Very strange Zone valve problem

[markythesparky]

Hi guys,

I have a really odd one for you all.

About four years ago we installed a heating systems for a swimming pool using various items but the main part of the heating was a Honeywell zone valve controlling the boiler.

The valve was controlled in the usual way via a programmer and stat, monitoring the pool water. Recently however we've been called back as the pool was loosing heat intermittently.

On inspection I found that the wiring was ok (no one had messed with it) but that some times, on heat demand, the valve wasn't turning enough to trigger the micro switch. So I bent the metal plate a bit so that it would press the micro switch earlier. This worked for a week or two but then the same thing happened.

I recommended changing the valve and this was done by a third party. This worked for a week but now the pool is loosing heat again.

I've not been back yet to see if it the same problem but if it is what could be causing the valve not to open enough?

I've not come across this is 25 years of doing working with these valves.

 

[HandySparks]

Check whether they changed just the body or the actuator or both.

 

[Devonchris]

Was the complete valve changed or just the head? Corrosion in the valve could be preventing it from fully opening.

 

[Ian1981]

Thermostat controls the valve so is it the thermostat?

 

[Strima]

Certainly sounds like the valve is sticking. As above they may have just changed the actuator.

 

[markythesparky]

Thanks for the replies.

The stat was changed so its not the stat.

The whole valve was changed so as to eliminate the corrosion possibility and they have done the whole thing.

 

[Ian1981]

How does the thermostat determine the heat needed for the pool?
A sensor somewhere ,rather than the traditional way of a room stat reading the air temperature?

 

[markythesparky]

Yep. the boiler heats water in a heat exchanger and the pool water runs around this water. there is a probe in the heat exchanger.

 

[Ian1981]

So has the probe been ruled out as the problem or possible settings/controls on the heat exchanger/boiler?
I know you mentioned changing the stat

 

[markythesparky]

I cant see it being the probe as if this was at fault it wouldn't cause the valve to 'half open'. it would just get the water temp wrong or not heat at all.

the only thing I considered was that the boiler was changed a while ago by a third party and although I've checked the wiring, which is ok, the new boiler is a Vaillant Ecotech and I noticed that when the valve does work, the boiler takes about 7 mins to fire up. I cant see that this is right. I know there are various installer settings on these boilers and I don't think the installer has done them correctly. That said, I don't see how this would affect the valve.

 

[suffolkspark]

is it a genuine Honeywell replacement? I've had the cheap "corgi" branded ones where the head doesn't want to sit properly on the spindle, then if you tighten it right down onto the valve it makes movement stiff.

 

[Wilko]

Just sharing some thoughts
Vaillant boilers have anti cycling feature and won't re-ignite if it's within the anti cycling period. This can be set from 2 min up. But if the boiler is cold or has been off for a period and the orange goes L there shouldn't be another delay. I agree with the previous replies and reckon the valve likely not fully opening, so microswitch not closing and no L on orange.

 

[markythesparky]

The original valve had a problem very similar to what you are describing and I had to loosen it off the base a little to get it to work. Honeywell told me that to refit the actuator the manual lever has to be pushed to the ‘manual open’ setting before refitting it. I couldn’t quite see why that was the case but that one had ‘Honeywell’ on the lid though.

The new one is a Honeywell unit.

 

[markythesparky]

Just sharing some thoughts
Vaillant boilers have anti cycling feature and won't re-ignite if it's within the anti cycling period. This can be set from 2 min up. But if the boiler is cold or has been off for a period and the orange goes L there shouldn't be another delay. I agree with the previous replies and reckon the valve likely not fully opening, so microswitch not closing and no L on orange.

I realise that no L on orange would cause the boiler not to fire. My question is why would the valve not turn enough to trigger the micro switch? It stops short. Brand new stat, complete valve, tested all outputs at each switch but the motor stops short.

 

[PEG]

Hi,have you measured voltage at the actuator when in operation?
Just a extra thought,as on rare occasions,damaged conductors or a poor connection,can hobble things,even with a paltry 20 odd watts added.

A high-five,for the 25W test lamp

 

[suffolkspark]

if you remove it from the valve and try to run it does it freely open all the way? if it does and the valve feels nice and free its got to be an alignment issue

 

[markythesparky]

So, been back today and the new valve was stuck in a position that wouldn’t trigger the micro switch. I moved the manual lever and suddenly the motor then moved the mechanism to the right position and the boiler fired.

When the stat was turned down the mechanism didn’t return as far as the old valve did.

Thoughts would be very welcome please.

 

[suffolkspark]

Did you try the head removed from the valve?

 

[Devonchris]

This sounds like the operation of a 3 port valve. I think we are all assuming it's a 2 port valve. Can you confirm.

If it is 3 port then you need power to the white and grey to move the valve all the way and trigger the orange CFH to the boiler. If you only have power to white then the valve will only move to the centre position.

Could be that the wiring was altered when the new boiler was fitted and its been like this since then?

 

[markythesparky]

Yes it’s a 2 port valve. Sorry, I should have said that at the start.

My client is refusing to believe it’s a sticky mechanics as this is the third he’s had.