Shower running cold

[Mickeydredd]

Hi
I have an oil fired AGA which is only used for cooking on, it is not linked to heating system or hot water - both of which is provided by an oil boiler.
Every year when we fire up the AGA the shower runs cold after a few minutes. Water from taps is still piping hot.

Have fitted a new thermostat in the shower but no joy.
Anyone got any thoughts on what the issue is?

 

[centralheatking]

I dont understand your post...Aga for cooking only...not linked to hot water so why would you expect the shower to work at all ? re read your post please. centralheatking

 

[Mickeydredd]

I dont understand your post...Aga for cooking only...not linked to hot water so why would you expect the shower to work at all ? re read your post please. centralheatking

Hi

The shower works off the oil boiler, which also runs the hot water elsewhere and the radiators.

My plumber, nor I, cannot fathom how the AGA can influence the shower yet when I fired up the AGA the shower issue reappeared. The shower only ever runs cold when the Aga is running.

AGA and boiler both run on oil

 

[Stigster]

The only thing I can think of that would make sense is if the Aga is in fact connected to the hot water, the water is getting ridiculously hot and setting off the anti-scald device in the shower.

Otherwise, if the Aga is most definitely not connected to your hot water system, as CHK says, how can it possibly affect your shower? If it is set up as you say it should have no effect whatsoever.

 

[Mickeydredd]

I bought the house a year ago and was told the water only runs off the boiler but agree that it seems like the Aga must be connected somehow. Presumably there would be pipes running from the Aga if this was the case?
I don’t think there can be a manual override - does the shower thermostat not manage that?
I will get the plumber in again but already down the price of a thermostat that clearly wasn’t the issue.

 

[centralheatking]

I bought the house a year ago and was told the water only runs off the boiler but agree that it seems like the Aga must be connected somehow. Presumably there would be pipes running from the Aga if this was the case?
I don’t think there can be a manual override - does the shower thermostat not manage that?
I will get the plumber in again but already down the price of a thermostat that clearly wasn’t the issue.

I wonder if the pipes are very close together and heat is being transferred by conduction
this might throw things out.....centralheatking

 

[Mickeydredd]

Shouldn’t be that, the Aga is in the kitchen and boiler is in beside small toilet room 20 feet away. Oil feed comes into kitchen and boiler room separately too, but kitchen first so I thought it could be an oil feed starvation when both running????

 

[Ziggie]

Just a lateral thought - is there a common fuel feed where switching on the aga cuts the flow to the boiler or share electricity? While you said that there are separate pipes, could it be a common joint to them at the connection to the storage. If this was not so, then is the pipe to the aga bigger than the one to the boiler. Even better? Does the air intake on the storage tank limit the outflow of fuel and the aga takes some and causes a vacuum in the tank. I am assuming gravity feed - would need to consider what drives the flow!

Still Prefer the water is connected in some way and a pump is sending cold water round.

 

[Mickeydredd]

That’s my thinking.
I believe this boiler holds a reservoir of hot water so I think once that is used then there is an oil feed or flow issue to the boiler when the Aga is on.
Only flaw in that thought is if you run a sink hot top it is piping hot

 

[Ziggie]

Or
Is your shower pumped . I had one with a separate pump for hot and cold.
The hot water tap in the sink doesn’t have this. Could something be cutting the supply pressure from the hot pump or raising the pressure on the cold pump?

 

[Mickeydredd]

i Don’t know tbh. The shower stays hot for a few minutes so I thought this tied in with my thought that something is stopping the boiler from heating the water replenishing the initial heated water sitting in the boiler.

 

[Ziggie]

Is it a power shower which would imply motors and you can usually hear them.

I remember that the pipes had controls fixed to them which regulated the pumps. Could be those misbehaving but I can't remember what they monitored. I will check this over the next few days.

 

[Mickeydredd]

It is a direct feed shower, will check the make tonight

Thanks for all input, appreciated

 

[Ziggie]

And last thought.
Could it be air getting into the system ? This would reduce the amount of water passing through the heater in the shower and therefore water I should cold. Further running would flush out the air and solve the problem.

There would be a drop in pressure coming out of the shower head

 

[Mickeydredd]

Would that drop the heat level or the pressure level though, and why just when the Aga runs?
[automerge]1570104766[/automerge]
Water pressure doesn’t drop either, just temp

 

[Gasmk1]

this sounds like when the aga is turned on it switches over for the aga to heat the hot water but the valve may be faulty so neither is heating the water, have yoiu turned of the aga to check you get hot water again

 

[Ziggie]

Tried a different approach . Assuming that the AGA causes the problem then there must be a common element.
So fuel - common tank
Water - ?
Electrical - common wiring or control unit?

 

[Brambles]

My advice would be to start from first principles and draw up the flow diagram of the the two ( or one) systems that you have.

Map out the available information from the pipework you can see (including pipe sizes) - then you can explore further to find or deduce the missing links.

It may be tedious, but will eventually give you the answer and give you a very useful document for the future.

If you suspect oil starvation ( which is unlikely in my view) set each appliance onto simultaneous full load.

 

[Mickeydredd]

this sounds like when the aga is turned on it switches over for the aga to heat the hot water but the valve may be faulty so neither is heating the water, have yoiu turned of the aga to check you get hot water again

The Aga is not connected to the water so it won’t switch over. I do get hot water when Aga is on, just it runs out in the shower.
If I turn the shower tap down when it starts running cool then it heats up again, albeit flow is reduced.
Also, I’m told if I run the cold sink tap then the shower runs hotter again! (The mrs does this)

 

[Brambles]

Mickey,

When troubleshooting these type of problems - map out the system as best you can (see previous post) and don’t be too hasty to make judgements on the outputs from mixer taps or showers with or without thermostatic valves - they can cause confusion! Always try to test the hot water before it enters a mixer or thermostatic valve. The former (if unbalanced) sometimes pass hot water into the cold supply (and vice versa) and the latter can be really confusing if the cartridge is faulty or if there is a lack of cold water to regulate the temperature.

A shower getting hotter when you run off cold water elsewhere in the house is symptomatic of those type of issues, or a non thermostatic shower valve.

 

[Mickeydredd]

The shower definately has a thermostat as my plumber changed that first

 

[Mickeydredd]

Hi All
Just a follow up to my query.

turns out it was a problem with the diverter valve in the boiler. Noticed one day that the radiators were piping hot despite the heating being off!

replaced the valve and all okay.

cheers for all thoughts and input