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call4heat

Hope someone can help?
I was called out to this breakdown today (just started boiler breakdowns after 12 years of installing)!
Symptoms... CH flow pipe heats when any hot water outlet is opened.
Only 1 hot water outlet (kitchen sink, closest to boiler) operates at a constant temperature, bathroom hot water outlets fluctuate in temperature!
I thought it could only be 1 thing, diverter valve!
I removed the motor from the valve and checked for correct movement of spindle which was fine
So I went off and purchased a spindle repair kit and replaced the existing which was scaled up and covered in black deposits!
The replacement was not easy as the installers had not left the correct clearances around the boiler which meant I could not remove the left-hand panel!
But I eventually managed to replace it, commissioned the boiler but the same problem occurred!
Thinking that I may have installed it wrong, I removed it and re-installed it, BUT annoyingly the same problems are arising!

I would appreciate any ideas/feed back please!
I have heard that a DHW heat exchange that is blocked can cause the diverter valve to not sit back to it's correct position and cause the CH flow pipe to heat up when the DHW is drawn!

Many thanks,
Mark.
 
If you've observed black deposits then the plate hex could be your problem? :welcome: to the forum by-the-way :)

If I suspect p-hex I carry out temp rise against MI's recomendations eg. 9 l/min 35[SUP]o[/SUP]C rise, whatever the mi's state yeh?
 
it is possible that it is the heat exchanger but i would be looking for a blockage somewhere first maybe disconnect the hot water and test again
 
Thanks Diamondgas,
Temperature rise is within MI's recommendations at first then only about 14 degree rise at 12 l/min, it fluctuates between these 2 readings in the bathroom but the hot water outlet at the kitchen sink remains constant and correct (this is what' s throwing me)!
If I have witnessed black deposits within the diverter valve spindle assembly then there is more than likely black deposits within the P-HEX and therefore it is blocked?
Why would a blocked P-HEX cause the CH flow pipe to heat-up when the DHW is drawn?
Thanks again,
Mark.
 
Thanks Diamondgas,
Temperature rise is within MI's recommendations at first then only about 14 degree rise at 12 l/min, it fluctuates between these 2 readings in the bathroom but the hot water outlet at the kitchen sink remains constant and correct (this is what' s throwing me)!
If I have witnessed black deposits within the diverter valve spindle assembly then there is more than likely black deposits within the P-HEX and therefore it is blocked?
Why would a blocked P-HEX cause the CH flow pipe to heat-up when the DHW is drawn?
Thanks again,
Mark.

Tends to be down to pump pressure is my understanding ... as the path through the p-hex gets restricted the pump puts more and more pressure on the diverter seals. At some point the seals give hence the hot heating flow!

Is it the bath tap where the issue occurs? Is it a tmv?
 
Makes sense!
Bath/shower mixer (manual)
Basin mixer (manual)
Shower (TMV)
All are fluctuating in temperature!
Hot tap at kitchen sink operates correctly!

Will remove and clean and add a litre of X200 (customers these days are not spending)!
Thanks!
 
Makes sense!
Bath/shower mixer (manual)
Basin mixer (manual)
Shower (TMV)
All are fluctuating in temperature!
Hot tap at kitchen sink operates correctly!

Will remove and clean and add a litre of X200 (customers these days are not spending)!
Thanks!

Hard water area? If you can, pop your hand on the return from the f&r of the p-hex ... massive difference tends to indicate a blocked p-hex too, especially if heating is working okay :)

If you've got the 35 rise then there's something a miss though! That tends to say the p-hex is okay!

Goodluck anyhoo's ... :)
 
had similar problem last year with a cxi and this is what i found . i was shocked at the price of the plate seals nearly £9 each.hot was forced back into heating pipe and reduced hot water
 

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I've had problems with my 24cxi ever since it was installed in 2006. Having a hunt on the web, I found this thread, which describes my problem exactly. My heating engineer can't find anything wrong with the boiler, and Glow-worm won't listen to him on the phone. I really think there is a design problem. When the weather is mild, this one:
- will not heat the water hotter than that in the heating circuit
- sometimes just runs and runs on 'low' until it has to dump heat into the radiators for safety.
I can't think of a single (i.e. only one at a time) fault that would cause both of these symptoms. By the way, I am an electrical, electronics and software design engineer, rather than anything to do with heating directly.
I've had to install a zone valve to bypass the radiators so I can get hot water!
Any observations?
 
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