Dodgy Glowworm 30CXI.... help!!

11 Aug 2007
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United Kingdom
I have a Glowworm 30CXI combi condensing boiler installed in the house I recently purchased. Unfortunately it doesn't produce constant hot water, but instead pulses hot, cold, hot, cold. This is the same when using a single tap or multiple taps. Each pulse or cycle is about 20 to 30 seconds. When the hot water isn't coming out of the tap it is feeding the central heating, as the radiator nearest the boiler starts to get warm.

We had a Corgi registered plumber in to take a look. The first guess was it was gunk from the old radiators clogging the valve that separates the outlet to the central heading from the outlet to the hot water. However, when the boiler was drained and the valve removed their was very little gunk at all and it was relatively clean. The valve and other components were thoroughly cleaned, greased and replaced back in the boiler... but the same pulsing problem occured.

Several calls to Glowworm and checks on other components (e.g. heat exchanger) later and my plumber has run out of ideas.

My options now are:

1) Get a Glowworm engineer round.
2) Replace the boiler (any recommendations BTW?)
3) Find others with similar experiences, who may know fixes, by reading and posting on online Forums like!!

Does anyone have any suggestions?

Many thanks in advance for you help.


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Andy, could you outline the dispute between the installer and Glowworm.

We may be able to give you some useful advice.

Has the plate HE been removed to clean it? If its where I think its quite a job to get it out.

I had the misfortune to comission one a little while ago and it did look like a fairly esy boiler to work on - which by the sounds of things is going to be a very necessary evil.

Air trooper look Here

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Agile said:
Andy, could you outline the dispute between the installer and Glowworm.

We may be able to give you some useful advice.

Has the plate HE been removed to clean it? If its where I think its quite a job to get it out.


I'm not dealing with the Installer, as the boiler was put in a number of years ago (I assume) and I just bought the house. Instead I'm using my trusty plumber, who is Corgi registered and a thoroughly competent and nice bloke. There is no dispute at all between him (or me) and Glowworm, he has been calling them for advice.

The HE hasn't been removed to be cleaned. The water in the system is very clean and the HE is right at the very back of the boiler, making it quite a job to get out.

Given the number of threads/posts on this forum regarding issues with the 30CXI I'm beginning to think a new boiler is a good option.... any and all suggestions welcome! Given I'll be in this house for the foreseeable future I'm happy to pay a little extra to get a "Rolls Royce" of boilers...

Thanks again

See my link then... but just 'cos the water appeared clean does not mean that there are flakes of radiator stuck in the primary side of the plate HE.
Thats what I thought about the plate being difficult to reach ! As Dan thinks its easy perhaps you could call him to do it !

All the symptoms indicate a blocked plate but a thermal survey would confirm that.

I might have to go to Poole to rip a cheque out of the soon to be dead hands of a bad payer... :evil: :evil:

So perhaps that is a possibility....

Ok deep breaths....

That's better...

A bit far to go in reality....
F & R isolators hold well and dont leak, 2 screws on the dhw hx and slides out from the left hand side. With access its a 20 minute job.
In my opinion all glow worms are dodgy rip it out flush system put a magna clean and a nice 30 cdi in.
Thats as may be but all that model I ever see are fitted inside cupboards or against LH walls!

Perhaps this fellow is lucky, or not?

Although the HX is at the back, it's not that hard to get it out.....
But it's easier if you remove the gas valve first.
Remove the pump, remove all those nasty plastic bits, remove the gas valve....

Compared with that Vaillant where they thoughtfully put the HX at the front it sounds like a bad design.

I dont like plastic boilers. That Glow Worm is too much like a Sonya Duval


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