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Charlieboy 08-16-2005 09:40 AM

Not so easy to install thermostat
I have tried to replace a thremostat in my hallway. Easy I thought. Old one (Honeywell T6060B, manual dial type) has three wires (live, neutral, therm). The new stat (Danfoss TP5, digital readout type) also has the same three wires. The wiring diagram is easy to understand and the job should be simple, replace the wires like for like as per the diagram.
How wrong could I be. The fuse in the wall near the boiler keeps blowing every time the thermostat tries to engage and switch on the heating system! I have gone through 13 - 3amp fuses and just can't figure it out! I have followed the wiring diagram to a tee. COM(1) = Live/Red, OFF(2) = Neutral and ON(3) = Therm.
Can anyone help me please. Open to all suggestions apart from call a plumber or electrician, which is my next step.

MgMopar 08-16-2005 01:29 PM

Since you only have one pole switch It is very hard to figure how this could be happening. First off, Why did you change the original. Just replacement upgrade or did it malfunction (like stop working) if it stopped working it may have just blown instead of the fuse from a short farther in the system. If you are changing just for a upgrade and everything was in working order then the only guess I can make is the on and off are both being signaled simultaneously for some reason. Some digital T stats have jumpers or switches inside that are switch for different systems, like boilers or electric heat. This can change on/off delays and stuff like that. I would read threw you installation guide and see if this may be a possiblity.

Charlieboy 08-17-2005 03:09 AM

The origional switch was working fine and when I re-connected it a few mins ago it still works fine and doesn't trip the fuse. The new digital T stat is just cosmetic as it looks more modern in keeping with the new decor.
Will read through the instructions again however, the wiring side is basic and the majority of the instructions are given over to explaining how to set the timers. I don't use the timers as I have a timer on the boiler. I just want to use the t stat manually.
Will get rid of the digital t stat and replace it with a new dial one instead. Far less hassle!
Thanks for the advice.

nicknackynoo 08-19-2005 03:31 AM

Seeing that you have only three wires to worry about you should check they are wired up correctly the other end.

A quick check but a bit cowboyish would be to swap over two wires and see if that works - as you are already blowing fuses another won't matter!

It's a bit difficult to check the digital stat as it only operates when power is applied, the old one you can simply turn, and using a multimeter work out what happens between the terminals when turning the stat on and off.

A good source of free advice is the helpline number they have to print on the info sheet


Charlieboy 08-20-2005 05:20 AM

Thanks for the advice but I had enough and swapped the digital for a modern looking turndial. Took the easy way out but my patience ran out.
Will stick to decorating and basic woodwork, leave the electrics to the pro.

dirkgently 08-26-2005 02:20 PM

It sounds like you are trying to replace a traditional thermostat with a volt free one. I would guess that the Danfoss TP5 only needs a switched pair but no live, I think the way you are trying to set it up just connects live to neutral, hence blown fuse.
