Separated Combustion Garage Heater

[meinckdp]

I'm looking into installing a ceiling hung natural gas heater in my garage, but am new to heaters and still learning. I like the idea of separated combustion and not having to worry about saw dust or fumes being a problem, but having to run a condensate drain line will be an issue. I don't have a drain in my garage to run a line to and there is no easy way to run a condensate line back to the house. Is there such thing as a separated combustion heater that you wouldn't need to run a condensate drain line on? I had trouble looking it up elsewhere.

 

[u3b3rg33k]

what unit are you looking into? an 80% won't have a condensate line. a condensing will, and you have to keep a set temp over freezing.

 

[Steve in UT]

Stick a hose/pipe out the wall with some heat tape on it. Run it into a bucket/barrel and dump when needed (install a full alarm.) Knock a hole in the floor and dig a few feet into the dirt and let the ground soak it up. Just a few ideas off the top of my head.

 

[BillK]

Why not just run the drain line through the wall like Steve said ? That is how my house furnace is.

 

[Showkey]

There will condensation ( small amount) either way........tip the exhaust slightly downward contrary to the instructions.* Allows the water to drip outside vs staying in pipe or worse back into the heater. They all drip some. My radon vent drips with just air venting not heated combustion exhaust. It will cause a similar ice sculpture as the picture.

Garage heater exhaust-



* some instructions say tip back towards the heater, seems wrong, suppose some might tip exhaust several inches downward which might cause a problem in venting. Water just needs 1/8-1/4” down over the exposed pipe.

Some instructions say the drain on 80% furnace horizontal vent is only required on commercial applications.


There is point where if sealed combustion is required or highly desired 90plus furnace makes sense. But that amplifies the condensation drain issue.

There’s as the other side where fresh air intake in garage heater is not that important.

 

[yeldogt]

What size is the garage ? Do you have NG

They are a bit more money ..but, I love my cabinet heater. They are only 80% no drain.

Nice thing about them is they are bit quieter -- they come with everything (vent). They use a single hole in the wall for the intake and exhaust. Easy install .. sealed combustion. The better ones are modulating ... really nice.

I think code would want at 18" -- they put the heat at the floor where it should be

 

[meinckdp]

what unit are you looking into? an 80% won't have a condensate line. a condensing will, and you have to keep a set temp over freezing.

I was planning on keeping the garage at 50 degrees. I've been looking into the Sterling GG75 heater, the Modine Hot Dawg 75 (not sure between the HDC or HDS model) and a Reznor.

 

[meinckdp]

What size is the garage ? Do you have NG

They are a bit more money ..but, I love my cabinet heater. They are only 80% no drain.

Nice thing about them is they are bit quieter -- they come with everything (vent). They use a single hole in the wall for the intake and exhaust. Easy install .. sealed combustion. The better ones are modulating ... really nice.

I think code would want at 18" -- they put the heat at the floor where it should be

Garage is approximately 32 x 22. I do have natural gas. Which cabinet heater do you have?

 

[yeldogt]

Garage is approximately 32 x 22. I do have natural gas. Which cabinet heater do you have?

Have an Empire -- the new Rinnai will modulate.

I'm talking about the sealed models -- not the vent free.

Have you done a heat load on the space? At only 750sf -- if you have it reasonably insulated and a decent door ... with NG .. the cost to heat may surprise you .

I can heat my whole 1700sf studio with a 38/40 80% unit when 0 out in PA -- I keep it in the low 60's .. and I have propane!. Unless you are on a really tight budget my guess plan on higher than 50.

 

[TurnipTruck]

I just hung an 80kbtu separated combustion heater (big maxx?) with the flue sloped down so any condensation drips outside. My shop is sealed pretty tightly (as tight as it can be with three overhead doors) and I wanted to control the infiltration air. Any modern common heater with intermittent pilot has an exhaust blower, so a rising flue is no longer necessary as it would be with a standing pilot.

 

[u3b3rg33k]

I've never seen condensation on an 80% exhaust, even in crazy weather. my guess is too much pipe outside allowing it to condense in the pipe.

