hot water cutting out! performa 28

[berthollywood]

my potterton performa 28 keeps cutting out whilst the hot water tap is on,
the led indicator builds up to 80 then cuts out,there is no fault light being lit on the fault panel,ive recently changed the hot water temp sensor and the problem is still there......

after it cuts out it restarts after about 5 sec,ive tryed running the CH and it doesnt cut out...

ive had a plumber out and he checked gas valve which he said was ok and he indicated that it could be a fault on the pcb which he quoted me £150 to change...

The problem has gradually got worse over the last 12 months to the point that we can no longer run a hot bath..

my water pressure is really good so i dont think its anything to do with that

does anyone have any ideas? thanks for any advice given

 

[CharterGAS]

its the water section!!!! Fire the plumber he doesn't know what hes doing !!

the diaphragm in the water section is weak and needs replacing. yo can be th e diaphram its self or the valve which takes about 30 mins to change!

Its the water section!!!! also known as the pressure differential valve !!

Fire your plumbing he doesn't know what hes doing hes only guessing!!!

You can but the diaphragm buy its self or the
valve assembly which is easy to replace

 

[berthollywood]

hi,would you recomend to change the whole valve or just the diaphram,thanks

is this the part you mean,thanks

Diverter Valve Baxi DHW Flow Valve 248063 on eBay, also, Plumbing, DIY Materials, Home Garden (end time 15-Jun-08 12:13:28 BST)

 

[CharterGAS]

yes thats the part but double check with potterton on your part numbers!!!

its easier to change the valve than the diaphragm as in less time!!!!

i would get another local plumber in to give you a definite diagnoses as i can only give limited advice as im not in site!!

 

[berthollywood]

ok thanks for your help,ive been studying my installers instructions and parts list and have got the part no for a pressure differential valve diaphragm but have noticed that there is a 3 way valve diaphragm aswell,would it be either of the diaphragms that would cause the same problem or just the pressure differential valve diaphragm?

is about £60 a decent price for this part?thanks

 

[CharterGAS]

i suspect just the pressure differential diaphragm, but like i say seek local expert advice to confirm

 

[berthollywood]

i checked the diaphragm in the dhw differential valve and also the one in the 3 way valve and both are ok......

when putting the boiler back together i swapped the CH temp sensor with the DHW temp sensor,the hot water seems to be working better....well it hasnt cut out yet,but will se how it goes over the next few days

I tried to start the CH to see if that was ok,but wouldnt start,so maybe the CH temp sensor was affecting the hot water...i dont know....i will se how it goes over the next few days and post results

 

[CharterGAS]

double check the ohms reading on the sensor at a high temp the reading should be low

at cold it should be a high reading

 

[berthollywood]

double check the ohms reading on the sensor at a high temp the reading should be low

at cold it should be a high reading

I take it this is something i am going to have to call a plumber out to do?

after swapping sensors hot water is still cutting out but not as often and the water is not going as cold before it heats up again

 

[CharterGAS]

yeah get some one out
sound like it the hot water ntc and still possibly the differential valve. when you say you checked it, how did the rubber feel? still tight or a bit loose??? it maybe that the rubber has lost a bit of elasticity and causing the problem

 

[berthollywood]

rubber felt a bit loose but was not damaged in anyway,the differential valve is still operating the pressure microswitch in the normal way,and is still operating microswitch up-until hot water cuts out,if the diaphram was damaged would the micro-swith not be operated?

CH working normal,the CH return stop-tap was closed preventing the heating from running,must of been closed by plumber last week.....

ive ran the CH for about 30 min to see if it was cutting out too but didnt,gas was modulating as it should,so still left with same problem of hot water cutting out

 

[CharterGAS]

is this the performs 28 i??
re diaphragm - if the rubber is any way deteriorated no mater how minor it could be enough to fluctuate the pin which hits the micro switch there may even be a tiny hole on it!!

my best bet would be to change the hot water ntc and then see how you go. then maybe think about replacement diaphragm if you don't want to get an engineer out.

 

[gascob]

I'm pretty sure you have a partially blocked plate heat exchanger on your performa, if it was a problem with the diaphragm i don't think you would have the on/off problems you are having.. it sounds like the restriction is causing the boiler to reach temperature before it has had chance to transfer the heat to the tap water.. also make sure the low gas pressure is set correctly...

 

[berthollywood]

can i strip the plate heat exchanger down and clean it or will it need replacing?also the central heating is running fine so does that cancel low gas pressure out?

 

[gascob]

you can take the plate heat exchanger out and give it a good rinse out through a tap whilst giving it a bit of a crack with some grips or a screwdriver, you should see some chunks of debris coming out.. if you live in a hard water area it could be scaled up which you will struggle to get out(i do know people who have soaked a plate in calgon overnight though) they are easy to take out on a performa but make sure the 4 washers are intact before you put it back together or it will be leak city.... i suspect the low gas will be ok with the ch being fine...