PLEASE HELP - Water in the coldwater tank HOT!!!

[Mark_H]

Problem: The water in the Cold Water Tank is getting hot!

I have tried lengthening the overflow pipe from the top of the cylinder, as I suspected that it was too short and resulting in hot water expanding into the cold water tank – made no difference.

So while looking inside the coldwater tank I noticed heat radiating from the hole which feeds the hot water cylinder tank, which would cause the water in the coldwater tank to get hot. I checked the coldwater feed to the hot water cylinder and it is very hot!! Is this normal? If not, what is the likely cause for this? Is there not a valve to prevent backflow? Is the tank getting too hot and radiating back up the coldwater feed?

The thermostat appears to be working fine and switches the valve off when it reaches 65 degrees?

Please help!!

 

[JohnD]

What is the height of the small Feed & Expansion tank that tops up the water for your boiler and central heating? Is (the water level inside) higher or lower than (the water level inside) the cold water tank?

Is your picture an accurate representation of the pipework?

Is the vent pipe dipping into the water in the cold tank?

 

[Mark_H]

What is the height of the small Feed & Expansion tank that tops up the water for your boiler and central heating? Is (the water level inside) higher or lower than (the water level inside) the cold water tank?

If I understand you correctly - the central heating boiler does not have a small feed tank as it is sealed. So the only job the coldwater tank does is to feed the hot water cylinder AND to provide water to the upstairs cold taps

Is your picture an accurate representation of the pipework?

Near enough

Is the vent pipe dipping into the water in the cold tank?

No.

 

[Rob]

its mixing somewhere. have you not had a new shower etc fitted recently?

 

[JohnD]

What is the pressure in your boiler (there should be a gauge in Bar)?

Is the filling loop to the boiler connected?

As rob says, it could be where you have mains pressure cold going in one side, and tank-pressure hot on the other. Most likely a mixer tap (shower, sink) but sometimes where a washing machine has been connected to hot and cold supplies. If you feel the "hot" pipes to such a mixer you may find one that is surprisingly "cold"

Have you had any recent plumbing changes?

 

[Mark_H]

What is the pressure in your boiler (there should be a gauge in Bar)?

2 bar

Is the filling loop to the boiler connected?

Yes

As rob says, it could be where you have mains pressure cold going in one side, and tank-pressure hot on the other. Most likely a mixer tap (shower, sink) but sometimes where a washing machine has been connected to hot and cold supplies. If you feel the "hot" pipes to such a mixer you may find one that is surprisingly "cold"

I'll check, but there are lot of pipes all over the house!

Have you had any recent plumbing changes?

Had a new boiler installed, but the problem existed before this.

With the previous boiler we turned the hot water temperature down on the old boiler (you could control the heating and hot water temperature separately). This seemed to solve (mask is probably a better word) the problem. Once the new condensing boiler was installed this year, with only one temperature control, that does both heating and hot water, the problem has reoccurred. If we turn the temp down on the boiler to say 3 (max being 9) then solves the problem also. So why is there a correlation between the two?

 

[JohnD]

Disconnect the filling loop from the boiler (it is only supposed to be connected when you are, ummm, "filling" it).

 

[Mark_H]

Disconnect the filling loop from the boiler (it is only supposed to be connected when you are, ummm, "filling" it).

It is physically connected, but isolated by two valves - which are switched off.

Please note additional info in previous reply re the boiler temperature.

Thanks for taking the time... much appreciated!!

 

[JPC]

mixer taps could be doing it..as stated.

is the pipe at the top of the cylider and going back a bit,,cold/cool (meaning mains water is mixing in a tap and travelling up the hot pipe, and back into the cylinder etc etc)

is the vent pipe clear of obstruction ?

cylinder stat setting at 60-65 ?

 

[Mark_H]

mixer taps could be doing it..as stated.

is the pipe at the top of the cylider and going back a bit,,cold/cool (meaning mains water is mixing in a tap and travelling up the hot pipe, and back into the cylinder etc etc)

No its hot.

is the vent pipe clear of obstruction ?

New vent pipe fitted today - so yes.

cylinder stat setting at 60-65 ?

set at 65.

 

[JPC]

tank in loft not overflowing ?

 

[Mark_H]

I have a power shower fitted with a pump that comes from the top of the tank, as shown below.

The pipe leading from the top of the tank to the hot water taps is hot all along, so no mains pressure into that.

The other pipe leading from the top of the tank to the pump as in the picture is hot initially then eventually turns cold. But then the shower hasn't been used since this morning. so I would expect a certain amount of radiation and for it to then cool the further along the pipe.

I have checked that the cold feed into pump is from the tank and not mains.

Still no further forward?

Any ideas as the correlation between the boiler temp and the CWST?

 

[Mark_H]

tank in loft not overflowing ?

No

 

[scaby]

do you have an electric emersion heater and is it switched on?is the cylinder stat held firmly against the cylinder?, is the hot water hotter than normal?

 

[Mark_H]

do you have an electric emersion heater and is it switched on?

Switched off

is the cylinder stat held firmly against the cylinder?

Yes

is the hot water hotter than normal?

No