Heating but no hot water

[rh2705]

A couple of days ago we noticed our hot water was tepid, then it just stayed cold.

Timer hasn't been fiddled with by the kids and when I select override for HW the boiler kicks in sure enough but quickly shuts off again.

When I feel the inlet and outlet of the tank heating coil, when I force override (HW) the top feed gets red hot very quickly, but the bottom pipe (the one connected to the motorised valve) stays cold.

Any ideas?

busted valve???
Air lock???

When I lower the stat temp on the tank I can hear the motorised valve whirring shut, but increasing the stat temp I hear nothing. The manual lever on the valve is loose and won't hook into the little slot when the stat is on normal temp, but as soon as the stat is lowered and the valve shuts it will slide under tension and sit in the little groove no problem - don't know if this is significant or not.

Any ideas as to how to fix very gratefully received - a few years ago I phoned several plumbers for HW but no heating I didn't get much enthusiasm from any of them to want to rush round and fix it - so any DIY fixes you can suggest would be enormously appreciated.

 

[picasso]

check that there is water in the small tank in your loft

 

[bengasman]

Is there a gate valve anywhere near the cylinder?

 

[rh2705]

I'll check tank in the morning - yes there is a gate valve which shuts off the supply from the small CH header tank - it connects directly to the bottom tank heater coil pipe after the 2 port valve, going down into the boiler in kithchen downstairs (tank is upstairs directly above boiler in airing+ cupboard).

(The gate valve is fully open)

 

[bengasman]

Should have specified, gatevalve on a flow or return valve; can be a bypass (should be almost shut) or flow limiter on coil connection.

 

[rh2705]

Nope - nothing like that - coil entry and exit are straight through runs of pipe and both disappear through the floor down to the boiler.

 

[bengasman]

Is the heating off when you run the dhw? Off at the timer AND off at the valve?

 

[rh2705]

Many thanks for your replies so far - most appreciated!

Just had a look in the loft - CH header tank is full

I've left the timer on HW OVERRIDE all night (CH OFF) and hot water temp is about 20­ºC at a guess (ie - NOT HOT!)

Nearest Rad to the boiler is in the bathroom and its toasting hot (CH OFF!).

I wouldn't know how to tell if the CH is off at the valve - theres six wires going into it: Live, Earth and Neutral plus one going to the tank stat, one to the room stat and the other one is a live to the boiler.

Is it worth closing a lockshield valve to the nearest Rad to see what happens?

 

[picasso]

tie up the ball valve in the small tank, then drain off some water from the system to see if the water level drops , I suspect the cold feed is blocked, make sure the boiler is switched off

 

[bengasman]

Nearest Rad to the boiler is in the bathroom and its toasting hot (CH OFF!).

In the olden days it was considered clever to stick the bathroom rad on he dhw circuit; turn it off for the moment, as it could well be "stealing" the flow from the cylinder.

I wouldn't know how to tell if the CH is off at the valve -

If it is off, the little lever on the ch valve will be hard to move as it is held in place by a spring. If you can move it back and forth effortlessly with one finger, the valve is either on, or broken.

 

[rh2705]

picasso it looks as though you have nailed it! drained off a good pint or three and the water level in the small tank has remained totally static.

As far as I can tell the pipe at the bottom of the CH tank goes directly to the gate valve mentioned above.

I risked loosening the bottom compression joint on the gate valve expecting a drip drip drip but nothing at all even when I loosened it off completely!

A ton of rags round the joint and I separated the valve from the pipe - guess what? NOTHING!!!!

Going to Wickes in a minute to try a new gate valve - watch this space!!!

 

[rh2705]

Fixed!!!!

I can thoroughly recommend Wickes pipe freezing kit - worked a treat!

The gate valve was clogged up with brownish residue of some sort - put a new valve in anyway - as soon as the ice plug broke down I could hear a very reassuring gluggidy glug glug glug as the supply filled up the pipes.

I've since run a complete bath and the tank is still roasting hot!

Pity theres no 'buy e-pint' button on each response - I owe you all one!

So very grateful its fixed now - Thanks everyone!

 

[bengasman]

If it was gunked up, you defo need to clean your system; plenty info in FAQ and wiki.
Sludge kills boilers.

 

[picasso]

another satisfied customer, happy to hear its fixed

 

[rh2705]

If it was gunked up, you defo need to clean your system; plenty info in FAQ and wiki.
Sludge kills boilers.

Thanks - I will definitely look into this!