Danfoss RMT230D installation.

Dec 09, 2009 2 Replies
M

Hi, I have currently a mechanical thermostat (honeywell) which I would like to replace with a slimline, flushmounting thermostat (RMT230D).



However I am a little confused by the wiring diagram.



The boiler connections are L1, L2, Earth, Neutral, and L3. Per the wiring diagram for the boiler, L1 & L2 are connected at the boiler end. Currently, there are two wires to the thermostat, and these connect to L1 & L3 on the boiler.



Wiring for the RMT230D shows 5 connections. NC, NO, COM, L & N.



L & N on the stat connect to L2 & Neutral respectively on the boiler. Earth on the boiler gets earthed to the backbox.



I am thinking L1 connects to COM, and L3 to NO (as NO is labelled "on" in the diagram). So what connects to NC (labelled "off" in the diagram)?



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R

What makes you think that *anything* needs to connect to it? You're just using it as an on/off switch, and thus just need to use 2 of the contacts - COM, plus one or other[1] of the others.

The fact that it has an additional contact which makes when the room temperature is above the set point probably just means that it can be used for cooling as well as heating applications.

[1]The terms NO (normally open) and NC (normally closed) can be confusing because it's not always clear whether 'normal' applies to high or low ambient temperatures. The important thing is to find out which contact is connected to COMmon *below* the set point - i.e. when there is a demand for heat, and use that one.
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P

I've just had a technical query (very simple) about an RNT230 answered by the Tech. Dept at Danfoss. They were very helpful and sent a prompt reply. Here's the e-mail address: Wynn Adrian [Adrian snipped-for-privacy@Danfoss.com]

Cheers Pete K.

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