Problems after change in mid position valve

Hi,

I'm new to these forums but have had a lot of good advice from them over the years. I'm comfortable with a lot of DIY but I'm quite happy to call in the professionals when needed.

I have a fully pumped sundial Y plan system in a small house (6 rads).

Boiler is a Worcester Greenstar 15Ri fitted in 2005.
Controller is a Drayton LP112 fitted at same time.

Last week I found my old Siemens 3PMP-R22 mid position switch made a loud clunking noise when the hot water was off or up to temperature. This continued about every second until the system was fired up again to head the hot water.

After research I decided the valve was likely broken and read that a Honeywell V4073A would be a better quality replacement. I had no problems swapping the valves over and wired the 5 wires from the Honeywell to exactly the same places on the connectors that the Siemens was attached to. (There is no standard junction box - just a box full of sections of wire connector block).

New valve works ok - HW on own is fine, Rads on own are fine. Responds correctly to both thermostats. When both HW and Rads on they are fine - so new valve seems good.

Problem now is when the system is up to temperature and stats tell it to turn off OR the programmed ON time expires and controller tells system to turn off - the boiler goes off for a few seconds, then comes on again. It ignites and pump runs even though the HW and Heating is "off" or the temperatures is above that set on the stats. After a while the boiler goes off again, then on again after a few seconds. Eventually it will stop and the blue light flashes - it is off then briefly flashes on.

Manual for the boiler says that this indicates "ignition lockout".

I think the next step is to carefully check the wiring to make sure it is wired correctly and that nothing has come loose when I changed the valve.

Has anyone had this same issue before? (boiler turning off briefly then starting again and igniting even though the controller has HW and Rads off OR the thermostats are both at the set temperature)

Is checking the wiring the next step?

Many thanks for any advice

Dave

The Greenstar Ri are sensitive to a Y Plan system anything from 70v to 110v usually from the grey wire, hot water off causes the boiler to fire. There is a kit available RC Device part number 8-716-109-275-0.

+1 for above. They detect a back feed from the valve and the kit contains a resistor that fits across the boiler to take this affect out. It's a common fault hence why Worcester made their own kit. You can do it yourself if you want.

Jon

Great advice from gas2air. Follow it.

Thanks Gas2Air, great advice. I've searched around and found this part for sale in a few places.

I've found a discussion on ukplumbersforum that mentions it and how to fit it - "this is fitted between Switched Live and Neutral (the leads either way round)" - also "switched live (3rd on RHS on ST2) and nuetral (3rd on RHS on ST1) Page 47 on my Greenstar Ri manual shows the circuit board digm. No more annoying clicks and lock outs". (included here in case it helps anyone else)

I'll get one of these and connect it as described - I've had a look in the boiler and it looks very simple.

I've been through all the wiring in the junction box and made sure there are no loose wires - all secured and no effect at all. As expected after your advice.

Thanks Jon and Jeff for your comments.

Dave

Thanks again for this advice - I bought the RC Device part and fitted as described above - works like a charm - no problems at all since.

I've noticed that the Honeywell valve is much better than the Siemens one it replaced - with the old one the upstairs radiators got warm with just the CH on - now they don't.

Thanks for getting back to us. Always nice to know the results.

Glad you're sorted

Jon

Old thread I know !
Does anyone have a link/information on how to fit this part ?
Will it cause any problems if left ?
Thanks

Just to confirm how useful this thread is. Our system had a Drayton 3-way diverter valve which seemed to need replacing far too often. From then on with the Honeywell replacement our Ri18 boiler kept clicking as if trying to fire up when there was no need. Finally, on learning that this is a known fault with older boilers I bought the Worcester part. There were no instructions and it looks like a fancy capacitor with two wires attached. Our service engineer was aware of the clicking issue but had always previously fitted an updated motherboard as solution. He agreed to fit the part and after phoning for support from Worcester Bosch he did the job in a very short time. The clicking is gone and all is working well. Expect this to cost £70 - £80 in total but well worth it. Worcester will only sell the part to Gas Safe registered personnel but there's no difficulty in getting it elsewhere.
As to whether leaving this issue unresolved will do any damage I don't know but it seems very likely to be a bad idea. Our Worcester Bosch Ri18 has been working fine with no other issues for over 14 years. It's a great boiler.

The fault is really with the design of some three way valves which give a smaller residual voltage on the output when the valve is not intentionally powered.

Most boilers will not respond to this low voltage but unfortunately the Worcester Ri boilers can and so the solution is to add an RC series combination to neutral. Probably about 0.1 uF and 300 ohms in series with the capacitor rated for mains voltage.

Another aspect to ensure the system and boiler work well for a long time is that the pump must be controlled by the boiler to ensure that pump over run is operating correctly.

A friend of mine must have been drunk a few months ago and on the spur of the moment had his old Potterton boiler replaced by a Worcester 18Ri. Huge increase in efficiency. But with the programmer and pump upstairs he did not have enough wires and fitted it without the boiler controlling the pump. I have tried to make him understand why it needs to be corrected but he seems to have a mental block about lifting floorboards. But he fitted the old Potty himself about 40 years ago.

Agile said:

The fault is really with the design of some three way valves which give a smaller residual voltage on the output when the valve is not intentionally powered.

Most boilers will not respond to this low voltage but unfortunately the Worcester Ri boilers can and so the solution is to add an RC series combination to neutral. Probably about 0.1 uF and 300 ohms in series with the capacitor rated for mains voltage.

Another aspect to ensure the system and boiler work well for a long time is that the pump must be controlled by the boiler to ensure that pump over run is operating correctly.

A friend of mine must have been drunk a few months ago and on the spur of the moment had his old Potterton boiler replaced by a Worcester 18Ri. Huge increase in efficiency. But with the programmer and pump upstairs he did not have enough wires and fitted it without the boiler controlling the pump. I have tried to make him understand why it needs to be corrected but he seems to have a mental block about lifting floorboards. But he fitted the old Potty himself about 40 years ago.

Click to expand...

I'm a bit sceptical about mid-position valves. I've always had W-plan with either/or valve and HW preference, and it's never been a noticeable problem, even with plenty of HW usage and a well furred up cylinder coil. The W-plan valve actuator is cheaper, simpler to wire and more reliable, as well as not giving the problems discussed here.
And if weather compensation is used the valve must be either/or, for reasons everybody knows.