Hot Water Pressure Problem Eco Tec Plus 831 Vaillant Boiler

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I think maybe I do mean flow. I am no expert. Basically when the heating has been on the amount of water which comes out of the hot taps or the shower is dramatically less.
 
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Flow is measured in litres per minute.

Pressure is measured in Bar ( previously pounds per square inch ).

Unfortunately schools have reached such a low level of basic education that very simple concepts like this are not being taught.

Nor are use of money and budgeting or personal relationships.
 
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I think I may have the answer, When the heating is on and hot, is the pressure gauge touching the red? If so, the problem is your expansion vessel is depleted. To explain, when the pressure is too high, the boiler will not go to high gas, Your themostatic shower is reducing the flow to try and get hot water for you.

Get yourr engineer to check this, if he i unaware of this 'fault' , it is only the latter software versions of the PCB that do this.
this is deffo a new one one on me, early or late eco's all work the same, if the system pressure is to high the pressure sensor wont see a change and fault f.75 never have i seen or heard of it holding the boiler on low fire or reducing the dynamic in the hot(impossible),
my tupence worth is blocked or reduced flow rates not presure as the op doesn't understand dynamic and standing presures and seems to be talking f/r's!!

Check your status codes S41 to be precise will stop boiler going to high gas, Try it, or call your senior tec, On latter software boards only. Ramp the pressure right up to 3 bar and check D34 or gas rate it. The flow is being reduce by the OP's thermostatic shower - he's unsure about the flow from the taps. He may also have a safemix on his bath tap so again flow would be restricted.
I said "I think I may the answer", and was only trying to point him in the right direction.

Btw The OP thinks he has also been told this by another engineer. Simply wait for a post back and see what actually happened when an engineer was looking at the thing.
 
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Then is is definitely the hot water flow. The boiler has just been serviced so I hope all the 'pressures' etc are right.

Last night and this morning I had the heating on. This morning when I turned the shower on, nothing but a drip drip drip! It starts of with some 'flow' but then as the water heats up it becomes less and less. If the boiler is cold and the heating hasn't been on then the flow is fine for the time I am in the shower. I have the Vailliant people coming out tomorrow morning but as of yet as I mentioned they haven't come up with a solution.

Thank you to all for your help and advice so far! Much appreciated!
 
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