Hot water cylinder help

MSaxp

If the pressure was too high, wouldnt the fact that its going through the valve, help it bring it down below 6 bar?

I think I have left the immersion heater permanently on now, so need to go and check.

As far as the programmer/thermostat is concerned, I let the hot water taps run and turned the programmer to ON, and the boiler did fire up. I also did get some water that wasnt freezing cold, but it wasnt hot either.

Heating seems to be fine.

macman

I don't know why you expect the boiler to fire up as soon as you open a hot tap? It will only fire when the tank temp drops below the set level.
Because an unvented cylinder is potentially hazardous, you should get an RGI in to service it for you and explain what the controls are. Make sure your RGI is qualified to work on an unvented cylinder-most are not.

MSaxp

My thinking is the following:

I open the hot water taps, it requests hot water from the system.

If the water in the cylinder is cold (below the thermostat temperature) then the cylinder tells the boiler to light up (assuming programmer is ON).

If its hot, it just supplies it and the boiler doesnt know about it.

Is that not right?
With that in mind, if hot water has been off for 24+ hours, I would expect the water to be cold and the boiler to light up when i ask for hot water.

matelodave

No the boiler won't light when you turn a tap on - that only happens if you've got a combi boiler. Your systems requires either the boiler or the immersion heater to heat the water in the tank where it's stored until you need it.

If you turn the boiler or immersion heater off and the tank gets cold then it will take the best part of 2-3 hours to heat your tank up from stone cold (15 degrees) to about 60 degrees (it takes about 7-8 kwh to heat a tank full, depending on the amount of water you are heating and how much you raise the temperature) - longer if you have it hotter.

You should have a programmer or timer which turns the boiler on & off and a thermostat on the tank which tells the motorised valve to open and fire up the boiler and start the pump if the water is below tank temperature. You might find also that you have another motorised valve, controlled by a room thermostat which does the central heating. If they both demand hot water from the boiler at the same time then it will take longer for the tank to heat up

Ideally try setting your hot water timer to start heating the water about an hour before you need it and then see if it heats enough for your needs, if not increase the time until it is. Any hot water that you haven't used should remain fairly warm until the next heating cycle.

A tank like that will lose about 1-2kwh a day if you keep it hot all the time so ideally you want to try and set your timer so that you aren't keeping it hot all the time. Twice a day for about 1.5hours at a time should be enough depending on how much hot water you use.

MSaxp

Ok thank you for the hot water tank lesson. Much appreciated. As is obvious, I never had one before. Only combi boilers.

It sounds like it isnt really a surprise that I am not getting any hot water, when what i do is to keep the boiler off all day (we havent moved in yet) and just turn it on when i go to the house to do stuff in the evening.

Sounds like once we move in, I can set the timer for like 6-7am and 5-7pm, so that we can have a shower in the morning and one in the evening.

A plumber is also coming to check the valve on Thursday, but not sure what the actual impact of the leaking valve is, other than the water wastage.

matelodave

If you've got water flowing through the tundish you have a fault - get it sorted out asap - 6bar is 90psi - you do not want one of the pipes being forced apart due to over pressure or in the worst case the tank splitting.
I would be turning off the main stopcock until it was sorted out - especially if I wasn't around. It's probably only the relief valve leaking but it's better to be safe than sorry.

I had a relief valve vent off inside the house whilst I was there last year and managed to shut the water off within 30 secs or so, but a hell of a lot of water escaped in that time - it was a pressure surge in the mains coupled with a faulty relief valve. We are in a bungalow, so it was just on the ground floor in the utility room rather than upstairs in an airing cupboard.

Our normal mains water pressure sits at 3 bar regulated by the pressure reducing valve but the surge meant we had to have the pressure vessel (your silver one) emptied and repressurised after the incident.
To check if it's ok tap it gently about half to three quarters of the way up the sides - it should sound hollow. If you get a dull thud when you tap the top then it's full of water and needs to be emptied and repressurised to about 2-2.5bar.

MSaxp

Ok, I will try to turn the water mains off. I was just wondering about that, as I wasnt sure if it is a good idea to drain the cylinder, because of the leak

matelodave

You won't drain the cylinder - as soon as you turn the water off nothing will come out of the cylinder apart from a small amount from the taps if you turn them on as the system depressurises.

The only way to drain the cylinder is to use a drain valve at the bottom where the cold feed enters - your hot water comes out of the top of the cylinder with the cold feed at the bottom.

Owain_Moneysaver

Please ensure your plumber has a G3 Unvented Hot Water Systems qualification.

This is what can happen when the safety devices on an unvented cylinder fail.

http://www.youtube.com/watch?v=61uDmQF5I2E

MSaxp

yes, this does seem to be not desirable

How do i check if he is?