frost stat question

[weseeyou]

I ordered a new frost thermostat type 26TXE21 (part No 550516) for a Halstead Quattro Gold but I'm now not sure if the fitted stat is faulty or I have been supplied with a faulty stat.?

The original stat is shown normally closed on Halsteads functional flow diagram which I assumed was correct but the replacement stat sent is normally open circuit ? Can someone please confirm that the replacement stat is incorrect

 

[doitmyself]

A frost stat is normally open at room temp and closes when the temperature drops.

I assume you tested it at room temp and got open circuit. Put it in the fridge for 10 minutes and then retest. You should now get continuity.

What is the problem which makes you suspect the frost stat?

Have you followed the fault finding procedure in the Installation Manual?

 

[weseeyou]

Hi thanks for the reply.
Problem originally was that the pump never switched off although the CH and DHW were working fine. I purchased new pump overun stat frost stat and limit stat because original parts at least 12 years old .
The new frost stat was open circuit ? the origininal is definitely normally closed so I just wanted to be sure which was correct. ?

Anyway last week we returned from a short break and noticed a slight leak from the auto vent valve and raised system pressure so I drained the system replaced the filling loop and shutoff valve refilled ,pressurized and bled the system .and then the boiler would not fire up.

Checked everything and found igniter pcb had suffered water ingress which had blown the resistor on the neutral imput of the igniter pcb .

Replaced igniter pcb and now have the igniter working but the no gas to the burner (CVI) .?

I have 30v on the modulator and 230v to the igniter pcb but havn't checked any further yet.