Performa 28 diaphrgm

A

AlexCarp

Many boilers still have diaphragms to prove pump pressure.

Those that use electronic pressure sensors tend to to be unreliable due to blockages.

You put those words in the wrong order.

The pump proving switch prevents the gas valve being operated until after there is pressure from the pump.

Tony

I don't think I did get them wrong. Turn on the hot water tap causes a water pressure differential, which lifts the diaphragm in the water pressure differential valve. This activates the pump (I observed this). The second diaphragm, gets lifted because the pump is running, activating another microswitch and energises the gas valve. That is what I wrote in that order.

You stated there was only one diaphragm. The MI clearly show two and looking at the valve it looks like one is under a cover on top of the 3 way valve.

The 3 way valve has a copper weep tube going to it. I don't know what that is for.
 
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AlexCarp

Many boilers still have diaphragms to prove pump pressure.

Those that use electronic pressure sensors tend to to be unreliable due to blockages.

Wouldn't one of these Fernox magnetic types of filter on the heating return pipe stop crud entering the boiler? And of course putting inhibitor in every 3 years. I would have thought a filter on the return would be essential on any combi. I read that many faults are because of sludge and dirt entering the controls. I intend to fit one along with my replacing the inhibitor every three years.
 
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I very clearly said there was only one diaphragm associated with the DHW.

The pump proving microswitch does NOT power the gas valve!

It only tells the PCB that the pump is working and there is flow through the boiler.

You could work that out for yourself by seeing that the pump switch can be made but the gas off!

Tony
 
A

AlexCarp

I very clearly said there was only one diaphragm associated with the DHW.

Which was not helpful at all. I had to ask about 4 question in as many posts to get something very simple out of you which you could have answered in one sentence, like..."the kit has in it, the gland nut which has an integral seal and the O ring which is for the back of the valve where the pin runs though". It was quite easy to write really and it covered all bases.

The pump proving microswitch does NOT power the gas valve!

It only tells the PCB that the pump is working and there is flow through the boiler.

You could work that out for yourself by seeing that the pump switch can be made but the gas off!

I did work that out for myself and just explained it as I did previously to that. It is obvious that the microswitch makes and tells the PCB there is flow and that switches in the gas valve. The PCB only stands between the microswitch and the gas valve. I explained the functional operation correctly.

I assume you are an amateur. There is nothing wrong with that but tell us up front.
 
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I did work that out for myself and just explained it as I did previously to that. It is obvious that the microswitch makes and tells the PCB there is flow and that switches in the gas valve. The PCB only stands between the microswitch and the gas valve. I explained the functional operation correctly.

I assume you are an amateur. There is nothing wrong with that but tell us up front.

I am afraid that you are wrong again!

The PCB decides if further heat is needed from the burner by comparing the set temperature with the measured temperature.

It then sets the modulation voltage and checks the pump proving switch and if this is met then it initiates the ignition sequence.

The gas valve is only powered after a further three safety checks are correct.

There is no direct connection between the pump proving switch and the gas valve.

Tony
 
A

AlexCarp

I am right again!

The PCB does decide if further heat is needed from the burner by comparing the set temperature with the measured temperature as you have just stated. But it needs the input of a closed microswitch first. Hence the pcb sits between the two as I observed and stated.

I correctly noted there was no direct connection between the pump proving switch and the gas valve.

I did ask what the weep pipe was going to the 3 way valve and you did not know. I found out that the pump proving aspect uses pressure differential as well, not just a the pressure of the pump to push up a diaphragm. I noticed the pin will stay up even after the pump is off and slowly drops as the pressure equalises. The pcb must take this into account and have a time delay or whatever.
 
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I did ask what the weep pipe was going to the 3 way valve and you did not know. I found out that the pump proving aspect uses pressure differential as well, not just a the pressure of the pump to push up a diaphragm. I noticed the pin will stay up even after the pump is off and slowly drops as the pressure equalises. The pcb must take this into account and have a time delay or whatever.

Wrong again!

The PCB is responding for a demand for heat.

It is not creating a demand for heat by the position of the pump proving switch as you seem to think.

Boilers are rather more complex than the simplistic operation that you imagine!

I could tell you what to do to demonstrate that but I am not sure that would be very safe in your case! As a professional I have to be careful not to give inappropriate advice.

Tony
 
A

AlexCarp

I was totally correct. The pcb will not provide heat unless the pump is running. Stop squirming. You got it wrong. It is all there proving you did. Stop wasting time and live with it.
 
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Clearly you know more that anyone who is Gas Safe registered and specialises in repairing boilers.

I am sorry that I even gave you any advice!

You are not another name for Dr Drivel are you?

Tony
 
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So if you know so much then why did you ever post asking for advice here in the beginning?

Did you not realise that most of the answers are given by professionals in the heating business?
 

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