Potterton Puma 80e - DHW going hot/cold/hot/cold

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Before you try anything drastic try replacing ( or in practice just remove ) the DHW flow limiter.

This is a plastic bit with a rubber "O" ring within the cold water inlet bits at the back of the boiler. Tricky to get at but is probably the problem as the ring swells up and is best removed completely.

The part you have replaced limits DHW outlet flow until the boiler has heated up and rarely gives a problem.

Tony
 
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Tony, could you please explain exactly where the "o" ring is. Is it in the limiter itself or in the cold water inlet pipe before the limiter?
 
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Crazi, the hot water limiter is in the hot water outlet AFTER the heat exchanger and reduces the flow to about 3 li/min until the water reaches about 32 *C.

The FLOW limiter is on the cold water INLET behind and under the boiler in a very difficult to reach position, I think (?) just above the isolating valve behind the vertical chassis plate. Its the standard two part plastic bits with an "O" ring which is forced forward to reduce the flow when the pressure is high. These can expand and block the flow almost completely. I dont know why but I have found this on an 14 month old boiler and on five year old boilers for no particular reason though perhaps due to faulty rubber composition?

I am giving away all these little known trade secrets here when this site operator and moderators dont encourage me to post here, I should be more discrete and keep them to myself! Anyone non-abusive is always welcome to privately email me though or ask me on gas-news or plumbingpages sites. I always like to help polite RGIs

Tony Glazier
 
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