What would make my hot water suddenly stop working and can I fix it myself?

[atticusclaw]

We have a log fuelled heating system and the furnace has been burning all day. I now have an accumulator tank containing water which is showing as being at 90 degrees.

Ran a bath for the DCs earlier today and it took a while for the hot water tank in the airing cupboard to heat up but it did heat up and the DCs had a bath. The water was still running hot when I turned off the taps and so I assumed there would be water for me a few hours later.

I've just run a bath and it's completely cold. The tank in the airing cupboard is also completely cold. I've switched on the water again but the tank in the airing cupboard is not heating up. Does anyone know what this might be and how I fix it? Might it be an airlock?

Thank you!

[PigletJohn]

what temperature does the stove show? (warning - it might be overheated).

Do you have any radiators that are hot?

Do you have a small water tank in the loft? Is there any water in it? Is it hot?

Do you have a circulating pump near the boiler or the cylinder? Is it very hot? Is it humming faintly?

Is there a hot tap running anywhere in the house?

Are you in the UK?

[PigletJohn]

What colour is the cylinder?

Is the "accumulator tank" a heatstore?

[ADishBestEatenCold]

Can your water tank be heated by ether the log fuelled system or by an immersion heater?

If so, that could be the problem.

My immersion coil shorted out, and (obviously) could not heat the water independantly. I wasn't too concerned at first, as I assumed I'd simply light a fire in the stove.
It didn't work. Even although I would not normally operate both power sources at the same time, the immersion had to be in working order for the fire to heat the water ! Maybe something to do with the thermostat .

Anyway, had to get an electrician in.

[atticusclaw]

Thanks for the replies, sorry, I fell asleep last night!

The furnace is a log gasification biomass boiler which was at about 90 degrees (in terms of water coming out) but has now cooled since the fire has gone out and there are only embers left. That feeds an accumulator tank which is now at 80ish degrees. The water exiting the accumulator is now around 69 degrees. The hot water cylinder in the airing cupboard is cold even though I've switched the water on three times now.

There is a cold water tank in the loft which is cold.

No radiators working either.

The accumulator tank is a 3000 litre akvaterm accumulator. Yes I guess its a heatstore. We heat up the furnace to heat the water in the accumulator and that then feeds with the heating and if we turn on the hot water it sends some through a coil to heat the water in the cylinder in the airing cupboard. We fire it up to about 85/90 degrees and it then drops about 7-10 degrees a day until we have to fire it up again 3-4 days later.

And yes we can use the immersion heater as an alternative so it could be something to do with that.

[PigletJohn]

What colour is the cylinder?

Did you find the pump, and is it surprisingly hot?

Is there a small cold water tank in the loft, about 2ft x 1ft x1ft? And has it got water in it? And is there thick mud in the bottom?

[atticusclaw]

The cylinder is copper. There is a pump for the shower(?). It isn't hot.

There are two adjoining cold water tanks in the loft, each about 4 ft by 2 ft by 2 ft. Both have water in to about 3/4. No mud in the bottom that I can see from peeking in with a torch but they have lids on them and are raised and so its a bit difficult to tell.

[PigletJohn]

with a copper cylinder, I expect it to be on a vented system, so there is a good chance that you have a sediment blockage. If you bleed the highest radiator in the house (preferably higher than the cylinder) does water squirt out forcefully and without dying away?

I am fairly confident that you will have a circulating pump, which should start when you turn the water heating on, to transfer heat from the thermal store to the coil in the HW cylinder. This is the other thing likely to be at fault. If you turn on the HW, this pump would get very hot if water is not circulating through it, which I think is likely.

Neither of these probable causes is a DIY fix unless you are fond of plumbing.

If it does turn out to be a sediment blockage, then as well as cutting out and replacing the blocked piece of pipe, ask the plumber to fit a System Filter, which will cost about £100 plus fitting, so is best done at the same time. If, as I think, you have a small feed and expansion tank, ask him to point it out to you, and you can paint the name on the side with a bit of white paint. If you are very lucky, the fault might be that the ballcock is old and jammed, which will be the easiest and cheapest fix.

As the causes I have in mind do not need work to be done on the thermal store or the boiler, any experienced and recommended local plumber can fix them. You will need a qualified person if it turns out to be your boiler, store or controls, though. You might prefer to go straight to your boiler maintainer, who probably has a higher charge rate.

[PigletJohn]

p.s.

if you already have a system filter, have a look to see if it has a lot of sludge in it. If not, the blockage is less likely.

[atticusclaw]

Thank you so much Pigletjohn, that is incredibly helpful