Modulating vs. Two-Stage Furnace

[msommers]

We're trying to decide between these two. We have a brand sorted but one installer primarily carries the modulating and the other carries the two-stage mainly. We need a variable motor to work with the heat pump we're looking at.

If there was no cost difference at install, what would you go with? We're looking at reliability and cost out of warranty as deciding factors - any sort of efficiency benefits I could care less.

I know the modulating is a bit more but how much more to repair/replace? Does anyone have a modulating they can comment on in terms of reliability?

[Ca_Silvia13]

Is there a large cost difference? Both probably come with an ECM motor and are just controlled differently.

Are you not forced to go with the variable motor due to your heat pump or will the heat pump work with either?

[msommers]

Both the modulating and two-stage have variable-speed ECM motors (optional 3T or 4T sizing). You're right, it has to be an ECM motor to talk to the heat pump.

I'm moreso inquiring about the gas valve types of two-stage vs. modulating. The modulating might just as reliable but it also seems to have more bells and whistles to go wrong. I just don't want to jump to conclusions about it when I honestly don't know.

[Tik-Tok]

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Both the modulating and two-stage have variable-speed ECM motors (optional 3T or 4T sizing). You're right, it has to be an ECM motor to talk to the heat pump.

I'm moreso inquiring about the gas valve types of two-stage vs. modulating. The modulating might just as reliable but it also seems to have more bells and whistles to go wrong. I just don't want to jump to conclusions about it when I honestly don't know.

The HVAC guy who installed my furnace recently told me to stay away from modulating gas valves due to their reliability. The gas savings are insignificant in Alberta, and the parts expensive.

[ExtraSlow]

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[msommers]

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The HVAC guy who installed my furnace recently told me to stay away from modulating gas valves due to their reliability. The gas savings are insignificant in Alberta, and the parts expensive.

This is inline with everything I could find online. Two-stage stuff seems to finally have the bugs sorted, modulating is a whole other can of worms of possibilities to go wrong. I don't give two shits about efficiency either, what like $1.50 more in usage (when 60% of the bill are various fees??!).

We found that some dealers will sell the same brands, but they won't carry the same models. We were between two companies and one was really pushing the modulating and the other (what we wanted) was the two-stage. Ultimately modulating company said they'd install the two-stage but with essentially no price change....yaaa no thanks, especially at a $1,800 delta.

[Cash Money Hoes]

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This is inline with everything I could find online. Two-stage stuff seems to finally have the bugs sorted, modulating is a whole other can of worms of possibilities to go wrong. I don't give two shits about efficiency either, what like $1.50 more in usage (when 60% of the bill are various fees??!).

We found that some dealers will sell the same brands, but they won't carry the same models. We were between two companies and one was really pushing the modulating and the other (what we wanted) was the two-stage. Ultimately modulating company said they'd install the two-stage but with essentially no price change....yaaa no thanks, especially at a $1,800 delta.

We installed modulating furnaces. They aren't worth it unless you go with a brand that has a communicating thermostat (Lennox SLP99V is what we went with) which provides a feedback loop to report how quickly temp is rising in a particular area and throttle the amount of heat the furnace is putting out accordingly.

The whole idea with modulating furnaces is when the zone it's serving is losing heat and temp would otherwise go down in the house, the furnace is introducing the same amount of energy to the area that is being lost. So they run at low output levels a lot of the time. Super quiet so you don't hear it and the temperature in the house stays exactly at your set point. Also cold rooms in the house now continually get heat and there is a more even temperature distribution through the house. Overall the house is way more comfortable.

We have 3 zones served by 2 furnaces and the overall temp in the home is spot on in each part of the house. You can also get room sensors with the Lennox that mimic having a proper zoned heating set up and will average temp between temp at thermostat and temp in the room that has zone sensor. Not ideal but better than having just a single thermostat only taking temp readings on the main floor of a typical 2 story home.

The furnace has a 10 year warranty on parts and our installer offers a 10 year labor warranty, so I'll worry about repair cost when that is up or maybe it will be next homeowners problem.

Anyway, my experience has been positive as compared what we had before and would recommend the modulating furnace despite the extra cost.