Quote:
Originally Posted by strider3700
I see no way of forming a steam rupture in my drainback vented non pressurized system.
I've seen the draft version of F379 so I can see that they're ultra paranoid about cross contamination.
I can accept them deciding that a single wall pex heat exchanger isn't good enough but the rules they are forcing has driven the cost of an approved system to levels making the systems not attractive at all.
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This hole(as in arse)obsession with HX's is silly. It's the lobby effort to confuse the polititians, which is easy, their nitwits. But it is GREAT for the industry, until no one can afford it. Can you say "Incentive"? Just a nice word for "Socialism".
I am assuming your going to use "plain water" in the collector side, that is why it is drainback, right? No pressure(static) holding tank, right?
So the cold supply side is 30psi+/-????
I won't say "NO" cross contamination can happen, but how much, for how long? Your holding tank will overflow. That could be a REAL BIG problem. Funny, do they have much concern on that?
The problem with the single wall HX in this application is "eduction". It is the the same force you have when rolling down the window in your car at speed.
The faster you go(more pressure outside), the more "eduction", or vacuum effect you have inside the car(less pressure).
A single wall HX can educt from the low pressure tank, given the right size leak/hole. But, it has to have FLOW to do this. The right flow, right hole size, etc. It is not real easy to make happen.
So, you can only have this happen when CALLING for hot water. The rest of the time your tank will be FILLING with cold water. A simple level alarm will tell you there is a problem.
That's about enough from me, it just pisses me off that the run around is so prevelent, and the knowledge/experience/reality seems lost to politics.
PS-- Would anyone have info on the failure rate of PEX, copper, etc. tubing as new, and as used. Like % per foot or ???? As compared to manufactured HX's, for example.