 

[yeldogt]

I just hung an 80kbtu separated combustion heater (big maxx?) with the flue sloped down so any condensation drips outside. My shop is sealed pretty tightly (as tight as it can be with three overhead doors) and I wanted to control the infiltration air. Any modern common heater with intermittent pilot has an exhaust blower, so a rising flue is no longer necessary as it would be with a standing pilot.

That's not the case -- you have to follow the manufacturers direction.

 

[thammel]

I have a reznor udas and as all say, the pipes are slightly sloped to the exterior. There is no need for a condensate line.

 

[Steve in UT]

Deleted

 

[Showkey]

I've never seen condensation on an 80% exhaust, even in crazy weather. my guess is too much pipe outside allowing it to condense in the pipe.

Two weeks below 0 will do it.
18” pipe from the wall is not uncommon.

 

[Jackfre]

All the Rinnai Direct Vent units have modulated since ‘91. All vents will condense at times. It is called the “wet time”. The goal is to limit the wt that each vent sees. This is accomplished with insulated pipe and limits on length of run, rise, etc, and material choice. If I was seeing condensation in an 80%’er I’d want to know how much of it is being produced, meaning trap the line and run it to a bucket. Flue gas condensation runs about 3.2 on a pH scale and is corrosive so keep it out of the HX. I have seen systems where people drill a hole through the slab to drain the condensate. It might work in Indiana where you have a Lime base soil, but in New England I saw a house that the owner stepped on his basement floor one day an the floor broke out below him. Concrete is a lime based product and the 3.2 water ate the slab from below. Substantial amounts of condensate should be neutralized. They make small neutralizer kits and you just have to replace the limestone chips.

 

[thammel]

Also....with my Reznor UDAS, all pipes leading to the exterior (horizontal runs - intake and exhaust) are type 3 stainless steel, so rust is not an issue.

 

[LS6 Tommy]

Keep in mind, fuel burning condensing appliances have to have a condensate neutralizer, regardless of where it drains to. Many locations also require it to drain to an "approved" waste receptacle or sewer line.

Tommy

 

[Showkey]

Also....with my Reznor UDAS, all pipes leading to the exterior (horizontal runs - intake and exhaust) are type 3 stainless steel, so rust is not an issue.

CAT III stainless exhaust has been required on all horizontal vents of garage style heaters for several years.

 

[cleanspg]

I have a Sterling GG with separated combustion. 80% + efficiency and no separate condensate line.
The instructions show how to setup the exhaust. Stainless is required.

For a horizontal vent it has to slope to the outside and it does drip a lot. This last week created a two foot tall icicle on the ground outside.

For a vertical vent any horizontal portion needs to slope back to the heater so that you don't have a place for condensation to collect in your exhaust.

Get the manuals for the heaters you are looking at, and look at the recommended installation. All the info is there and could be different depending on the model. Likely any 80% efficiency model will be the same or similar as what I have described.

 

[TractorJeff]

30 by 22?
I would "ASSUME" a 50k Unit would be plenty big enough??

 

[yeldogt]

I have a Sterling GG with separated combustion. 80% + efficiency and no separate condensate line.
The instructions show how to setup the exhaust. Stainless is required.

For a horizontal vent it has to slope to the outside and it does drip a lot. This last week created a two foot tall icicle on the ground outside.

For a vertical vent any horizontal portion needs to slope back to the heater so that you don't have a place for condensation to collect in your exhaust.

Get the manuals for the heaters you are looking at, and look at the recommended installation. All the info is there and could be different depending on the model. Likely any 80% efficiency model will be the same or similar as what I have described.

The condensate line is for those that are designed to condense -- they have the secondary heat exchanger. The main flue has to follow the instructions -- the manufacturers test the equipment and they have to factor in the "what if"

 

[cleanspg]

The condensate line is for those that are designed to condense -- they have the secondary heat exchanger. The main flue has to follow the instructions -- the manufacturers test the equipment and they have to factor in the "what if"

Got it. As I under stand it the secondary heat exchanger pulls more heat out of the exhaust creating a condition where you will always have condensation because of the colder exhaust and this is how you get to 90%+ efficiency.

