Question

[317069]

Hello all

if we have a 150 feet uninsulated duct connected to air handler.
is there rule of thumb to put reheat coils.
thank you

 

[MintJulep]

No.

 

[lma1]

If you’re trying to put a reheater in the duct run because it’s long and uninsulated, it’s hardly the practice. Reheater is not a substitute for duct insulation, it’s selected & installed because of a system design requirement.

 

[cdxx139]

return or supply?

Assuming supply, is the air at the end of the uninsulated duct to cold? if so, then provide reheat. Uninsulated supply may be against code



knowledge is power

 

[ChrisConley]

150 feet really isn't that long. You could work out the heat loss of the uninsulated duct, convert that to a temperature loss of the supply air and then increase your supply air temperature accordingly.

The duct is exposed in the space it serves (which is the only time I see uninsulated duct) then the duct is losing heat into the space anyhow, and no additional heat is required.

 

[317069]

Thank you all
the duct is runing into a conditioned space, but it was a point of question between me and a contractor who come to estimate the cost.

 

[cdxx139]

If the duct is within conditioned space, local code here requires insulation if the supply temp is a greater differential of 15 degF from the ambient temp, due to condensation I believe.

knowledge is power

 

[thesnipe]

In my opinion, the cost of insulating the duct vs. increasing the supply temperature year over year is a more cost effective and green solution.

150 ft. is not that long of a duct run so you could try seeing how large of an impact insulating it or turning up the output temperature has and determine whether or not the difference is worth the effort =) Good Luck!

Snipe