s it the controller or 2 port valve thats failed?- UPDATED

21 Oct 2003
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United Kingdom
If got quite a complicated control system on my heating system:

2 heating circuits and 1 HW circuit ( each opened/shut with 2 port valve )

1 heating circuit has it's own Room stat and timer. ( this one has the problem)

the other timer controlls the other heating and HW citcuit ( this one works fine)

So on the problem circuit:

timer on, room stat calls for heat = no operation of valve, no firing of boiler, no heating.

Is there an easy way to tell if it is the 2 port valve or the timer?

If the timer is ok and it is just the valve, should manually opening the valve, complete the circuit from the timer and so power pump/fire the boiler? cos it doesn't.
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You need to check this heating circuit with a multimeter to find where the 240VAC is not getting to.

Only do this if you are competent and confident working with 240VAC live electrics.
It'll be the valve. You can usually prove it by using the manual lever to move it to the open position. If the boiler starts up and you get heat then it's the valve. Change the motor head.
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you really need a meter to check if you're getting power to the valve motor, if you are then the problem is more than likely to be the motor, if not then either the room stat or timer is not switching on.

moving the lever does not usually give enough movement in the valve to power the boiler, although some will.

You should get some heating to the dead circuit by locking the lever in the manual position then turning on the other heating zone or hot water.
A second thought, what type of programmer is it?

If it's a Horstman 3 channel, ie 2 heating + 1 HW, then the programmer battery dies and the programmer stops functioning properly. So it could be this.

It is just possible to change the battery but not recommended as it is a non-standard battery that requires soldering in on the older models. A new programmer may be the way to go in this case but they are mighty expensive.
valves are much more likely to go than timers.
easy enough to check if you get power out from the timer
it is all 230 volts so don't fiddle with it unless you know exactly what you are doing.
Thanks for all the replys.

Manually opening the valve doesn't kick the heating into life.

It will be a struggle for me to test the electrics as they are all rear entry to the stats/timers and junction boxes, plus my confidence levels aren't that good working on live electrics.

I have manually opened the valve and turned up the room stat on the functioning heating circuit ( I'll be roasting in this half of the house, but at least the lodgers side should be warmish).

If the plumbers can't come for a week, it will be a stiff whisky and I'll dig out my circuit tester.

after a couple of days waiting for the plummers to call, the heating seemed to 'spring, back into life'

It has been fine, up until last night ( 10pm)! then it decided not to work again.

( temp fix was to manually lock valve open, turn on other circuit).

this morning the valve 'lever' was unlocked and working on automatic ( normally) again.

So my first question:

If the valve works automatically, will it put the lever back on to automatic ( taking it off the manually locked open position) ?

It has now decided not to work again, so my choice is phone plumber ( and wait a few days) or try and fix it myself.

oh decisions, decisions.
If the valve works automatically, will it put the lever back on to automatic ( taking it off the manually locked open position) ?
It would have helped if you'd told us what make the valve is. If it's metal head it's probably Honeywell.
Most of them will unlatch from from Man if the valve opens.

It could be a faulty contact stopping the motor operating, a stuck valve motor or mechanism , or a faulty microswitch in the valve. A heating guy would be able to tell a lot by the feel of its operation but it's hard to put into words.
Thanks for your help

since i posted the heating 'sprang back in to life' once more and now has stopped again ( it does knock the valve off manual)

( it is a Drayton zone valve with ZA5 actuator)

I think it is the actuator but I've got a plumber comming tommorow!

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