Furnace Room Air Conditioning in Winter

[sfxf]

In my project, the furnace room has large amount of heat exhaust, and need cooling in the summer. My question is how to design the furnace room for the winter time. Can we use the heat from the furnace to heat the room? That means, we may only need to stop or decrease the heat exhaust in the winter, instead of running the heat exhaust in the winter, and at the same time install another heating unit to provide the heat to the space. The project is in Canada.

Thank you very much for any advice.

 

[quark]

How are you exhausting the heat? Where from the heat is exhausted? Conceptually you can do it but it is better if you provide more details.

 

[sfxf]

Quark, thanks for response. I haven't got this detail yet, but most probably the exhaust duct is part of the furnace. If the exhaust system is interlocked with the furnace, I am wondering if I can do anything to control the exhaust cfm.

 

[quark]

You can use Heat Pipes, Runaround Loops and Waste Heat Recovery Wheels to extract heat out of the exhaust gases yet maintaining the same exhaust rates. Waste heat recovery is most widely used in once through systems, where room temperature is to be maintained above ambient temperature. Heat is exchanged between supply and exhaust air.

 

[ChasBean1]

sfxf -

The heat that's gained in the mechanical room is lost from the equipment within the room. Heat loss from operating equipment is system efficiency loss. If you decide to hack off a piece of insulation from a steam pipe, for example, to keep the mechanical room warm in the winter, you'll be doing a disservice to the steam system because the boiler will have to fire that much more to make up for that loss, amounting to higher fuel costs.

This might work during cold weather, because you'd eat more fuel anyway firing a unit heater to warm up the room. Equipment surface heat loss is an uncontrolled heat source, however, that would also be emitting the same amount of heat while you're trying to cool the room in the summer, making the cooling systems work that much harder.

It would also be much more efficient to heat the space with a system designed for heating, such as with a unit heater with fin-tube coils. The fin tubes offer high heating efficiency while random heat losses from system surfaces are much less efficient in heating a room.

The answer here is to insulate all of your mechanical equipment such there there is very little heat loss from system piping and the furnace's surfaces. Use unit heaters in the winter to warm the space and draw-through cooling in the summer. No. Do not heat the room with the furnace - insulate the furnace and minimize equipment heat loss.

-CB

 

[quark]

CB!

I think sfxf is talking about heat of exhaust gases of a furnace independant of HVAC system which is otherwise wasted. What is wrong to use it during only winter?

 

[VEEKRISH]

I agree with QUARK. It should be possible and worthwhile using an ENERGY WHEEL. Alternatively, use an air-to-air heat exchanger. This will provide the requisite heating during the winter months.

 

[ChasBean1]

Quark/Veekrish - there was one statement in the original post:

"That means, we may only need to stop or decrease the heat exhaust in the winter, instead of running the heat exhaust in the winter"

That lead me to believe it was general heat loss from equipment. You can't stop or decrease combustion exhaust flow unless you want serious side effects - just noted the second post (guess I read it too quickly).

sfxf: I've seen the exhaust recovered via water side economizer for boilers, and as Quark notes, this could also be used in small, closed loops to heat room unit heaters if you have the imagination to design outside the box, but don't vary the flow because it will change the combustion fuel/air ratios...

 

[sfxf]

Thanks for all your advices. An Air Handling Unit with heat pipe heat exchanger inside is what we finally came up with. In the winter, the outside air will have heat exchange (sensible heat) with the exhaust air through the heat pipe. The unit with rotary wheel was actually a better option, for it provides both sensible and latent heat exchange (it is very humid in the winter in this area),but in this case, we didnot use it for the concern of contamination.