Single stage stat on a two staage furnace, can I do that ?

[shankle]

I have a Honeywell Pro TH4110D single stage stat, running a Goodman two stage 80% furnace. Goodman said this is the acceptable way to connect it up /run it, any thoughts on doing this ?

Seems like my old set up with analog stat and single stage furnace worked better / kept house warmer (at same temp setting)

[George2]

I have a Honeywell Pro TH4110D single stage stat, running a Goodman two stage 80% furnace. Goodman said this is the acceptable way to connect it up /run it, any thoughts on doing this ?

Seems like my old set up with analog stat and single stage furnace worked better / kept house warmer (at same temp setting)

The proper stat with that furnace, to make the home more comfortable, would be a 2-stage stat.

[George2]

P. S.
It could be that they put in too big of a furnace. That happens alot. Then it doesn't work as it should.

[jtrammel]

You could do that but to get the full potential out of the system you need a 2 stage heat tstat

[tedkidd]

Ecobee baby! Dial right in when that sucker stages.

[shankle]

The furnace (Goodman) states right on the inside cover "this furnace is designed to be used with a single stage stat" despite furnace being two stage (as in the control for the stages resides on the furnace internal board not the stat).
Should I still be using a two stage stat anyway? Not sure it's even wired up for that.
thanks for all !!

Seems our house is always COLD, we're constantly waiting for the stat to click on, takes forever to cycle (I've tried different cph settings, that did nothing)

[George2]

The furnace (Goodman) states right on the inside cover "this furnace is designed to be used with a single stage stat" despite furnace being two stage (as in the control for the stages resides on the furnace internal board not the stat).
Should I still be using a two stage stat anyway? Not sure it's even wired up for that.
thanks for all !!

Seems our house is always COLD, we're constantly waiting for the stat to click on, takes forever to cycle (I've tried different cph settings, that did nothing)

It will work with a single stage stat. It will (then) work based on the timer. That's not the issue. To give you the comfort, you should have a 2 stage stat.

Also, I've seen where a system is short on return air, the new furnace will bump the limit.
This (shortage) did not effect the older style furnaces as much.

[shankle]

Do I have to rewire it to get/use a two stage stat ?

what does this mean --->
Also, I've seen where a system is short on return air, the new furnace will bump the limit.
This (shortage) did not effect the older style furnaces as much.

for whatever its worth, the original furnace and old type stat heated/maintained temperature in my house much more evenly

thanks so much !

[BaldLoonie]

If it is a GMH, you can't use a 2 stage stat

[shankle]

The Goodman model is GMH80904BNA, is there a better stat I could be using with it instead of the current Honeywell Pro TH4110D

thanks

[George2]

Do I have to rewire it to get/use a two stage stat ?

what does this mean --->
Also, I've seen where a system is short on return air, the new furnace will bump the limit.
This (shortage) did not effect the older style furnaces as much.

for whatever its worth, the original furnace and old type stat heated/maintained temperature in my house much more evenly

thanks so much !

If the ductwork (supply or return) and/or the registers/grilles (supply or return) are not adequate, then the heat exchanger will get too hot and turn off the burners.

The blower continues (to blow) so the homeowner doesn't even know the "heat" is off. This normally only happens when it's really cold outside unless the ductwork really sucks.

[54regcab]

If it is a GMH, you can't use a 2 stage stat

The fact Goodman makes a 2 stage furnace w/o the capability to be optimized with a 2 stage stage leaves a bad taste in my mouth about Goodman...

[54regcab]

If the ductwork (supply or return) and/or the registers/grilles (supply or return) are not adequate, then the heat exchanger will get too hot and turn off the burners.

The blower continues (to blow) so the homeowner doesn't even know the "heat" is off. This normally only happens when it's really cold outside unless the ductwork really sucks.

It can also happen during recovery from setback.

[54regcab]

I've found in most cases you can just leave the 2nd stage unhooked completely since furnaces are typically sized twice as big as needed. Set the system as "two stage" and never use stage 2.

[tedkidd]

If it is a GMH, you can't use a 2 stage stat

+1

Not really a 2 stage furnace. Won't be polishing that one...

The fact Goodman makes a 2 stage furnace w/o the capability to be optimized with a 2 stage stage leaves a bad taste in my mouth about Goodman...

Hmmm. Not sure that's fair.

I've found in most cases you can just leave the 2nd stage unhooked completely since furnaces are typically sized twice as big as needed. Set the system as "two stage" and never use stage 2.

Sad but too true. Most with multiple stage furnaces spent xtra and got nothing for it. GMH at least is cheaper than a real 2 stage furnace.

[George2]

It can also happen during recovery from setback.

I had not thought of that, but so true.

[beenthere]

+1

Not really a 2 stage furnace. Won't be polishing that one...



Hmmm. Not sure that's fair.



Sad but too true. Most with multiple stage furnaces spent xtra and got nothing for it. GMH at least is cheaper than a real 2 stage furnace.

It IS a real 2 stage furnace. It has 2 stages.

[tedkidd]

It is a "modified 2 stage" system. Low can run for the first 5 minutes, or 1-12 minutes at the BEGINNING of the cycle. To me, this is a soft starting single stage.

I guess technically it is a 2 stage, but it misses 90% of the benefit of 2 stage. Any furnace that can't run high first then low, in my view (energy and comfort), misses the point. Ideally a 2 stage can cycle back and forth, modulating in an attempt to match envelope losses.

(http://site.mypointnow.com/documents/25-k120602.pdf p12. Also, notice it doesn't even list a low output on spec sheet. )

The real problem comes in when the sales person who like to oversize doesn't understand how this turd operates. He figures he can size to low stage and have "high for fast recovery". Now you have a grossly oversized piece of equipment you can't even lock on low.

I Audited a house with one of these. 2200 sf, 120,000 btu. Client replaced a 30 year old furnace a year before I got there (same size of course). Bill analysis showed NO ENERGY SAVINGS and they have all kinds of comfort issue.


IMO, calling it 2 stage is like painting a dog turd gold and calling it a gold brick. Makes true 2 stage devices look bad by association.

[Shophound]

I can see the timed two stage approach working correctly if:

a) The high stage is sized for the winter design day (not low stage)

b) Setback swings are minimized or eliminated

c) The building envelope is above average in thermal integrity (including duct leakage)

I would agree with you, Ted, that if the furnace high stage is being sized for "fast recovery", that's foolish. How is "fast recovery" quantified in engineering terms? "Oh, it should warm your house back up from 55 to 72 in about fifteen minutes". Sure, if you have a volcano blazing away inside the box, that might happen.

The benchmark is the winter design day, not sizing low stage for winter design and then relying on high fire for setback or other recovery demand.

[tedkidd]

What it does is provide a gentle start. It puts some btu to the duct so that when the fan ramps up it's not blowing really cold air at max velocity.

But imagine my frustration spending hours trying to figure out how to manage staging so I could help improve comfort and energy consumption, and my disappointment when I finally understood what this thing is.

It's the epitome of "heat UP and shut off" design philosophy.