Ideal S28 boiler diagnosis req'd

[1norab]

Hi, My boiler is an Ideal S28 system boiler. My problem is the DHW isn't working, CH is ok. Both the motorised valves on the CH and DHW seem ok.
With the help from some good people on this site, I have managed to spot the problem but...

With CH on, call for DHW and the boiler shuts down. If I call for DHW alone, the pump/fan and Motorised valve kick in but just as you think the boiler is going to fire up, it doesn't.
I have removed the flow switch and when i manually press the switch the Boiler fires up in all 3 positions (CH/DHW/CH+DHW).
With the switch back in it's place, I watched the pin protrude from the diaphram in all 3 positions... call for CH = protrudes 11mm. Call for DHW = protrudes only 8mm. CH on, then call for DHW the pin retracts back (3mm) to 8mm.
The pin disengages from the switch when DHW is called to join the CH. The pin doesn't reach the switch when only DHW is called.
What is causing this to happen. Any advice or suggestions would be most welcome.

 

[Agile]

I dont know why you have started a new thread!

Have you checked all those things I asked you to look at?

To remind you:-

If what you say is really correct then you have a blockage in the primary HE of the boiler

OR

much more likely dirt in the eye of the pump!

OR

very unlikely a problem with the flow switch diaphragm

OR

rare, but possible, the bypass screw on the left of the flow switch diaphragm is loose and needs to be screwed fully in.


Have you done those or are you mistrusting my advice and trying to start all over again and hoping to avoid doing anything?

Tony

 

[1norab]

I started a new thread because I wanted to check something with you first so I left a reply on Monday and checked the site for any feedback and didn't get any. So I assumed (wrongly) that my original thread was lost/forgotten amongst all the new threads. I am new to this Forum thing and ask forgiveness.
Please dont assume I ignored your advice and hoping to avoid doing anything will certainly not fix my problem!
After your last advice I spotted the following and wondered if this shed any light on the problem...

I have just rechecked the test using the plastic rod pressing into the flow switch. It took the boiler 4 attempts to fire up for HW (i didn't release the pressure on the switch at all). But it did fire up!
What I then noticed was that the pin protruded approx. 11mm. when CH only was pressed.
If I pressed for HW only it came out approx. 8mm.
If I pressed for CH and then pressed for HW to come on 30 seconds later, the pin would retract to 8mm again!!? The pin retracting 3mm is disconnecting the switch?
I checked the diaphragm which looks ok. I looked for the bypass screw and couldn't find one?
I wondered if the Primary HE and the Pump diagnosis you gave would affect the CH as well as the DHW, because the CH is ok

 

[Agile]

Yes I know about the pin! I had already worked out that it was not protruding in all modes. You could have done that too from the diagnostic codes. Now you have to follow my advice if you want to find out whats wrong.

Its better that you dont select which tests you do because your reasoning is flawed. Stick with my tests and I will help you to find the problem. I repair boilers every day!

The bypass screw is on the left of the flow switch diaphragm and projects through the hole in the diaphragm. It has a slotted head and a hole through the middle.

You should have been checking the pump at the same time while the boiler was drained! Saves time!

Its odd that you checked something I said was less likely but did not check the pump which I said was more likely!

Tony

 

[1norab]

Hi, I took off the pump and a piece of rubber the size/shape of a half penny piece fell out. I also found the screw on the diaphragm to be a fair bit loose, so I have tightened that up. Thinking the problem should be sorted, I refilled the system and tried it. The pin still failed to engage the flow switch on DHW and now it fails on the CH also.
I have taken off the primary HE and flushed it through and found no problems.

 

[1norab]

Do you think it could be the pump not working to its normal capacity?

 

[Agile]

Yes, I thought there was that piece of rubber in the pump!

Are you sure that you have fuly bled all the air including from the pump screw? It can take over 20 minutes alternating from CH to DHW to clear all the air!

I still have two other possibilities but want to be sure you have emininated all the air first!

Tony

 

[1norab]

I have refilled the sytsem and bled the rads, topped up again and bled once more (just to be sure). Also opened up the pump screw a few times during the process and release air each time until now nothing comes out.
Then tried to fire up the boiler but its still the same.
Is there anything more I should be doing to bleed the system of air?

 

[Agile]

Is air being ejected by the AAV ?

Have you repeatedly run the boiler alternately on CH/DHW as this aids clearing air.

Are you sure that you have not damaged the flow switch diaphragm?

Tony

 

[1norab]

There is no air coming from the AAV. I have run the boiler from CH to DHW several times and rebled the sytem to clear any air.
As for the diaphragm, there seems to be more slack in it than I would've imagined should be there, it's very soft and I would have guessed it to be tighter? When I push the pin back manually a very small droplet of water hangs off the end of the pin.
I have since noiticed the same droplet sometimes (not always) appears on its own on the end of the pin, without any interference from me.
There doesn't appear to be any pin holes in the diaphragm that I can see? I have gently pushed the diaphragm in using my fingers and the only place drops of water come out of is the bypass screw hole.

 

[Agile]

It can take 20 minutes and about 30-40 operations of the CH/DHW demand to clear the air!

If you are really sure that all the air is ejected you can run a kitchen tap at half flow and manually operate the flow switch and see what the pin does after the boiler heats up. That sometimes drives the air out!

Also push the pin slowly in and see if that helps! It sounds as if the pin gland is leaking a little!

Do that first before before my next instruction.

Tony

 

[1norab]

Tony, SUCCESS Both the CH and DHW are now working as it should. I bled the system once more this morning and done as you said re: switched from CH to DHW 30-40 times for 20mins or so and then also run the tap while the boiler was on. The pin doesn't appear to be leaking and it's a lot harder to push back in than it was.
Thank you so much for your patience and invaluable help, it's going to be so nice to come home from work and not have to think about my boiler
Would you say the problem arose from the piece of rubber in the pump and the fact that the bypass screw was loose.
Would you hazard a guess that my pump may be on its way out as bits of rubber are falling off?

 

[Agile]

Nothing in the pump is made of rubber!

The problem was probably a combination of the bit of rubber and the flow switch screw. I cannot guess which was the greatest contributor.

I hope that you and anyone else reading will have noticed that when I ask you to get rid of the air and that it may take 20 minutes then you really do need to spend 20 minutes!!!

Tony