No heating - cold rads, but have hot water

[Sparky]

Hi all,

Just hoping you guys can give me some help on my central heating system. I am having issues with the radiators not heating. I have hot water, the boiler fires and the pump appears to be working.

The system is a conventional setup, with the tank in the loft space. It would appear that the radiator in the bathroom is the only one working, but I assume this is the way it was designed so I have warm towels.

The thermostat has been turned right up and this hasn't helped. I have also bled most of the radiators (will do the rest this evening). All the pipes surrounding the water tank are hot with the exception off one. However it appears that one other is warm (as it is near the pump) and appears to run downstairs, but gets colder further down the pipe (this could be the water return pipe. I have checked all radiator pipes and they are all stone cold! Could it be the switching valve?

I'm not sure whether the switching valve is the following: its a white box with two lights on it both of which illuminate when the CH and HW are on. Could it be that this is the fault? Like I say I've no idea what else this could be other than the valve.

The bolier is a Potterton Suprima 30 is this helps. (Had to have the PCB change cos of the famous lock out issue).

Any help would be appreciated.

Thanks,

Mark

[Geronimo W. Christ Esq]

Is there a lever on the valve ? Try applying the lever. If the heating starts coming up then that is your problem, likely the valve head needs replaced.

It's weird that your bathroom radiator is heating up. That suggests it is on the same circuit as the hot water, and one of the other radiators is the bypass. Of all the radiators in the house, which ones do not have TRVs ?

[TheScullster]

"Sparky" wrote

snip...........

How old is the system? Look around the airing cupboard or wherever the pump is located and try to trace the piping from the pump. You are likely to find either a three way valve (flow from pump and discharge to either hot water, heating or both) OR two 2 way valves also controlling water to hw cylinder or heating ciruit.

If you are getting no (or very little heating) it is possible that the 3-way valve (or the two way leading to your heating circuit) has failed. Try to confirm this by turning on/off room thermostat and check for valve activity and pipe temperature. Try altering the hw tank stat first so you know what to expect when demand in on/off.

Phil

[John Stumbles]

[richwoodblue]

Hi mark, sounds like the diverter valve has gone, this is either silver, white or blue box which has 3 pipes connected to it soundz lik it is possibly seized. Hope this helps! approximate time to replace on is an hour

-- richwoodblue

[Sparky]

Hi all,

I got in last night after doing some web research yesterday and went straight to the 3 way valve. I placed in onto manual override and bingo the one cold pipe warmed up instantly followed by the rads. I let it heat up for an hour or so like this before returning the setting to auto. Left it on and still had heating. I then switched the heating off, let it all cool down and restarted the system, again worked perfectly. Tried it again this morning before leaving for work and yep its still going. The motor must of got jammed or something in the valve. I'm now a happy chappie.

Thanks for all your comments guys, all of which were spot on. I appreciate the quick responses.

Just out of interest. The 3 way valve in question is a Myson Power Extra. Any idea on the cost for one of these little babies, just in case it does need replacing?.

Cheers and thanks again,

Mark

[Roger Mills]

It's more likely that the wet part of the valve had stuck and that moving it with the manual lever freed it.

If you *do* need to replace the valve, it doesn't necessarily have to be a Myson - there are lots which do the same job. For example, Screwfix do a Horstmann valve for £38, a Danfoss for £50, a Drayton for £65 and a Honeywell for £70.

In cases where the actuator (the electrical bit rather than the wet bit) is faulty, you can usually replace just that bit without any need to drain the system - but I don't think that applies in your case. [You can even replace just the motor for about a tenner in many actuators].

If you get any further problems, it would be worth unbolting the actuator from the valve (but don't disconnect the electrics)and turning the valve spindle back and forth a few times to make sure that it moves freely.

[Clive Mitchell]

In message , Sparky writes

Those hideous little valves are a balancing job between a spring, a motor, a diode and some resistors. It's very easy for them to get stuck on the tiniest spec of dirt or just anything really. That's assuming the motor doesn't pop it's clogs because it spends most of it's working life in a stalled state.

I wonder how many of these valves are sitting with an elastic band holding them in their bypass mode on a permanent basis.

[Clive Mitchell]

In message , Roger Mills writes

Have they genuinely standardised on the wire colour for these components?

[Dave Fawthrop]

|!In message , Roger Mills |! writes |!>If you *do* need to replace the valve, it doesn't necessarily have to |!>be a Myson - there are lots which do the same job. For example, |!>Screwfix do a Horstmann valve for ?38, a Danfoss for ?50, a Drayton for |!>?65 and a Honeywell for ?70. |! |!Have they genuinely standardised on the wire colour for these |!components?

I just bought a new valve, and the colours were much the same as the one which I b*gg*r*d up.

[Roger Mills]

I believe so - as long as you get the right *spec* of valve. So all 3-port mid-position valves should be the same, but will differ from pure diverter valves - which have no useable mid position. Similarly with 2-port valves, of which there are several flavours depending on whether they have auxilliary contacts and if so, whether the contacts are on/off or change-over. But, for a given flavour, the wiring should be the same, regardless of make.

[John Stumbles]

most, not all - see

[Roger Mills]

However, my understanding is that non-spring return valves are relatively uncommon in domestic situations.

[John Stumbles]

True statistically overall, but if you happen to have one on your system they're 100% common for you! Point being it's best to check before assuming you can just replace it with any old spring-return valve (been there, done that :-()

[Roger Mills]

Yes, that's true. I plead guilty as charged of failing to mention the non-spring return variety.

[John Stumbles]

That's better! I sentence you to rewire a Y-plan system from a fully motorised to spring return where all the wiring is connected with individual chock-block segments crammed into the back of the single pattress of the FCU which is located at the back of the airing cupboard ;-)

[Roger Mills]

Ugh! Do I have the option of a custodial sentence instead?

[Ed Sirett]

That's exactly the job I was faced with last autumn. It became very clear that if I and my apprentice were going to get home starting from scratch with a double-gang wiring centre was the only way.