Isolation of winter time radiation from year-round reheat

[BronYrAur]

I have no first-hand experience but have always heard that when isolating a wintertime piece of radiation you should always put valves on both the supply and return. I am looking at some drawings where the reheat coils and the other radiation (unit heaters, cabinet heaters, etc.) are all on one hot water loop. The other radiation will only be used in the winter whereas the reheat will be used year-round. The supply lines have 2-way control valves for isolation, but the return lines do not.

I have always heard that the heat will migrate through the return lines and heat up the radiation. Is this a concern? Do I need isolation valves on the return lines?

 

[IRstuff]

Do you mean "radiator?"

TTFN

FAQ731-376

 

[BronYrAur]

no??? Don't know what you mean? I use "radiation" as a generic term for a coil, fin tube, etc.

 

[IRstuff]

"Radiation" usually refers EM energy that's radiated, ala balckbody radiation:

http://en.wikipedia.org/wiki/Black_body

TTFN

FAQ731-376

 

[ChrisConley]

Radiation also commonly refers to wall-fin and other heating devices.

2-way isolation valves are not typically required on the inlet and outlet of equipment typically as the 'migration' of heat is generally caused by gravity circulation (cold goes down, hot goes up small flows are generated in the pipe). Proper piping practice (say that three times fast) is what is required to eliminate ghost flows from gravity circulation.