No hot water, but central heating working

[jxm]

We have a conventional boiler with a hot water cylinder. But we're not getting any hot water, it's just coming out luke warm, but the central heating is working fine.

Looking around online it seems like the most likely case is the motorised 3 way diverter valve. Indeed, with the hot water and central heating switched on at the control panel if I touch the 3 pipes then the input pipe is very hot, the A pipe (to heating) is very hot and the B pipe (to water tank) is warm (although getting less warm the further from the valve).

I've seen a video that suggests if you have hot water but no central heating then you can switch the valve from auto to manual. However, I tried that and it made no difference so I assume it only works that way round (no heating), and not the other (no hot water).

So in the short term is there anything I can do to fix this? (ps. I tried switching on the heater in the water tank, but keeps tripping the RCD in my fuse box, so much for that 'backup').

Also, what are the chance the fault is with the 'head' part (and what are the chances I can get one from B&Q)? I'm confident enough with electrics to replace the head if I can get one on a Sunday, but replacing the whole unit is beyond me.

 

[kay-jay]

firstly when you move the lever open manually, there is a little hook in the slot that you need to catch the lever in. this will ensure the valve is in the open position and should work until you can fix it.

secondly if you remove the head from the valve you can see if the spindle on the valve moves freely, if it does then just change the head, if its stiff replace the lot.

 

[kay-jay]

screwfix best bet for a sunday. check stock online first

 

[jxm]

firstly when you move the lever open manually, there is a little hook in the slot that you need to catch the lever in. this will ensure the valve is in the open position and should work until you can fix it..

Does this work both ways? I heard that this is the fix when the central heating isn't working, but it was unclear about if the hot water wasn't working (and I can't really see how it could work both ways if there is only one manual setting? surely there would have to be a setting for manual water and another for manual heating...?)

secondly if you remove the head from the valve you can see if the spindle on the valve moves freely, if it does then just change the head, if its stiff replace the lot.

Can this be done without switching off the electricity?

 

[kay-jay]

Yes

Yes, but you need to isolate the heating circuit. There should be a swivhed fused spur adjacent to your timevlock/programmer for this purpose. You should check the wiring centre with a neon screwdriver/voltage tester/multimeter to be sure

 

[kris]

You might find that the heads working fine but if the body has started to cease then the motor sometimes struggle to turn the paddle, you need to remove the head first and check if the paddle is loose and moving freely, sometimes bit of wd40 or grease added to paddle to help, if it's the head then make sure you get the correct replacement as theyre not all universal,

 

[Mike Jackson]

You need to do some more checking before diagnosing a faulty 3 port valve head. It's unusual for it to fail in a position which leaves you with no hot water as the hot water is the rest position. My first thought would be programmer or cylinder stat. Time to get busy with the multimeter.

 

[Taffman]

I agree with Mike with this.

 

[gassafe]

I went to a job exactly as you say 2 weeks ago, the motor in the 3 port was seized in the heating position.
If you turn the power off to the ch system the valve should close & the lever on the 3 port should have resistance on it to ope the valve manually. If its all slack then it may be seized in the heating posistion!

 

[jxm]

You might find that the heads working fine but if the body has started to cease then the motor sometimes struggle to turn the paddle, you need to remove the head first and check if the paddle is loose and moving freely, sometimes bit of wd40 or grease added to paddle to help, if it's the head then make sure you get the correct replacement as theyre not all universal,

I've taken the cover off and looked inside. The manual/auto lever doesn't appear to be doing anything - nothing else inside appears to move when I operate it. Also, if the valve has seized would you expect to hear the motor attempt to turn? Because the motor is doing nothing - no noise, no attempted movement.

 

[jxm]

If you turn the power off to the ch system the valve should close & the lever on the 3 port should have resistance on it to ope the valve manually. If its all slack then it may be seized in the heating posistion!

Just to be clear if the valve is "closed" does that mean it's going to CH or the water heater?

 

[kay-jay]

normal (un energised) position is open to hot water closed to heating.

the lever not moving the motor/no resistance may be because you are calling for heat? please confirm that when you are moving the lever the programmer is set to off for both heating and water. if there is still no resistance on the lever then the motor is goosed.

 

[jxm]

The plumber has just fixed it. It was the 3 way valve, totally
apparently, including the level.