Copper in plaster radiant ceiling - supply temp? longevity?

Andruid_2

I am adding some radiators to an old heating system (35 years).  The existing system heats a radiant ceiling with soft copper tubing embedded in plaster.  The system loop is tempered with a fixed 4-way mixing valve (I'm trying to sell her a Taco 3-way iValve).  What is a normal supply temperature range for a radiant ceiling like this?  My guess would be slightly higher than a radiant slab - 125-140.  But, I don't want to guess.  I want to be certain.  And, although it's been working fine for years at a certain temperature, I'd like to know if it's warmer than it needs to be.



Also, the homeowner asked me about copper tubing embedded in plaster.  Is it doomed?  She's been told by others that it would fail like the copper in her basement slab did.  I had to be honest and tell her that I could not say.  Does it have to do with the materials in other parts of her hydronic piping?  I will be removing some galvanized and cast iron parts that have corroded.  Does it have to do with water quality?  Does it have to do with the ingredients in the plaster?

Gordy

Radiant ceiling

 I have it.  60 years old, and running strong. I use 115* supply on design days. I still have the original Taco panetrol mixing valve. Love my radiant ceiling. I would keep the supply temps in that range if it will keep up with the heat loss.



  I have done some remodeling, and inspected the condition of the pipes in the plaster, and they are like new. So as long as you manage the system water quality (PH), and don't over circulate the insides should be okay.



What eats copper pipes up in concrete is a fly ash mix design, acidic soil, Cinders etc.  Plaster is a different animal. Like I said mines 60 years old never had a leak.



Gordy

Andruid_2

ph range

As a hydronic heating professional, I need to know this.  What is the proper ph range for water in the systems I build?

Jean-David Beyer

As a hydronic heating NON-professional ...

... I know this about my present boiler whose main load is a radiant heating zone that is mainly 1/2 inch copper tubing in an at-grade concrete slab. This is in a house built in about 1950. It originally had an oil-fired GE boiler. It now has a W-M mod-con. It does not leak as far as I can tell. I assert this on the basis that when my new boiler was installed, so I assume its pressure gauge was working, I turned off the make-up water and watched the pressure for several months and it did not go down unless the indirect was running, but went right back up when the circulator to the indirect shut off. The pressure drop was due to the location of the pressure gauge. I dared to turn off the make-up water because the boiler claims its control board detects low water conditions and that some jurisdictions accept this. Mine does not, so I also have an M&M RB-122-E Low Water Cut Off.



The entire time the GE boiler was in there, the makeup water was always on. It used city water. I called the techie at the water company and he said the water analyzed at pH 7.2 to 7.6. hardness 6 grains, chlorine concentration < 2ppm. The GE boiler was not leaking. There were two leaks while that GE was in there. One was a globe valve that failed and it dribbled a little for a day or so until I could have it replaced. The other was a badly soldered pipe pulled apart and sprayed water all over my garage for about 12 hours until I got home one winter evening. I had to fix it myself myself. So there was A LOT of make up water introduced then. The former owner said he drained water from the system until it ran clear about once a year. I do not know how much water was actually involved. I did not do that, and I understand it is not a good idea to add fresh water if it is not needed.



I am not sure that a single number for the pH of the system is sufficient, and that it is necessarily a compromise. For example, the heat exchanger in the boiler is some cast aluminum ally or other, and has a pH range specified (7 to 8.5). There is some steel pipe that is shiny metal (i.e,. not black pipe, not galvanized) inside the boiler. Most of the system is copper tubing.The nearest boiler piping is black pipe, but not as black as the gas pipe. No Pex. The circulators are cast iron. The Indirect specifies the pH should be between 7 and 8. It is a W-M tank within a tank type (actually T-T). Domestic inner tank is some stainless alloy, outer tank is some other steel alloy. Microbubble air eliminator is mostly brass.  Valves seem to be all brass, but slightly different colors. So lots of dissimilar metals.

Andruid_2

Water treatment

Wow!  Thank you for those excellent answers.  I must make it a habit to test water for pH.  Is it necessary to test hardness?  What are the problems of water with a high or low pH?  What are the problems of hard or soft water?



And, if I determine that one or both are off, how do I remedy them?

Jean-David Beyer

if I determine that one or both are off

you might wish to consult with water treatment professional, as well as hydronic heating system professionals (not me). Rhomar make water treatment products for hydronic heating systems. You could call them for advice. They will need to know what is in the system (brass, aluminum, cast iron, etc.) as well as the quality of water in it.