Solar water preheater project based on builditsolar $1000 system

[strider3700]

Originally Posted by Piwoslaw

Unless you find laws which state that your heat exchanger must not only be double walled, but also certified, then you can try to make your own. For example, instead of making an open solar loop that dumps into the non-pressurized tank, make the solar loop closed and use that tank as the double walled heat exchanger, something like a heat buffer. That way you can use glycol in the solar loop (to prevent freezing) and still keep it two walls away from your city water.

If you want/need to keep the solar loop open, then get a hot water tank with a (single walled) heat exchanger loop inside and hook that up to the loop in the non-pressurized tank.

Or go a step further and replace your hot water tank with a heat buffer. It should be a tank with two coils - one for input, one for output - while the tank itself and all of its water only act as heat storage (and as double walled heat exchanger).

I've been told the US requirements for double wall heat exchangers state that there must be 2 metal walls between any heat transfer fluids so your cases wouldn't work because the fluid in the tank between the two coils could contaminate and then contaminte the other coil should both spring a leak at the same time. Totally insane I know but still the law... no wonder noone cares about the rules in most cases.