I have a flow problem on my Potterton Puma 80e, help pls?

[nycolas21]

When any tap in the house is switched on, regardless of CH on or not, the flow of the hot water stays low (half - compared to what it has been), the water quickly boils up (very hot) and then the boiler decides to turn off (possibly on over temp.

when the above happed the system pressure gets to 4 bar too.

Any help will be highly appreciated.

Could it be the flow switch mechanics or diverting valve? boiler engineer has said it is the heat exchanger but i am scepticle as he want to replace the whole thing....... if it was the H Ex i would expect the temp of the water to decrease and then increase as the tap restrics the flow????

thank you for reading ... look forward to any resolutions

 

[Agile]

It sounds as if you have two problems with your boiler one of which is the expansion vessel. That may have failed or might just need repressurising.

These are quite repairable boilers although they are not terribly reliable but its always cheaper to repair than to replace.

Tony Glazier

 

[steve32]

dhw flow limiter assembly part no 929673 item no 22 in mi's
the valve is on hw supply as the hot water temperature increases the wax capsule opens and flow increases
not to be confused with wax capsule in diverter valve


Steve

 

[nycolas21]

dhw flow limiter assembly part no 929673 item no 22 in mi's
the valve is on hw supply as the hot water temperature increases the wax capsule opens and flow increases
not to be confused with wax capsule in diverter valve


Steve

Steve, I have been told it is the heat exchanger by my boiler engineer... although I did have doubts - when i was told the boiler must be replaced, more to add... I have found that: when the DHW is turned on, the flow is half of what it should be (since the last three days), and you can tell that the boiler is struggling from the pressure noises heard, i have also noticed that the pressure goes up to and past 3 bar then hot water floods out of the PRV as well as the boiler cutting OFF (posibly on high temp).

Finally - no issues with central heating side, and the water problem as mentioned prior - is present wether the htg is on or not.

would you still say, it is the dhw flow limiter (DHW water valve)?


thank you for your help.....

 

[Agile]

Most unlikely to be the flow limiter. I have never needed to change one!

Far more likely to be a blocked supply filter.

Tony

 

[nycolas21]

Most unlikely to be the flow limiter. I have never needed to change one!

Far more likely to be a blocked supply filter.

Tony

supply filter has been checked, and completely clear, any other suggestions?

 

[steve32]

the flow limiter has a wax capsule in it when a tap is first turned on the wax capsule will reduce the flow at the tap, as it heats up the wax capsule opens allowing more flow, hence when a tap is turned on flow increases as water heats.
if the wax capsule is faulty this will cause a slow water flow and combi will overheat
i have changed approximately 6 in the past.
to check if it is the wax capsule or heat exchanger the flow limiter is adjustable by adjusting to max flow it will increase flow to hot tap.
i have in the past removed the flow limiter and connected the hot outlet direct to combi to test if the flow at hot tap is better this will determine if it is the flow limiter or heat exchanger blocked hot water will not get very hot with limiter removed

Just checked in van part no has been changed new part no is 10-19849


Hope this helps Steve

 

[nycolas21]

the flow limiter has a wax capsule in it when a tap is first turned on the wax capsule will reduce the flow at the tap, as it heats up the wax capsule opens allowing more flow, hence when a tap is turned on flow increases as water heats.
if the wax capsule is faulty this will cause a slow water flow and combi will overheat
i have changed approximately 6 in the past.
to check if it is the wax capsule or heat exchanger the flow limiter is adjustable by adjusting to max flow it will increase flow to hot tap.
i have in the past removed the flow limiter and connected the hot outlet direct to combi to test if the flow at hot tap is better this will determine if it is the flow limiter or heat exchanger blocked hot water will not get very hot with limiter removed

Just checked in van part no has been changed new part no is 10-19849


Hope this helps Steve

Thanks steve all your input is much appreciated, can you tell me the best way to connect the hotoutlet direct to the combi? do you need to make up a bit of pipe or is it easier than that? I have now changed the HW flow switch and must admit the problem still remains. would you class replacing the heat exchanger a hard job? as my boiler engineer has declined to due so.... thanks once again....

 

[steve32]

can you tell me the best way to connect the hot outlet direct to the combi? do you need to make up a bit of pipe or is it easier than that?

you need to make up a pipe, turn off combi and cap off dhw flow switch connection possibly not a diy job

would you class replacing the heat exchanger a hard job?

no takes about 1.5 hrs

The appliance contains an automatic flow regulator supplying a
nominal flow rate of 10 litres/minute (80 & 80e) and 7.6
litres/minute (Saver). These flow rates will give a nominal
temperature rise of 35°C & 45°C respectively. Should it be
desired to set the appliance to give a higher temperature rise,
the flow rate can be further reduced by using the manual flow
restrictor (clockwise to reduce) located in the manifold below the
mini expansion vessel

try increasing flow to max to see if flow increases


Steve

 

[Agile]

Even if the temperature dependent flow regulator was stuck at minimu m then I dont see any reason why a correctly set up boiler shoul,d overheat.

Nor do I see why the OP has changed the flow switch and is now talking about replacing the heat exchanger.

I like to correctly diagnose the fault and then replace just the one part which may be necessary.

Over 50% of puma flow switch problems I manage to fix without replacing anything.

Tony

 

[nycolas21]

Even if the temperature dependent flow regulator was stuck at minimu m then I dont see any reason why a correctly set up boiler shoul,d overheat.

Nor do I see why the OP has changed the flow switch and is now talking about replacing the heat exchanger.

I like to correctly diagnose the fault and then replace just the one part which may be necessary.

Over 50% of puma flow switch problems I manage to fix without replacing anything.

Tony

Mate, do you look at my boiler?