2 stage furnace information

[iowahomeowner]

This is my first time posting to this forum, which I found while googling for information on furnaces. I have found some valuable information on these sites, but I still have some questions.

I moved into my house last February, so only used the original furnace 2 months or so. It was an 82,000 BTU Lennox furnace which was about 25 years old. When I went to start it this fall, it needed a new blower, and the electronic ignition was obsolete, so I needed to purchase a new furnace.

I chose the Bryant 95I Preferred variable speed 2 stage furnace, and had a Lux TX9000TS single stage thermostat installed with it.

In reading about multi stage vs single stage thermostats, I still am not sure which would be the best set-up. It seems people differ on which is best. Right now with the single stage thermostat I have, it appears the furnace is doing most of the decision making on when the furnace runs. I notice that the high speed runs more than the low speed (which I understood would only happen in the coldest of weather, which I took to mean in the low teens and below). I also notice the high speed sometimes runs well past the set point on the thermostat, sometimes to the point where it almost gets to hot in the house. The other thing I notice is that sometimes the furnace won't come on right away when the temperature shows 2 to 3 degrees below the set point, and thus it gets a little cold. Is there some kind of timing interval on the furnace to keep it from running again to soon, so it doesn't overheat (I think I read this somewhere)?

My understanding of a 2 stage furnace was that having 2 speeds allows the furnace to run longer at a lower speed, thus giving a house more even and constant heat. I thought the high speed would only be needed occasionally. But it seems to run more than the lower speed. Wouldn't a 2 stage thermostat help cut down on these variations of temperature? Having a timer determine when the furnace runs, doesn't seem to be the most efiicient way to use this furnace.

One last concern: There is a loud gurgling sound on the vent pipe on the outside of the house. It doesn't do this all the time, but I do notice it mostly when I come home from work in the evening. Could this be due to the furnace being set at a lower temperature (62) during the day, and then going back up to a higher temp(68) in the evening? Is this normal, as I don't hear it on my neighbors vent pipe (she doesn't have a two stage furnace, so maybe that's the difference)? Seems this could be a concern with the condensation backing up and causing rust/mold issues.


By the way, last week I had foam insulation sprayed in the side walls. I have not noticed any change in the furnace running. I thought by putting insulation in the walls, the heat loss would take longer, and thus the furnace would run less. Is there some adjustment I should have the furnace installer make to the furnace default settings due to the insulation in the walls?

Thanks for any insight you can give. I appreciate it.

[garya505]

You'll be happier with a good 2-stage thermostat to control the staging of the furnace. A good thermostat will also eliminate those temperature fluctuations. Tell your contractor you want a good name brand like Honeywell or White-Rodgers.

[k-fridge]

Moving to Residential HVAC where you'll get more responses.

[commerce48]

I vote for a good two stage stat as well. It will make a much better decision about which stage it should be in. Your installer was remiss in not setting you up with a two stage stat.

Not that it really matters if you do the right thing and get a better stat, but there are a couple of parameters that could be changed on your current setup. It appears that your stat (or perhaps your furnace board) is set to overshoot the set point. There could be a swing setting on your stat for this, or possibly a cycles per hour setting.

The other setting is a timer for how long the furnace runs in low stage before it switches to high stage. This is a furnace board dip switch setting in the case of a single stage stat. You can set the timer for a longer period, and it will run in low most of the time. The downside is that it will take longer to recover after a set back.

You probably should have a tech install a new thermostat. There may be some furnace settings that need changing.

By all means shop for a stat you like though. Ask for advice here. In your shoes, I would probably go with the Ecobee. They have an iPhone/Android app where you can easily change your settings anywhere. Coming home earlier/later than expected from work? Adjust the set back appropriately. Expensive of course, but you are halfway there with a good two stage stat anyway.

About your insulation, there are any number of good calculators online to figure out the energy savings from upgrades. While any upgrade is good for the pocketbook and your personal comfort, you will see that items such as sidewall insulation and windows typically don't do as much as the same money spent in better attic insulation.

[garya505]

By all means shop for a stat you like though. Ask for advice here. In your shoes, I would probably go with the Ecobee. They have an iPhone/Android app where you can easily change your settings anywhere. Coming home earlier/later than expected from work? Adjust the set back appropriately. Expensive of course, but you are halfway there with a good two stage stat anyway.


The OP has problems with staging, run times, and temperature control, and you suggest getting an Ecobee? Sure it's a high tech stat, but you don't need all that to address the problems as stated by the OP.

[commerce48]

The OP has problems with staging, run times, and temperature control, and you suggest getting an Ecobee? Sure it's a high tech stat, but you don't need all that to address the problems as stated by the OP.

I said what <I> would do! In no way did I say it was necessary, and said it would cost double. And I stated what is probably its only real benefit over other stats, unless you happen to admire how it looks. That's a lot to pay for one feature, although a very useful one for many homeowners.

