Cylinder touch test ?

[Softus]

I suggest that you answer chrishutt's questions.

 

[Ravel]

Would this be a dual coil cylinder by any chance?

No just a single one thanks.

Regards Ravel.

 

[chrishutt]

What type of thermometer are you using? What sort of heating coil does the cylinder have - where on the cylinder are the flow and return tappings to it?

Ravel, it would help if you took the trouble to read the posts of those who have gone to the trouble of trying to help you. You haven't answered these questions.

 

[Ravel]

What type of thermometer are you using? What sort of heating coil does the cylinder have - where on the cylinder are the flow and return tappings to it?

Ravel, it would help if you took the trouble to read the posts of those who have gone to the trouble of trying to help you. You haven't answered these questions.

I did read all of the posts, and needed time to give the correct answers, but a domestic household problem occured which I needed to deal with, so please keep calm, and be assured I fully appreciate the help I'm receiving.

The handheld thermometer with a corded probe is the RS 650-419 which is checked every 6 months by an accredited engineer with a certificate issued.

Regarding the coil I only know from appearance that it has a pipe output at the bottom and a pipe input about one third up the tank actually at the same level as my stat.

Regards Ravel.

 

[D_Hailsham]

The stat is a Drayton HTS3 which like most other makes has a bi metal strip at it's rear but there is always at least 5 mm air space between tank and sensor which is provided by the plastic unit housing spacer, and i'm convinced that if the strip was in physical contact with the tank metal it would be much more responsive, but that's not how they tell you to do it.

They are designed to have a gap between the bimetallic strip and the tank.

... as a further test I switched on the immersion heater and after five minutes the stat changed over to off.

Did everyone miss this

If this is correct, then there is nothing wrong with the stat and the problem lies with the cylinder/coil or the flow to the coil.

 

[chrishutt]

there is nothing wrong with the stat and the problem lies with the cylinder/coil or the flow to the coil.

That's exactly what I was trying to get at. It appears that the coil is normally positioned yet fails to heat the water at its own level - very bizarre.

Ravel, can you confirm that there is circulation from the boiler to cylinder coil and that the boiler flow temperature is high enough (say 65°C or above, both on boiler stat setting and actual temp on flow pipe entering cylinder)?

Could you also describe the boiler and control system - e.g. gravity or pumped, 2 x 2 port motorised valve, 3 port mid position valve, etc.?

 

[Softus]

... as a further test I switched on the immersion heater and after five minutes the stat changed over to off.

Did everyone miss this

I don't think anyone missed it - it's the reason that the fault-finding is still underway.

 

[Ravel]

Ravel, can you confirm that there is circulation from the boiler to cylinder coil and that the boiler flow temperature is high enough (say 65°C or above, both on boiler stat setting and actual temp on flow pipe entering cylinder)?

Could you also describe the boiler and control system - e.g. gravity or pumped, 2 x 2 port motorised valve, 3 port mid position valve, etc.?

Yes there is circulation from boiler to cylinder coil, and the boiler stat on setting 5 normally goes up to 70 degs C, but I find my measurements at the coil input pipe rarely match those on the boiler indication usually being slightly lower.

It is a pumped system with one 2 way motorised valve giving me heating and water together or just water on it,s own.

Regards Ravel

 

[ChrisR]

Have you checked for air at the vent point V ?

 

[chrishutt]

So are you saying that water is being pumped into the coil (at the higher tapping?) at, what, 65°C and this water then exits the coil (lower tapping) (at what temp?) yet the water around the coil doesn't heat up however long the pumping continues?

Since you've got a state-of-the-art thermometer how about some more temp measurements. There's something very odd going on and any good data would help. Perhaps you have a major hot water leak which is causing cold water to continuously enter the base of the cylinder? Can you check this?

Edit - just saw ChrisR's post above. do check this first of all. It's a much more plausible explanation of the problem.

 

[Ravel]

Have you checked for air at the vent point V ?

The pipe on your diagram goes from the upstairs airing cupboard through the ceiling into the loft F&E tank, and I,m not sure if you mean feel the open end for any air passage.

 

[Ravel]

Just so you guys don't think I'm not taking notice or failing to reply, I am going to do some more temperature tests at various points, but it will be later as Saturday afternoon is always shopping in Chester with my wife.

Regards Ravel.

 

[Ravel]

Ok here are my readings as taken after turning the boiler stat up to position 6 which is nearly maximum.

Top coil pipe surface temperature =70.1 degs C

Bottom coil pipe surface temperature = 60.2degs C

Water out of bath tap next to cylinder cupboard =48.3 degs C maximum.

Looks like a poor heat exchange what do you think, and it's now not surprising that the stat set at 50 C does not operate.

Regards Ravel.

 

[EliteHeat]

How about the bottom of the cylinder is full of scale thus preventing efficient heat exchange?

 

[ChrisR]

Ohmigod this is like Topsy.
If the pipe marked V goes on up, you probably have gravity "powered" hw heating, (which is cr*p).
If it's fully pumped than you may well have "pumping over" in the loft - have a look.
If it is gravity, a small amount of anything can stop circulation.
Which is it?