room thermostat wired wrong?

[paperback]

hi.

I am replacing my current Satchwell room stat with a Drayton RTS 1. The current stat seems very insensitive, a large temp gap between activations. In the process of figuring the wiring I think the current stat has been incorrectly wired.

The current stat has a normal three core cable with only L & N used and the Earth terminated. The L&N are connected to the stat as Live and neutral on the wiring diagram inside the stat. (see pic:

Satchwell wiring diagram

• paperback
• 30 Jan 2011
• 1

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when the stat has reached temp and turns off the boiler there is 240 volts metered across the L&N. When the thermo turns the heating back on the voltage across L&N is 0 but there is 240v across the N & earth.

I'm assuming that the Earth and live "coloured" wires are in fact Live and Switched live. but which is which?

The new stat requires 3 wires N , L & SwL. So any help would be appreciated.

Thanks

 

[Agile]

Your stat has been wired without the heat anticipator connected.

You dont have enough wires to use the new stat. ( Unless you use the earth as neutral which is not really correct )


You should buy a battery operated digital stat!

Tony

 

[paperback]

Hi, thanks.

I understand that the wiring is incorrect and will replace the cable if needed.

Are you saying that the cable is currently wired

Earth = neutral

neutral & Live = Live & switched Live. ??


Thanks

 

[Agile]

I expect that the earth is the earth.

But you could test for that and also view the connections at the boiler end.

You should not guess or speculate with electrical connections.

Tony

 

[D_Hailsham]

The current stat has a normal three core cable with only L & N used and the Earth terminated. The L&N are connected to the stat as Live and neutral on the wiring diagram inside the stat.

Which terminal numbers are the live and neutral wires connected to?

Is the earth connected to a terminal (which) or not connected at all?

As Tony says, you need to get a battery operated thermostat such as the Honeywell DT 90E.

 

[TicklyT]

From what you have said, you do not have a neutral at the 'stat. Just live and switched live.

When you are testing, what you are seeing as 'neutral' is the switched live. it is eventually connected to neutral, but only via all the internal components of the boiler, It is just waiting for 240 Volts to be connected to it. Once connected, current flows towards that neutral to make those components do their job.

The earth wire, (if it is connected through the wiring centre as it should be) will appear to be a neutral connection too, as the neutral conductor is linked to earth at many points in the electricity distribution network.

Multimeters have a very high input impedance, which is good for many applications, but that makes it impossible to differentiate between neutral, a switched live in the 'off' state, and earth by simply measuring voltages between any two conductors.

Do not be tempted to use the earth, or Circuit Protection Conductor, for anything other than an earth connection. Even if it isn't required by the 'stat itself, it is part of the protection system for your domestic wiring.

IMO anyone who does use the protective conductor for any other purpose should be flogged within an inch of their life using a sock filled with their own excrement.

 

[paperback]

The current stat has a normal three core cable with only L & N used and the Earth terminated. The L&N are connected to the stat as Live and neutral on the wiring diagram inside the stat.

Which terminal numbers are the live and neutral wires connected to?

Is the earth connected to a terminal (which) or not connected at all?

As Tony says, you need to get a battery operated thermostat such as the Honeywell DT 90E.

Neutral is connected to T1 and Live to T3

Earth is not connected.

Thanks

 

[paperback]

From what you have said, you do not have a neutral at the 'stat. Just live and switched live.

When you are testing, what you are seeing as 'neutral' is the switched live. it is eventually connected to neutral, but only via all the internal components of the boiler, It is just waiting for 240 Volts to be connected to it. Once connected, current flows towards that neutral to make those components do their job.

The earth wire, (if it is connected through the wiring centre as it should be) will appear to be a neutral connection too, as the neutral conductor is linked to earth at many points in the electricity distribution network.

Multimeters have a very high input impedance, which is good for many applications, but that makes it impossible to differentiate between neutral, a switched live in the 'off' state, and earth by simply measuring voltages between any two conductors.

Do not be tempted to use the earth, or Circuit Protection Conductor, for anything other than an earth connection. Even if it isn't required by the 'stat itself, it is part of the protection system for your domestic wiring.

IMO anyone who does use the protective conductor for any other purpose should be flogged within an inch of their life using a sock filled with their own excrement.

thanks for the very useful info.

If, as you say the two connections are live and switched live and the earth is indeed earth I presume I will be able to trace the wiring back to the connection box and verify that the earth is correct. Otherwise I have no way of knowing, using a Multimeter, which is which.

I would very much like to understand what is going on with the system.

Thanks

 

[picasso]

The current stat has a normal three core cable with only L & N used and the Earth terminated. The L&N are connected to the stat as Live and neutral on the wiring diagram inside the stat.

Which terminal numbers are the live and neutral wires connected to?

Is the earth connected to a terminal (which) or not connected at all?

As Tony says, you need to get a battery operated thermostat such as the Honeywell DT 90E.

Neutral is connected to T1 and Live to T3

Earth is not connected.

Thanks

cant be right, 4 is neutral, 1 is switched live and 3 is live in, if it was as you say the stat would blow as you would be connecting neutral directly to live, best advice you have had to to get yourself a digitat room stat, you only need to connect the live and switched live, no neutral required.

 

[paperback]

The current stat has a normal three core cable with only L & N used and the Earth terminated. The L&N are connected to the stat as Live and neutral on the wiring diagram inside the stat.

Which terminal numbers are the live and neutral wires connected to?

Is the earth connected to a terminal (which) or not connected at all?

As Tony says, you need to get a battery operated thermostat such as the Honeywell DT 90E.

Neutral is connected to T1 and Live to T3

Earth is not connected.

Thanks

cant be right, 4 is neutral, 1 is switched live and 3 is live in, if it was as you say the stat would blow as you would be connecting neutral directly to live, best advice you have had to to get yourself a digitat room stat, you only need to connect the live and switched live, no neutral required.

My meaning is that the colour of the cable wired to the stat is...
Neutral is connected to T1 and Live to T3

I understand now from all of the informed replies that the two connections are live and switched live. Also that the voltage I am seeing to the earth coloured wire doesn't indicate it is live at all and is an anomaly caused by me using a multimeter.

I think the replies have now pointed me towards a new stat to use instead of the Drayton RTS 1.

Thanks

 

[Agile]

All this confusion demonstrate the importance of realising that wires should not be described by what the MIGHT be connected to.

Blue, brown, red or green are merely colours of wires!

When we visit a heating system we cannot make any asumptions as to what any wire is used for.

Tony