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Grimly Feendish
Hello budding Sherlocks.
All the clues you need to solve this mystery are laid out before you. It's not rocket science and I know that some of you guys have the nous to unravel the puzzle.
Boiler: Vaillant Combi Compact VCW GB 240H circa 1993 (ie very old!)
Problem: I've just moved into this house and the DHW is fecked. Here are the facts: -
1. CH works fine.
2. When I open a hot tap, the water gushes out pretty much at mains pressure and the boiler fires fine, but the water only ever gets tepid.
3. I have to turn the tap down loads to get an acceptable heat, ie slow the water through the boiler. Of course, if I turn it down too much the burner shuts off. It's bordering on unusable, especially for a bath. Also it wastes gallons of water.
4. The DHW heat exchange was the original black plastic "four cylinders fused together" type, and it leaked like hell and was encrusted outside with loads of limescale. I've had it changed to a new plate HE. It has solved the leak problem but made no difference whatsoever to the dhw supply.
5. Here is a funny thing - which could be the crucial clue you need: when I have the CH on the DHW works ABSOLUTELY FINE!
6. A heating engineer mate told me that it can't be limescale because I get such a powerful flow from the hot tap. Another heating engineer told me it doesn't need power flushing because the ch works fine.
7. I rang Vaillant (and had to pretend to be Corgi registered - he must have thought I was the most incompetent Corgi gas fitter in the country!) and described the problem. The first question he asked was "Have you checked the burner pressure" and he then gave me some mystical runes to which the burner pressure should apparently conform. I have not checked the burner pressure, but all burners are ignited with a nice blue flame. The supply is admittedly 15mm not 22mm but I'm told that is not so crucial and obviously the boiler worked fine in the past.
8. Another mate told me that, from my description, it is either a "gas problem" or an "electrical problem" - all Greek to me. He insisted it could not be the diaphragm because there is no problem with the boiler firing. When I told him about the DHW working when the CH is on he said "Aha! The diverter valve!"- but he still seemed very unsure and his closing advice was "Get Vaillant in".
I cant afford to get Vaillant in. I've already spent £245 on the bloody thing and Vaillant will cost another £200 plus just to visit and diagnose - we're starting to enter "uneconomical - get a new boiler" territory.
OK Sherlocks! Over to you...............
Grimly Feendish
All the clues you need to solve this mystery are laid out before you. It's not rocket science and I know that some of you guys have the nous to unravel the puzzle.
Boiler: Vaillant Combi Compact VCW GB 240H circa 1993 (ie very old!)
Problem: I've just moved into this house and the DHW is fecked. Here are the facts: -
1. CH works fine.
2. When I open a hot tap, the water gushes out pretty much at mains pressure and the boiler fires fine, but the water only ever gets tepid.
3. I have to turn the tap down loads to get an acceptable heat, ie slow the water through the boiler. Of course, if I turn it down too much the burner shuts off. It's bordering on unusable, especially for a bath. Also it wastes gallons of water.
4. The DHW heat exchange was the original black plastic "four cylinders fused together" type, and it leaked like hell and was encrusted outside with loads of limescale. I've had it changed to a new plate HE. It has solved the leak problem but made no difference whatsoever to the dhw supply.
5. Here is a funny thing - which could be the crucial clue you need: when I have the CH on the DHW works ABSOLUTELY FINE!
6. A heating engineer mate told me that it can't be limescale because I get such a powerful flow from the hot tap. Another heating engineer told me it doesn't need power flushing because the ch works fine.
7. I rang Vaillant (and had to pretend to be Corgi registered - he must have thought I was the most incompetent Corgi gas fitter in the country!) and described the problem. The first question he asked was "Have you checked the burner pressure" and he then gave me some mystical runes to which the burner pressure should apparently conform. I have not checked the burner pressure, but all burners are ignited with a nice blue flame. The supply is admittedly 15mm not 22mm but I'm told that is not so crucial and obviously the boiler worked fine in the past.
8. Another mate told me that, from my description, it is either a "gas problem" or an "electrical problem" - all Greek to me. He insisted it could not be the diaphragm because there is no problem with the boiler firing. When I told him about the DHW working when the CH is on he said "Aha! The diverter valve!"- but he still seemed very unsure and his closing advice was "Get Vaillant in".
I cant afford to get Vaillant in. I've already spent £245 on the bloody thing and Vaillant will cost another £200 plus just to visit and diagnose - we're starting to enter "uneconomical - get a new boiler" territory.
OK Sherlocks! Over to you...............
Grimly Feendish
