Help draining part CH system

[Milleniumaire]

Hi, for the second time in as many months another of the 2 port motorised valves on my CH/HW system has failed. This time it's the one controlling the supply of hot water to the HW cylinder.

It appears the actuator head has failed but I can't seem to find any similar replacement model, possibly because it's over 6 years old. The info reads; orkli 60520604. I can find models with different numbers but I've read they are not compatible with earlier versions.

I'm considering changing the valve to a Honeywell (like the CH valve that was replace a couple of months ago). However, if possible I would like to avoid having to drain down most of the central heating system. Here's a photo of my setup, the boiler is above the photo to the right and so the two vertical pipes are the flow and return:

If I were to close the magnaclean valves on the return I think this would isolate the HW flow and return and the boiler. I was thinking of draining down the boiler and then disconnecting the HW valve. I realise there will still be water in the flow and return pipes identified above, but this should prevent the water from the rest of the CH system from being drained.

It will probably be messy!

My main concern is refilling the boiler and the pipes that have just been emptied as I'm guessing there will be an air lock that I won't be able to easily get rid of. I did consider fitting a drain valve to the bottom of the flow valve that runs horizontally across the bottom of the photo, which would help.

Any thoughts on my idea for partially draining the system?

Thanks.

 

[aptsys]

Closing the Magnaclean valves will only isolate the return to the boiler. You might be able to part drain the system depending on where the cylinder and boiler are in relation to the rest of the system, or you might be ok releasing the pressure and doing a quick swap of the valve.

If you're not confident, then just drain the system down fully.

I doubt you'll get an air lock, but you may well get air collecting in the boiler which will need to be purged - either with the internal valve if fitted, or elsewhere.

 

[Milleniumaire]

Hi aptsys, thanks for your reply.

As you say, closing the Magnaclean valves will only isolate the return to the boiler, but the CH and UFH valves are normally closed, so these essentially isolate the flow to the radiators and underfloor heating, which is the majority of the system. This only leaves water in the boiler and the flow/return pipes to and through the cylinder. If I also drain the boiler, or even just close off the supply and return from/to the boiler this only leaves the flow and return pipes to the cylinder you can see in the photo.

I have a plumber friend coming round one evening next week, but may just have a go myself at the weekend, given that I've got 3 days to do it as I'm getting tired of having to manually force the HW valve to fully open each morning

 

[AGAS]

crack on and snatch it

 

[gas112]

pressurised system just close any auto air vents turn off boiler isolators then drop the pressure . no need to drain it

 

[Terry lambert]

Could just need the synchronous motor changed, looks standard to me and a five minute cheap job.

Buy a couple and keep one spare

 

[gas112]

was going to say that to terry but says he want to change to honeywell

 

[gasmanstu72]

pressurised system just close any auto air vents turn off boiler isolators then drop the pressure . no need to drain it

agreed, put a shallow square tray (cat litter tray is what i have) where that bit of pipe insulation is and change it, you shouldn't get much water,