no hot water through central heating

emmkat · 23 Jan 2015

Hello

I have recently changed my 3 port valve because I was not getting any hot water via central heating, I had to use immersion only. I assumed it was the valve stuck in heating position only as the manual lever on the valve was floppy and not doing anything. it was quite old valve and hasn't been replaced for years. so put new valve on tested heating which was fine but pump did not start up when I changed it to water only. the Honeywell controller light came on but that's all. Have I changed this for nothing and is it possibly a fault wiTh my boiler ( glowworm micron )

stem · 23 Jan 2015

If the radiators are getting hot then the boiler is working, so no problem there. The motorised valve at rest sits in the hot water position anyway, so it is unlikely to be that.

The first place to check is the hot water cylinder thermostat. With the central heating set 'off' and hot water set 'on' at the programmer, turn the cylinder thermostat to minimum and then slowly up to maximum. Can you hear it click as you do so? and if it does, does the boiler fire when it's turned up? The water in the cylinder must have cooled when you try this. If it's hot because of being heated by the immersion this won't work.

If it does click but nothing happens, then it will be necessary to check the wiring with a multimeter, is this something you have and would be able to use if you were told what to do with it?

emmkat said:
as the manual lever on the valve was floppy and not doing anything.

That's as it should be when the valve is energised, shows that it's working.

emmkat · 23 Jan 2015

Thanks

just tried turning cylinder stat back, as I did got to about 30/40 and heard the motorised valve move. started turning up slowly heard click but nothing happened

stem · 23 Jan 2015

OK. In hot water only mode, the boiler is controlled by the cylinder thermostat. So for some reason it would appear not to be doing that.

There is one more thing you can try if you don't have test equipment, but it will involve disconnecting some wiring from the cylinder thermostat. if you feel able to continue, post details of the type of cylinder thermostat you have.

I'm assuming that the system has worked OK at some point in the past, and that the only thing you have done is to swap the motorised valve over. In other words, that all of the wiring is as it should be.

emmkat · 23 Jan 2015

Im sure stat has been changed before. So maybe wired wrong

emmkat · 23 Jan 2015

View media item 88757 View media item 88758 View media item 88760

stem · 23 Jan 2015

That looks like a Honeywell L641A and if you have a 3-port valve, you will need three wires at the cylinder stat as follows:

C. Live from programmer
1. Switched 'hot water required' live to boiler
2. Switched live for 'hot water not required' signal to motorised valve

So one wire is missing and it looks as if the one that is there isn't doing what it should.

Unfortunately it looks as if the whole wiring arrangement will need checking out. Can you tell what the other end of the blue wire is connected to? It looks to be the grey wire of the motorised valve, if so, that's wrong that should be in terminal 2 at the cylinder stat. And what about the disconnected (earth?) wire, where does that go at the other end? You may have to follow the wiring in and out of the wiring centre.

emmkat · 23 Jan 2015

But the cylinder stat comes already wired doesnt it?

emmkat · 23 Jan 2015

Yes blue wire in with grey wire from valve

emmkat · 23 Jan 2015

Apparently was told earth did not have to be connected

emmkat · 23 Jan 2015

I have a Drayton mid position valve

stem · 23 Jan 2015

emmkat said:
Yes blue wire in with grey wire from valve

Well that's the 'hot water not required' signal that closes off the hot water port on the valve. So, totally wrong. It will close the hot water port on the valve when hot water is actually required. That should be connected to terminal 2.

emmkat said:
But the cylinder stat comes already wired doesnt it?

No it doesn't

emmkat said:
Apparently was told earth did not have to be connected

That is correct. That is why I asked where the other end went. Often it is used (incorrectly) for one of the live wires.

emmkat said:
I have a Drayton mid position valve

Then you will need all three connections

emmkat · 23 Jan 2015

ok. so would you be able to tale me through the wiring from stat to terminals. for a start is the wiring in the stat correct, if not what goes where and do I need to connect the yellow wire to one of those terminals. I don't know how it could've gone so wrong

stem · 23 Jan 2015

The wire going into terminal 'C' should come from the programmer Hot Water 'on' connection. Usually this is the brown wire, so this may be OK, but check it if you can.

The wire going into terminal '2' should be the blue wire (presently in terminal 1) that ends up connected to the grey wire at the motorised valve.

The wire going into terminal '1' should go to the boiler switched live supply. Now it could be that the green / yellow (earth) wire has been used for this, which is why you need to check where it actually goes at the other end. If it does go to the boiler switched live, this should then go into terminal 1 of the cylinder thermostat. But do not make this connection, until you are sure it does, otherwise you could cause damage to other components.

Here's a link to a wiring diagram. Yours is a 'Y Plan' click on the respective schematics and you will see what should be happening depending upon the status of the system. Schematic Wiring Diagram

emmkat said:
I don't know how it could've gone so wrong

Only the person that did it would be able to explain that.

emmkat · 23 Jan 2015

ok i'll look through it . the yellow/green wire isn't wired at either end

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no hot water through central heating

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