[Tech23]

One last concern: There is a loud gurgling sound on the vent pipe on the outside of the house. It doesn't do this all the time, but I do notice it mostly when I come home from work in the evening. Could this be due to the furnace being set at a lower temperature (62) during the day, and then going back up to a higher temp(68) in the evening? Is this normal, as I don't hear it on my neighbors vent pipe (she doesn't have a two stage furnace, so maybe that's the difference)? Seems this could be a concern with the condensation backing up and causing rust/mold issues.



Thanks for any insight you can give. I appreciate it.


Welcome to the site,

Aside from staging and thermostat concerns...your last concern here sounds like an issue that you may want to call the installation company out to look at. This could be an issue due to the flue or drain not being installed correctly.

Good luck and take care.

[BaldLoonie]

I sure wouldn't have a 2 stage furnace without a 2 stage stat!

Gurgling probably means a sag in the flue. If it gets too bad, the furnace will shut off til it drains then restart.

[crmont]

I sure wouldn't have a 2 stage furnace without a 2 stage stat!

Unless you have a York 2-stage and a Honeywell stat. York specifically mandates not using staging with most 2 stage Honeywell stats.

It's been an issue since the inception of the current York 2 stage lineup.

Sorry for the hijack.

[garya505]

Unless you have a York 2-stage and a Honeywell stat. York specifically mandates not using staging with most 2 stage Honeywell stats.

It's been an issue since the inception of the current York 2 stage lineup.

Sorry for the hijack.

But only on the TM8V and TM9V.

[hvac1966]

I have a two stage furnace in my home just installed beginning of fall. I have a single stage stat, amd allow the high stage to cycle based on time. I pulled out a lennox atmospheric burner at 100,000 in and replaced it with an 80000 2 stage ,high stage has never come on it was 5 below last night. My house has never dropped below set temp. I did not get the variable speed blower, it sounds like your furnace is doing the opposite of what it is suppose to be doing in reguards to the staging. water is a product of the combustion, i dont now why your hearing it unles it;s maybe collecting where it shouldn't . I would suggest you contact the installing contractor and ask these questions.Good luck

[BaldLoonie]

1966, if you haven't hit high even at -5 out, you are WAY oversized!

[hvac1966]

oversizing heating systems ???? never heard of that ...

[iowahomeowner]

Hi everyone,

Thanks for all the great responses.

Actually, I did have the installer out yesterday because there was a booming noise coming from the furnace (just started a week or so ago, that I noticed). From what I read, it could have been a serious issue involving the gas. But it ended up being an expansion issue (of course it didn't make the noise when the installer was here yesterday). While he was here I asked him about the gurgling also (once again, it wasn't doing that when he was here). He checked the venting pipe by using a level, and he did say it was suppose to be at a slight slant toward the furnace. He also showed me where he had installed a small pvc pipe to drain any liquid that might accumulate. So I guess it is doing what it is suppose to.

When I first had the thermostat installed, I called the contractor because I was thinking of going with the 2 stage therm at that time. The office manager called Bryant Customer Service to ask about this, since they always install a Honeywell one stage therm with this model furnace. She was told by corporate that a one stage therm should be used. According to my installer (who has been doing this for some time), he has always used a Honeywell (couldn't get the model # from him), ever since he has been installing this furnace. They also said the therm I am using should be ok.

I still think I might go with the 2 stage, but I think I will give it another month to see what my heating bill is, as I haven't got a bill for a full month use yet. Will wait to see what that shows before making any decisions.

I know you all had some recomendations for a 2 stage therm, but are there any that you would stay away from (that is if you can say it within this forum)?

Thanks again for the input.

[crmont]

He also showed me where he had installed a small pvc pipe to drain any liquid that might accumulate. So I guess it is doing what it is suppose to.



I want to see this.

[b26440510]

my mfg calls for 1/4" per foot so not sure if that's "slight."

ditto on posting some pics of that drain he installed.

[sktn77a]

I still think I might go with the 2 stage, but I think I will give it another month to see what my heating bill is, as I haven't got a bill for a full month use yet. Will wait to see what that shows before making any decisions.

The 1 stage vs 2 stage stat won't make a measurable difference with cost/efficiency - it more about comfort.

[westval]

iowahomeowner,

The trap sounds suspicious. If the pipe is sloped correctly it will drain to the furnace and come out of the collector box just like the rest of the condensation. Sounds like there is a "swayback" in the pipe and it is pooling moisture there.

I would go with a 2-stage thermostat too.

[mayguy]

Get a two stage stat, no questions.

I am not sure why Bryant is telling dealers this.. My in laws, and friend who had a new furnace put in, they told them too to use the single stage.. I end up changing it out to a two stage, and they noticed a better comfort!