Zone valve question

[Dan S. MacAbre]

My mum and dad had no heating last week, but they did have hot water, so I went to see if I could fix it. Their CH is a bit strange, I think. They have no main room thermostat, but each radiator has a TRV (am I right in thinking that at least one should not have a TRV?). It was easy enough to discover that the zone valve for the heating wasn't opening, so I took the head off and opened it by hand, assuming the worst that could happen would be that now, the hot water would no longer have priority over the CH. But thinking back, the spindle was very stiff - I could only just open it by hand. Are they supposed to be so stiff? I don't think I've encountered another one that was.

[www.GymRatZ.co.uk]

You haven't clicked the lever into the lock-out position by any chance?

You can manually use this lever to open the valve or lock it open against the spring.

Normally the bathroom radiator/towel rail would be the ideal candidate to leave without a TRV but if it's got one then simply leave it open.

[Robin]

It depends on the system. Some boilers which need a bypass loop have them fitted separately which means every radiator can have a TRV. See

- but NB most of that is beyond me :(

[Roger Mills]

No, they're not supposed to be stiff - you should be able to rotate the shaft with your finger and thumb. That one has obviously seized, and didn't open because the motor didn't have sufficient grunt to unstick it.

You could try to free it by rotating it back and forth a few times with pair of pliers. If that doesn't work, it's new valve time.

[Dan S. MacAbre]

I'll have to take a closer look at it, I think. One of the first things I did in our house was to make a wiring diagram for the CH, and to try and work out where all the pipes went. Wasn't much fun, though, and I've not tried it for my mum and dad yet.

[Dan S. MacAbre]

That's what I was thinking. I'm not sure it's worth replacing, given that there is no room thermostat. I might just leave them both opened. OTOH, they use an immersion heater whenever they need hot water, which isn't often, since they have a power shower and dishwasher. I guess fitting a room thermostat would save a bit of money in the long term.

[Roger Mills]

That may or may nor work, depending on how the system is configured.

If there are two separate zone valves - one for HW and one for heating - that suggests that it's an S-Plan system. They normally work by using the auxiliary contacts in the valve actuator to tell the boiler to fire once the valve is fully open. I suppose that if the actuator is still in circuit but not physically attached to the valve it will go through the motions of opening valve, and turn the boiler on. The downside with holding the valve open manually is that the radiators will get hot whenever the boiler is heating the hot water, even if you don't want them on.

I might just leave them both opened.

Yes. the CH actuator should be switched by a room stat - and likewise the HW actuator by a cylinder stat.

Then, the boiler will only fire when either or both are calling for heat.

[David]

Not sure why they use an immersion for hot water if they have a boiler - AFAIK it is cheaper to use the boiler to heat the water tank, and the immersion is normally for emergencies.

With your particular problem, of course, the economics could change.

Cheers

Dave R

[Dan S. MacAbre]

Okay, thanks. I'll familiarise myself with the S-plan wiring, and try to work out if that's what they've got.

[Dan S. MacAbre]

Mum and dad aren't the most logical of people. Whenever I try to do something to make their lives more efficient, they always fall back to doing what they've always done.