Furnace

[ToolsRCool]

Had to disable my decent 80% efficient ceiling hung warehouse unit because I went over the chimney area with solar panels. Thought I'd drop a pic of its new (to me) high efficiency replacement. Garden hose natural gas line, 2 bare wires jammed into the end of an extension cord, blower side panel atop as an air vane, exhaust going wherever it wants, and a chip clip on the door switch.

 

[The Cobbler]

ugm... you're not serious I hope

 

[ToolsRCool]

ugm... you're not serious I hope

Just a 60 second test run before I go through all the work of installing it horizontally up in the attic.

And, I think I may have come up with a way to discharge the condensate outside of the wall without having to (electrically) heat its drain line. This aspect has been somewhat of a hold-back on the project. Can be somewhat difficult to run a HE furnace in a freezing climate if you use it as on-demand only and the temps drop below 32F, due to the condensate trap and line freezing up.

 

[4x4Pete]

Looks good!

 

[PoorUB]

And, I think I may have come up with a way to discharge the condensate outside of the wall without having to (electrically) heat its drain line. This aspect has been somewhat of a hold-back on the project. Can be somewhat difficult to run a HE furnace in a freezing climate if you use it as on-demand only and the temps drop below 32F, due to the condensate trap and line freezing up.

Good luck with that! I wouldn't attempt to run a 90+ randomly in a cold climate.

 

[ToolsRCool]

Good luck with that! I wouldn't attempt to run a 90+ randomly in a cold climate.

Tell me more. I do hear a few people say that, but not sure why.

Is it only because of the condensate handling? For that, I think I am going to blow the warm'ish exhaust right at the condensate drain tube on the outside of the building to keep it from freezing when running. Such ideas still TBD, but I don't want to use heat tape.

Also not sure if I am going to use it as on-demand and have it perform from cold starts, or if I'll always have it on and a minimum set temp of 40F. It is able to come on and heat from a cold start now, so as long as I can be creative on the condensate trap and discharge handling, I think it can work, and even safely. Make a trap out of looped rubber hose instead of PVC so it won't crack if frozen full of water, heat the discharge area so it does not dam up, etc.....

I am interested to hear of any other predicted challenges though. I ran the heater for a while as a stand-alone test, and it seemed fine, even on re-starts. I'd much rather have a high efficiency unit than a hot exhaust unit, because of fuel cost, and ease of installation.

 

[Bert_]

If the condensate trap freezes, even if you keep it from breaking, how long will it take to thaw?

 

[ToolsRCool]

If the condensate trap freezes, even if you keep it from breaking, how long will it take to thaw?

Right, great question. The furnace will be 2nd story mounted. I am thinking of dropping the condensate drain tube all the way down to nearly the base of the 1st floor. This will give that amount of vertical distance (or volume of tube) for the furnace to run and heat the interior, and hopefully the frozen trap as well, before it backs up and shuts the furnace off. The condensate water falling down the tube onto the ice block in the trap will also be warm'ish, and should help thaw.

If need be, I could also route the warm furnace exhaust or even a heat outlet duct across the trap to thaw it quickly. Put the trap right at one of the heat vent outlet ducts, or even in the ductwork itself. With a vertical hose rise, it will act as a time delay to enable the furnace to start and run for a while before a limit switch is tripped. I think it may work just fine.

I'm not saying I'm a specialist in this, but I do very much at least enjoy trying unconventional solutions to common problems, as almost a hobby in itself.

 

[4x4Pete]

Maintain minimum temp as required by the manual. Usually 50°+ You may get away with just above freezing or like 40°F. The furnace life expectancy may be shortened. Realistically who cares? If you're only running it a few times a week in the winter it'll probably last 20 years.
Edit: be creative like your thinking with the condensate and it'll probably have no problems. As long as the trap doesn't crack from freezing, you may need a heat gun to start it up after letting it go below freezing.

 

[Bert_]

You really do have ideas for a lot of the problems. I'll be interested to see the outcome.

I salvaged some parts and converted the furnace in my garage to intermittent pilot. That was good enough for me.

 

[PoorUB]

Tell me more. I do hear a few people say that, but not sure why.

