Cylinder stat for torpedo tank

[Vicario]

I've just had a new boiler and storage tank (slimline torpedo). The tank has a strap-on stat but no matter where I place it the hot water is still very, very hot. I've set it to 50 degrees and it's now almost half way up the tank - at this rate I'll have cut out more insulation than there is left on the tank! Could the stat be faulty? Would turning down the boiler stat do any good? - it's where the fitters left it, at about half way between Low and High.

 

[mysteryman]

Check that it actually does turn off when you set it to the minimum setting. If it doesn't, you have a wiring or other fault. If it does, it is not making good enough contact with the cylinder. You need to scrape it to bare shiny copper.

The cylinder thermostat should be above the coil - the advice about fitting them one third of the way up was OK in the days of gravity primaries and slow recovery cylinders, but it is not good practice with fully pumped high recovery cylinders.

 

[Vicario]

So how high up a torpedo tank? The gas fitters left it about 9 inches from the floor, which is clearly too low. I have my Stanley knife poised......
On that subject, is there anything I can stick over the holes I've made (two) in the insulation so far?

 

[TicklyT]

... is there anything I can stick over the holes I've made (two) in the insulation so far?

Use the foam you cut out for the next hole

A squirt from an expanding polyurethane foam aerosol would do the job (that stuff gets used to fix just about anything according to one builder I know )

An offcut of polystyrene packing would be better than nothing.

 

[mysteryman]

Put it well above the primary coil connections - the upper one will be somewhere in the middle third of the cyl.