I am in the middle of hooking up an outdoor wood boiler and have a question. I am installing the heat exchanger into my ducting and there are only two options. One is to install it into the return line but I think I will lose some heat that way plus I will have to make a place to put a new air filter above the exchanger (the present air filter is on the bottom of the furnace right at the blower). The other option ,which is the easiest, is to mount it under the A coil but this will put it right above the heat outlet from the oil furnace. It will be about 5 or 6 inches from it. Is this to close. The oil furnace I have is tall and has the return line and feed line both on top of the furnace so I don't have many options. I can make it work either way but the feed line with the A coil is the easiest. I can send a picture if it helps.
OWB installing heat exchanger location
- Thread starter trt3
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Steveguy
ArboristSite Operative
Between the furnace and the A-coil in the discharge plenum is the preferred location for your HX . In my application there wasn't room there so I had to put it in the plenum above the AC A-coil. Some people are concerned about freezing th HX in the summer with it above the AC , but I don't think it would happen. It hasn't for me anyway. So, it sounds like you are on the right track.
nparch726
ArboristSite Operative
I put mine just a couple inches above the A/C coil. I think I heard on here about the HX freezing when the A/C is on in the summer, but I have a hard time buying that one. I just fired up my new OWB last week and so far everything is working great with my setup. Good luck!
There is no room on top of the a coil so it has to go under it. There is about 9 inches between the furnace and a coil in the plenum. My concern was how close is to close to the oil furnace. I guess I am concerned about the heat that comes from the fire box of the oil furnace.
applefarmer
ArboristSite Operative
I had the same problem with my setup in my low headroom basement. My hx was the same diminsion as the hot air discharge on the oil burner. I trimmed the lip off the sheetmetal on the furnace and mounted the hx directly to it. Then remade a hot air plenum to mount to the top of the hx. Worked great no problems!
mtfallsmikey
Addicted to ArboristSite
If the HX gets that cold, there will be a lot more going wrong first...like a frozen evap. coil. Most of the time, discharge temp. from an A.C. evap will be in the low 50's
beagledog
ArboristSite Member
Mine is about 12 inches from the oil burner chamber. No problems.
upsnake
ArboristSite Operative
Ok i know this is an old thread, but I am in the same boat. I am getting close to having the install done, and when i started looking at the furnace, the AC coil sits right on top of the furnace.
I think i can move it up the 6 inches to get the HX in there but it would be a lot less work to put it on top of the AC coil.
I don't use my AC that much, i think last summer I might have used it 5 times. I don't want to mess up my HX though. Haha I am not sure if any of the people that said they did the install this way are still actively reading the boards but if they are or if anybody else did the install this way how is it working for you?
Thanks
Jay
I think i can move it up the 6 inches to get the HX in there but it would be a lot less work to put it on top of the AC coil.
I don't use my AC that much, i think last summer I might have used it 5 times. I don't want to mess up my HX though. Haha I am not sure if any of the people that said they did the install this way are still actively reading the boards but if they are or if anybody else did the install this way how is it working for you?
Thanks
Jay
loadthestove
ArboristSite Guru
I installed on my cold air return side.my heat exchager is fastened directly on furnace inside return air duct work.
I have 4 different furnaces in my house, I have it installed on the returns on 2 downflow units, installed above the a coil on one, have below the a coil on another. I measure the duct temps, they run about the same. I cannot see any difference where the coil goes.
The outlet temps on my heating vents are higher with the OWB than the propane furnace. I'd think that would be the same case with your oil furnace. That tells me the heat from the propane furance is lower than the temps coming off my OWB HX. I could be wrong, if so, someone correct me.
mtfallsmikey
Addicted to ArboristSite
Not sure what outlet air temps. these new furnaces are producing, industry standard used to be 190 deg. After return air drop, and fan speed corrections, you should have, for example 130-140 deg. air temp. from a coil supplied with 180-190 deg. water. Mine averages 130 or so.
coyotencuttin
ArboristSite Member
If you put the hx in the return make sure you have a high quality air filter installed before the air enters the hx.air flow is the biggest reason why a/c coils are installed after the blower. You move more air after the fan than before it. Generally return duct work is sized larger than the supply ductwork and if you need X cfm for the proper btu from the hx you may only get 1/3 or 1/2 the btu in the location. Something to think about. Good luck, Harold
Penguins87
ArboristSite Member
Upsnake, I had the same situation as you. I installed my HX above AC coil in the plenum. Now three years later I have had no problems. But one thing I did was put a shut off valve on the feed side followed by a boiler drain right before the HX. Then another shut of on the return side. Isolating the HX. When I shut my OWB off for the summer. I close both valves and open boiler drain which would allow for expansion if there is freezing. In the fall, close boiler drain and open the two valves. Don't think it's was necessary though.
i'mstihlaguy
ArboristSite Operative
I kinda did the same thing. More for maintenance and so I could bypass the HX. I have a single loop so this lets me bypass the HX and still supply the side arm on my hot water heater. I have unions at the HX for removal if necessary but I haven't had any issues leaving it installed. The air handler was oversized a little to ensure proper air flow.
woodcuter ms361
ArboristSite Member
Just started building me a owb,all my duck work is overhead in my home,has anyone put hx overhead?where is a good place to buy heat exchanger?Thanks
mhyme71
ArboristSite Member
This is how i did mine. I added a illustration from central boilers website. They know a little something about these owbs
upsnake
ArboristSite Operative
mhyme71: Do you have AC in your house? If so I am assuming that your evaporator coil sat far enough above the furnace in the plenum that you could put your HX in.
That was my plan (CB's recommendation) until I opened up the plenum to see the AC coil sitting right on top of the furnace.
haha
i'mstihlaguy & Penguins87: I like that idea. I am planning on going that route, as it will save a lot of time and money redoing the furnace plenum, and eliminate the possibility of damaging the HX during the summer.
Thanks for all of the ideas and suggestions.
Jay
That was my plan (CB's recommendation) until I opened up the plenum to see the AC coil sitting right on top of the furnace.
haha i'mstihlaguy & Penguins87: I like that idea. I am planning on going that route, as it will save a lot of time and money redoing the furnace plenum, and eliminate the possibility of damaging the HX during the summer.
Thanks for all of the ideas and suggestions.
Jay
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