Heating only until the Megaflo is up to temperature

[toftaj]

After an uneventful summer the heating has finally been turned on only to find that the boiler only fires for as long as it takes for the Megaflo to come up to temperature. During this time all the radiators in the house get toasty but then the boiler switches off and everything cools back down until we next draw some hot water.

I've two motorised valves (two way) that both seem to work when I fiddle with the manual over-ride slider at the top of them but forcing them to manual doesn't seem to help. The sliders return to automatic with a satisfying whirr when I take them off manual so they seem OK (but what do I know?)

The pump doesn't seem to do anything. I'm guessing that this could be the problem but, to be honest, I don't know how it behaved when the system did work OK. I've seen the Wiki entry on how to check it and will do so tonight, but I'm anxious for input from the experts in case I'm already heading down a blind alley.

I'd be grateful for some advice please.
Andrew

 

[kevplumb]

sounds like

wiring

 

[doitall]

sounds like

wiring

I thought that Kev, but can't see how it can be, unless the thermal cut-out is cutting out

 

[kevplumb]

yeah

 

[toftaj]

Thanks to both of you. A wiring problem would make sense. Once in the middle of the night during the summer there was a leak from the piping above one of the motorised valves (the one with the plastic cover over it in the picture - the water dripped from the black valve (?) above it).

The water tripped the fuse in my fusebox. I dried everything out, ran it up and all seemed well. I put the cover over as a precaution but it hasn't happened since - however that incident could well have caused a wiring problem that has gone unnoticed until now.

Do you know of any checks that I could make to establish whether it is wiring?

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• toftaj
• 9 Oct 2009
• 1

 

[doitall]

Can we see a pic of the other valve and the pump.

Is there any air vents that need bleeding.

 

[Boilerman2]

Sounds like the Micro switch in the HEATING valve has failed, fit a new head to the Heating 2 port valve

 

[bengasman]

... Once in the middle of the night during the summer there was a leak from the piping above one of the motorised valves (the one with the plastic cover over it in the picture - the water dripped from the black valve (?) above it).

Water getting into the electric side of a zone valve.
After that, the heating doesn't work properly.
I wonder if there is a connection.

 

[toftaj]

Thanks, all. I've a much better idea of what to do now.

 

[toftaj]

... Once in the middle of the night during the summer there was a leak from the piping above one of the motorised valves (the one with the plastic cover over it in the picture - the water dripped from the black valve (?) above it).

Water getting into the electric side of a zone valve.
After that, the heating doesn't work properly.
I wonder if there is a connection.

Yep, I suppose the sarcasm is warranted. In fairness, I had tried the valve in manual and it didn't seem to make any difference. What I didn't realise, and I do now thanks to others' comments, is that the valve contains a switch that links it to the boiler and pump. But then, I'm no heating engineer - which is why I came crawling to you guys for help.

 

[bengasman]

... Once in the middle of the night during the summer there was a leak from the piping above one of the motorised valves (the one with the plastic cover over it in the picture - the water dripped from the black valve (?) above it).

Water getting into the electric side of a zone valve.
After that, the heating doesn't work properly.
I wonder if there is a connection.

Yep, I suppose the sarcasm is warranted. ...

The joke was not directed at you. Just a nudge at the boys that are better at conventional systems than I am.

 

[toftaj]

Can we see a pic of the other valve and the pump.

Is there any air vents that need bleeding.

For what it's worth, here is the other side of the system (as good as it gets without moving the fridge).

The pump is a Grundfos UP515-60
Underneath that is a Honeywell 272848
The other motorised valve is a Honeywell V4047H

I believe the two motorised valves are actually the same - but you'll know that.

The megaflo itself is actually being serviced on Wednesday, so I guess that would get any bleeding out of the way.

Thanks for your interest.
A

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• toftaj
• 10 Oct 2009
• 2

 

[doitall]

I would say the micro switch in the heating valve is duff.

The motor is turning the valve "on" but not putting power on the orange.

Stick a new actuator on and it should work.

 

[Agile]

Yes, I agree they have worked out that the microswitch in the heating valve is not being operated.

That can either be as a result of an internal problem in the microswitch or its not being pushed hard enough by the cam.

If you push the switch button manually with an insulated stick then you will see if that brings on the boiler. If it did then you might be able to bend the cam to suit.

If not then the microswitch could be changed by anyone good at soldering who can search for a replacement or find an old valve to canabalise for the switch.

Tony

 

[toftaj]

Just a note to say that I have replaced the drive for the motorised valve and all is toasty once more. Thanks to all who commented.

For those of a morbid nature, here's what the water did to the switch.

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• toftaj
• 14 Oct 2009
• 1