CPVC and Air in the System

NRTDave

We are looking to help with troubleshooting on a couple projects. Similarities with the projects include geothermal heat source, radiant floor radiating, air handler units providing both heating and cooling, CPVC piping in the mechanical room, and air in the hydronic heating system. Different installing contractors and different parts of the country. The question I want to ask the wall pertains to the CPVC piping and air in the system. I understand CPVC pipe does not included an oxygen barrier and the hydronic components in the system are supposed to be non-ferrous. Refer to attached pictures of a pump header for one of the projects where they are having circulator failure and air issues. Also, I understand that oxygen can pass through the CPVC tubing and cause corrosion issues. But can this same oxygen or other gaseous elements or compounds also pass through the wall of the pipe resulting in the formation of gas bubbles that the homeowners are complaining of as air in the system?



Thank you in advance for replies.

Tim McElwain

Dave my concern

with PVC and CPVC and temperatures on venting would certainly apply here. What are the temps the system is subjected to? I find that on high temp circumstances the chloride does more damage when high temps cause a break down in the CHLORINATED poly vinyl CHLORIDE. That would certainly create some problems with the inside of circulators. Now we run pools with pvc and cpvc but we do not create high temps so no problem. Just my .02 worth.



By the way I am in an ongoing study of PVC and CPVC so I would be interested in any findings you come up with.



As to the air issue I am not sure about that one but certainly not an impossibility.

icesailor

System corrosion:

I don't know about PVC and CPVC but the Taco circulator has the wrong gaskets installed. I don't know about the rest. Those red rubber gaskets aren't OEM, the black square cut O-rings are. If the manufacturer wanted you to use red rubber gaskets, they would put them in the box. Does the fact that they only sent the black square O-rings tell you anything?

Using PVC and/or CPVC in the heat side of a hydronic heating system sounds like a bad idea gone worse.

Mark Eatherton

Oxygen diffusion is an issue...

But they only way you can determine that is to look at the INSIDE of the pump, and I can pretty much tell you what you are going to see. Significant amounts of rust.



There are three prescriptive methods of controlling it.



1st, Mechanical isolation of ferrous components from non ferrous components, which would be impossible to do in your case.



2nd, the use of all non ferrous components, expensive for what what saved in the cost of piping....



And lastly, chemical water treatment. Treatment must be done on a regular basis if it is to be effective.



The exterior rust appears to be caused by condensation of atmospheric moisture. In order to avoid exterior condensation, the chilled surfaces MUST be well insulated with an air/moisture proof insulation, and that is nearly impossible to find for cartridge pumps made in the USA. I have seen European pumps that have chilled water jackets, but no NA pumps.



As for air accumulation, if you can run continuous circulation (3 way bypass valves @ FCU's etc) and have a good micro bubble resorber in place, you can keep the system virtually quiet and air free, but as soon as yo shut off the circulator, Ma Nature will kick in and will balance the O2 content out between the inside and the outside of the pipe, and the air problem will be back. Microbubbles meeting, greeting, and hanging out in areas of low velocity and high elevation and low pressure. Kind of like the people who come up to the mountain hideaway I maintain in Heeney... :-)



What in the world drives people to do things like this without checking first to see if it is OK?



I saw a snowmelt system (by others) that was using that new fusion welded PE piping in the mechanical room. Looked neat and clean, and I am not worried much about corrosion because of the inhibited glycol, but I understand they are starting to use that stuff in space heating systems as well.



Does anyone know if this PE tubing has any kind of O2 barrier built into it?



Some times great ideas are not thought out completely. I've used fusible PE in snowmelt systems before for underground distribution, but I'm not sure I'd consider it in a high temp (up to 180 degrees F) application.



Anyone?



ME

icesailor

CPVC

Ah Mark,

that'just a trifling thing. It will be working when they leave. It's for "others" to worry about it. And the first one to tell them it is wrong will be labeled an **** and they will hire someone else to tell they did good.