Gas Hot Water System Not Working

[johnny37]

not sure if this in the correct section but hope someone can answer.

Hot water has stopped circulating.

There are three sections: upstairs rads, downstairs rads, h/w cylinder.

Each section has a motorised valve. Unlikely they would all stop at the same time.

Boiler and pump are working but hot water does not get past the pump.

all downstairs rads are full of cold water.

all upstairs rads are full of air. Venting them does not work. they are still full of air.

When discovered last week the header tank was empty. Pushed the cistern down and it does work. Filled it again today just to see if i could bump the system. Where did the water go? Cannot see any leaks.

I know i will need to get someone in but has anyone got any ideas before i get ripped of? What is the daily rate theses days?

Thanks

[The Builder]

I;m confused, Johnboy...

When the header tank was found to be empty, the ballvalve was surely in the lower, dropped position?

In which case, it should have filled itself up again.

[johnny37]

builder: yes it is odd. when the plumber inspected the tank he said the inlet valve was partially closed. It occurs to me that if the flow entering the tank was limited eventually it would drop so low the outlet pipe may have been sucking air into the system. In my limited knowledge this should be solved by venting the rads, but it has no effect. May be a red herring.

Methyl: I have tried flicking the switch on each valve to no effect. As far as i know nothing has happened that could cut off the power to the valves

[The Builder]

Johnners, air in the system will possibly affect operation of the motorised valves.

I would replace the inlet valve in the header tank. Cheap and easy to do.

[johnny37]

forgot to mention, the h/w cylinder is cold, even though the immersion heater switch is on (ie the red light is on). Suggests to me the cylinder is full of air too.

[The Builder]

Now I'm really confused, Johnners :o(

I was talking about the header tank for the central heating. Are you saying that the header for the hot water system ran dry as well?

[johnny37]

i didnt know the cylinder has a header tank. whatever, the tank is cold with the immersion heater switch in the ON position. must be some sort of safety mechanism if the tank is empty.

[Togo]

Has your pump packed in and the system boiled dry?

[The Builder]

If your immersion cylinder is a mains pressure (unvented) type, then it won't have a header tank in the roof.

If it's the more common gravity system, then there will be a tank up there.

Even if the immersion header tank runs dry, it can't possibly result in an empty cylinder because hot water comes out of the top of the cylinder. It will always be full unless it's drained from a fitting at the bottom.

So, I guess that it's cold because the motorised valve(s) aren't operating correctly. As I mentioned earlier, fix the inlet valve in the central heating header; fill the system; purge the air; then see if the motorised valves work again.

All being well, the immersion will then get its share of heat to get the cylinder hot again.

[johnny37]

the h/w cylinder does not have a header. checked the power to the motorised valves. all correct. Guess i'll just have to wait and see what the man says.

Thanks for all your answers.

[johnny37]

found out that i am covered on my house insurance for emergency repairs to heating etc. only costs me £5 a year! Man came and found a blockage in an upside down T junction which enters the cylinder at the bottom and the boiler (i think) in the other direction. Wish I could get a diagram of all this pipework. He cut through the pipe and cleared the blockage using a very technical tool - a wire coat hanger. Resealed it with an isolation valve and the system us now working. Still some pockets of air in the system but he said this should clear over time. Advised that the system is jet cleaned but that is not part of the insurance cover. Would a Karcher do the job? I'll put that as another question.