Why does CH boiler switch off while temp < thermostat tem

[jsnahil]

We have a problem with our Central Heating that even a Corgi certified Engineer does not know how to fix it.

We have Potterton NetaHeat 80 boiler.

1. The room thermostat is set to 25 degrees
2. The Water tank thermostat is set to 60 degrees
3. The Honewell CH control is set to Continuous Heating and Water

The boiler comes on. The radiators start to warm up. The water gets very very hot and the CH boiler shuts down.

If we up the the Water tank thermonstat temperature then the CH boiler comes on again and then stops again when the water reaches the temprature set on the Water tank.

The engineer has changed the fan on the boiler, water pump, honeywell 3 -way switch in the airing cupboard and the thermostat on the water tank (Total cost around £500) but the heating is still not working.

Any help would be appreciated to solve the problem.

Thank you.

Regards,
Jo

 

[doitall]

Did you say the water in the cylinder gets hot but not the rads.

Diverter valve We assume he checked and is working.

problem must be on the heating side air, sludge, or no water.

 

[jsnahil]

Thanks for a qucik reply.

Yes, the water coming out of the taps is very very hot, the radiators do get warm but the boiler shuts down before the radiators get hot enough to raise the room temprature set on the thermostat (25).

I think that the boiler shuts down because the water in the Tank in the airing cupboard has reached the temprature set on the thermostat attached to the Tank. But why the water is not pumped around the radiators?

Jo

Did you say the water in the cylinder gets hot but not the rads.

Diverter valve We assume he checked and is working.

problem must be on the heating side air, sludge, or no water.

 

[doitall]

you sure you got a plumber looking at this ?

Have you tried heating only on the programmer, the valve should move to port A, (no hot water)

Do you have thermostatic valves and are they turned as high as they go

 

[Gasman1015]

Seems like your three way valve has been fitted on the wrong ports.
Which is why the water gets hot and the radiators only luke warm, they are being controlled by the wrong thermostats due to the incorrect ports.

 

[jsnahil]

Thanks again for quick responses. I am so glad that I joined this site.

1. None of the Radiators have thermostat valves.
2. All Radiator valves are fully open
3. All radiators have their air taken out

It looks to be that the new 3-way value in the airing cupboard is fitted the same way as the old one. The lever on the valve is in the middle right now. Can it be wired wrong?

Jo

 

[jsnahil]

What does "Seems like your three way valve has been fitted on the wrong ports." mean and how do I check it rather than calling the plumber again?

Jo

 

[doitall]

The valve has A or B and AB the middle port which port goes to the cylinder

 

[jsnahil]

The following shows the ports for the 3-way valve in the airing cupboard:

A---------------[3-way Valve]-----------B----> water Tank
| |
| |--------------
| Pump |
| | |
| | |
V V V
All these pipes go downstairs

Position of the lever on the 3-way value

Auto-----X------ Manual

I hope this helps.

Jo

 

[jsnahil]

Diagram got bit messed up. It was ok when I typed it.
Anyway here it again:

A - Goes Downstairs
B - Water Tank
AB - Goes to the water Pump thatbgoes downstairs

Jo

 

[keego]

The valve is on the right way, it must be wired wrong. Try moving the lever on the end of the valve to manual open & see if the rads warm up