S Plan 2 Zones, Need Advice Please

[whatsoccurring]

I have a Glow worm 100 FF about 12 yrs old, 2 Honeywell V4043H zone valves (installed a couple of years ago), a pump always set to its fastest speed.
 
The boiler wouldn't start 6 days ago. In the few days before this I had heard, rather more often than usual, the sound of a zone valve doing its spring return operation.  
 
I suspected a faulty zone valve or its motor. I found I could manually latch the CH zone valve open, thereby bypassing the roomstat. 
 
This didn't >immediately<  turn on the pump as I had expected, but the boiler and pump are working OK now, just when they decide to! I have looked at the boiler booklet, and realise that it is the boiler's circuit board that turns the pump on and off. 
 
I can't understand what is controlling the boiler and pump now. The boiler is coming on for reasonable burn periods with reasonable rests in between, ie it is not operating at its max performance, and it is also varying day by day. Doing well today and house rather cold yesterday.
 
Can anyone help narrow down where the fault may lie? Thanks.
I am a school technician and can safely do basic electrical testing with a multimeter.

 

[kme]

OK

The zone valves are fitted with a microswitch ( grey & orange wires) which are n/o when the valve is closed.

Demand for CH or DHW should provide power to the valve. The valve should open (or be opened manually) until the microswitch closes - this is the switching signal for the boiler, the "fire" signal, if you will; be it 230V or a boiler specific low voltage signal - it doesn`t matter.

If you were hearing the spring return of a zone valve, that would indicate a "satisfied" signal was being sent by the controlling object ( be it timeswitch, thermostat or other) - so either a thermostat or timer is faulty, there`s a loose connection on one of these, or you`ve a faulty valve (unlikely from the description - a failed zone valve usually won`t operate at all, therefore the microswitch doesn`t operate, and no "fire" signal is sent to the boiler.

HTH

KME

 

[whatsoccurring]

Thanks, KME, I understand all of that, but I don't understand what exactly is going on since I latched the CH zone valve open.

I did that so that I could eliminate the roomstat from my enquiries and also the zone valve motor. 

So, with the valve latched open (and therefore its microswitch latched closed), why doesn't the pump immediately and constantly run? And why is the boiler not burning nearly all the time?

Is it purely the boiler's own thermostat which is running the show now?

It has been behaving erratically for months, so I am  keen to understand it fully.

 

[ProDave]

So, with the valve latched open (and therefore its microswitch latched closed), why doesn't the pump immediately and constantly run? And why is the boiler not burning nearly all the time?

As KME was explaining, the normal situation is the room stat and programmer actuate the motorised valve, and then the feedback switch in the valve (grey and orange wires) tell the boiler to fire up.

If the boiler is not coming on when you manually activate the valve, you have pretty much eliminated the room stat or programmer.

So it must either be a faulty switch in the head of the motorised valve, which is a common fault, or a fault with the boiler itself.

Does the boiler fire up normally for hot water?  if so you can probably rule out a boiler fault.

So assuming it's a faulty feedback switch in the valve, you can either take the actuator head apart yourself and replace the switch, though that can be fiddly and requires a soldering iron, or just buy a new actuator head for the motorised valve.

 

[wozz]

OK

The zone valves are fitted with a microswitch ( grey & orange wires) which are n/o when the valve is closed.

Demand for CH or DHW should provide power to the valve. The valve should open (or be opened manually) until the microswitch closes - this is the switching signal for the boiler, the "fire" signal, if you will; be it 230V or a boiler specific low voltage signal - it doesn`t matter.

If you were hearing the spring return of a zone valve, that would indicate a "satisfied" signal was being sent by the controlling object ( be it timeswitch, thermostat or other) - so either a thermostat or timer is faulty, there`s a loose connection on one of these, or you`ve a faulty valve (unlikely from the description - a failed zone valve usually won`t operate at all, therefore the microswitch doesn`t operate, and no "fire" signal is sent to the boiler.

HTH

KME

Just pointing out its the brown and orange.  The grey is the perm.  

 

[Doc Hudson]

KME is correct the wires across the normally open micro switch are the Grey & Orange. The Brown is the live to drive the motor.

Doc H.

 

[ProDave]

Just pointing out its the brown and orange.  The grey is the perm.  

You are thinking of the three port valve that does indeed use the grey as one if the inputs.

 

[NozSpark]

As the guys have said there is a micro switch within the valve head,,, however you cannot manually move the mechanism far enough to operate the switch, it only allows you to open the valve

 

[wozz]

Oops sorry my mistake must be the way I do it in my head, grey perm, orange boiler on and brown switch it works in my head.

 

[ProDave]

As the guys have said there is a micro switch within the valve head,,, however you cannot manually move the mechanism far enough to operate the switch, it only allows you to open the valve

Every one I have ever used operated the microswitch on manual override.

 

[whatsoccurring]

NozSpark, thank you very much for that gem of information... finally I understand why latching the lever did not immediately fire up the boiler.  The boiler was only getting its signal when the HW zone valve motored open.  This valve is working fine under the control of its thermostat. It also explains why I wasn't hearing the click of a microswitch when I used the lever on either Zone Valve.  
 
So, since I latched the CH zone valve open 6 days ago, our central heating has been controlled by the HW Cylinder Stat! 
 
I have been drawing a diagram of the wiring in the bathroom junction box, and what wires connect to what. We used to have non-spring return zone valves, motorised in both directions, so there are some wires parked in the connection block which are from the change-over contact of the stats, which connect to nothing now. They will go live when a stat is satisfied, so it's good they are parked properly.
 
Tomorrow I will disconnect the roomstat and link a Live directly to the brown that supplies the motor of the CH zone valve, as I am pretty convinced it's the roomstat which is the problem.
 
Thanks for all the replies, I'm getting there... 

 

[ProDave]

What make and model are the zone valves?

 

[NozSpark]

Why not just remove the stats cover and fit a temporary shorting link?

 

[whatsoccurring]

Honeywell V4043H1056

V4043H1056
Normallyclosed,    22mmcompression.
SPST endswitch.6.9KV.   0.55bar  maxdifferential pressure

 

[Riggy]

Every one I have ever used operated the microswitch on manual override.

Honeywell definitely don't, if you give them a good shove they make the switch momentarily.

 

[whatsoccurring]

The official documents for this valve also say:    "Manual lever for filling & draining the system"  so I am not using the lever as intended. It may be a deliberate design to stop the lever moving far enough to operate the microswitch.

 

[ProDave]

Honeywell definitely don't, if you give them a good shove they make the switch momentarily.

I didn't know that.  Are they the horrible ones with a metal can over the actuator, the ones that are a pig to fit or remove?

I much prefer Danfoss, they DO operate the switch on manual override.

 

[whatsoccurring]

Why not just remove the stats cover and fit a temporary shorting link?

The stat is in a ridiculous place behind a bed, so it's easier to do this at the bathroom junction box. Plus it's two floors down, so in the bathroom I can immediately check the valve operations. 

 

[Riggy]

I didn't know that. Are they the horrible ones with a metal can over the actuator, the ones that are a pig to fit or remove?

I much prefer Danfoss, they DO operate the switch on manual override.

Yes, they're the metal can ones, by far the most common locally. None of the local merchants keep the heads, you have to buy a whole unit and throw the valve away!

 

[steptoe]

I have one of those actual valves on my van so I can check the operation of the microswitch/lever for you tomorrow,

Too late tonight. :|