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[Dano]

Got a new OWB trying to figure out where to put the heat exchanger. I can put it in the return with some rework on the filter. Or i can try and put it befor the air conditioner exchanger. No room after the air conditioner because of head space. Any thoughts would  be very helpful and appreciated. Like to try and get it going befor it gets to cold Thanks Dano

[Scott7m]

As long as it's in the flow your fine, if it's before the filter, I often just make a new filter space right before the coil, so your not pulling dust into your Coil

[banjoman]

I have mine in the inlet side of the furnace and moved the filter back before the HX coil. I was wondering if the excess heat near the fan could be a future problem? I have had one episode that the fan would not turn off. I assume there is a thermal switch somewhere that is keeping the fan running when it sees a high temp. My furnace is a ThermoPride oil unit. Any ideas?

[Midnight Farms]

Is this practice of putting the heat exchanger in the cold air return a common one?

I have two furnaces with AC coils, and very little room. They are fed by a common air return. Could I put a large heat exchanger in there to service them both?

Risks? Concerns?
Thanks!
Nick

[Jwood]

Sure you could. Only problem having them on the return is heating up your fan and possibly shortening the life of the fan mine is on the return and works great. Think of it like this, as long as air is passing through it then its heating your house.

[slimjim]

The biggest issue I have seen with the exchanger mounted in the return has already been mentioned here, it could keep the fan on as there is a snap disc on the cabinet that turns on the fan when the cabinet gets hot, if the exchanger is on the intake and naturally convects heat into the cabinet it will turn on the blower, this can be controlled by only turning on the circ for that loop in a call for heat.

[Midnight Farms]

So, if it is one large heat exchanger, I could put a bypass valve on it that would only send hot water through the exchanger if either of the furnaces called for heat?
Nick

[Jwood]

Correct but if your furnace is newer it might just have a timer delay on the fan that's how my furnace is.

[pullerbob]

I also have mine on the return side as I have my A coil for my central air on the outlet side and had no room to put the HX there. I relocated my filter to go before the HX and it has been working good this way.

[Jwood]

Mine works great that way also!