Performa 28 diaphrgm

A

AlexCarp

I noticed a small leak on the pin that activates the micro switch on the diaphragm assembly. That is easy to fix by replacing the diaphragm and O ring seal. I noticed that on the bottom of the diverter valve assembly that the diaphragm assembly is bolted to, there is a small hole. It looks like a breather hole. It was damp around the hole with water "very slowly" leaking out. Will replacing the diaphragm solve this weep from this hole?
 
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The leak on the pin needs a new gland.

The diaphragm only needs changing when its failed.

There is an "O" ring at the back which can cause what you describe.

Tony
 
A

AlexCarp

Thanks for the quick response. The diaphragm kit comes with an O ring, washer and gland nut. The O ring at back you refer to. Is this a separate order? Is this O ring at the back a part of the three way valve assembly? Thanks.
 
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Its in the back of the diaphragm unit.

The one supplied in the kit is whats needed.

Tony
 
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AlexCarp

Thanks again. Does the brass gland nut provided in the kit have the seal integrated in the nut? And the O ring provided is for the back?
 
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Its not a gland nut but a gland incorporating the seal.

Tony
 
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AlexCarp

Thanks. So I was right in my assumption, the glad nut is also the seal.

The operation of this. I am not sure how this works. i have the MI on-line and does not into this in depth. The three way valve at the back of the water pressure differential unit. Does the pin of the pressure differential unit move backwards into the three way valve housing and move the three way valve. I noticed the three way valve also has a diaphragm.
 
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Yes.

There is no other diaphragm in your diverter valve associated with the DHW.

Tony
 
A

AlexCarp

Thanks again. There is a pin which moves up and activates a micro switch on the three way valve. There are two micro switches that are activated by pins on the three way valve and pressure differential assembly. What pushes the pin up on the three way valve?

Edit: Agile, I just looked at the MI and there is clearly two diaphragms on this combi.
 
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There is no other diaphragm in your diverter valve associated with the DHW.

Tony

The other one can be called the pump proving switch.

In spite of what people think they rarely give any problems!

Tony
 
A

AlexCarp

The small one is the flow switch activated by the pump.

The small one? is this the one in the three way valve assembly? How does it work? The differential switch moves a pin. This does something in the three way valve. What does it do? <confused>
 
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It tells the PCB that there is sufficient flow in the primary circuit to initiate ignition sequence.
 
A

AlexCarp

Thanks. The pin on the 3 way valve lifts when either CH or DHW is called. But when CH is turned off it stays up and slowly drops back. Staying up is not encouraging. It is a flow switch to ensure the pump is running before the gas valve is energised. Got it. Does the pump pressure force the diaphragm up? Or some sort of pressure differential?

So the DHW pressure differential switch allows its pin to move which moves the three way valve, which is spring loaded. I assume there is a seal on the three way valve that the pin acts against. This could be leaking? Is so, does the seal come with the three way valve kit?

I see there is a bypass pipe off the three way valve. Where and how does that come in?

I can see why makers dropped all this mechanical proving and two diaphragms. A lot of complexity.
 
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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
 

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