I'm trying to troubleshoot a problem before calling a plumber/gas engineer: when hot water is turned on the radiators become hot. It's a conventional boiler with a hot water tank.
Is there an easy way to find out whether or not the problem is due to a faulty valve or a more serious and costly to fix reverse circulation plumbing problem?
I figure that leaving the problem as it is is at best going to be burning money - hot water running uselessly around the radiator pipework.
If you have a system with motorised valves to control each circuit then it is odds on that one of the valves is stuck open. By listening carefully around the house you may be able to hear the motor running continuously where it is trying (but failing) to close the valve. I have had several go over the years. If it is the motor itself that has packed up, it is often possible to fit a new one without interfering with the valve itself (i.e. no plumbing required).
I'd bet my money on a faulty motorised valve. I freed our stuck 3 way valve (tap with a hammer did it), and sprayed a bit of PTFE spray in. It's been fine for the last 4 months since doing that.
Generally, the valves have an electric motorised section and a mechanical section that actually shutrs off or diverts the water. You can google your valve number and find out how to remove the motorised bit, then see what manipulating the mechanical bit does.
Same diagnoisis from here
I'm not a betting man usually, but this seemed like a sure thing. :)
I tend to agree with the other responses[1] - but a few questions, just to be sure . . .
I assume that it *is* a fully pumped system. In other words, the pump runs for just HW, just CH and both, not just for CH?
How many motorised valves are there, and what type? Assuming it's a fully pumped system, you'll likely have either one 3-port or two 2-port valves.
Has it ever worked properly in summer - when you've wanted HW without CH?
[1] Except, if a valve *is* stuck open, you're unlikely to hear any motor noise because most valves only use a motor to *open* them, with a spring return
While I would agree with the other posts here, if it's just a small amount of ciculation, and not in the reverse direction, I would suspect the ball in the 3-way valve. They tend to stay in one position throughout the summer and receive an "imprint" of the valve so become non-round with line-marks. When it moves it'll allow a small trickle of water past the ball and so cause pipework to heat up.
To clarify my earlier bit about motor noise. Twice I have had valves that have stuck and the flimsy coupling twixt motor and valve has given way resulting in the motor running continuously. In both cases the valve had stuck in the open position. Whether the motor was attempting to open or close it is anybody's guess.
To clarify - when you say "hot water is turned on" - you mean hot water is selected at the programmer, or you mena when you turn on a hot tap?
If its a case of the rads getting hot when you have the boiler theoretically running to heat just the cylinder, then as with the others, yup stuck valve. Isolate electrically, take the head off, lubricate, wiggle the shaft back and fourth a bit with pliers etc.
More on the beasties here:
Might get a tad warm in the summer as well!
We had the very same problem. Have replaced the 30year old Honeywell diverting valve last weekend. The ball in the valve had come off the spindle as well as the motor being dead. Got a replacement off ebay and was able to fit it without any problems. Norma
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