Problem with hot water from Baxi Combi 130 HE

4 Jan 2005
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United Kingdom
I have a Baxi Combi 130HE Boiler that is about 2 years old and has developed a hot water problem. I have to keep the flow rate of the hot water low to get hot water :!:
Up to now flow rate for HOT water has been excellent.
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When the boiler is doing hot water, is the burner operating at full power? reduced flame? cycling on and off?
When the hot water is turned on, it sounds as if it is firing on full, but I wouldn't know for certain. It sounds as if it is firing constantly.
I left the boiler running for about 10 mins. at the start the temp on the front reported 32C and went up to 52C but the water from the hot tap could only have been about 30C
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Sounds very much liker your secondary heat exchanger (which does the hot water) is partly blocked. If the boiler is responding to demand (by firing up) and then keeps going all the time the HW runs with no error indication, then it's probably not a control problem. Fortunately, taking off the HX and checking for blockage is easy. But it might not be the cause....

1. Switch the CH and HW off for a while so thet the pipes cool down.
2. Assuming you have the M&I manual for the boiler, follow the instructions for removing the outer casing.
3. With the CH OFF, turn on a HW tap and check whether the pipe leading to the RADIATORS from underneath the boiler (22mm, third from the right) is getting hot. If so, there's a problem with the 3-port valve inside the boiler.
4. Locate the secondary heat exchanger and the internal pipes leading to it. with the boiler running on HW, these should be HOT! (take care not to burn yourself and also beware of electrical hazards). If the supply pipes to the HX are HOT and the delivery pipe to the taps (first on the left below boiler) is cool, then the HX is the problem.

Procedure for removing it is on page 38 of the M&I manual. If it's blocked on the primary side, physical flushing may work. If it's limescaled on the secondary side, you could try descaling it, otherwise replace altogether.

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