Help Required ... 3 Way Valve not always switching to Hot Water

[Ray1000]

I've read the already discussed posts but not found the answer.

The Honeywell valve was renewed June 2019

I was asking on here in April 2023 about a buzzing sound emanating from the valve which could be stopped by simply turning the power off and back on again.

We have a Nest Thermostat, the heating goes off at 11pm the Hot Water is due to come on 6am to 7am and the heating at 7am.

The last few days the hot water hasn't kicked in but the heating as at 7am.

Later, just choosing Boost Hot Water and it works normally.

It just seems incapable of making the contact after being stood all night.

Don't know if there is a relationship between the buzzing and the failing to start.

Is there any part of the mechanism I could exercise or adjust to improve the contacts?

I wonder if these valves have a long warranty period with Honeywell?

Thank you very much

Ray

 

[CBW]

Could be the motor sticking.

 

[cross thread]

It’s nearly 5 years old don’t think it’s under warranty,asCBW said probably synchron motor

 

[Ray1000]

Thank you,

The hot water failed to come on this morning.

Just now, at 0730 I turned the heating off and boosted the hot water from the Nest App and it’s still on 7 minutes later, just the same as yesterday and the day before.

The motor seems to work normally the second time of asking???

Ray

 

[Johntheo5]

So, when HW is programmed on in the morning, the CH remains on and you require HW & CH?, if so the valve then starts to move (under spring return) until it reaches the mid position where its held in this position by a DC current.
If you switch on the HW & switch off the CH then the valve will move fully over under spring return to the HW position, you then boost the HW and everything is OK??, have you then RE tried requiring both HW & CH??

 

[Ray1000]

Thank you for your help… I’ll do a few tests while watching the valve action and let you know

 

[Ray1000]

Our Nest schedule never has CH & HW on together.
Last action was CH on then off this morning.
Went into loft with Nest App
CH on for a few minutes - turned off - waited 3 mins for afterrun to stop each time.
HW on for a few minutes - could hear the valve action - turned off
CH on - could hear the valve action - HW on at the same time - valve action heard.
On test it seemed to work exactly as it should. I expect if I leave it the HW will fail to start at 6am tomorrow.
I had thought about setting it for 0530 for 30 mins then 0600 - 0700 to see if it would start at the second attempt?
Ray

 

[Johntheo5]

Can you check the Honeywell valve number, you might have a Diverter Valve and not a mid position valve.
Could you just now programme it on CH only (or if allready on CH, ensure roomstat is calling, turn it up if it isnt), then programme the HW to come on in the same way as in the morning, ie, CH off HW on?, or whatever method you use, except programme the HW to come on now as distinct from boosting it initially.
If (can) you programme both on together does the HW take priority?

 

[Ray1000]

I’ll try that …

I’ve always imagined the HW would take priority if they were both on together but I’ll check that out now and see what happens.

 

[Ray1000]

We already had the CH on when I went to check them both together. Turned the HW on using the App. Strangely this affected the boiler sound … it seemed to go quieter.

Without a tester I couldn’t tell if the valve was favouring the HW … the rads seemed to remain the same.

Before checking I was convinced it would be a mid position valve if that’s the type allowing CH & HW to be on together, but it says it’s a diverter !!!

Are we being disadvantaged by it ?

 

[terryplumb]

It should allow heating and hot water to be on together,or independently of each other in a Y plan system. Judging by the info in your original post ,that's what you have historically had ,and your recent issue is a deviation of that isn't it ?

 

[Ray1000]

Thank you, sorry for any confusion … my only issue is … the hot water isn’t coming on in a morning as set by the Nest schedule
6 - 7am HW only
7 - 8am CH only if below temp

 

[terryplumb]

My question was ,did the system work fine with the valve you have ,until recently ? If it did ,and nothing has been altered to the systems controls or wiring,replace the complete valve.

 

[Ray1000]

I understand, yes it’s just the last few days it’s not kicked in at 6am

 

[Johntheo5]

If you are have the CH programmed on and roomstat calling (CH on) and the programmer then calls for HW then the valve will only change over to HW if the cylinder stat is calling as well, its HW priority, not sure if your cylinder stat is calling for heat in the morning but imagine it is from your description of events.
It says in the attached that port A is the HW port, the HW port on a MPV is B, so just check which ports are which on yours in case someone (unlikely) changed the MPV to a diverter valve in 2019.

W Plan central heating system

W-plan central heating system operation and wiring diagram

flameport.com