Solar single wall heat exchangers

[Inspektor Ludwig]

I came across this the other day on a jobsite and had to do a little research. A guy had a Solar heat exchanger installed by a professional company that specializes in this type of system. The problem was the single wall heat exchanger. The company used Propylene Glycol saying it was non-toxic but the msds gave it a "1" for health. The UPC prohibits toxic substances in heat exchangers unless it is double walled. So I had do some research and found out that the Propylene Glycol cannot be used in a single wall exchanger because it IS toxic. The company said that they've never been called on it before and the package says "non-toxic" so what's the big deal. The UPC references some old archaic toxicology book that we had to find to confirm the code call. What a pain in the arse! So the company is now going to use a Glycerin based antifreeze and since Glycerin is ok by code we have to allow it. I can't seem to find what the other ingredients are, probably proprietary information, but still, I don't know if I'd want something that's going to make me just a "little" sick even close to my potable water. Now I'm wondering how many of those systems have been installed with Propylene Glycol? Any thoughts on this one?
(shoulder shrug)

[frankflynn]

So was this a closed loop? I'm thinking that if there was a leak in the heat exchanger the domestic hot water is under pressure and would fill then over fill the Glycerin / Glycol side then flood the basement or spew from the roof. At any rate it would be notices and the problem would not be Glycol getting into the domestic water but domestic water getting out.

[Dana]

So was this a closed loop? I'm thinking that if there was a leak in the heat exchanger the domestic hot water is under pressure and would fill then over fill the Glycerin / Glycol side then flood the basement or spew from the roof. At any rate it would be notices and the problem would not be Glycol getting into the domestic water but domestic water getting out.

You're presuming that the potable water pressure will always be higher than the glcol loop. Experience indicates otherwise, independently of the installer- pre-charged pressure or PRV settings on the glycol loop.

[peter_]

I came across this the other day on a jobsite and had to do a little research. A guy had a Solar heat exchanger installed by a professional company that specializes in this type of system. The problem was the single wall heat exchanger. The company used Propylene Glycol saying it was non-toxic but the msds gave it a "1" for health. The UPC prohibits toxic substances in heat exchangers unless it is double walled. So I had do some research and found out that the Propylene Glycol cannot be used in a single wall exchanger because it IS toxic. The company said that they've never been called on it before and the package says "non-toxic" so what's the big deal. Now I'm wondering how many of those systems have been installed with Propylene Glycol? Any thoughts on this one?
(shoulder shrug)

Generally, you don't need double wall heat exchanger unless you have potable water on one of the sides in your system. For example, in radiant heating systems for snow melt is widely used 30%-40% propylene glycol mix. Does it means you need a double wall heat exchanger? ...

How old was that solar system?

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Will getting a new heat exchanger solve the problem?
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[mkiernan]

You can use propylene glycol in single walled heat exchangers so long as the unit is marked with class 1 substance as recommended by the fda and ipc and the unit is UL listed. the fda website goes into a little more detail but it will meet code.