Mira Coda shower going hot then cold

[Brigadier]

Hello All,

potterton performa 28 combi feeding it.

possible problems / solutions appreciated

 

[Newboy]

Insufficient flow causing the boiler to cycle.

Try cleaning the shower head/descaling the heat exchanger/changing the shower cartridge/cleaning the shower in-line filters

 

[dilalio]

If it’s just the shower having problems then it’s the shower... follow @newboy ’s advice

 

[gas112]

does hot tap work ok ? is problem just with shower

Wrong dilalio it can be this boiler if it is just shower playing up

 

[Madrab]

OP: Does the boiler cycle on and off when the shower is on at the temp setting you require? If so then the boiler is getting too hot and shutting off until it cools enough and then firing up again and then repeats. If that's the case then you need a boiler engineer in to check, diagnose and offer possible solutions.

 

[dilalio]

Wrong dilalio

Not yet! Let’s see. We have to deal with the info we’re given on here and it’s never the same as being there... this is the only place I suggest possible diagnoses. For paying customers, I will always visit before drawing conclusions.

 

[gas112]

you are wrong you said if it is just the shower then it must be the shower , that is wrong simple . It could be the boiler venturi that only shows this fault whilst shower is on and not taps
Regardless if it does turn out to be shower

 

[Brigadier]

Thanks for all of the replies

I am struggling to get someone out to service the boiler, and sort the shower issue out at the same time.
Me and plumbing are not happy bedfellows so, if taking the shower off and cleaning it out is not a certain fix, I'd rather leave it to a specialist!
I'll persist with phoning around, and dipping in at out of the cold!

 

[dilalio]

that is wrong simple . It could be the boiler

Declaration/supposition
“is” vs “could be”. FFS.
I take your point but let’s begin with a process of elimination eh?

@Brigadier start with shower then proceed accordingly. If shower is restricted and not asking the boiler for enough flow then one begats the other... remove shower head and hose as first test, then think flow cartridge in shower... how old is the valve, do you have problems with hard water?

 

[Brigadier]

Declaration/supposition
“is” vs “could be”. FFS.
I take your point but let’s begin with a process of elimination eh?

@Brigadier start with shower then proceed accordingly. If shower is restricted and not asking the boiler for enough flow then one begats the other... remove shower head and hose as first test, then think flow cartridge in shower... how old is the valve, do you have problems with hard water?

Hello dilalio,

I've took the hose and head off, and they seemed fine.
Yes: we have hard water.
As said before, I'm not too enthusiastic about taking the shower off (can't isolate it, so have to turn off whole house plus boiler to fiddle), unless it's simple, and guaranteed.

 

[dilalio]

Don’t know this shower valve without looking up MI’s... does it have built in isolators?
It’s also a combi you have, so it’s not a big issue to off supplies and take a look, maybe you can stick a couple of lever valves into the Shower feeds, so you can then isolate the unit and investigate at your leisure, but, if you think it’s beyond your abilities then get someone in who can investigate both potential suspects.

 

[gas112]

do the hot taps work ok ?
when shower is on and goes cold does the hot water demand light at boiler go off ?

 

[Brigadier]

do the hot taps work ok ?
when shower is on and goes cold does the hot water demand light at boiler go off ?

I'll have a look later

 

[Brigadier]

Yes, the hw demand light goes off, when the shower is running.
I ran a bath tonight (hot tap only), and the same thing happened, so I'm guessing it is a fault with the boiler itself.
Need to keep phoning around then.....

 

[dilalio]

Yes, the hw demand light goes off, when the shower is running.
I ran a bath tonight (hot tap only), and the same thing happened, so I'm guessing it is a fault with the boiler itself.
Need to keep phoning around then.....

More info... and it sounds indeed like your boiler needs attention. Thanks for the update. And kudos to those who made that leap from the original description.