Cylinder coil split?

[Boodle]

Evening all. Been reading a lot of threads on here to try and find the cause of my issue, but they don't line up 100% with my issue.

My water tank in the loft is constantly overflowing. It feeds the hot water cylinder below. It has a new float and valve fitted. Also in the loft is the feed and expansion tank for the radiators. This is a smaller tank and the top is lower that the hot water cylinder header tank.

Now, all I've read suggests that the radiator f&e tank should be the one to overflow, any reason why it's the higher bigger hot water cylinder header tank which constantly overflows?

The hot water cylinder looks fairly old, but does have insulation factory fitted to it.

Currently I have tried the ball valve on the cylinder header tank and have emptied the water from it to see if it fills. Currently the f&e tank isn't dropping as fast as the overflow was, I haven't seen or heard it refill yet, it's been an hour.

Anything else I'm over looking?

 

[Dan Robinson]

Duff mixer with mains cold and gravity hot water cross flowing.

 

[Boodle]

The only mixer without nrv's on is on the bath, decent mains pressure cold, with 3bar pumped hot from the cylinder.

I have been up to check the tank, the hot water header tank has risen by more than 1cm

 

[Dan Robinson]

Isolate the pump and start again.

 

[Boodle]

If it makes a difference, no taps have been on since I drained the header

 

[Boodle]

Isolate the pump and start again.

I think I installed a stop valve in the pipework to or from the pump. Simply turn this and check the level again then?

 

[Dan Robinson]

Pretty much.

 

[Boodle]

Ok, no isolator installed, but there is a nrv between the pump and cylinder, so this should quash that theory?

 

[denso13]

Turn the cold off at the main stopcock and see if the storage cistern stops filling. It isn't a split coil.

 

[Boodle]

All other taps in the house ie,bathroom sink, kitchen sink have nrvs fitted. All are fed mains water and hwc hot water.

I thought this may have been an issue before. Like I said the bath hot tap has one fitted before the pump, same as the mixer shower,

 

[Boodle]

Turn the cold off at the main stopcock and see if the storage cistern stops filling. It isn't a split coil.

Should that read, if it doesn't it's not a split coil?

 

[denso13]

Should that read, if it doesn't it's not a split coil?

No, it isn't a split coil in any event. The lower feed and expansion cistern would overflow it it was.

 

[Boodle]

Ok. Mains water turned off. I'll check the level in the tank in the morning.

How close should nrvs be to the taps and is just fitting to the hot tap is sufficient?

 

[FiremanT]

Faulty NRV in addition to microcrack in casting off a mixer? This would pass regardless of taps on or off, Is there any excessive condensation on the cold pipes going to any mixer?

 

[Boodle]

All nrvs are less than 12 m old. As are all mixers.

If I'm being honest, the shower mixer (in wall type) does seem to get condensation on it, and buzzes constantly, it drives the pump a bit silly. I could install another nrv about 2m away from the mixer without much hassle if that would help.