Replacing thermostat connected to a ehc-Fusion boiler

[lt8480]

The boiler's circuit board is unlabelled, but based on the current configuration hope someone can help check my deductions/proposal...

At the moment:

Programmer/Timer (Sunvic Select 107XL)
N/L connected to its own fused spur power supply.
1/COM is connected with a Brown/Live cable to the Boiler
3/ON is connected with a Brown/Live cable to a separate Thermostat's L connection.

Dial Thermostat (Honeywell)
L connected to programmer as above
N connected to the Boiler with a Blue/Neutral cable.

Boiler (EHC Fusion - Electric boiler running heating only)
The connections are unlabelled, but the programmer and thermostat are connected as above. There is a large label above the circuit board that states "NA - Volt free control stat connections".
(This circuit board does have some labelling but these are just holes and do not have connection blocks, they are labelled e.g. X1-PSK, X9-Tzas +/-, X8-Tco2, X7- etc.)

Proposed:

We have a new wireless programmable room thermostat (Salus RT510RF) to replace both the Dial Thermostat and the separate Programmer/Timer.

The new programmer has the following connections NO, COM, L, N

Based on the existing wiring to the boiler I understand the connections to this should be as follows:

L/N to the fused spur
COM to where the L/Brown cable currently connects.
NO to where the N/Blue currently connects.

Not that savvy on this, replaced a couple of Thermostats before but used to seeing labels on the boiler! - so if someone could check/confirm the above that would be great and all help much appreciated.

 

[stem]

Based on your description above, I have made a sketch below of how I understand the existing set up to be. Is this correct?



If so, and if I understand...

Based on the existing wiring to the boiler I understand the connections to this should be as follows:

L/N to the fused spur
COM to where the L/Brown cable currently connects.
NO to where the N/Blue currently connects.

...to be as below, then you are correct.

 

[lt8480]

Hi Stem, yes that's the correct (the ? in your first diagram is labelled N).

Many thanks!

 

[stem]

Are you sure it's actually marked N? A thermostat is just a switch. When 'on' both wires are connected together, 'off' and they are not. You would never connect a L & N together

Some thermostats do have a N terminal for other purposes, but if there are only two wires to yours it won't have been used.

Anyway, as it's coming out, it doesn't really matter.

 

[lt8480]

Are you sure it's actually marked N? A thermostat is just a switch. When 'on' both wires are connected together, 'off' and they are not. You would never connect a L & N together

Some thermostats do have a N terminal for other purposes, but if there are only two wires to yours it won't have been used.

Anyway, as it's coming out, it doesn't really matter.

Just double checked and on the thermostat they are labelled 1 & 2... I must have mis-read my notes and reading the cable colours.

Many thanks again.

 

[lt8480]

All sorted and working great.

Thanks again!