My main point was that I don't know of any 90% efficiency garage unit heaters and if the ones he is looking at are in the 80% range, he will not have to deal with a separate condensate line as it won't have one. Condensation in the flue is an issue at 80% and it is dealt with by following the manufacturers directions for installation.

I believe this was the original issue being discussed. You can't just drain a condensate line to the outside as it might freeze and back up and draining it on your slab is a no go etc. It requires in most cases an internal drain to send it down. None of this should be an issue because the heaters he is looking at will not have one.

Separated combustion != condensing.

I assume the confusion comes in because most "normal" furnaces that are set up for separated combustion are 90% + efficiency and will have a condensate line.

 

[danski0224]

I'm looking into installing a ceiling hung natural gas heater in my garage, but am new to heaters and still learning. I like the idea of separated combustion and not having to worry about saw dust or fumes being a problem, but having to run a condensate drain line will be an issue. I don't have a drain in my garage to run a line to and there is no easy way to run a condensate line back to the house. Is there such thing as a separated combustion heater that you wouldn't need to run a condensate drain line on? I had trouble looking it up elsewhere.

Yes, there are "separated combustion" unit heaters with an 80% AFUE rating. These do not create condensate.

Some heater manufacturers have a "residential" line of unit heaters, and these separated combustion heaters might be listed with the commercial equipment.

 

[danski0224]

Garage heater exhaust-

Type B vent is not approved for horizontal installation.

 

[cadunkle]

No condensate line on Sterling GG heater. I have a 45k unit and it has worked well for me. Currently venting through vertical B-vent as it was already there when I got the place, from a previous repurposed house furnace.

Supposedly if I run the intake outside for separated combustion it's worth another 3% efficiency. Any savings would be trivial as it only costs about $.59/hr to run full tilt, an hour to get to temp then cycles maybe a couple times per hour. It not pulling air from inside might make it a bit more comfortable from not pulling cold outside air into the heated space, and of course has the benefit of greatly reduced risk of incident if it ever gets particularly flammable inside. I may change it to separated combustion eventually.

 

[Showkey]

Type B vent is not approved for horizontal installation.

Yup :Not news to me...............that’s CAT III

 

[yeldogt]

Burning NG or Propane produces lots of CO2 and H2O -- with 85% equipment the heat of the burn is enough to take the H2O up and out. Sealed combustion does have the "help" of a fan typically .... there were old units that just had intakes (so it can get confusing)

Also -- sealed combustion is not the same as having no flame exposed (explosion proof)

Once you start to go above the 85% -- the only way to get this extra efficiency is to try and capture the heat that you would otherwise allow to go up the flue. The flue gas is allowed to cycle around a second heat exchanger ... before it goes outside. When the flue gas is in this second heat exchanger -- it is cooled ..normally by the air coming back from the room ...or returning water in a boiler. This air or water is now warmer than it would otherwise be as it enters the main heat exchanger. More heat out of the fuel. This lower temp cools the flue gas --- lots of water comes out of this exhaust. Condensation ..... it has to go someplace. Normally gravity or a pump.

with 85% equipment -- if the flue is too long or pitched incorrectly .... the lines can drip. Most equipment is designed to take a bit a water .... this will happen on cold start ... but once the flue heats up .. this water quickly evaporates.

High efficiency equipment still has lots of water in the flue .... anyone with a 96% will still see lots of moisture on a cold calm day coming out of the pipe. That's your 4%

With a boiler -- the key is to get that return water low ... that's why radiant works so well with high efficiency boilers. Cool water coming back -- cool secondary heat exchanger. If you have high temp water coming back = no condensing. That's why you don't typically get all the savings when you have baseboard with a wall boiler.

 

[iowa27]

Interested in this thread. I bought a Modine separated combustion and want to vent it vertically. I'm a DIYer but need some advice on correct venting supplies. Cat 1, Cat 3, stainless steel, etc ?

Also, I've looked all over the web but haven't found a good illustration of what I'm trying to do. I will be blowing cellulose insulation and wondering about how close the insulation can be against the exhaust vent.
Thanks in advance for any advice

 

[nadogail]

Separated Combustion with a Condensate line, are you describing a Steam System?