Glow worm space saver mk 2 water problem

[flinty]

Hi,
the problem is this. The boiler is a Glow worm space saver mk 2.
If you put it on for hot water only the pump does not run and after a very short time the hot water starts venting into the overflow tank and the boiler you get loud banging noises.
If you put the system on for hot water and central heating then the system pump will run and there is no unusual noises from the system.
Is the most likely cause the diverter valve or the pump?
Any help is greatly appreciated.

 

[twgas]

strange one that because the boiler and pump would normally be wired to the same connection on the diverter valve which would mean the pump wouldnt know that heating or water is called for

 

[flinty]

Yes this is what has me confused

 

[twgas]

are you new to the house and has the problem always been there

 

[flinty]

rented house.. it has worked fine for the last 9 months

 

[twgas]

is there 240v to pump when just hw selected

 

[flinty]

haven't checked that

 

[flinty]

apart from that anything else you can think of?
Is the diverter valve inside the boiler casing?

 

[namsag]

Sounds like it MAY be a gravity system do you have 4 pipes coming of boiler two 22mm one side and two 28mm the otherside if so it sounds like your boiler stat COULD have gone . Reason you don`t get it straight away with heating on is pump is taking excess heat away but if it was left on long enough it would thunp and bang also.

Are your rad far hotter than normal

 

[flinty]

Hi,

no I don't see any 28 mm pipes.
The central heating has been on for ages and no banging noises.

very strange.

 

[twgas]

do you have a thermostat on the cylinder, it would be strapped to the side about 1/3 up?

 

[flinty]

Had a quick look and can't see one.

 

[Garfeild]

rented house.. it has worked fine for the last 9 months

Call the landlord and get him to send his Plumber round,you shouldnt be trying to sort it yourself,its not down to you.

 

[flinty]

I am responsible for anything inside the house.

 

[ChrisR]

You've been asked - how many pipes come from the boiler?

What sort of valve(s) have you got?
pic if you don't know what they are...?
Are several at least of the rad valves open?