immersion heater thermostat keeps tripping on..

[mutley racers]

A direct unvented. I am thinking that the element is just full of scale so keeps over heating and cutting out. But is the way to test these by resistance on coil and resistance across thermostat? I have read on here that testing on points with casing is good? What does this do? Is the casing acting as the earth? And is this a live test for juice?

Cheers chaps. Have a great day

 

[Ermintrude]

Photo and shall explain

 

[mutley racers]

I have not been there yet but here is th thermostat schematic

 

[Ermintrude]

Can't see post the link.

 

[mutley racers]

Can't see post the link.

here you go:

http://www.santon.co.uk/docs/36006153_Standard_issue_01.pdf

 

[Ermintrude]

So when power on red and black should have 240v

Un plug immersion and should be a massive resistance from coil live terminal to earth.

 

[mutley racers]

So when power on red and black should have 240v

Un plug immersion and should be a massive resistance from coil live terminal to earth.

massive resistance? is that 20 ohms? If I do have all the above, then should I check the resistance on the stat? Or, if above is ok, will that automatically tell me the stat is knackered? I have heard that if a stat is knackered, it is knackered. You won't be able to keep resetting it?

Also, when I was on the Baxi course, he said that the only way you could tell if a stat was knackered or not was by checking how many amps it was getting. What do you think of these tools

 

[Ermintrude]

If stats working you will be getting 240v at red and black. 20ohms is not massive that's a short. Massive is 20k ohms and above. Normally off the scale on multi meter. Check 240 where mains comes in on the connector block.

 

[mutley racers]

doh me stupid. I was meant to write 20k. That is great, thanks Ermin

 

[Ermintrude]

You 4g? Make sure new stat is compliant.

 

[mutley racers]

don't think so. only 3g on my s3

 

[mutley racers]

You 4g? Make sure new stat is compliant.

yeah, i was going to phone the manufacturer to see if i have to buy their stuff or I can pick up one from a shop?

I am G3!!

 

[Ermintrude]

Mfr original best

 

[townfanjon]

Buy a clamp meter pal, turn on at programmer if stat is working ok. On the wire coming out of the stat, put the clamp meter on and the imm heater will draw approx 13 amp. If it does, its working.
Just a couple of other things which may help, just getting 240 at the stat does not prove its drawing elec the clamp test proves it is working. The stats in immersion heaters are absolutely shi*te these days and even though it might be working on a test doesnt mean it wont turn off 20 degrees to early or late. I have my own patented stat tester, its called 'johns stat testing rig' . LOL. It works a treat and If I have time I usually test every brand new stat I buy before I fit them.
In the van I always keep a roll of 2.5 mm cable with a plug on the end, if I want to rule out the stat is faulty I remove it and wire t

 

[townfanjon]

rest should say ---------------------- it straight in to the mains

 

[Ermintrude]

If there is 240v at outlet of stat means stats not locked out.

You don't need a clamp - these only identify induced voltage feild. If you wish to measure current, set up multimeter rated for 20A AC in between the red lead and the pin it was supposed to go on. Set meter to record max and min. Go sleep in van for 30mins. Or service boiler .

 

[mutley racers]

rest should say ---------------------- it straight in to the mains

the stat seems to be working as it keeps tripping.

 

[townfanjon]

I assume the cylinder is set at 60, so if the water is at 60 (or thereabouts) and its still tripping it sounds like a knact stat.