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Andrew Smith
Andrew Smith, Engineer
Category: UK Plumbing
Satisfied Customers: 3632
Experience:  Domestic Gas, Commercial Gas, LPG, Unvented Hot Water, Part P Electrical, Commercial Catering
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I have tried to replace an old TLX 2304 Satchwell dial room

Customer Question

Hi there. I have tried to replace an old TLX 2304 Satchwell dial room thermostat with a new Heatmiser Smartstat, which is a combined programmer and thermostat and can be controlled remotely via the Internet, but I have been unable to get the new one to function. The old one has a 240v 3-core and earth cable, with red, blue and yellow wires. The red is live (I tested it with a mains tester) and I believe that the blue is neutral and the yellow is a switched live. I wired the new one on that basis, following the diagram in the manual for a switched live connection, but the unit did not power up at all. I then reversed the blue and yellow wires. The unit powered up but immediately switched off and then cycled on and off constantly (the whole unit, not just the thermostat function). The thermostat controls a Potterton gas boiler which has a separate Potterton timer/progammer for hot water and radiators (separately). I called Heatmiser but they said to get an electrician in! Can you help please? I have put the old Satchwell stat back and it works fine but I feel that I have wasted my money on the new Heatmiser.
Submitted: 2 years ago.
Category: UK Plumbing
Expert:  Andrew Smith replied 2 years ago.

Ok, take it off again.

Separate the wires and turn the heating on, let me know which wires have 240V when the tester is on the L and the metal back box?

Customer: replied 2 years ago.
Thanks Andrew. I can't do that today but will get back you when I have done so, tomorrow if I get a chance.
Expert:  Andrew Smith replied 2 years ago.

No problem, I should be on again at this sort of time