DHW Thermostat Test

[bullvine]

Can any of you experts guide me in the right direction in testing a DHW thermostat correctly.
This is how I tested it
I took out the temperature probe from the boiler pocket and placed it inside a cup of water at 90 plus degrees with a digital thermometer beside it.
I disconnected the two live wires going to and fom the main thermostat and tested for omms and continuity with a multimeter.
on the side of the thermostat reads Ranco T70, part number 5106362 for flowsure oil boiler.
I guess it operates up to 70 degrees ?
Through the course of the test it had no continuity or omms until 81 degrees C and as the temperature fell the resistance went up as it should because of the metals inside the bulb solidifying.

My question is should I only see resistance and continuity only at 70 degrees C which is when the thermostat stops the DHW being heated too much ?

Bully

 

[oilhead]

This will be a straightforward switch. Forget the ohms, just measure continuity. It will have a common terminal, and a normally closed terminal (possibly a normally open terminal also, depending on the no which will be prefixed with a 'C'. As it is an oil boiler stat, it should peak at about 85c. It may only range from 55C.