High efficiency furnace question

[Ultradog MN]

Any furnace men here?
This is Minnesota. It gets COLD here.
I have a 65K btu high efficiency furnace I want to install in my shop.
I do not plan to keep the heat on in there all the time. I would like to be able to just turn it on as needed.
I am concerned about the condensate part of the furnace freezing.
There is an external water trap on the side of the furnace. It connects to the condensate collector box with 1/2" NPT threads.
I am thinking about removing the trap, adding about a 14" long plastic pipe through a wall into my office which IS always heated and reconnect the trap in there.
Would this work okay?
Sorry if I don't know all the correct terminology but I hope you get my drift.

 

[PoorUB]

I would not install a high efficiency furnace in a space you do not intend to keep heated all the time. Pretty much that simple.

First off, the condensate with freeze inside the furnace and block the drain and possible pressure switch tubing. Every time you restart it, it will be a two hour operation. Also the frozen condensate could possibly cause damage to the furnace it's self.

As for extending the drain trap into the heated space, how are you going to keep the condensate from freezing before it gets to the heat?

I worked in HVAC for years and have an 80% in my garage, and I keep it heated all the time.

I have gone into houses where the high eff furnace failed and the house got below freezing. Every time it was a pain in the *** to get the furnace running again after the repair was made.

The only way I would do this is to install the furnace in a heated alcove. Put an electric heater in the furnace alcove to keep the furnace from freezing up when it is off.

 

[fitter30]

Condensate will not drain when burner is on. Burner fan is on the heat exchanger is in a negative pressure and needs the trap to drain to break the negative pressure. 65k furnace makes 83.2 oz an hour condensate. Condensate needs a neutralizer it's acidic.

 

[manwithtools]

Condensate needs a neutralizer it's acidic.

Not to derail this thread, but it's interesting that our condensing tankless water heater condensate drain exits our garage into the wife's flower bed. Her Knockout Roses have gone wild this year. Come to find out, it's due to the fact the roses actually prefer acidic soil.

 

[fitter30]

Not to derail this thread, but it's interesting that our condensing tankless water heater condensate drain exits our garage into the wife's flower bed. Her Knockout Roses have gone wild this year. Come to find out, it's due to the fact the roses actually prefer acidic soil.

They must like the acidic dirt. Condensate 3.5 to 4.2 pH . Roses like 6- 6.9 pH

Balancing Soil pH for Growing Roses

Master Rosarian Steve Jones explains how to balance the pH of the soil in the rose garden, which helps to grow great roses.

www.google.com

Interesting.

 

[Bert_]

Condensate won't drain without the trap. Furnace will run for a while until condensate fills up the heat exchanger, then everything will shut down.

 

[Ultradog MN]

Condensate won't drain without the trap. Furnace will run for a while until condensate fills up the heat exchanger, then everything will shut down.

Perhaps I wasn't clear.
It would have a trap.
The trap is located on the outside of the furnace and screws into the collector box - which is inside the furnace, with 1/2" npt thread.
All I would be doing is moving the trap from the cold shop to inside the heated office via a 12" long piece of 1/2" plastic pipe so it won't freeze.
I built this place with a closet big enough to put this furnace in.
The door, woodwork, cabinets, etc free from a tearout by the way.
But now I like having the closet and it would be harder to install/ replace the furnace and harder to do the duct work into the shop area with the furnace in the closet.
If I have to I can and will put it in there tho.

 

[Bert_]

Perhaps I wasn't clear.
The trap is located on the outside of the furnace and screws into the collector box which is inside the furnace with 1/2" npt thread.
All I would be doing is moving the trap from the cold shop to inside the heated office via a 12" long piece of 1/2" plastic pipe so it won't freeze.

I think that would work.

I'm not sure if it will completely protect you from freezing. There will probably still be some condensate in the furnace

 

[Ultradog MN]

I think that would work.

I'm not sure if it will completely protect you from freezing. There will probably still be some condensate in the furnace

Thanks. I edited/added to the above post.
I could put a 25w incandescent bulb inside the furnace too and leave it on.

 

[Shiftless]

Thanks. I edited/added to the above post.
I could put a 25w incandescent bulb inside the furnace too and leave it on.

If you do that, I suggest finding a 130 volt low efficiency bulb so that it will last longer. If that bulb burns out and you don’t know it, your condensate water might freeze up. How about heat tape??? That comes with a thermostat.

 

[RegeSullivan]

I'm not a furnace guy so take that into consideration when reading my comments... if the furnace is running the garage should be above freezing allowing the condensate to flow assuming you have 1/8" per ft or more fall on the condensate drain. Even if you shut down the furnace the garage is likely to stay above freezing long enough to drain the line except the trap which moving to the office solves.

 

[Bert_]

I'm not a furnace guy so take that into consideration when reading my comments... if the furnace is running the garage should be above freezing allowing the condensate to flow assuming you have 1/8" per ft or more fall on the condensate drain. Even if you shut down the furnace the garage is likely to stay above freezing long enough to drain the line except the trap which moving to the office solves.

The question is does it ever drain completely?

Anytime I have been into a secondary heat exchanger, it was wet inside. Even when the furnace had been off for a while.

 

[American Locomotive]

So standard efficiency furnaces have temperature limitations, in that it's not good to run them at very cold temperatures because they can condense, damaging the unit.

...but do high-efficiency condensing furnaces have that limitation? Could they just leave the heat at say 38-40 when they're not in there?

 

[brewchief]

What brand and model furnace? The design of some equipment will do better in this situation then others, some furnaces tend to hold condensate in places that would be a much bigger problem then on others, anything where the inducer holds water may be a problem.

Some brands have section in the installation instructions that deals with this and heat tape is one answer.

 

[Crazyjake8493]

It would probably work if you bring the trap inside a conditioned space. As stated, there will be some residual condensate inside the furnace but if installed correctly it should drain enough to not freeze.

The furnace should be installed with a slight forward pitch to make sure all condensate evacuates the secondary heat exchanger. I see a lot of H.E. furnaces installed perfectly level, which is not desirable.

Personally I would just set the shop thermostat low but warm enough to keep from freezing. It shouldn't take much unless your shop is wildly uninsulated.

 

[Ultradog MN]

It would probably work if you bring the trap inside a conditioned space. As stated, there will be some residual condensate inside the furnace but if installed correctly it should drain enough to not freeze.

The furnace should be installed with a slight forward pitch to make sure all condensate evacuates the secondary heat exchanger. I see a lot of H.E. furnaces installed perfectly level, which is not desirable.

Personally I would just set the shop thermostat low but warm enough to keep from freezing. It shouldn't take much unless your shop is wildly uninsulated.

Thank you.
Good idea on tipping the furnace to insure it draining internally.
How much out of level would you go?
1/4" from back to front?
3/8"?
As for insulation, I put R15 in the walls when I built the place and have the blower reserved for tomorrow to blow about R-50 of pink Attic Cat in the ceiling.
I spent a bunch of dough on this project this fall. New nat gas upgrade from the street to the house, new gas meter. New 2 psi gas line from the house to garage. New drywall in the ceiling of my 600 sq ft shop area, insulation, duct work, etc, etc.
And I still don't have a clue what it will cost to heat the place.
Of course I'm hoping to always keep it above freezing in there but I'm also wanting to hedge my bets cost wise by having the option of letting the shop go cold if need be.