Heating Temp not constant , Help

[wagggy]

Had a new boiler fitted in summer. No problems with it except that when thermostat clicks on, the boiler fires and heats the house. when thermostat reaches correct temp it turns off boiler.
the problem is the house gets really cold before stat clicks on again and boiler refires. House is constantly going hot and cold.

Boiler is Ideal Logic + 30w . New thermostat is Honeywell T6360B fitted in hallway.

Rechecked wiring and thermostat is wired correctly according to Ideal guide and Honeywell guide. It uses the 3 wire version.

Is there something i can check as it doesnt seem right.

Thanks

 

[TCCHeating]

You need to check that the neutral is wired properly. The situation you are describing suggests to me that there is something wrong with the neutral connection to the thermostat. You may have all 3 wires at the thermostat. But are you sure they are all connected at the other end?

Without a neutral connection, the thermostat will still work, but the temperature range between switching on and off will be much bigger.

 

[wagggy]

Hi, Its wired using 4 core cable direct to Thermostat , its only about 3 metres away. I tested the wiring with a DMM by disconnecting and shorting out each wire to earth wire and all tested ok . I have double checked the connections and the Neutral is connected from boiler Neutral to Stat terminal 2. Boiler Room stat connections to Stat terminals 1 and 3. This is what the boiler diagram shows.

My old boiler Potterton Lynx2 worked ok on this setup.

 

[Agile]

It is important which of the switched wires are connected to which of the thermostat connections.

How far away is the nearest rad to the thermostat?

Tony

 

[wagggy]

The thermostat is in the hall , the nearest rad is in the hall on the opposite wall about 2 metres away. it hasnt got a TRV on it in case you ask.

The top 2 terminals on the boiler are not marked individually, only says Room Stat. Its wired as per diagram .

Boiler top term 1 goes to Timer, then Timer return wire is connected to term 3 on stat . term 1 of stat is connected to term 2 on boiler. Neutral on boiler connected to stat term 2.

Hope this makes sense. would be easier to draw a diagram.

 

[TCCHeating]

Swap t1 and t3 wires at the thermostat. If that doesn't work. Then replace the stat for something more accurate

 

[wagggy]

Ok i will try that and get back to you with result ... thanks

 

[Agile]

If that does not fix it then you may need to reduce the heat input to the hall rad.

Measure or feel the top of the rad and close the lockshield until it gets about 10 C lower and try that.

Tony

 

[wagggy]

Swap t1 and t3 wires at the thermostat. If that doesn't work. Then replace the stat for something more accurate

I swapped the wires and it certainly made a big improvement. I Noticed when I turn the thermostat theres only 1 degree between on and off. Before it was about 3 degrees.

Thanks for the help.
Alex