Best immersion safety-thermostat brand - Cotherm?

[jason1958]

Picked up a new (safety) thermostat at short notice.
- No approval marks (no BEAB, no CE)
- Only 12.5A rated (ok under 17th Uo is 240V, or 3.0kW)
- Screw slots so thin had to file a jewellers screwdriver
- Plastic lid so badly designed it partly obscurred terminals
- Terminal hole just big enough for 2.5mm CSA (Butyl)

Old cotherm unit was 16A, approvals marked, big terminals.
Element cold 19.8ohms on calib 3050DL, Uo 242V at SFCU.

Q - Anyone know the best branded unit as spare?

Cotherm? Anyone else? I would prefer a safety cutout circa 85oC.

 

[Softus]

Backer, Cotherm, Sunvic - all good makes.

BTW, surely 1.5mm² is plenty big enough for 13A, or have you derated it for being in a warm cupboard?

 

[jason1958]

Thanks softus, much appreciated.
Ordered a Cotherm, its an increasingly elderly relative.

Re derating...
- Indeed 1.5mm is adequate.
- However 2.5mm butyl is just £3 from screwfix (note 1m lengths only).

Clothing stored above, two jackets on tank, solid fuel backboiler fed by gas fire, all seated over horizontal chimney. Cable upgrade cost little.


Sadly I think people miss the real problem on immersions.
- Clean the terminals - most fry ups are from bad connections, not 1.5mm cable
- Check the terminals - tightness of Neutral is as important as Live

This one had dead thermostat, cable clamp stripped, neutral loose, butyl cable blistered, U-screw-clamps showed tiny bit of arcing, plenty of blackening. Replaced the cable clamp with an identical one off a new element, cleaned terminals, new safety thermostat.

I considered using proper crimps, but it looks like 2.5mm provides a larger contact area than a crimp ring - some crimps are 90oC, PIDG are 105oC as I recall.

I am surprised no-one has done a clear immersion heater cap?
Sort of like Clipsal 56 plugs so anyone can do a visual wiring check, pity Clipsal 56 plugs ruin the idea with rubber rings that fall out of the plug.

 

[spacethegas]

clear cap sounds like a good idea.

cant think of a downside.

 

[Agile]

Most clear plastics have a lower melting point. Anyway they cost more which is definate no-no !

Even 2.5 mm HR cable is going to overheat if its covered with clothes to insulate the heat loss.

I had to replace a 6 mth old boiler because the users had covered the light bulb in the airing cupboard with clothes which then caught fire.

They did not seem to have any insurance!

Tony

 

[Softus]

Most clear plastics have a lower melting point.

And yet they're used in all manner of luminaires.

Anyway they cost more which is definate no-no !

Just like copper tubing then.

Even 2.5 mm HR cable is going to overheat if its covered with clothes to insulate the heat loss.

So what are you saying? Use 4mm² flex?