Problem with Glow-Worm Combi cycling on hot water supply

[Guff666]

I've just moved into a rented three bedroom semi. It has a new'ish
Glow-worm Compact Electronic Combi that was put in to replace a
defective back boiler. I think there may be a problem, but before I
tackle the landlady, I'd like a bit of advice.

Mains water pressure is quite high. I say this in case it is relevant.

After turning on a hot tap (I noticed it first of all when I ran the
shower) the water warms up to hand hot, then cools down to nearly cold.
It continues this, but never gets too hot to the touch. Altering the
temperature control on the boiler seems to have no effect.

Monitoring the boiler I can see that it is cycling on and off.

Experimenting with the hot tap next to the boiler: if I just crack open
the tap then water temperature goes quite high, but still fluctuates a
lot. The greater the water flow, the lower the highest temperature
reached.

On the face of it this seems to indicate a boiler fault, especially as
the boiler controls seem to have no effect, but what do others think?

====
Guff

 

[chrishutt]

Definitely a fault. Since you don't have to fix it, we don't need to identify it.

When you moved into the house, you should have been given a copy of the Gas Safety Check record. Your landlady has a legal obligation to have all gas appliances Safety Checked each year. A proper safety check would have identified the problem. I would be interested to know what paperwork, if any, you have.

 

[Agile]

We dont have to do anything, but you do need to be able to determine if there is a problem and landladies can often do with some help too!

Your boiler is designed to give about 9 litres per minute raised by 35*C.

Set the hot tap to 9 litres per minute and see if the incoming water at say 10*C is raised to 45*C which is just too hot to keep you hands in.

If you can keep your hand in it and particularly if it fluctuates hot/cold then this is the classic symptom of debris blocking the domestic heat exchanger.

This is caused by a second rate installer who has not power flushed the system before fitting the new boiler. He should be called back to sort it out free of charge but being realistic he probably fitted it for only £200 and has now gone back to Poland to retire.

Tony Glazier

 

[Guff666]

Chrishutt
I have the gas safety certificate.
There's nothing on it, but then it was a safety check, and this isn't really a safety issue.

Agile
Thanks for the advice. I'll see if I can try your suggestion.

 

[Agile]

Chris said "A proper safety check would have identified the problem".

A fellow I was training recently had been with another firm for four months. During this time he had been to ELEVEN CP12s and NEVER seen even a soundness test being done! Only filling in the form!

One Landlord took advantage of their lack of testing and phoned to say " my boiler is not working after your safety inspection! "

They had to come and repair it free of charge!

Tony Glazier