Central Heating not working properly

[Jimbobmufc]

Hi, sorry don't have a volt meter but have been doing some more investigation.

When the HW and CH are switched on at the same time, and I manually operate the CH 2 port valve the CH throughout the house gets hot. As soon as the HW turns off either from thermostat in cylinder or timer the CH also goes cold.

The CH doesn't work on its own for longer than 2-3 minutes.

Any ideas, I think it might be a faulty 2 port valve on the CH, as the pump works and it works when I manually operate it.

There is also what looks like a bypass pipe with a gate valve from the supply after the pump back to the return pipe to the boiler should this valve be open or closed?

 

[JohnD]

the bypass might be too wide open

 

[D_Hailsham]

Hi, sorry don't have a volt meter but have been doing some more investigation.

That's OK Let's try another way.

When the HW and CH are switched on at the same time, and I manually operate the CH 2 port valve the CH throughout the house gets hot. As soon as the HW turns off either from thermostat in cylinder or timer the CH also goes cold.

That means the microswitch in the valve, which connects grey to orange, is not closing.

We have established that the valve motor works OK (lever stiff when off, loose when on), so all that leaves is either valve is not opening completely or the microswitch is burnt out.

Does your Honeywell CH valve have a small bump on the metal lid at one end? If so, you can remove the actuator (metal box).

Take the lid off and then remove the actuator (no water will escape) to reveal the shaft. This should turn easily by hand (about 20°). If it is stiff, a small amount of WD40 or silicon lubricant may help. Replace the actuator and try again.

If the shaft turns easily or there is no difference after you lubricate the shaft, the fault will be in the actuator. You can buy them from any plumbers' merchant. Swapping over is easy: just change each wire at a time, so you don't get the colours mixed up.

There is also what looks like a bypass pipe with a gate valve from the supply after the pump back to the return pipe to the boiler should this valve be open or closed?

The bypass should have been adjusted when the system was installed. Leave it alone.

 

[Jimbobmufc]

have taken the head off the valve and it turns easily by 20d, and going replace 2 port valve next week.

Thanks for your help with the fault diagnosis, hopefully this will solve the problem. Thanks again.

 

[D_Hailsham]

have taken the head off the valve and it turns easily by 20d, and going replace 2 port valve next week.

You don't need to replace the complete valve (draining down etc); just replace the actuator - 10 minute job.

 

[Jimbobmufc]

ok, will do. Out of interest whats the purpose of the bypass pipe?

 

[D_Hailsham]

What's the purpose of the bypass pipe?

To provide a path for the water when both valves are closed and the pump is in overrun (after the boiler goes out).

It sounds as if you have just a gate valve on the bypass, which means there is a flow through the valve all the time. Modern practice is to have an automatic valve, which opens as required.

Which boiler do you have?

 

[Jimbobmufc]

its a gloworm 40FF. The pump doesn't seem to work on overun.

 

[D_Hailsham]

its a gloworm 40FF. The pump doesn't seem to work on overun.

Is that the Ultimate 40FF? If you have fully pumped, then you should have pump overrun. The pump should be wired into the boiler. See Installation Manual

In this case, the purpose of the bypass is top maintain a minimum flow rate though the boiler. Automatic bypass valves will do the same thing.

 

[Jimbobmufc]

Hi

Replaced the actuator on the zone valve, but this has created a new fault. Central heating circulation is good, all radiators are hot. However the only way I can control the heating is via the room stat and not the time clock. When the time clock is off, but the room stat is at high temperature the heating comes on. What have I done wrong.