Baxi 105HE Diverter pin explanation

[anthonyl123]

I'm trying to confirm the sequence of the operation so that I can better come back and explain the problems I'm facing.

The DHW Pin (the one at the front) comes straight out when the hot water tap is switched on, and retracts when turned off. What is the microswitch it hits actually doing?

The CH pin seems to be up all the time. I've not tested the microswitch manually nor yet attempted to manually push the pin back down, and won't until I have a better understanding of when the pin should be up, retract and what the microswitch is doing.

I understand that internally the valves divert the water flow and Central heating is working, hot water is working, most of the time.

The diverter assembly was replaced with a new unit 7 years ago.

 

[CBW]

The microswitches are to signal the boiler to fire up for the relevant demand

 

[anthonyl123]

So when the boiler is doing nothing, no pump, no burners, the CH pin should be fully retracted? When timer comes on the pump starts, there is flow through the diverter, pin extends, hits microswitch and burners fire up. When temp is reached, burners turn off, pump continues for a while. Should the pin drop immediately or is the microswitch still engaged? If no further call for heat the pump stop and pin retracts (fully)? If that is what should be happening I'll look out more carefully because I don't think that is what is happening and that is why I need a clear explanation. Thank you.

 

[gas112]

its not a CH pin its the pump proving microswitch .
When pump comes on for either CH or HW then that pin moves up activates the switch which then sends signal back to board telling board to start iggnition sequence .
If the pin constantly stays up with no CH or HW demand then it needs stripped and cleaned

 

[gas112]

And yep the pin will stay up after a demand whilst the pump over run is still running to get rid of heat and then it will drop back down when pump goes off after a few minutes

 

[anthonyl123]

The boiler has long been prone to Error 60 especially when the shower is on. Though after the shower has been on a while it seems to be ok. When the CH went on a month or so back Error 60s' were coming up at least once, and maybe twice, in 24hrs. An Off/On generally got rid of the error for a few more hours. Engineer came last Friday and thought it was a furred up heat exchanger and injected some Fernox Cleaner Express F3. He said to leave the boiler running at a fairly high temp continuously for 3 days. Again no more than 24hrs without Error 60. On Monday turned temperature down (it was 23deg in the house!) and set the inbuilt timer to give breaks every couple of hours, resulting in some improvement. I noticed the pressure was down a little bit and then opened the front panel to expose the diverter valve and there was a drop of water on the DHW pin. Running the hot water tap induced another drop. Topped up about 0.5 bar to just under 1.0 bar. Boiler has been fine now for ~48hrs.

I don't think I'm up to stripping and cleaning the diverter though I do have the old one to experiment on. The guy who put it in 7years ago created as many problems as he fixed. Friday's guy didn't even look at the diverter. I don't know what the Pin behaviour was before the Fernox. I had intended to have a new boiler over the summer but for various reasons it didn't happen and now I'd like to "limp" through this winter and have it done next Spring. I'm not confident I can find someone who I will be happy with but that's a separate issue.

As the boiler is more or less working ok with the CH (pump proving microswitch ) pin apparently engaged* all the time what harm is being done? On Friday I will have a closer look to see if it is *engaged or just retracting enough to clear the microswitch. Thanks.

 

[gas112]

look at your spare ... 4 little screws hold the top section to body
take them out and you have a pin attached to a bearing plate even a very slight amount of crude on that pin can cause it to stick needs cleaned with wire wool and silicone grease smeered on it
you then have a diaphragm if you remove that under it in the centre is a small hole this can also slightly block and needs cleared out .
All this can be done in situ without removing anything else .
Small bundy tube at the back also needs removing when in situ