I have a vaillant eco pro 28 combi boiler. The pressure on water flow was not as high as it used to be so got a plumber out to service boiler. He said it was all fine, no probs. The water board then came out and flushes some stones from system which meant an improved water flow and pressure. Now the water does not get warm. Had another plumber come out he could not understand why no hot water. He fixed a leak from the overflow little plastic tube at bottom rear of right hand side of boiler and fixed some pressure that was low in the big silver grey bag tank thing. But when he left, I turned hot water to 'on' and had the tap on very low and the water finally got hot to about 32 but when I turned tap on fuller for more flow the water went warm to cold really fast back down to 17 degrees. It means I can't just turn on hot tap and have instant hot water and I can't have a shower unless prepared for a small water flow and luke warm temperature. The last plumber did say that the heat exchanger was not hot and that it should be, but may that have been cause the hot water was not turned 'on" at boiler. There does appear to be a small amount of hot water that comes out the tap eventually after a long run but I have to keep tap turned down really low so its not full on.
Oh some of these there was a small black heatexchanger just for hot water they some times block up . or it could be a blockage in the water section where it flows in .I know Valliant have a very good tech line and fitters who do house calls .
SOURCE: Combi Boiler - Running warm & then cold!? HELP!
the problem was solved on my system by replacing thermostatic valve on shower and putting non return valves on hot and cold feed to shower . the problem was caused by cold water getting into the hot water line through the shower hope this helps
SOURCE: vaillant combi boiler,dirty water comes out of hot
Hi ,
Can you please tell me the model of the vaillant, and the approx age?
I can solve this problem
I await your reply
Thanks
Steve :)
SOURCE: vaillant eco tec pro 28 every time cold tap is
try reducing water pressure to cold tap and see what happens
SOURCE: warm water only
You can eliminate the shower control knob possibility by turning on your hot water anywhere else in the house. If you get hot water in other places, then it could be the knob causing it. A substantial lime buildup in the tank can also cause poor heat transfer from the elements to the water.
SOURCE: Vaillant ecoMAX 828/2boiler goes on & off when running hot water!
water must be set at 3lts a min ,check diaphragm valve move when hot tap is on, check microswitch ,best of luck
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Yes , thanks Steve and to all other posts from those who have replied. The combi is five years old, and was recently serviced two weeks ago. The boiler was working fine before the water pressure got fixed by water board. I have to say though that the pressure used to be as it is now when we moved in, and the boiler worked fine then. The heating is fine its just the lack of hot water.
To Sgentry130, The previous plumber turned down the tap at the incoming tap to see if it helped but it did not unfortunately.
I now have hot water!!! I reduced the pressure further to almost zero at the water inlet and the water was freezing, but when i turned it up just past that the water started heating up and stayed hot! I tried the shower and the flow was not great but water was at a steady 40degrees.! I eventually went and turned up the tap a bit more water inlet and the water stayed hot! It was probably still up too high after the previous plumber adjusted it. So now got great pressure and toasty water!
Just wanted to add, the leak was caused by me! I had tried to adjust the bar pressure which is a little hand (pressure gauge) inside what looks like a clock in the front right hand panel of boiler. I think I let too much water into the boiler pushing up the pressure to nearly 4 bars. Its now at 2 bars,as fixed by the most recent plumber I had out. I was told it should never be above 1 and half bars.. Its all double dutch to me though. All I know is that playing about with that pressure gauge probably led me to all the problems. Just a tip. If you don't know what your doing leave well alone. I probably would have saved myself a lot of money, if I had just tried to resolve it myself like I have done at the water mains incoming tap.
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