Rads hot when only hw switched on

[Bluepeteten]

I have a gas fired CH system about 9 years old, Ideal Classic Boiler LXRS & RS sealed gas boiler, Grundfos pump, Honeywell V4073 3 way port valve.

I have noticed that although the thermostat (Drayton) operates correctly the rads remain hot regardless of the setting. If I switch the CH off the rads stay hot until the HW is switched off. I also seem to be getting water, hot, feeding back into the header tank. Could it be I have a problem with the 3 way valve and how would I check it?

I have had no other problems with the system.

Regards
Bluepeteten

 

[Softus]

Something I would try is this: remove the powerhead (isolating it electrically first) from the 3 port valve, and operate the valve manually.

If you can make the system behave as it should, then you have a faulty powerhead or a fault in the electrical supply to it.

If operating the valve manually doesn't fix the problem, then it's likely that the valve isn't shutting off the CH flow correctly.

During the 9 year life of your system, has anyone ever added a chemical corrosion inhibitor?

 

[Bluepeteten]

Thanks for the reply. What is the power head and how is it removed? Is it the electrical piece on top of the three-way connection if so do I have to drain the system?

As for inhibitor, it was added when it was first installed.

Regards

Bluepeteten

 

[Paul Barker]

Yes the powerhead is the part with flex coming from it. Honeywell make is tin, some makes are plastic.

Honey well requires small electrical screwdriver to remove tin cover then two screws hold it to body of valve.

Plastic ones usually have plastic push lever to release them.

Manually open valve first and make sure main power is off, usually there is a double pole fused switched spur, sometimes a three pin plug, sometimes other means.

 

[ChrisR]

Lift top cover off head after loosening the one screw.
Get someone to turn CH ONLY on (from all off)and you should see gubbins motoring round.
Start position is HW only, Mid is HW + CH, End is CH only

Yours will probably not be doing that, probably because it's stuck (though could be mis-wired)

Either the head, or the valve, can be stuck.
With electric off, you should be able to use the lever on the end of the valve to part-open the valve. Push fast and it should go further, and spring back to Start

Assuming the top of the head has a pimple on it, you can remove the head dry.

Loosen the two screws holding the head on and you might hear it spring back, if it's jammed.

With the head off, feel the shaft sticking out of the valve. It should turn freely but only about 30 degrees. If stuck wiggle more, it might free off.

Use lever to help line slot/shaft up when reassembling.

Should have agood idea where the fault is now.

 

[Bluepeteten]

Thanks, Do I have to buy a three way valve or can I just buy the powerhead?

Regards
bluepeteten

 

[Softus]

This might not be true for every brand under the sun, but you can buy the powerhead on its own for a Honeywell (since 1986).

You can even buy just the synchron motor, which requires no more skill to install.

What make/model/size is it?

 

[Bluepeteten]

Thanks Softus, its a Honeywell 4073

Regards
bluepeteten

 

[Softus]

That's easy then - go to any decent plumbing/heating merchant, or a branch of HRPC (aka PartsCenter), and expect to may IRO £10.