Motorised Valve Problem

[cartman1]

I have a 25 year old heating system that has functioned fine up until recently. Occasionally now I have a problem where the heating is on at the boiler but no heat is going to the radiators and the hot water from the taps gets really hot. This happens maybe once a week now.
There's a Honeywell motorised valve in the tank cupboard and if I push the metal slider on it over to the other side, I hear a whirring sound and the radiators immediately heat up, making me think that the motor itself is on the way out.

Given the symptoms and the fact that I really don't want to have to drain the system, is replacing the powerhead with one of these a reasonable fix? I seem to remember that I did this once before, maybe 12-15 years ago.

Thanks in advance.

 

[blup]

Replace the mv, it’s had a good innings

 

[cartman1]

The whole unit (ie drain the system) or just the synchron motor within it?

Even if it's only temporary I'd prefer to not have to drain the system & mess things up at this time of the year as the wife won't be happy.

 

[Justin Passing]

If there's a pimple on top of the head, you can remove the head without getting wet. I think there's a picture here in the faq's or something.
It depends on access, but even simpler is just to replace the synchron motor:

WOw the last one I bought was about 6.99. Very cheap ones are (were) poor though.

These motors fit all the heads, but on a Hwell you'll need to join the wires iirc- so leave the old motor wires long.
You'll want a skinny T10(?) screwdriver, it's easier.

 

[Mottie]

Even if it's only temporary I'd prefer to not have to drain the system & mess things up at this time of the year as the wife won't be happy.

Why not buy the whole thing, change just the head now and change the body in the summer? That should keep the wife happy.

 

[Dereekoo]

Could be a sticking micro switch, gently tap the unit with a piece of wood a few times and see if that actuates the motor

 

[Madrab]

3 port valve heads are notorious for going faulty, it's the way they work. They all eventually burn out over time. Just match up the valve head types and then change the head.

In the summer it might be an ideal to change the system over to an S plan, as long as there is enough space in and around the pipework then it's a relatively straightforward job to do. with a bit of a change to the wiring.

 

[Hugh Jaleak]

3 Port Valves are generally spring loaded to default to HW, they require powering open to CH, so would suggest the Motor has gone weak, but it could also be the Valve is worn (it's far exceeded the expected lifespan of these thing by the sound of it!), and so even a new motor may struggle and prematurely fail if the resistance of the workings is higher then the motor's designed torque output.

I'd bite the bullet after 25 years and replace the entire Valve, or even better as Madrab advises, change to S plan with 2 Valves.

 

[blup]

The whole unit (ie drain the system) or just the synchron motor within it?

Even if it's only temporary I'd prefer to not have to drain the system & mess things up at this time of the year as the wife won't be happy.

I’d do the whole unit

 

[Madrab]

I find 3 ports (and 2 ports) rarely have an issue if the system has been kept nice and clean. If the valve spindle can be easily moved end to end by hand without feeling any resistance and there's no sign of water staining from the spindle base then the valve is probably ok.

 

[Harry Bloomfield]

Given the symptoms and the fact that I really don't want to have to drain the system, is replacing the powerhead with one of these a reasonable fix? I seem to remember that I did this once before, maybe 12-15 years ago.

If you can remove the actuator head, then remove it, and check the valve below for leakage stains. If none, and if the spindle turns with your fingers, or slightly more, you are likely fine just changing the actuator. Check and order the correct actuator, they are not all the same.

Possibly, the valve is breaking up internally. So it might be worth buying both parts as a complete kit, just in case.