How do I wire a cylinder thermostat to a central heating pump?

Question

I have an HTS3 cylinder thermostat that I want to use to turn on an off a Wilo Gold RS50 pump.

This is part of a very simple system I have created in a garage. I am heating the water in the tank separately from any boiler or the like, and that's not the issue.

When the water in the tank reaches 50 degrees, I want the pump to circulate the water out of the tank and into a single radiator and back again.

Simple.

The HTS3 stat has three connectors in it. One is 'common, one is '1' - call for heat, and the other is '2' - satisfied.

The pump has three connectors too - live, negative and earth.

THE QUESTION:!!!

How do I wire the stat to the pump? I will have cable coming from 240v mains supply - -three wires, live, negative and earth.

Many thanks.

Answer 1

first live from mains to common on the thermostat, then wire from 2 to the live terminal on pump. The pump will require a neutral and earth to be connected or it will not run. set the thermostat to 50 and away you go.

Answer 2

ok, I do not know the thermostat you are talking about but you need to think logically here. First the pump has live, earth and neutral. 3 wires. The stat will also have 3 however these will be earth, in and out. A stat is basically a switch, so it would normally be used to turn off the supply to the heating element. You want to use it to turn on. This is not so simple.

The wiring to turn off would be like this. Pump earth to mains earth. Pump neutral to mains neutral. Stat earth to mains earth. Pump live to one connection on stat, the other connection on stat to mains live. So when the correct temperatur is achieved the stat will disconnect the live in and the live to the pump. You need to find a two way stat. This would have one extra connection. It would connect live to one terminal when tank is cold and to the other when hot. This way, when the tank reached the right temp, the heating element would cut out and the pump would cut in.

If you cannot find a two way stat there are other ways to do it but you shoud speak to an engineer. For example, a relay could be wired in to the stat. When the power to the stat is cut, the relay would turn off connecting the pump to the mains at the same time. Confused?

Email me if you have any difficulties.