Radiators hot heating off!

[Mycroft]

Two or three of the upstairs radiators get hot when the hot tank is calling for heat and the central heating is off.
New 3 port value fitted (old one knackered) problem still persists.

Inherited problem from moving in. Any suggestions for cure welcome

 

[seco services]

could be reverse circulation.

check the valve first the pipe to the cylinder should be hot the pipe to the heating should be cold.

 

[Mycroft]

Hi,
Thanks for posting.

The feed pipe from the valve to the Hot tank is hot as are the pipes connecting to pump and central heating.

only first 2/3 radiators on system (upstairs affected) dpending on length of time hot water calling for heat

 

[seco services]

is the pipe on the otherside of the valve hot ?

 

[Mycroft]

Yes

 

[seco services]

if all three pipes are hot from the valve then the valve is not closing fully on the heating port.
make sure you feel the heating pipe from the valve all the way along not just a few inchs.

what make/model is it ?

 

[Mycroft]

All pipes hot over a distance, not just close to 3 port valve head (Honeywell can't easily read model).

Originally thought that radiators heating up was due to failed old valve. This replaced, like for like over winter.

Could it be wiring? Wiring a 'bird's nest' contained under plain plastic box..nothing marked!!!

 

[Agile]

Was this a "brand new" recent manufacture motor valve?

If it was very old stock then its possible the sealing surface has been deformed and is not properly sealing. The ball may be stuck and not rotating freely as it should to present new sealing faces each time it closes.

There could be dirt on the seat !

I would guess that as only a few rads get hot its not full flow to the CH circuit and as a result of leakage.

Tony

 

[Mycroft]

Thanks Tony.

The valve was, I believe a 'Honeywell V4073A 3 Port Mid-Position Diverter Valve 22mm'. Can't say if it was old stock, but think not.

Thought that the valve it replaced may have had dirt on seat but this one has done it from new.

As you say it appears to be leaking past seal. Odd that 2 have same fault though.

I'll dismantle once the weather settles and check the ball and seals.

Could it be electrical ie motor not receiving long enough signal to close 100% (if that's possible) Motor definitely throws arm.

 

[seco services]

hw position doesn't use the motor it is in it relaxed position.
the only time the motor is used is to open the valve to mid or heating only

when hw is called for the motor has no power to it and relies on a spring to pull it back to hw open heating closed.

you could open the top and check the springs

 

[Agile]

If you are familiar with them you can get a pretty good idea of the spring force and that the shaft is free by manually operating the lever.

You seem a little vague about the age of the valve! On the label end it has a date at the end of the last line "Made in Canada 0914" if it was just made for example. Did you get it from a questionable source like an Ebay private sale?

Is the pump on a higher setting than "2" and over pressurising the circuit?

Is the flow throught the heating coil too restricted? There should be about 10°C differential across the coil !

Tony

 

[Mycroft]

Thanks for your patience Tony.
Shaft moves freely.
Valve 0738 (label on back rear of airing cupboard/mirror etc!!)
Pump speed reduced to 2 (I'll monitor that)
Coil doesn't appear restricted.