Hot Water but No Heating

[Sandyzoo]

Hi,
I wonder if someone could offer me some advice regarding my central heating system?
Everything was working fine up until about a week ago. Suddenly one evening, I noticed that there was hot water, but no heat to the radiators. It was very cold, and it was a week before Xmas, and I have guests coming!!


I am no expert with these things, but did some investigation.


1) The pump is turning
2) The room thermostat is sending a signal to the junction box in the airing cupboard
3) The boiler does fire up - but only until the water is hot. The room thermostat has no effect here.


After reading posts on this forum, and others, I focused on the motorised valve. It looked ancient. I put the switch in manual position, and hey presto - heat!! But only until the water is hot, then it cuts off again.


Ok I thought - and bought a new actuator head. However, sadly after this was installed the behaviour is the same. Hot water - yes. Heating no (well actually I do now get heating int he upstairs radiators while the water is heating up, but to get heating in the downstairs ones I need to put the actuator on manual).


I turned the cyclinder thermostat up, to see if this had an effect. This kicked the heating back into life, and the radiators stayed on for quite a lot longer - long enough to heat the house. But the hot water will now melt the skin off you... so not an ideal situation


So I find myself wondering what the fault could be. Could it be the control box sending only the Hot Water signal? Is the motorised valve not turning enough under the power of the motor, and so not sending the "fire up!" signal to the boiler?


I'd appreciate any advice.


I have an ex council house with an old back boiler. The airing cupboard upstairs has a hot water cylinder, a randall control unit and the pump.


Paul

 

[Chalked]

Will be a sticking motorised valve.The body, Not the motor. ( body sticks then burns the motor out) The best way way is to swap the whole thing (I presume its a "y" valve, ie three ports).
i would always swap to a honeywell. Most merchants will stock these.
https://www.google.co.uk/aclk?sa=l&...=5&ei=FBu4UtCFOIWN7AartIDACA&ved=0CLoBEKcrMAc

 

[Ermintrude]

Yep that's probably my prognosis but check u got all the wires in right places also. If u take head off u could move the valve with your fingers? Normally very slight movement .

 

[Sandyzoo]

Ah ok.. thanks for the replies.
Hmm. No I could move it with my fingers... but I could with a little wrench. Also, it moves on the little manual switch. The wires appear to all be okay.
It is indeed a three port valve.
Now i have bought a head, is it going to be possible to buy just the valve part?

 

[Sandyzoo]

Could someone please tell me... Is it possible to "force" the valve open in fully working order? I never heat the water without heating anyway.
When I have it on "Manual" I get heating but only until the water is hot. It is possible to open the valve in such a way aas the rads work on the thermostat? (I guess I don't understand what sends the signal to the heating system to fire up for heating once the water is hot)

 

[Chalked]

What make is it.

 

[Sandyzoo]

Oh... I'll have to check. I think Honeywell (certainly the actuator head was Honeywell.)

 

[Sandyzoo]

I can confirm that the motorised valve is a three port honeywell item.
I have now ordered a replacement.
Is it possible to force it open over Christmas, so that the radiators work alongside the room thermostat, rather than the water temperature?

 

[Chalked]

Could someone please tell me... Is it possible to "force" the valve open in fully working order? I never heat the water without heating anyway.
When I have it on "Manual" I get heating but only until the water is hot. It is possible to open the valve in such a way aas the rads work on the thermostat? (I guess I don't understand what sends the signal to the heating system to fire up for heating once the water is hot)

did you get a "y" valve replacement head or a honeywell zone valve head. They look the same but have different wiring.?

 

[Sandyzoo]

did you get a "y" valve replacement head or a honeywell zone valve head. They look the same but have different wiring.?

On the old head it said "Use 40003916-003 Replacement Head", which is what I ordered.

 

[LPC]

When I have it on "Manual" I get heating but only until the water is hot. It is possible to open the valve in such a way aas the rads work on the thermostat?

1)Put 3-port valve in 'manual', as you have.
2)Turn down the thermostat on the boiler to a 1 or 2
3)Turn up the thermostat on your cylinder to almost maximum.

Now put your timer onto water mode, and your heating should stay on. The rads won't be as hot as they normally would be though.

And please don't attempt to change a 3-port valve body unless you are fairly competent in these matters. At least, not before Christmas anyway

Be very careful with the water branch if it is close to the cylinder.

 

[Sandyzoo]

Thank you all. I turned up the cyclinder stat and turned down the boiler stat, and had decent heat last night. This is where it will stay until after Christmas.
Much appreciated.
I'll revisit this on 27th at the earliest

 

[JusKel]

Let us know how you get on.
Do you also have a timeclock to turn the water or heating on ?
Your wiring would need to be checked electrically.
A light coming on doesnt mean its working etc.