Alpha CB28
- Thread starter stevemcn
- Start date
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As a service agent when I encountered this I used a hacksaw blade to make a slot then used a flat screwdriver, failing that there is a small brass part beneath with another similar screw undo that one instead take both parts off together and drill it out on the bench.
Alpha didn't let us drill and tap it, we had to fit a new brass body if we drilled it out. This is because they didn't want a claim. there is mains water pressure held back by the job that screw does.
It is a PITA part of the job.
Not sure why you need to remove the DV. If you did the test I described you will know if you need the diaphragm or the microswitch. You can change the diaphragm from the right after removal of pump (which is easy job by comparrison, need 2 new 1" fibre washers for pump) You need a new 1/2 " fibre washer (not tap cpnnector washers decent boiler fibre washers) for the plate heat exchanger to Water section of diverter valve union. IF memory serves me well you do need to loosten off all the plate unions. Then undo the cheese head screws holding the two shels of the water section together hold tight against the spring, replace diaphragm.
Though I expect it's more likely to be your microswitch which you just flip off with a small screwdriver to change. Make sure new one is bedded properly.
I described already how to test.
Alpha didn't let us drill and tap it, we had to fit a new brass body if we drilled it out. This is because they didn't want a claim. there is mains water pressure held back by the job that screw does.
It is a PITA part of the job.
Not sure why you need to remove the DV. If you did the test I described you will know if you need the diaphragm or the microswitch. You can change the diaphragm from the right after removal of pump (which is easy job by comparrison, need 2 new 1" fibre washers for pump) You need a new 1/2 " fibre washer (not tap cpnnector washers decent boiler fibre washers) for the plate heat exchanger to Water section of diverter valve union. IF memory serves me well you do need to loosten off all the plate unions. Then undo the cheese head screws holding the two shels of the water section together hold tight against the spring, replace diaphragm.
Though I expect it's more likely to be your microswitch which you just flip off with a small screwdriver to change. Make sure new one is bedded properly.
I described already how to test.
Access is clumbsy you need boiler engineers plethora of tools and skills initiative drive and sense of awareness while working or it can go horrible wrong and without water until experts arrive if not flooded out. Alpha engineer fix that boiler in less than an hour, if it's microswitch in 2 minutes.
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Hi Paul... the chap who was fixing the boiler has had to shoot of to spain to sort out his ill mother inlaw, so now it is back to me. I have changed the microswitch, your right, it only takes a minute. I have bought diaphragm kit and am eager to fit. I was informed to remove heat exchanger & valve but as I cannot remove the thing I got to thinking about the pump side, as you rightly say I can gain access from this side. Looking at it it looks as if there are a couple of nuts, one on top and one below.
When I finaaly get to undo diaphragm housing does anything ping out of it(not sure ifit is spring loaded). Paul, your information is really valued.
Do you think it`s abit late in the day to attempt this ? how long should it take.
When I finaaly get to undo diaphragm housing does anything ping out of it(not sure ifit is spring loaded). Paul, your information is really valued.
Do you think it`s abit late in the day to attempt this ? how long should it take.
You can usually trust the flow and return isolators not to leak afterwards on this boiler so close them, drain boiler with the purpose made drain accessed from underneath middle/right i had a box spanner but holding door flap right you can get it with grips.
Undo pump unions, remove pump.
Undo right shell union with plate maybe loosten other unions to assist in reassemply afterwards. Undo all cheese head screws, holding back against very strong spring.
Yes it will fly apart like a jackinabox.
Remember which way the preassimbled diaphragm spring pushrod assembly went it, there is one further loose spring remember where it goes.
Biggest first attempt person mistake is not to centre the new asembly so that it will leak. THe edge of the diaphragm provides the seal between the two shells. Get it propely centred and as I said the whole DV plate assembly is clumbsy to say the least. need to loosten off all nuts to plate and possible free it where there is no nut by working it so that you can get sufficiently correct angle to start the one nut you have fully undone then retighten all together so to speak.
It's not that bad just one of the nuts to get on it you end up using grips backwards, but if fibre washer good doesn't have to be too tight.
The two pats which use orings need a quality red coloured o ring and at the top of the pipe to the primary heeat exchanger there is another which may leak following the disturbance.
In short were I doing job I would have all seals and would renew all. In your case may get some drips until your plumber returns. Not the end of the world.
Undo pump unions, remove pump.
Undo right shell union with plate maybe loosten other unions to assist in reassemply afterwards. Undo all cheese head screws, holding back against very strong spring.
Yes it will fly apart like a jackinabox.
Remember which way the preassimbled diaphragm spring pushrod assembly went it, there is one further loose spring remember where it goes.
Biggest first attempt person mistake is not to centre the new asembly so that it will leak. THe edge of the diaphragm provides the seal between the two shells. Get it propely centred and as I said the whole DV plate assembly is clumbsy to say the least. need to loosten off all nuts to plate and possible free it where there is no nut by working it so that you can get sufficiently correct angle to start the one nut you have fully undone then retighten all together so to speak.
It's not that bad just one of the nuts to get on it you end up using grips backwards, but if fibre washer good doesn't have to be too tight.
The two pats which use orings need a quality red coloured o ring and at the top of the pipe to the primary heeat exchanger there is another which may leak following the disturbance.
In short were I doing job I would have all seals and would renew all. In your case may get some drips until your plumber returns. Not the end of the world.
Thanks Paul, I am not going to try it tonight, loaded up with man flu.
Funny you should mention possible leak on heat exchanger, by the looks of it it has been weeping since installation, tightened it up last week now no leak. I`m looking forward to this, there is not much I will be beaten on. But if you are passing my house........
Funny you should mention possible leak on heat exchanger, by the looks of it it has been weeping since installation, tightened it up last week now no leak. I`m looking forward to this, there is not much I will be beaten on. But if you are passing my house........
Finally got round to changing diaphragm today, taking the pump off much easier than trying to take diverter valve off, thanks Paul for that idea. Did not even take an hour to do. However, now the boiler fires up on hot water setting ( wouldn`t before ) but still no hot water, luke warm from taps cold from shower. I was just wondering whether I put the thing in correctly. The diaphragm is on a spindle with more spindle at one side of the diaphragm than the other. I am pretty sure when I took it out that most of the spindle went to diverter valve side & this is how I reassembled it.....I suppose it could be the DV itself that has gone into up yours mode or I could look at the thirmisters again, what do you think.
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