My shower is run off a combi boiler and recently started to go cold for a couple of seconds every few minutes and nobody is running water elsware in the house.

call in a plumber. it sounds like it is malfunctioning.

Changing the heating system will not affect an electric shower as it is run from the cold water supply,sound like the temp thermostat has blown ,contact bristan or there website to get a replacement thermostat,telling them which model electric showrr you have.

Check the 94282000 cartridge for debris on the filters. If your boiler requires a certain flow rate to come on, then you must get enough flow through the cartridge to make that happen. Also, if your boiler is producing very hot water, the cartridge will self regulate and reduce the hot flow accordingly. try lowering the output temperature of the boiler to resolve that possibility.

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could be a number issues 1 the hot and cold water supply going to shower could be of unequeal pressure thus the fluctuating 2the heat exchanger in your boiler is conjested with debris 3 the gas bed in boiler is cross burning giving an unbalanced "heat pick up"out put !2 &3 would apply if your on a combi boiler system .if your on a conventinal system you could be pulling air from the head of the cyclinder ,

Sorry to read about your problem, I hope this helps you out.

yes 2 both answer, you pipes can be frozen for days, in the walls, and the control could have failed due to the cold/ice.

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ITsounds like you still have air in your lines try bleeding lines out some times it takes a while .or your getting air in lines some where try looking at the boiler at fittings .

hi there, your boiler will perfectly match the mira excel ( a great choice i might add) a 24cdi will give about 9.8 litres a minute flow rate hot water.
The mira excel is suitable for any plumbing set up and there installation instruction are very well laid out & their helpline is fantastic.
The hot water will fluctuate accordingly to the time of year as the cold water temp coming into the property will vary. but the boiler will modulate to compensate.So in brief in the summer you will notice it hotter than you would in the winter, this has nothing to do with the boiler just the incoming temp of the cold water.

Kindly

Richie

Modern shower valves have an "anti scald device" in them to prevent scalding from to hot water.

They come preset at 120 degrees.

Sometimes they can start to malfunction and all you get is warm, not hot water, they can also be intermittent.

This will only effect the shower valve though, not the other faucets.

mixing valve must be replaced

either the h/w flow switch or diaphram reqs replacement or the secondary heat ex or (calorifier) is blocked and prevents the heat from leaving the biler to hget to he taps- the heat starts ok but backs up to the boiler very quickly causing it to shut down