Is it only because of the condensate handling? For that, I think I am going to blow the warm'ish exhaust right at the condensate drain tube on the outside of the building to keep it from freezing when running. Such ideas still TBD, but I don't want to use heat tape.

Also not sure if I am going to use it as on-demand and have it perform from cold starts, or if I'll always have it on and a minimum set temp of 40F. It is able to come on and heat from a cold start now, so as long as I can be creative on the condensate trap and discharge handling, I think it can work, and even safely. Make a trap out of looped rubber hose instead of PVC so it won't crack if frozen full of water, heat the discharge area so it does not dam up, etc.....

I am interested to hear of any other predicted challenges though. I ran the heater for a while as a stand-alone test, and it seemed fine, even on re-starts. I'd much rather have a high efficiency unit than a hot exhaust unit, because of fuel cost, and ease of installation.

If the condensate trap freezes, even if you keep it from breaking, how long will it take to thaw?

Exactly, plus it isn't just the condensate drain, it is the drain lines inside the furnace, plus the lies to the pressure switches. Keep in mind there is moisture in all these lies, maybe not a huge amount, but when it freezes it can cause the furnace not to run until it is all thawed out.

I did HVAC service for a few years and have run across homes with 90+ furnaces that stopped working and the home froze up. We have taken propane Knipco style heaters inside homes and aimed them at the furnace to thaw it out as it was easier than tearing it all apart and thawing out each individual part and hose. I had one that failed and I couldn't get heat to it and it took me 2-3 hours to get it all thawed out so it would run on its own.

The only way I would put a 90+ furnace in a building I was not going to heat all the time would bet to put it in a small room and put electric heat in the room, then then put back draft dampers on the supply, and maybe return ducts to trap the heat in the furnace.

Also, keep in mind a high efficiency furnace can easily produce 10 or more gallons of condensate a day. Perhaps you can just dump it outside, but over winter it will be a lot of water and you will have a big ice berg next to your building.

Do yourself a favor and figure out a way to vent you existing heater, or buy one that will vent out a side wall. Your life will be so much simpler!

 

[ToolsRCool]

Exactly, plus it isn't just the condensate drain, it is the drain lines inside the furnace, plus the lies to the pressure switches. Keep in mind there is moisture in all these lies, maybe not a huge amount, but when it freezes it can cause the furnace not to run until it is all thawed out.

I did HVAC service for a few years and have run across homes with 90+ furnaces that stopped working and the home froze up. We have taken propane Knipco style heaters inside homes and aimed them at the furnace to thaw it out as it was easier than tearing it all apart and thawing out each individual part and hose. I had one that failed and I couldn't get heat to it and it took me 2-3 hours to get it all thawed out so it would run on its own.

The only way I would put a 90+ furnace in a building I was not going to heat all the time would bet to put it in a small room and put electric heat in the room, then then put back draft dampers on the supply, and maybe return ducts to trap the heat in the furnace.

Also, keep in mind a high efficiency furnace can easily produce 10 or more gallons of condensate a day. Perhaps you can just dump it outside, but over winter it will be a lot of water and you will have a big ice berg next to your building.

Do yourself a favor and figure out a way to vent you existing heater, or buy one that will vent out a side wall. Your life will be so much simpler!

Interesting perspectives, you make some good points, especially regarding the moisture in the other 2 pressure sensor hoses and such, I did not consider that. I just went and tried it again from a dead cold and dark start, and it fired right up first shot. I'm still going to try it as an install, but maybe not sell my 80% just yet.

Appreciate the insight from various angles. The condensate water is supposedly very acidic? Going to want to keep that off the building for sure. Luckily there is no grass where it will exit.

 

[BillK]

Appreciate the insight from various angles. The condensate water is supposedly very acidic? Going to want to keep that off the building for sure. Luckily there is no grass where it will exit.

I don't think the acidity is as much of a problem as people say. Mine on my house runs outside and under my gravel driveway to an "undisturbed" area and the weeds and ivy grow around it just fine. Its been like that for 25 years or so.

 

[PCustoms]

I don't think the acidity is as much of a problem as people say. Mine on my house runs outside and under my gravel driveway to an "undisturbed" area and the weeds and ivy grow around it just fine. Its been like that for 25 years or so.

Some plants like acid.

Concrete doesn't. Keep furnace condensate away from concrete!