3 way valve not working got hot water no heating help

[Nursek]

I have an old Potterton suprima boiler with a hot water tank and pump. We have hot water but no heating, the light on the boiler is showing amber (no call to heat) I have been told that this is likely due to the 3 way valve or motor on it (Myson Power Extra). I am wondering whether to try and change the Myson unit myself or not
We are very short of cash at the moment so getting a new boiler or paying for expensive repair would be practically impossible. I'm also struggling to find a plumber willing to deal with such an old system.
Can anyone help?
Thanks
Kate

 

[ShaunCorbs]

Room stat calling / 30 dc ?

Hot water is turning the boiler on correct eg the boiler fires up and heats the cylinder?

 

[fowlerboi]

How good are you with a multimeter? Ideally you would want to do a test on the whole system before randomly changing components.

You can take a stab at changing the valve/ head which would be the easiest option but if its not the problem you incur the cost of the valve and time doing it on top of what other fixes need doing.

 

[Nursek]

Room stat calling / 30 dc ?

Hot water is turning the boiler on correct eg the boiler fires up and heats the cylinder?

Yes it does no problem with hot water at all

 

[Nursek]

How good are you with a multimeter? Ideally you would want to do a test on the whole system before randomly changing components.

You can take a stab at changing the valve/ head which would be the easiest option but if its not the problem you incur the cost of the valve and time doing it on top of what other fixes need doing.

I'd like to try change the valve head as a first step, would it be most likely that was the issue?

 

[fowlerboi]

Its almost a straight guess. While the valves have a higher failure rate than the room stat or programmer we have no idea what condition they are in.

The other aspect is that 3port valves often need the whole valve changing not just the head otherwise they fail again within a year or 2. Your valve isn't a particularly well branded one so I have no idea on the failure rate of them as I've just never seen one.

You pay your money and take your choice

 

[John.g]

With HW only selected pull the manual lever on the side of the actuator and latch it in, if both HW and rads get hot, unlatch it and then try HW & CH, if no CH then more than likely the actuator.

 

[Nursek]

Its almost a straight guess. While the valves have a higher failure rate than the room stat or programmer we have no idea what condition they are in.

The other aspect is that 3port valves often need the whole valve changing not just the head otherwise they fail again within a year or 2. Your valve isn't a particularly well branded one so I have no idea on the failure rate of them as I've just never seen one.

You pay your money and take your choice

Thanks, I think I'll give it a try, if it needs the valve changing as well I'll have to get a plumber in as definitely not confident or competent to drain the system myself. The Myson unit is from a local company, might go and see them if they have any tips etc.

 

[Nursek]

With HW only selected pull the manual lever on the side of the actuator and latch it in, if both HW and rads get hot, unlatch it and then try HW & CH, if no CH then more than likely the actuator.

I will try that, thanks. Could I not just leave it on manual if that gets the CH hot?

 

[John.g]

Yes, you could, but you would have to set the HW cylinder stat very high to keep the boiler firing, otherwise once the cylinder stat is satisfied then the boiler stops firing so no CH., If you are worried about a high HW temperature (children etc) then as a temporary measure you could set the boiler flow temperature to say 60C/65C. and the cylinder stat to 70C,

 

[Nursek]

Yes, you could, but you would have to set the HW cylinder stat very high to keep the boiler firing, otherwise once the cylinder stat is satisfied then the boiler stops firing so no CH., If you are worried about a high HW temperature (children etc) then as a temporary measure you could set the boiler flow temperature to say 60C/65C. and the cylinder stat to 70C,

Ok so it's not really a long term solution then really I think

 

[Basher]

Ok so it's not really a long term solution then really I think

You could try making an offer

Myson Power head Extra 322 Actuactor | eBay

<p dir="ltr" style="margin-top:0; margin-bottom:0;">Myson power head actuator 322 new and not used but box worn</p>

www.ebay.co.uk

There are complete one's with the valve for a bit more

Or the valve separately:

Myson 22mm 3 Port Zone Diverter Valve Body Only, MDV22 | eBay

Myson 22mm 3 Port Zone Diverter Valve Body Only Myson 3 port diverter valve. 22mm Compression fitting. For use with Myson MPE322 3 Port Motorised Valve

www.ebay.co.uk

You need to check these are the right model - I think they are but I'm not promising!

 

[Deleted member 120897]

Not much wrong with Myson, not a terrible make, and not known afaik for high failure rate. You can get good and bad in everything and Honeywell seemed to nosedive when they changed to Resideo. You might be better investing in a multimeter or 2 pole voltage indicator. You could also try @John.g ’s method.

 

[Nursek]

With HW only selected pull the manual lever on the side of the actuator and latch it in, if both HW and rads get hot, unlatch it and then try HW & CH, if no CH then more than likely the actuator.

I finally got a chance to try this! So I tried this and with the lever set at manual HW and CH work. When I set it back to auto still HW and CH work?! Does this mean the problem is fixed? Maybe the valve for CH was jammed and now it's released? Or does this mean I've still likely got a dodgy actuator? Thanks 👍

 

[John.g]

So, (Lever on Auto) does HW work on its own?, valve doesnt move and if HW&CH selected (roomstat turned up) does it go to mid position? anf if CH only selected does it go fully over to CH only?.