hot water coming out of overflow


Old 03-26-07, 11:28 PM
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hot water coming out of overflow

hi all
i've got hot water coming out of the heating water header tank (feed and overflow for boiler)
here is my system
i've a boiler which has motor vavles to give "hot water" or "hot water & Heating"
the controls work as so
turn on hot water control, power to hot tank stat (hich closes if temp low) on to the motorsed valve which the power closes (the additional relay in the motor valve sends power to the boiler temp stat-allowing the boiler to start)
the heating motorised valve works direct from the control box,(but because of the way i'v setup the control of the hot water, it means once the water tank is up to the temp, the boiler should stop, and then heating water will cool)
anyone think of a reason why all of a sudden the overflow should start ?
Old 03-27-07, 12:33 PM
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My Boiler has an over pressure release valve for 30PSI. On my boiler pressure meter I've never had it go over 20 to 25 PSI max. This usually happened recently when the boiler stopped running due to a poor maintenance call. Once I DIYed the maintenance I ran the boiler and was surprised to see the pressure so high. I believe this is due to a cold startup with air pockets etc. It ran a while to get up to temperature and that is when I noticed the pressure. I have an automatic air bleeder before my two zone valves. I did a test on the pressure release valve and the extra pressure finally went away. So my quick answer is test your pressure release valve on your boiler and make sure it works that should settle your pressure problems. Blow out some crud.
My pressure normally is around 10-12 PSI and 15-20 with the circulator pump running.
BTW, my zone valves will not come on until a certain temp if the temp was low when the boiler kicks in because of too much hot water usage...
Old 03-27-07, 03:25 PM
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When you say "overflow" , I think you mean the safety PRESSURE RELIEF VALVE . It will open to release pressure above 30 PSI.

A few things can cause the pressure to go outta control.

waterlogged (or failed diaphragm) expansion tank.

failed auto fill (pressure regulator) valve.

if you have a tankless hot water coil in the boiler, that can have a hole in it and pressurize the boiler beyond 30 PSI.

ummm, what else...

What's the pressure read on the gauge ?

see if a quick search of the past posts won't get you a LOT of info on expansion tanks... (some with pics too!)...

Last edited by NJT; 03-27-07 at 03:37 PM.

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