Problem with newly fitted diaphragm...

[hooper]

I have an Ideal Mini C24 (which i believe is the same as a Biasi M90) and had the diaghram replaced today by a reliable heating engineer. The heating wouldn't come on unless you turned a hot tap on!

I was at work when the work was done, but when i got home, the house was nice and warm. When the timer clicked to turn the heating back on at tea time, nothing. Turned the hot tap on, nothing. Great. No heating OR water now!. I had a look at the boiler, removed the microswitch and turned the hot tap on. The pin that is pushed out by the diaghram is being pushed out, but very slowly. By the time it has come out enough to push the switch, the boiler has tripped. What I can do though is turn the hot tap on, and before the boiler trips, activate the switch by pressing it with a small screwdriver, firing the boiler which gives me hot water. If i leave the screwdriver activating the switch for 10- 20 seconds, i can then rehouse the switch as the pin is far enough out to keep the switch pressed in (hope that makes sense). The same is true for the central heating. So the diaghram will push the pin out far enough, it just does it too slowly, so the boiler trips before contact is made.

Could this be a hole in the new diaghram, or am i completely barking up the wrong tree?

(btw i'm waiting for the guy to call me back, i'm just curious)

 

[Gasguru]

The diaphragm could be incorrectly fitted or holed but I've yet to change a differential diaphragm. They don't normally wear that much since they only have to operate a microswitch.

Other posibilities are blockage of the drillings into the diaphragm housing, slow or blocked pump, blocked heat exchanger(s), sticking gland seal

 

[hooper]

thanks.....i thought a new diaphram was just too good to be true he left the old one which was really stretched and out of shape.

 

[tazman]

Sounds more like circulation problem rather than diverter valve diaphragm. Pump may be slow, blocked etc.

 

[hooper]

Definitely not a diaghragm problem!

Had a look at the pump, it rotates smoothly and if i get the circuit running its ok.

I've realised i made a bit of a mistake in my original post. The pin that is pushed out by the diaghragm only does so when the system is up and running, and not before ignition.

If the flow is ok once the boiler is running, why wouldn't it be ok before it fires?

 

[nickso]

did he clean whatever venturi/orifices that control the diaphragm? that would be my first guess.

 

[hooper]

not sure on that one...he did it while i was at work and i can't get hold of him. Is that something i could do myself ( i ended up checking the diaghram myself)?

 

[nickso]

yes. but it will involve draining the boiler down and removing the diapragm.

all you are looking for are one or two small holes that may be blocked up with black sludgey stuff.

 

[hooper]

a blockage looks likely...

i have put the boiler into service mode and turned on the hot tap, and when it tripped out it was showing the following error;

Faulty primary circuit (no water or absence of flow). The pump seems to be working ok, so apart from checking the diaphragm inlet, can you suggest what else i should (or could) check before i have to call an engineer?

 

[Agile]

i have put the boiler into service mode and turned on the hot tap, and when it tripped out it was showing the following error;

How do you put the boiler into "service mode" ?

I would be checking the eye of the pump first !!!

If that did not work then email me and I will sugest something else!

Tony

 

[hooper]

there are 4 dip switches on one of the pcb's. Flicking #1 to OFF then ON again puts it in service mode and from the way the 3 led's light up, you get your fault.

email sent

 

[Agile]

OK, but you can also get it permanently into what I would call diagnostic display mode by moving the rear link down one notch.

Your method only lasts for a limited time and can be achieved by moving ANY DIP switch !

Tony

 

[Garfeild]

i always change BOTH diaphragms on these,as when youve got it drained down it aint a problem,could that be the problem?

 

[Garfeild]

i always change BOTH diaphragms on these,as when youve got it drained down it aint a problem,could that be the problem?

 

[hooper]

will drain it down in a bit and have a better look at the pump.

I've had a look through the service manual and there is no mention of a DHW diaphragm. That may be on a different model (does the C24 have a magnetic assembly for dhw?). The link to the manual is here