Guys, I get hot water from my showers and hot water taps, but as soon as I add some cold water either in the shower or through other mixing taps the boiler switches off. When in heating mode everything including hot water works ok. Heating engineer replaced the diaphragm in the boiler,( although when he took it out it was in good nick) (baxi combi 30 HE 8 years old) No improvement. He suggested the mixer taps are sometimes the problem so I've replaced the cartridge in the main shower mixer just in case. no change. I've isolated each set of taps / shower taps / toilets one at a time individually, then ran the water with same results. However there are 2 set of taps that I can't isolate. Any suggestions would be very much appreciated short of replacing each mixer tap as I go along ! If I've got to work through fixes one at a time then the cheapest options first please! Thanks Bill
What's your water pressure like? I'm wondering if pressure is marginal and turning on a cold tap further reduces water pressure to below the minimum required for the boiler, so it turns off.
pressure is ok according to the engineer. I'm working through this now. one mixer will not fire up the boiler at all (hot, cold or mixed), one mixer works fine and will fire up the boiler with cold mixed in, both showers only give hot (boiler goes off when cold mixed in) (I've changed the cartridge in one) as does another mixer.(!!)
hi with the heating system off, feel the flow pipe from the boiler, should be cool. now turn on hot water, if the flow pipe gets hot, that's the problem.. either divert valve playing up, or blocked dhw heat exchange regards peter
The only thing I can think is restrictors in the mixing taps. It would seem to me that the boiler is not sensing a hot water flow when the cold water pressure at the mixers is reduced by turning the cold water on. Flow sensor on boiler faulty, another possibility?
Hi Had another thought, measure the flow rate of the hot water, and cold water separately, Do this by running the tap, and timing how long to fill 1 lt, 60/sec, = l/p/ min 30kw should give you 12 lt per min, with temperature rise 35. C So measure hot and cold temp, and flow rate, that may give the answer to the problem Regards Peter
Thanks for the advice, but should I do this from any tap or do I need to do it from each one individually?
Probably bath taps, less mess, turn on cold tap, put jug in flow, then measure temp of cold Same with hot With the figures you can confirm the performance of the boiler Regards Peter
Thanks for the input guys, just for your info the engineer tracked the problem down to 'the hydraulic venturi', plastic cap was gone and the spring fully extended. He replaced it and boiler good.
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