new Lennox SL280v not set up for two stage

[545GAlady]

I have a quick question regarding our new upstairs furnace that was installed last July.

Our Lennox SL280v was never wired for "true" 2-stage operation, so the unit runs on low fire for 7 minutes then switches to high. My question is, is it better to have true 2-stage operation where the furnace will only run in high stage when it needs to or is the setup fine the way it currently is? I would like to have true 2-stage operation but I want your opinions on it first. I'm surprised how the installers never ran a W2 wire to the thermostat. The technician who performed our furnace tune-up/inspection several weeks ago said that he could add a wire but said it was optional and it is not impossible to have one added. The thermostat is a Honeywell RTH6450D and it is compatible with multi-stage systems.

[martyinlincoln]

Up to you. Set up as a two stage via the thermostat gives longer run times and increased comfort. Second stage has a better combustion efficiency so getting there from the timer is not a bad thing.

[gravity]

As Marty stated. Having w1 and w2 hooked up at stat will be more comfortable to others.

Having the furnace fire in only w2 will save you more energy and give you the most heat.

A lot of people are against me but, I only set furnaces to high fire and tune them with a combustion analyzer. With certain formulas and data I can prove high fire costs less money and gives you more heat.

[545GAlady]

Thanks for the input. I appreciate it. Our upstairs is 1400 sq. ft. and the furnace is 66,000 BTU input on second stage and 43,000 BTU input on first stage. Our furnace is the smallest size the SL280v it comes in. I think that having true two stage control will probably be more ideal because with the furnace running on low the majority of the time, it won't short cycle and will provide more comfort. Also since the upstairs only being 1400 sq. ft., 66,000 BTU sounds a bit too much so that will make the furnace rarely run on second stage.

[catmanacman]

I feel it's just laziness on the part of the install company to sell a 2 stage furnace then not wire it properly, I wll say where I work they do the same crap

[beenthere]

Have it set up for 2 satage operation by the thermostat. It provides better comfort, by not giving you that sudden cool feeling when it shuts off like single stage furnaces do, or just running in high fire.

[pacnw]

I feel it's just laziness on the part of the install company to sell a 2 stage furnace then not wire it properly, I wll say where I work they do the same crap

X2

and the funny thing is the guys where I work say they set it up right, but the manual is still sealed in the package and I know they do not have the info from another source.

[54regcab]

I'd just disable the 2nd stage entirely, it's not like you need it. The only time I would see the 2nd stage being handy is if you setback your thermostat at night and want it to warm up quickly in the morning.

[syndicated]

That's a modulating furnace, it shouldn't be set up for 2 stage operation anyways.

[545GAlady]

Thanks everyone for the recommendations. I can tell that obviously having the 2 stage control can provide better comfort.

I'd just disable the 2nd stage entirely, it's not like you need it. The only time I would see the 2nd stage being handy is if you setback your thermostat at night and want it to warm up quickly in the morning.

We always set back our thermostat at night time like for instance the thermostat is set at 67* all night and in the morning the setting goes up to 71*. That will probably be the only time the furnace will ever run in 2nd stage.

[RyanHughes]

That's a modulating furnace, it shouldn't be set up for 2 stage operation anyways.

No it isn't. The SLP98v is modulating. The SL280V is a 2-stage, variable speed 80% furnace.

[545GAlady]

I knew that syndicated was wrong because I clearly checked Lennox's website.

[gravity]

If your going to run in 1st stage all the time, have someone verify operation with combustion analyzer to make sure your flue gases are hot enough and they wont condense before leaving exhaust pipe, which would eat away the flue pipe and heat exchanger.

[545GAlady]

No it isn't. The SLP98v is modulating. The SL280V is a 2-stage, variable speed 80% furnace.

That's true that the SLP98v is modulating and the SL280v is only two stage. It clearly says it on Lennox's website.

[545GAlady]

If your going to run in 1st stage all the time, have someone verify operation with combustion analyzer to make sure your flue gases are hot enough and they wont condense before leaving exhaust pipe, which would eat away the flue pipe and heat exchanger.

Thanks. I'll call our HVAC company one day to take a look at that.

[54regcab]

Thanks. I'll call our HVAC company one day to take a look at that.

FWIW I've never seen a flue pipe corrode in less than 20 years in the South. Heat simply doesn't run enough.

[Kevin Weaver]

You could have a Honeywell IAQ thermostat installed and this thermostat will not require you to have a new thermostat wire pulled. It can do 2 stages of heat with the current wires you have now.

[gravity]

54regcab.....I guess it helps if I look at his location.

Yea it will take a while to rust out. It should still be properly tuned.

[54regcab]

54regcab.....I guess it helps if I look at his location.

Yea it will take a while to rust out. It should still be properly tuned.

We have bigger fish to fry than combustion analysis. Down south we're simply trying to get the ductwork installed right for decent airflow It isn't uncommon for units down here to be riding the high limit switch...

[gravity]

Wow...We have our fair share up this part too.