Hi, we've got a Baxi Platinum Combi 24HE boiler. Recently took out the bath and fitted a new shower, all ok for a couple of weeks but now every tap and shower in the house runs hot then cold/lukewarm then hot then cold etc. The boiler is firing up, water temp (on digital guage) goes up to 92, then it shuts down (demand light still on but flame light goes out) temp drops to 72 then if fires up again and the cycle begins again. Could this be related to my new shower or is this most likely a coincidence? Thanks
How easy on this boiler for a diy'er? I've changed a couple of diverter valves on other boilers in the past. If not, what's the likely cost? Boiler is at least 7 years old so don't want to throw money at an old boiler if it would make more sense to just fit a new one. Thanks.
Very simple diy job. Power off. Close cold water inlet and open hot tap and wait on water stopping. Close flow and return isolation valves then use boilers drain to empty water from boiler. Unplug the diverter valve motor and remove the pin holding the motor (this creates a bit space). Place towels below the boiler. Then it’s just 2 screws holding it in.
Also whilst I was watching the boiler with hot tap running, at one point a fizzing noise started and the central heating pressure gauge was fluctuating Like maybe a boiling noise. This was with the tap maybe half open.
The water can’t pass through the plate heat exchanger quickly enough so it will be starting to boil then trips the overheat sensor so the boiler turns off until it cools then the process starts again. If you can afford a new one, I’d do that which will come with new seals.
You should try this product which is used for removing sludge and limescale from central heating systems. Just pour it into the removed Plate Heat Exchanger and leave it for an hour or two. *
Thanks. Further to the hot and cold, tonight when the Mrs had a shower she noticed a couple of radiators upstairs had got hot. I'm guessing this is the divertor valve? Could the whole problem be the valve or am I looking at the heat plate AND the divertor valve? Thanks again
Divertor could just be lifting slightly due to plate offering resistance. Clean or replace the plate heat exchanger first. If your unsure just close the flow isolation valve when using the hot water and see what symptoms you then get.
Flow isolation valve? Is that the switch on the front for DHW or CH? Or is there a physical valve to close? Thanks
Under the boiler there will be a flow and a return pipe which carry hot water to and from your rads. Each should have an isolation valve that can usually be turned by hand. Put your heating on and see which pipe gets hot first - that will be your flow. If you isolate the flow then test your shower/taps again to see if the temperature still fluctuates. If it does, you can disregard the diverter valve as a possible cause.
Ok I've got the manual and found the valves, however the flow will not budge. I dont want to force it cause its a plastic handle. The manual says to change the heat plate you have to remove a gas ignitor so I guess that means I'll need a plumber. If it means professional repair, would it be better in the long run to spend that money towards a new boiler when it's 7 plus years old? Thanks
Have you considered it may be as simple as air trapped in the system? The boiler would behave in a similar manner if so.
Ok I've managed to turn off the flow. Strange thing is the pipe still get red hot on both sides and the dhw still fluctuates
I’m not expert on Baxi boilers, but I think you have to force to boiler into an air purging mode, from memory, switch off boiler power and wait 10 seconds. Whilst it’s off, turn the central heating temperature dial to the minimum setting, (pointing to 12 o’clock) Turn power back on, then as soon as it powers up, turn the central heating temperature dial a quarter of a turn (to 3 o’clock position) then back to zero then repeat this straight away.. (so you spin the dial a quarter turn, turn it back, then a quarter turn and then back again, all within 2 seconds) Boiler should then be in purge mode and will take about 10 mins to do this.
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