Richard J Kinch wrote:

Cram writes:


So with the pump not pushing water to the zone, I am still getting hot
water forced up into the zone. I don't see how this could happen.


Gravity feed. Hot water systems were designed to run without any pump at
all, at least in the old days.

Yes, if that's it you can prevent it by installing an "anti-thermosyphon
valve" which in the olde days we called a "gravity valve". It's a
weighted check valve which remains closed and blocks the weak
thermosyphon pressure differential but gets lifted opened by the higher
pressure created by the circulating pump.

Go he

http://www.wattsreg.com/

and look at a 2000-M5 valve.

HTH,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."