Hot water system - Only getting lukewarm - thermostat / motorised valve?

[bengeorge]

Hoping for some help with my boiler please. I have an S plan heating system, with a newly installed boiler. Logic boiler with Honeywell motorised valves (old valves - not replaced). Since the new boiler has been installed, the HW system has been playing up on and off.

When playing up, I am only getting luke warm water (not cold). The system appears to be functioning as it should, I.e. valve clicks, calling for heat from boiler, boiler fires, HW pipe into tank heats up. But the water is only heated to luke warm temperature. If I run the HW cycle for an extended period (say 4 hours) it does get up to temperature.

Other times, it all runs normally and produces hot water as it should with a 1 hour cycle.

I am thinking maybe either an issue with the motorised valve/microswitch or an issue with the tank thermostat? The change between working and not working (this could potentially be a coincidence) seems to be linked to when the mains power is switched on / off, so potentially a wiring issue?

Any thoughts or advice would be much appreciated? Or any advice on how best to diagnose where the issue might be?

 

[terryplumb]

The change between working and not working (this could potentially be a coincidence) seems to be linked to when the mains power is switched on / off, so potentially a wiring issue?

What exactly do you mean by switching the mains power on/ off ?? What ,and why ,exactly are you switching on / off ?

 

[bengeorge]

Thanks for the response. Unrelated to the boiler, I have been having some electrical work done which has required the mains to be switched off over the past few weeks. As I say, potentially a coincidence but a few weeks ago the mains was off/on and then the HW didn’t work for a few days. After a few days, the mains was again switched off/on and the HW started working again.

 

[terryplumb]

Ok thanks, I doubt switching off the mains power is related to your issue. If the boiler is firing up and continues to do so,and hot water isn't heating up as it should , it's a circulation problem. I would suspect the gate in the motorised valve isn't fully opening, and intermittently it is.

 

[ChrisJP]

But the water is only heated to luke warm temperature. If I run the HW cycle for an extended period (say 4 hours) it does get up to temperature.

I agree with terryplumb. The fact that if you run the HW for long enough it does get properly hot indicates that the flow around the HW tank heating circuit is slower than it ought to be, which suggests the motorised valve in this circuit is not opening fully some of the time. The Honeywell motorised valves have removable actuators and, once removed, you can access the valve operating spindle which should be free to turn 45 degrees between fully closed and fully open. If it is free in this way, it'll be the actuator that needs replacement, and these are available separately. If it's not free to turn, then the whole valve will need replacement, which of course will need the system to be drained first.

 

[bengeorge]

Thank you both. Really appreciate the responses. I will take a closer look at the motorised valve to see if this is causing the problem.

 

[gas112]

is there a gate valve on the return from the cylinder make sure this hasnt been more or less closed

 

[CountryFan]

If you’re able to remove the actuator, maybe remove this, put the spindle into fully open and try this.