Is it possible for a zone valve to only half open?

[RAFTech]

Here is my problem:

I have an oil fired Grant Vortex boiler that gives me hot water and central heating to two zones of the house. There is no problem with the hot water and no problem with the Far central heating (which I think tells me that the boiler and pump is all ok?).

The Near central heating seems to only provide heat to a couple of radiators close to the system. When the heating is on and the thermostat is switched on and off it appears that the zone valve motor is operating but how can I tell that it is moving the valve fully or indeed at all? The suspect zone valve model number is: Tower 2 port VAL222MV.

Of course I could be barking up the wrong tree completely so any help or guidance would be very much appreciated.

 

[dcawkwell]

Could be with the heating off try operating the zone valves manually
and feel.
OPen the problem one manually and you should be able to latch it open.

I would suspect perhaps the zone with the problem needs the radiators balancing. The water is finding it easy to run around the nearest radiators
and back to the boiler.

 

[RAFTech]

Could be with the heating off try operating the zone valves manually
and feel.
OPen the problem one manually and you should be able to latch it open.

I would suspect perhaps the zone with the problem needs the radiators balancing. The water is finding it easy to run around the nearest radiators
and back to the boiler.

Thanks dcawkwell,

I have tried the levers on the zone valves and with the heating off they both feel the same as regards the resistance and I can latch them open. Also the motor is working when the thermostat is switched.

I see what you mean about the balancing but of course everything was working fine and now suddenly not. So, last night, I effectively shut off two of the nearest rads and that had no effect. I wonder; if I was to close all the rads and turn the heating on should I expect the feed pipe of all the rads to be hot? (As the water should be circulating in the system but not going through any rads). Would this be an effective way of testing that I have good circulation?

Again, many thanks

 

[dcawkwell]

Could be with the heating off try operating the zone valves manually
and feel.
OPen the problem one manually and you should be able to latch it open.

I would suspect perhaps the zone with the problem needs the radiators balancing. The water is finding it easy to run around the nearest radiators
and back to the boiler.

Thanks dcawkwell,

I have tried the levers on the zone valves and with the heating off they both feel the same as regards the resistance and I can latch them open. Also the motor is working when the thermostat is switched.

I see what you mean about the balancing but of course everything was working fine and now suddenly not. So, last night, I effectively shut off two of the nearest rads and that had no effect. I wonder; if I was to close all the rads and turn the heating on should I expect the feed pipe of all the rads to be hot? (As the water should be circulating in the system but not going through any rads). Would this be an effective way of testing that I have good circulation?

Again, many thanks

Sounds like there is a blockage. With all the other radiators off the radiators that aren't getting hot should get hot.

 

[RAFTech]

Ok, would you recomend draining and flushing the system then? is it likley that that would clear it?

 

[dcawkwell]

Ok, would you recomend draining and flushing the system then? is it likley that that would clear it?

Try all the other radiators off but the one you want to clear and you may find all the pump force applied to the one radiator may get it moving.
If that works attach a hose to the drain valve and keep the system topping up as it's running the flush out the system.
Otherwise it's flushing it out with mains cold applied at each of the radiator connections.

 

[RAFTech]

Ok. I think i've narrowed this one down. I've taken the motor assembly off the top of the suspect valve to expose the valve shaft. I found that the shaft was loose and would turn easily with finger and thumb. Then to my surprise the shaft came out and the hot water was pouring out! I guess i have to get a new zone valve. This knackered one is a tower 222mv but the other one is a honeywell. Think i'll buy a honeywell!

 

[Armo74]

Honeywell would be a better investment in my opinion

 

[oilboffin]

Danfoss man myself