So here's my problem. Running the shower for it seems any longer than about 10 minutes turns the boiler off. It's a bit random, but it's ptretty much always takes at least 10 minutes of being in the shower for this to happen. When I say the boiler turns off, I mean the pilot light goes out as well, which led me to think it's a boiler problem . However, after a couple callouts they think the problem lies with the shower unit and not the boiler (has had full service), as it does not happen with any other taps (left it running hot for almost an hour and boiler still working).

The shower I have is a Mira 415 mixer shower (not sure what generation it is). When running it, it gets hot just fine and apart from swinging to a bit hot or cold sometimes, runs pretty well, until the boiler turns off and of course it just goes cold again.

For reference, my boiler is a Ferroli Optima 901 combi boiler (yes I've heard it's a bad boiler, but it's actually in very good condition according to the Engineers).

Could anyone give me some advice on what potentially the problem is, and how to go about fixing it? I'm pretty good with DIY and happy to replace the shower myself if needed, I just don't know what I'd need to buy (preferably the minimum to fix it). Oh also, the shower is now dripping, so I think I might have to replace the main mixer unit anyway.

Any help would be really appreciated. I've attached a photo of the mixer unit so maybe someone can tell me what generation it is.

The 415 is a pressure balancing mixer valve pre 1988.

A good service and a new pressure balancing cartridge assembly (902 91) should do the trick.

You may want to type the shower doctor into google, where you should find the schematic, and be able to order the part,

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Have you tried running another hot tap at a very slow rate for 10 mins or so, to repliacte the shower working?

It coulbe be the shower, or maybe the boiler isn't modulating down properly. Could be the max/minimum burner pressure has not been set properly.

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Dave

www.drlgas.co.uk

Tried running a hot tap at a slower rate, but if its too slow the boiler doesn't even kick in, but when the boiler is on (even at reasonably slow flow rate) it stays on just fine.

Just another quick question, would I be right in assuming that if could replace the whole unit with the same model and as long as the cartridge assembly on the replacement is working fine, it should fix the problem? Reason I ask is I can hopefully get a used replacement pretty cheap - a lot cheaper than cartridge assembly anyway.

If you get the same model and it works ok, just change the lot.

Assuming the boiler is old ish, has the problem recently started and getting worse.

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problem started about a month ago, not really getting any worse. has had the full service and a few parts replaced since but this problem wasn't resolved.

thanks for all the help by the way, really impressed with the quick responses! :D

It's almost certainly the cartridge.

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Or a blocked showerhead

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Or a blocked rose (showerhead) good point Razor

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Hmm showerhead seems fine, no visible blockages and water comes out just fine.

The shower has eco conscience and is trying to make you shower in less time, therefore help save the planet.
Why can't you shower in less than 10mins anyway - busy eh?

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Sciatica is a pain in the Ar5e ............ and leg

This happens to my boiler too when using my thermostatic Mira shower, the plumber reckons my water flow is so low the boiler can not reduce the flame strength enough to keep the water temperature below the 65C safety trip out. The flow rate is terrible, I can only run one tap at a time in the house.

Did the poster get to the bottom of this? As my boiler has a similar problem it would be interesting to find out your solution. Shorter showers are fine for me but the misses like to shower for 30 mins! I've tried to convince her that she's no cleaner than she was 10 minutes into the shower!

At the moment the gas supply is turned down as on full filt it the boiler shuts off after 2 minutes. The hi/low gas regulation is set for CH only (upon install), hot water gas flows are factory set according to the manual. (Heatline S24) I do have very low water flow which is what the last plumber blamed the problem on - surely a boiler should be able to regulate the gas enough to cater for that?

I need to get this fixed before winter as the turned-down gas bodge will affect the central heating. PS I do have a carbon monoxide alarm - I'm aware that restricting the gas flow may alter the way the boiler burns, affecting CO emissions.

First if you expect an answer you don't bodge Gas, end of thread.

Your problem is not the same as the Op so start another with details.

What is the mains pressure/flow in Ltrs/min.

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