ceiling radiant

harvey

I lookedat a job today with 3/8 copper in a plaster ceiling. The ceiling is cracked where the tube is. The boiler has no mixing at all and the H.O. says the supply never gets higher than 160 degrees :(. What it the max. water temp for this job? What is the chance the ceiling will crack again if we use the proper temp? THANX!

Mike T., Swampeast MO

A good book I have on plastering essentially says that any such ceiling will crack if gypsum was used as the heat recalcinates the gypsum. It says that big hunks will eventually fall out...

They found MUCH better results using a Portland cement based plaster for the scratch and brown coats (plus the fill-in coat if the tubes are larger than 3/8") with a final finish coat of lime and silica sand.

It says this construction will handle heat indefinitely.

Can you tell if it's a Portland base? It will be MUCH harder and likely greyish instead of white.

harvey

i don't know how to tell but i thought in the 60's they did use the cement base.

Mike T., Swampeast MO

If cement (and the old-timers were correct) the heat shouldn't be causing the cracking...

Geno_15

Unbolt

the house from the foundation and flip it over, the radiant is supposed to be in the floor.

Sorry, couldn't help myself, seriously you may want to contact Taco and check into their new mixing block and maybe recalculate as best you can the heat loss, they may be able to help and send out a rep. What's nice about the Mixing Block is you can change the temp of the loop and dial it in, I think the lower the temp you can run the less ceiling damage you'll get. This may be a no win scenario but you may be able to minimize the damage and make you sure the customer understands that.

Something that old may be not able to run a real low temp due to lack of insulation or reflectors or both.

Gordy_2

Ceiling radiant

I have ceiling radiant circa 52 3/8" copper also. 120* Max is all you want,mine only gets to 115* after the panetrol mixing valve (original) at the boiler on a design day. By the time it gets to the ceiling its about 105* to 110* which translates to about 85* plaster surface temp. I have a feeling the plaster can't dissipate the heat fast enough with 160* water temp., and the copper is expanding faster then the plaster can transfer the heat. You would not run those temps. through radiant concrete so why plaster? My plaster is in wonderful condition,and that 1952 paneltrol has not been touched since its install back then. So the installers knew their stuff. But then again my tubing is 6" centers and yours may be a wider spacing which would need the higher water temps. The benefit of tighter centers is lower supply temps.

For all you radiant floor lovers out there ceiling radiant is a great method even temperature floor to with in 6" of ceiling. No hassles with floor coverings and furniture taking away from the transfer of the radiant floor. Don't get me wrong I love radiant floor. Combine them both and you gotta pastrami on rye.

tim smith

copper radiant in plaster

i have an old buddy who has designed hundreds of these systems, he's almost 90 and still working. Proffesional PE mechanical. I take care of one he designed appx 15 yrs ago, max temp is 140. I guess from what he tells me, real plaster has about the same expansion coefficient as copper tube in this application. No cracks in this 3 million dollar town home, 15 yrs and counting.

Gordy_2

Tim

I stand corrected,I was using my own systems sucess as a reference who can argue with a 90 year old man. Thats passion for your work, admire that. I dug out my Chase Copper Brochere. it does state in it that the water temps for ceiling panels range is 120 to 150 degrees and floors are 90 to 140 degrees. I would stay as low as possible.