Varible Speed Furnaces under 50,000 BTU

[54regcab]

Who currently makes furnaces 50,000BTU or less that have variable speed blowers? A 80% furnace preferred, in southern climates a 90% doesn't have a reasonable payback time.

[mark beiser]

Who currently makes furnaces 50,000BTU or less that have variable speed blowers?

Unobtainium. :(

While we are daydreaming about it, lets make it 2 stage heat and 14.5" wide.:whistle:


A 80% furnace preferred, in southern climates a 90% doesn't have a reasonable payback time.

What, you don't think an ROI greater than the expected service life of the equipment is reasonable? :confused:

[54regcab]

In the south we don't use the heat much at all. Gas is only $6.00 per decatherm. I'd take a 90% to get the VS in a 50K or less furnace. I don't care about width unless its over 21"

[BaldLoonie]

In upflow, Rheem RGPE-05. Most of your dreams come true. 2 stage, variable speed, communicating but 17.5" wide.

[wogpa67]

carrier makes an 80% and a couple 90%s .
http://www.residential.carrier.com/products/furnaces/gas/index.shtml
trane xv80
http://www.trane.com/Residential/Products/Gas-Furnaces/XV80-Gas-Furnaces

[hvacvegas]

GMVC95045. Variable speed, 95% gas furnace. 2 stage. High stage Input: 46k, Output: 45k.
http://www.goodmanmfg.com/Portals/0/pdf/SS/SS-GMVC95.pdf

GMVC80604. Variable speed, 80% gas furnace. 2 stage. High stage Input: 60k, output: 48k.
http://www.goodmanmfg.com/DesktopModules/GoodmanProducts/ProductFiles/31SS-GMVC8.pdf

I've put in a GMVC95045 before.

If you don't consider goodman a real manufacturer (as some here do), and your load dictates that small of a furnace, run a furnace in first stage only.

[CraziFuzzy]

In california, you won't likely find a low BTU furnace that is going to work for you, because the AC is going to require a lot more CFM that what it will provide. Typically, california homes, the A/C is sized for the home, then the furnace sized for the A/C. Not really ideal, but it's the norm.

The solution, really, is to use a Hot water + DX fan coil. That way everything can be sized just right. Use an efficient water heater for the heating AND hot water (it will likely be plenty).

[mark beiser]

None of the above linked furnaces does it for me, as they all have 1st stage heating output that is higher than the design day heat loss for the applications I'm wanting small furnaces for.
I guess I should clarify that I want a 40k btuh INPUT capacity 2 stage furnace, with a VS blower.
A 50k btuh input furnace is getting close to what I want, but the Rheem one BaldLoonie mentioned has a 1st stage capacity that is 70% of 2nd stage, so is no better suited for what I want than the 60k btuh input furnaces we currently use that have a 60% first stage. :(

I absolutely hate the uneven temperatures, and short run cycles caused by an over sized furnace.

For my personal house, I'm probably going to replace my two water heaters with one high recovery water heater, and ditch my gas furnace in favor of a hydronic heating coil in an air handler.
That way I can tune the heat output to the heating requirements of the home.

[mark beiser]

This discussion reminds me of a few years back at a particular manufacturers dealer meeting when they were talking about the new product lines.
The particular manufacturer didn't have a VS 80% furnace.
Someone asked the speaker when they were going to have one.
The speaker made a comment about them only offering a VS 90+ furnace because they didn't believe there would be much demand for a VS 80.

This was speaking to a room full of HVAC contractors in Texas.

After he made the comment, the room went dead silent...

[wogpa67]

you could use a mod con boiler with an indirect and lower its max firing rate for the heating side.

[mark beiser]

you could use a mod con boiler with an indirect and lower its max firing rate for the heating side.

Yeah, but the ROI based on the fuel savings would be longer than the most optimistic expected service life of the boiler, probably by several decades. :p

8-9 months out of the year, my gas bill is about $39/month, the minimum charge if you have gas service.
My highest winter gas bill, in the 5 years I've been in this house, was $79.
This is with a gas stove, oven, cloths drier, two 30 gallon water heaters, and a gas furnace.

[skippedover]

Who currently makes furnaces 50,000BTU or less that have variable speed blowers? A 80% furnace preferred, in southern climates a 90% doesn't have a reasonable payback time.

Okay, so what's the payback time on an 80% furnace?

[mark beiser]

Okay, so what's the payback time on an 80% furnace?

