Heating stuck on with hot water...

[andyoxon]

I have the wall thermostat right down, and the heating off at the timer, but some of the rads (with higher rad stat settings) are on (with the hot water).  I guessed this has something to do with the "Mid Position Actuator" (Drayton MA1).  I've had a look in the box, and I can see a loose ~1.5cm brass spring.  What are the options here - can I DIY anything or is it time to call the heating engineers?  Thoughts?

[mrcharly-YHT]

erm, depends on what sort of system you have.

The most common setup is a 'Y' valve diverter. These often jam up. If you post your boiler make and model we could try to find out.

The likely fix is a replacement valve, which will mean draining down your whole system.

[Gaston Lagaffe]

In my dim and distant memory I recall something similar to what I think you're describing being down to the ballcock in the loft expansion tank being stuck, ie no water in the tank.  Might be worth a quick check?

[andyoxon]

erm, depends on what sort of system you have.

The most common setup is a 'Y' valve diverter. These often jam up. If you post your boiler make and model we could try to find out.

The likely fix is a replacement valve, which will mean draining down your whole system.

Thanks.  The boiler is a Glowworm 24hxi convential condensing boiler, and we have a hotwater tank in the airing cupboard/coldwater tank in loft.  Vented I think. 

[andyoxon]

In my dim and distant memory I recall something similar to what I think you're describing being down to the ballcock in the loft expansion tank being stuck, ie no water in the tank.  Might be worth a quick check?

Ok, thanks.

[mrcharly-YHT]

erm, depends on what sort of system you have.

The most common setup is a 'Y' valve diverter. These often jam up. If you post your boiler make and model we could try to find out.

The likely fix is a replacement valve, which will mean draining down your whole system.

Thanks.  The boiler is a Glowworm 24hxi convential condensing boiler, and we have a hotwater tank in the airing cupboard/coldwater tank in loft.  Vented I think.

Ah, that is a different sort of system

There should be a motorised 3-position valve somewhere, very likely outside of the boiler and possibly adjacent to your hotwater tank. This will have a lever on it to manually set the position (hot only, heating only, select by motor).

Something like this:
http://www.discountedheating.co.uk/shop/acatalog/Horstmann_Zoneplus_22mm_3_Port_Motorised_Valve.html?language=en&currency=GBP



It is usually possible to take the motor off (disconnect from power first) and manually move the valve back and forth with a spanner. This might free up the valve.

[andyoxon]

Thanks.

This is what we have...



http://www.screwfix.com/p/drayton-ma1-679-3-3-port-motorised-valve/81844?kpid=81844&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&gclid=CJ6_w4Ks5bYCFZLKtAodW00AAw

[mrcharly-YHT]

Looks like you can push in a button at one end and lift off the motor/actuator.

I'd do that then work the valve back and forth with a spanner.

[nuttycyclist]

Thanks.

This is what we have...



http://www.screwfix.com/p/drayton-ma1-679-3-3-port-motorised-valve/81844?kpid=81844&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&gclid=CJ6_w4Ks5bYCFZLKtAodW00AAw

That is exactly what I had in the last house, and we also had one rad that was always hot.   If I turned it off the water flowed through to the second rad in the chain and made that hot.    If we turned off all the rads then the hot water flowed through the underfloor pipes only and kept the whole house hot.

Plumber changed it a few times under warrenty, but no good.   In the end he said he thought it was a crossed pipe/some other issue causing enough pressure to let water squeeze through the valve - and his only option was to lift all floors and inspect/renew all piping.

I thanked him, let him go, and then put a lovely big red shiny stop cock into the heating pipe.   Come spring, I turned the heating off electronically and then manually closed the stop cock.

[tom_e]

Definitely try the valve first, it would fit the symptoms.  If the valve works you can swap the actuator without draining the system.

But like nutty when I had similar symptoms I found the problem was in more creative pipework elsewhere.  I managed to solve it eventually with some exploratory floorboard lifting, panel cutting, pencil and paper and head scratching.

[andyoxon]

I think this spring action may be significant...

Off: 6 Seconds under Spring Return

A spring seems to have fallen off.

[Tim Hall]

The mention of a loose spring suggests something is broken in the actuator.  Actuators can be purchased separately, and replacing is a matter of an clipping the old and clipping on the new,plus wiring it in. No draining down is needed.

However, when faced with a similar situation on our system, I balked at the price of a replacement actuator. A bit of investigation revealed that the plastic nip one end of the spring hooked onto had broken off. A handy bit of brass rod, araldite and creative filing soon fixed that at no cost. That was 4 years ago I think and it's still going strong.

[Wombat]

You can get replacement actuators, a straightforward replacing the wires one by one, job.  About £50, mind you.  It is not rare for these to play up.  Mine did, so I bought a replacement actuator, ans its been fine ever since.  One day I might consider actually fitting the new actuator, its still in its box!  Many of the valve s are moderately crap, count yourself lucky you don't have a switchmaster one!

You may find it cheaper to buy the entire valve and just use the actuator, this is what I did, keeping the actual brass valve mechanism as a voodoo charm against future failure.  The whole valve is a MA1/6798-3, and the instructions are available on Drayton's website.

[Canardly]

try pushing the lever over manually