Boiler gives really hot water when flush toilet!

[Sicandar]

I have a vokera syntesi boiler and the boiler struggles when the water pressure is high, i think. It gives lukewarm/tepid but not really hot water most of the time and then goes really hot if someone flushes the toilet or opens a cold tap somewhere else. (I have turned down the max temp on the boiler to prevent scalding)

My dad keeps wanting to turn down the pressure at the stopcock but that seems a poor solution as then when someone uses the toilet the shower turns to a drizzle. At the moment i flush the toilet before jumping in the shower or turn the shower flow down a to half way to get the hot water!

Surely the boiler should be able to cope with a decent water pressure? Is there something I can easily adjust? Or do i need to call someone? If so what should they be looking at?

I wold appreciate any advice please

 

[Jackrae]

Suggest that you have a restricted flow of cold water to your house. Once you have solved this you should be able to turn up the boiler thermostat to give you correct boiler DHW temperature. Sounds as if you also have a problem with your boiler controls since there is no way it should give scalding water if the input pressure/flow drops

 

[oilhead]

Can you not restrict the flow to the boiler through the isolating tap on the cold water inlet manifold? This should help, but you need to check how it is affected when the toilet is flushed.

 

[Sicandar]

Thanks for the replies, there is a stiff yellow knob i can see on the inlet pipe on the underside of the boiler, apart from that i have no way of restricting the flow to the inlet to the boiler alone, shall I turn that?

I know we had a leak draining water for many years (unknown to us) which was discovered last year and fixed, improving our water pressure as a result. The boiler was installed well before that. Do you think there is something else that might need resetting or re calibrating in the boiler itself?

 

[spareshunter]

Yellow is gas tap, DO NOT restrict that.

Your dad is on the right wave length restrict the flow on inlet (stop cock) if that works put re-stricter in incoming mains to boiler. When you flush the loo that's exactly what's happening.

 

[Sicandar]

Phew - Glad I didn't turn that one
Thanks

I will probably have to ask someone to fit a restrictor,

but is there nothing in the boiler that is supposed to do this job already though? would i be better spending money on getting that fixed?

 

[spareshunter]

Try mains as dad says any good? This will of course affect the flow to the WC and anything off the mains but good for a test.

On the right hand side is a lever valve this will do the same job as mains throttling at stopcock but for boiler only and will affect the flow rate to the hot tap only. Off course if the wc is flushed the pressure/flow will drop. If the water still gets very hot the boiler is not modulating or related fault. (warning maybe gas related problem don't touch).

Be careful, the valve may be stuck through lack of use and may leak but there it is.

If all works to plan pop £ 10.00 into charity of your choice

 

[hazetimesfive]

is this not a problem with the plate exchanger

 

[spareshunter]

Don't know not there!