you do not have a true 2 stage feeding your furnace. Regardless if its a thermostat or otherwise. Your installer took the easy way out. Not sure how your unit can be configured for the faux 2 stage setup. The install manual will have details, it might be as simple as a DIP switch setting.

Setback on a high efficiency unit is like trying to set back a heat pump 5 degrees or so at the most. IF it takes 2 hours to recover, you have gone to far.

tomns

@ratio The zone control board is a Honeywell 32003618-005 Rev E
Furnace is American Standard S9V2C080U5PSBBA
The thermostats are Wyze smart thermostats (they are rather new - Wyze makes a ton of products and I have several). I will read through the manuals later today.

@wmgeorge I prefer sleeping in a cooler room so I set the temp down at night. Could that really be part of the problem? When the 2nd stage starts up correctly the house warms up in 10-15 minutes. It's just on stage 1 that it takes 2 hours. Stage 2 frequently comes on during the day and it warms up quickly. It's just in the morning when I really want it that stage 2 won't come on.

ratio

That number doesn't come up with anything for me. I think it'll be something like HZ311 or HZ432. A picture of the panel with the cover will help identify it.

tomns

@ratio
  

wmgeorge

tomns said:

@ratio The zone control board is a Honeywell 32003618-005 Rev E
Furnace is American Standard S9V2C080U5PSBBA
The thermostats are Wyze smart thermostats (they are rather new - Wyze makes a ton of products and I have several). I will read through the manuals later today.

@wmgeorge I prefer sleeping in a cooler room so I set the temp down at night. Could that really be part of the problem? When the 2nd stage starts up correctly the house warms up in 10-15 minutes. It's just on stage 1 that it takes 2 hours. Stage 2 frequently comes on during the day and it warms up quickly. It's just in the morning when I really want it that stage 2 won't come on.

My unit is sized so close to the actual heating load, it takes a long time... even on high fire to get up to temp setpoint. In Iowa, and I heat with gas 1600 sq ft (built 1963 with updated windows and Ins) and a 24x24 garage/shop to 45 Deg except when working in it. My house setpoint is 74 day and 72 night... we just had another cold snap so my bill went up. I pay $162 per month for total.

In your case read that furnace manual, its got to be a setting or jumper to change. Or if you have a 2 stage zone control wired up, maybe that is the issue. As I recall they can be set so maybe X number of zones Need to be calling for Heat before it goes to 2nd stage?

So according to the post about the panel above, you only have single stage out. Its got to be in the furnace setup.

tomns

Ok, looks like I'm spending this evening with a tall cold one and a manual. I'll post what I learn.

ratio

Old style Honeywell zone controller, before the TrueZONE® series. It's single stage, and it doesn't look like a discharge sensor is attached, so it should just either call or not. It's got to be in the control board of the furnace. I can't understand how it's related to the outside air temp though. I can't imagine that the furnace has any kind of OAT sensor. Perhaps it's a venting issue, that could vary based on outdoor temp; but I think it smells like a control board wigging out.

EBEBRATT-Ed

I would just look at the furnace wiring. The furnace is either 1 stage or two stage. Then use a jumper to confirm both stages operate.

If there is a discharge air sensor or an ODA sensor in the mix the furnace wiring will tell you that

Cut to the chase and worry about the thermostats and zone panel after you know what the furnace is capable of

mattmia2

I would look very carefully at the sequence of operations in the manual for the furnace. My assumption is that it would lock out altogether if it has a vent issue but maybe it tries low stage first.

HVACNUT

Yeah that zone panel is for single stage heat only. 
I'm thinking W1 and W2 is jumped in the furnace and stage 2 is opening on limit.

ratio

Doesn't fit with the description upthread. Above 20° the unit stages up after 10 minutes & runs in high stage until satisfied. Below 20° outside it stages up & then drops back down after a few minutes. Even if the specific numbers aren't reliable, when it's cold out it doesn't stay in high fire. I think it's going to take feet on the ground to figure this out. Maybe a call to tech support.