Hot Cold Water Storage Cistern

[ajtomlins]

Hi

I have an indirect hot water system, comprising of boiler/cylinder/large cold water cistern/header tank for radiators, the two issues that I am experiencing are;

1) The overflow from the large cold water cistern keeps frequently running, sometimes it takes four/five days for this to occur but a lot of the time it occurs twice a day. I have tweaked it so many times I have lost count.

2) I have noticed that the water in the cold water cistern gets quite warm, with lots of condensation forming on the roof of the cistern, one of my friends commented that this should not be the case and I wonder whether the two issues are linked.

The electronic timer is set to Central Heating Off, Hot Water On.

I have been hearing the circulating pump coming on and off but am led to believe that this should operate regardless of the central heating timer being set to off.

Any suggestions gratefully appreciated.

Many thanks

Alan

 

[mylesy]

id try a new ball valve altogether with (1) also check if you have any mixer taps, could be mains being forced through a hot tap, even though this is unusual as you shouldnt put them on an unbalanced system, but youll be surprised. with (2) are you on about the little tank or the big one? even though heat can travell upto either as it is where the expansion goes when the water is hot. nothing to worry about if its only a little. the pump does usually have an overrun especially on low water content boiler to remove to heat away from the boiler to protect it from overheating.

 

[ajtomlins]

I have tried a both a new ball and valve, when watched it shuts off quite nicely I can't fathom it out when over a longer period.

There are two mixer taps, one in the kitchen (1 year old) and one in the down stairs bathroom, I am unsure as to your unbalanced reference, all the radiators have been balanced but this is probably not what you are refering to, if you could elaborate that would be great.

It is the large cold water tank that is heating up, I am aware that this is where the expansion goes but as the tank is large Ferham BCT50(22"x19"x43") in order to make it luke warm I would have thought it would require a substantial amount of heat and was just wondering whether it was a symptom of something else

 

[mylesy]

unbalanced is gravity hot water pressure but mains on the cold. the cold pressure being higher and can forces up the lower hot pressure pipework. a combi system for example is balanced hot and cold as they are both mains pressure. also water can vapourise as long as the air temperature around it is cooler than the water. as the cooler heavier air will alow the warmer water to become bouyant and float on the air in the for of vapour until it touches a cooler surface where it will condense, like the lid on the cistern, is it fully insulated? it should be ok if its below around 25 degrees. ideally below 20.

 

[mylesy]

because mixer taps share a chamber in the tap body it can cross over and it would fill the cistern up, it can happen slowly. id isolate the two taps you mensioned with isolation valves just before the taps and see what happens. if it rectifies it id put non return valves on them just before your isolation valves. if it carries on it going to be something else which i cant think of just now. hope this helps pal

 

[mylesy]

but as the water passes through the cylinder any bateria should be killed off its its around 65-70 degrees anyway. id make sure its well insulated. once you rectified the filling problems that is

 

[AWheating]

have you noticed a change in your hot water temps recently?

 

[Kimou]

It is a regulation to have a single check valve on your supply to your cold tap anyway so you may as well put one on the hot, too. There are bi-flow or twin flow mixers that mix outside the tap also.

 

[Kimou]

I have a querie on the circulating pump. Is this a secondary pump for destratification and deadlegs? Then you'd know if it's supposed to come on or not without boiler controls activated.

 

[mylesy]

i agree kimou, but you only have to put a non return valve on if its going to a mixer tap. and only if it mixes in the body. you dont need them if it mixes in the tap nose. even though id put them on hot and cold anyway, and on any mixer too, even if it is the latter.

 

[mylesy]

no need for them on idividual taps

 

[Kimou]

Sure, it's just good practise to have them due to the potential of taps being changed at some point in the future.
Why pay someone else later when you can pay me now?

 

[ajtomlins]

After a lot of further investigation I have worked out that the problem is the cold water tank in the loft is being filled by the expansion water pipe from the hot water cylinder. This isn't just a drip but a steady pouring of water, which then comes out of the overflow.

I am struggling to understand 1) how to stop this occuring and 2) why it occurs when both the hot water & c/h are turned off at the timer?

Any assistance would be greatly appreciated.

Regards

Alan