CENTRAL HEATING PROBLEM ALPHA 280E BOILER

I have an unusual problem in that when heating water sometimes it stays hot but more often than not it runs cold after a few minutes then goes hot again. This is regardless of whether the radiators are on or off. Just to be awkward occasionally it will run efficiently (provide hot water) for several hours then stop again. I have also noticed that sometimes the radiators are not as hot as they should be but are the same temperature all over. The needle showing pressure remains in the green sector.

We have a contract for maintenance with British Gas and have called them out probably 6 times. They fiddle about and it will work ok for about 6 hours after they have left then its back to normal

The system was installed about 6 years ago and worked great until it had a service from British Gas about 6 months ago. The last engineer said he had done all he could and suggested we were loosing heat from the pipes that were not lagged (boiler is in garage attached to house). Fair point and I will lag them but the system worked fine before without lagged pipes.
The boiler is an Alpha 28e and there are 10 radiators on the system.
We are desperate for advice so we can TELL BRITISH GAS WHAT TO DO and have a shower without a nasty shock.

I have not heard of a 28e, do you mean a 280e or possibly a CB28?

Whatever you have I would get them to replace the ch primary NTC first, then if this has not worked, take the plate HE out and clean it, it could be blocked on the system side, but as it is not going to overheat I would go for the NTC first.

The above assumes that the BG engineers have thoroughly checked the min/max burner pressures already.

Thanks for your advice. Have logged it and when I get the BG in will bring it to their attention. By the way it was a 280e as you identified.
Cheers Tayler

can someone enlighten me as to what is NTC, where do i find it on an Alpha cd50 and what it stands for.

thanks
BL

NTC is basically the same as what is referred to as a thermistor.

The CD50 has 3.

Look in your MI's and this will tell you where each one is and what they control.