Replacing Digistat SCR with a Combi-Stat 24028 (RTS8)

[DCP]

Hi all,

Looking to replace Digistat SCR with a Combi-Stat 24028 (RTS8) .Initially thought it would be a question of disconnecting Digistat SCR, thought would be just 3 wires, new RTS8 to go in the same location. Both have L,N,Earth but DigistatSCR has wires to 1,3,4 but new RTS8 has just 2,3 ?


3 amp fused spur into Danfoss programmable timer, the Digistat SCR then the boiler which is an Ideal Isar HE30

Can anyone offer advice on wiring please?

Conventional combi boiler with CH / HW system.

Any advice much appreciated

 

[ericmark]

Digistat SCR needs power to work and has volt free contacts, so L (Line) and N (Neutral) 1 Common 3 Normally open.
Combi-Stat 24028 (RTS8) L (Common) 2 Normally open. The Line and Neutral may not be used it depends on the voltage used by boiler.

So get a connector block for Brown and Blue don't connect to new thermostat, and put the greys in 1 and 3.

It may be you can connect neutral but since we don't know better to play safe and not connect Line and Neutral.

 

[CBW]

L and 1 to L
N to N
3 to 3

Although, I’d consider whee this existing receiver is located, as you don’t really want to be putting a room thermostat underneath your boiler.

 

[ericmark]

L and 1 to L
N to N
3 to 3

Although, I’d consider whee this existing receiver is located, as you don’t really want to be putting a room thermostat underneath your boiler.

If the existing control is 24 volt you have just wrecked the boiler, since we on a forum don't know if 24 volt or 230 volt control safer not to connect the 230 volt. If it is 230 volt control then the neutral connected to the anti-hysteresis resistor would help, but we don't know.

I agree it seems a down grade, however the wall thermostat with many gas boilers is only there to stop the boiler cycling as warmer weather arrives, the thermostat radiator valve (TRV) does all the work of keeping the rooms at the right temperature, or doesn't, realised it was cold in my bedroom and on looking on phone see my batteries were discharged in the TRV head, just changed them.

 

[denso13]

since we on a forum don't know if 24 volt or 230 volt control

Boiler and RTS8 are both 230v.

 

[ericmark]

Boiler and RTS8 are both 230v.

It seems from diagram

the way the frost stat is connected it is 230 volt control, however I would not want to take the chance, I would be testing with meter first, it does seem an odd way to label, would be so easy to think it was three phase.

 

[CBW]

Boiler output on room stat is 230vac, so on a forum, I do know. As @denso13 has indicated. I get where you’re coming from and some boilers like the Vaillant EcoTec pro 28 newer models support both.

 

[DCP]

Thank you one and all