Boiler not heating hot water tank?

kittennose

stator wrote: »

Find the 3 port valve.
Turn on the HW but off the heating.
(carefully) Feel the pipe going from the 3 port valve into the HW tank. Is it warm or really hot?

Identify the type of 3 port valve motor you have. Remove the 3 port valve motor (most of them pop off by pushing a switch) and turn the 3 port valve with a large screwdriver. (It only moves a little bit, not a huge amount).
If you can manually turn the 3 port valve into the HW position and HW then flows to the HW tank, then you know the fault is either with the 3 port vale motor, or with the control system wiring to the 3 port valve.

If you can find the exactly model you can fit a like for like replacement 3 port valve motor yourself, just take careful notes and photos of the wiring before you remove the old one

Found the 3 port valve and the pipe going into the hot water tank is cold at tank side of the pipe and gets progressively hotter going towards the valve side. It's only about 1m in length.

The pipes going into the valve are red hot.

I have had the hot water on for 3 hours and no radiators have heated up.(Begs the question where is the hot water going?)

For what it's worth, when the heating or water is on, I get no resistance in the lever located on the side of the valve if I try and move it. However when the system is on, I do get resistance.

According to this youtube video: https://www.youtube.com/watch?v=Yyn_fBEH90U this is the opposite of how a working 3 way valve should work?

kittennose

Johnhowell wrote: »

Kittennose,

As per message No.5 above - Did you check the cylinder's thermostat? These can be turned down quite easily by the unwary. If the tank has an insulation blanket over it, as this can moved by the adding/taking out of bedding and blankets onto the storage shelves in the airing cupboard.

Could be the thermostat or port valve had failed and the previous owner switched over to immersion heater instead of getting it fixed.

I once noticed the hot water was getting hotter than usual and the dial had been nudged around.

Good luck

Thanks. Checked and it's on 70?

kittennose

Alex1983 wrote: »

Just realised you said it's gravity, do you mean old fashioned gravity hot water and pumped heating. If so you will have no valves and if the heating is working can only be airlock or blockage.

Yes 20 year old boiler + gravity with pump. Though it seems a 3 way valve too...

Alex1983

It can't have a 3 way valve and gravity. It's a fully pump y plan system.

If you put hot water on only and the boiler fires then i would think it has to be a fault with the 3 way valve, if you put hot water on only and the boiler doesn't fire then it's likely to the cyclinder stat or 3 way valve.

As to where the heat is going it's likely that there is abypass pipe which is taking the heat back to the boiler.

Alex1983

Can you post a picture of the airing cupboard?

I_have_spoken

Sounds like a typical Y-plan system with 3-way valve with an expansion tank in the loft with a pipe to the boiler.

Things to check

1. The cylinder will usually have a thermostat strapped around it, if this is faulty or turned right down, the programmer will not open the 3-way valve as it senses the tank is already at temp.
   
2. The programmer is faulty or isn't programmed to energise the 3-way valve
   
3. 3-way valve is stuck if it's not been in use for a while
   
4. The room thermostat has been incorrectly wired to the programmer causing it to override the HW controls in some way

>(Begs the question where is the hot water going?)<

The boiler will have a safety cut-off thermostat that is triggered if there's no circulation of water through the heat-exchanger and/or it'll be venting boiling water into the expansion tank.

getmore4less

You should hear the motorized value.

Could be the hive was not installed correctly.
Check the wiring.

Alex1983

Most valves motor to heating and spring backs to hot water.

kittennose

Alex1983 wrote: »

It can't have a 3 way valve and gravity. It's a fully pump y plan system.

If you put hot water on only and the boiler fires then i would think it has to be a fault with the 3 way valve, if you put hot water on only and the boiler doesn't fire then it's likely to the cyclinder stat or 3 way valve.

As to where the heat is going it's likely that there is abypass pipe which is taking the heat back to the boiler.

Sorry my mistake - I assumed it was a gravity fed system. Attached is a pic of the airing cupboard, red lines show the pipes that get hot when the water is on.

Thanks!

kittennose

If it helps - we had some work done some time ago which involved a guy turning most of the taps in this cupboard off - when the issue was fixed the water was turned on but he forgot the top most left tap and as a result the pump made a terrible sound.

Not sure if possibly related...I turned it on and the noise went away.