Glow Worm 30cxi Combi - H.W. Runs Hot Then Cold

[courage best]

Happy New Year To All!

This problem with my G.W. 30cxi started off as two problems at the same time, but the problem with the heating seems to have resolved itself. The h. w. problem still exists. Here's what happened;

HEATING
A week ago, I turned the room stat on, and after approx 8 minutes the boiler stopped. The heating was still a few degrees below what I had set the room stat at (18 degrees). After a while the boiler came on again for longer, but cut out again. In all, the boiler cut out approx 3 times before reaching the temp set on the room stat. Gradually this fault got better, and now seems to have disappeared.

HOT WATER
During an average shower, the h.w. goes cold three times. Each time, you have to turn the water off, wait a few mins, and turn back on. All hot taps run cold after a while if they are left running for a while. This fault started at the same time as the heating fault, and it is still happening.

Any ideas would be appreciated.

 

[courage best]

Bump. (Apologies, 'Er Indoors nagging me - cold shocks whilst showering annoying her! )

 

[Slugbabydotcom]

I see a few possibilities here.
Reduced flow through primary circuit / heat exchanger /plate heat exchanger
Maybe in turn caused by a pump that was or still is a bit sticky
Maybe a temp sensor HW or CH
Possibly a faulty HW flow switch
I dare say others may suggest more
All in all it is too much really to try and guide you through a forum

All I can suggest with the current information is to check that the pressure is between 1 and 1.5 cold.
Also
Check that the rose on your shower is clean. If its badly blocked it could perceiveably cause the flow switch to malfunction.

Then call a repair specialist

 

[mickyg]

When you say it goes cold, does the boiler actually stop running?

 

[courage best]

Thanks for your replies.

Pressure is 1.4. Don't think its a shower problem, flow is great and other hot taps run cold too if left running for a while.

Good question Mickyg. Not sure. With the heating fault (that now seems to be OK) the boiler stopped completely. Trouble is, boiler is in the loft. When my better half starts showering, I will get in the loft and see if it cuts out altogether, or if any fault codes appear.

It may be my imagination, but the rads seem to be a little hotter than normal. Don't quote me!

Slugbaby - Not sure if this is related, but a few months ago, I had the heating on, and I could hear a loud rapid constant banging/hammering (like pneumatic drill) coming from boiler. Switched off heating, and it never happened again.

 

[fitz1]

min gas pressure is the first thing id check.