Heating on constantly - Glow Worm Micron 50FF

[Dazzh]

Hi All,

Back on looking for some boiler advice.

My Son has a Glow Worm Micron 50FF controlled by a Hive. I think it's a 'Y' plan system.
Yesterday the boiler was heating the radiators constantly despite the Hive being turned off for both Heating and Hot Water.
His wife phoned me today to look for some advice(my sons away with work commitments). On checking the boiler its running constantly.
On turning the control knob on the boiler down, to almost off, it goes off. When you turn it back up the boiler reignites even though the HIVE is nor requesting heating or hot water.
He has had the valve under the water tank replaced several times, although not recently, could it be this thats stuck open?
Once again I hope you can point me in the right direction with any advice to narrow down the problem.
Thanks again.

 

[terryplumb]

If it's Y plan ,the 3 port valve would be most likely cause.

 

[Dazzh]

Thanks @terryplumb.
Is there a way to test the valve?

 

[terryplumb]

What make/ model is the valve ? Are you able to do voltage testing at the wiring centre ?

 

[CBW]

He has had the valve under the water tank replaced several times, although not recently, could it be this thats stuck open?.

Yes, it could be as @terryplumb has said. Cheaper market ones don’t seem to last long.

 

[Dazzh]

Hi @terryplumb
Sorry won't be up there until tomorrow, so don't know make and model. I can take my multimeter up with me so what should I be looking for?
I think your right re the valve being the issue, being that it has been replaced several times, but don't want to assume this is the problem.

 

[Hugh Jaleak]

Might be worth giving the valve a thump with a closed fist, or (gently) with a hammer or suchlike, you may hear it whirr back to rest position, depending on type, and the system will shut down. This will prove the valve is the issue, although as said above, it's unlikely to be anything else.

Boiler and pump are powered via the valve, as it moves to open position, it operates a microswitch to send power to the boiler/pump in order for them to operate. If valve has jammed in position it will be sending constant 240V to the boiler/pump, hence why the stats are ineffective. Turning the boiler down will switch it off as the water is above temperature in the boiler.

 

[Hugh Jaleak]

Good wiring diagram for the Sundial wiring plans with current paths can be found here. Honeywell Y-Plan Explanation (octaveblue.co.uk)

 

[Dazzh]

Thanks @Hugh Jaleak for your replies, I'll take my hammer and of course my multimeter

 

[Dazzh]

There are 2 actuator valves, I’ve given them a tap with a hammer but no change the heating remains on constantly.
I’ve attached pictures if there are any suggestions to try next. I can pick up an actuator motor at Screwfix if you think this would be worth replacing.

 

[terryplumb]

The system isn't Y plan . One of those valves goes to rads ,the other to the hot water cylinder. Trace the pipework and establish the one for the rads,and replace the actuator head.

 

[ianmcd]

I can pick up an actuator motor at Screwfix

OH luck you and you have Osma gold fitting , leak city time

 

[CBW]

replace the actuator head.

If you find it’s the Siemens one, IMO, I’d replace the complete valve

 

[Hugh Jaleak]

You've got the 'S Plan' by the look of it BTW.

 

[Harry Bloomfield]

I can pick up an actuator motor at Screwfix if you think this would be worth replacing.

It's not a motor you need, it is (perhaps) a complete actuator, possibly actuator complete with valve - if it is the valve itself jamming.

It's worthwhile to remove the actuator from the valve and check that the valve spindle is free to move. It should almost turn with just your bare fingers, but maybe gently with pliers.