He is talking about the payback on the difference in total installed cost between an 80% and 90% furnace.

For me, and many of my customers, a 90+% furnace would optimistically save around $30, or less, worth of fuel per YEAR.
Even if the total cost difference was only $500, and the high efficiency furnace cost no more in maintenance and repairs than a standard furnace would, the ROI would be >16 years.

In my home, the average annual cost to heat my home has been less than $150, closer to $50 this past "winter".
The ROI for me would be longer than the life expectancy of the furnace, AND the one it was replaced with!

High efficiency furnaces just makes no economic sense at all in my climate.

[54regcab]

Okay, so what's the payback time on an 80% furnace?

I'm working under the assumption the furnace will be replaced anyway, a 90% furnace would only lower the gas bill about $50/yr compared to a 80% model.

[CraziFuzzy]

rinnai makes some decent looking (and decently priced) hydronic furnaces (multispeed ECM motors, full controls, built in water pump, etc). I don't have personal experience, but they offer a number of different blower and coil configurations. They even will put priority to domestic water heat, so you aren't starving your domestic hot water to run the furnace.

[mark beiser]

rinnai makes some decent looking (and decently priced) hydronic furnaces (multispeed ECM motors, full controls, built in water pump, etc). I don't have personal experience, but they offer a number of different blower and coil configurations. They even will put priority to domestic water heat, so you aren't starving your domestic hot water to run the furnace.

Those look interesting, I'll have to investigate them more.
I've been looking at AS/Trane ForeFront/Hyperion air handlers with the hydronic heating coil option, but it is good to have choices.
First Company also has a good selection of air handlers with built in hydronic and DX coils.

I won't be using a tankless water heater though, because they just don't make any sense for most applications in my area.
Conventional high recovery water heaters cost way less up front, and are much less likely to require modifications to the gas supply system.

For me personally, outside of heating the house 2-3 months a year, the potential savings of a tankless water heater is exactly $0 because the rest of the year I am already paying the very minimum the gas utility will ever charge me. This despite maintaining 60 gallons of hot water in two 30 gallon tanks.

[CraziFuzzy]

Those look interesting, I'll have to investigate them more.
I've been looking at AS/Trane ForeFront/Hyperion air handlers with the hydronic heating coil option, but it is good to have choices.
First Company also has a good selection of air handlers with built in hydronic and DX coils.

I won't be using a tankless water heater though, because they just don't make any sense for most applications in my area.
Conventional high recovery water heaters cost way less up front, and are much less likely to require modifications to the gas supply system.

For me personally, outside of heating the house 2-3 months a year, the potential savings of a tankless water heater is exactly $0 because the rest of the year I am already paying the very minimum the gas utility will ever charge me. This despite maintaining 60 gallons of hot water in two 30 gallon tanks.

Agreed on the tankless and cost recovery... that said, living in a household with a wife and 2 daughters, I couldn't imagine anything else. That one time expense was worth it for the endless hot water supply.

[54regcab]

Agreed on the tankless and cost recovery... that said, living in a household with a wife and 2 daughters, I couldn't imagine anything else. That one time expense was worth it for the endless hot water supply.

Agreed, with 3 women in the house a tankless water heater is the way to go for sure !! A tankless water heater + hydronic coil could do the work of even a standard 100K furnace since those tankless heaters have such large burners.. Doing a water heater/hydronic could *almost* handle the load for my house. The issue I would run into is running out of hot water when outside temps were cold, I would need some sort of aux heat for times of high hot water demand. I suppose 5KW of strip heat used occasionally wouldn't hurt the power bill too much. I then look at cost, a 80% furnace is cheaper than a hydronic coil system + 5KW of strip heat...

I will say I did a hydronic at my last house and it worked great except during times of high hot water demand when it was cold outside. My wife worked at the plant that made the fan coils for hotel rooms so we got a "test unit" for free. The engineers at my wife's work thought I was nuts, but was surprised when it actually worked. The units are designed for commercial applications for use with a boiler/chilled water but worked great for the 800sqft house we used it on.

[mark beiser]

Agreed on the tankless and cost recovery... that said, living in a household with a wife and 2 daughters, I couldn't imagine anything else. That one time expense was worth it for the endless hot water supply.

Yeap, endless hot water is the only real reason for getting one for most people.

The conservationist in my cringes at the thought of burning through that much water at a time though.
I'm not an environmental loon, I just believe in sensible conservation of resources, and have spent most of my life in relatively water poor areas. ;)