Thermostat Help

[Stevo90]

I am a second year apprentice and i'm looking to help someone out by wiring up a new thermostat, have a wee problem as i'm unsure how to, it is the danfoss TP5000RF Si range, i also have a wiring diagram if you follow the link ->http://danfoss-randall.co.uk/PCMPDF/RX1.pdf . Be much appreciated if someone could tell how to wire this thanks

 

[WDMDL]

Simple.
Supply to N and L.
The output is a voltage-free contact.
So, if it was a mains voltage circuit you were switching, say for a simple combi boiler or, say, feeding a contactor, your feed from the programmer would come in on COM and out on "Zone 1 ON"
Maybe you'd be using a triple+cpc and have a L, N and SL. In which case you'd link L to COM in the 'stat.

For other heating system "plans", eg Y-Plan, you'd need to refer to the system wiring diagrams. Danfoss have examples of those too.

Simon.

 

[telectrix]

beat me to it there, WD. one problem you might have though is if the old stat is a 2 wire, L & S/L, no neutral. that would entail rewiring in 3core/E

 

[Stevo90]

Thanks alot guys, much appreciated. So if deffo just bring in my L and N and link my L and COM together ?

 

[Marvo]

Yep, that should work. The NO contact then supplies the load.

 

[Stevo90]

Thanks marvo, A think i was just thrown off by no voltage contact

 

[Stevo90]

Also just another quick question before i commence with the job. The boiler is permanetly on just now, it is connected through a joint box, would it be ok for me to take my twin and earth out the joint box and terminate as said or does my cable from my boiler have to connected into my thermostat in different terminations ?

 

[WDMDL]

Depends on the boiler.
Most use mains voltage controls, others use 24v or other control voltage.
If the installation and servicing manual isn't to hand, you could download one.

Is it a combi or conventional system?

I think the Potterton Puma my Mum used to have used 24V controls, but my Baxi is mains voltage.

In either case there is usually a pair of terminals with a link wire on them labelled for thermostat.

But with conventional boilers you need to know which "plan" you have, as the stat will be controlling a motorised valve, rather than the boiler itself. (A microswitch in the motorised valve then controls the boiler)

Simon.

 

[Stevo90]

Am sure its a combi, i was just wanting to make sure that if i take my T/E out of the junction box to my thermostat that this would suitably control it ?

 

[WDMDL]

Remember if all that's feeding the boiler is one T&E, then fitting the stat inline will cause you a problem:
You will not be able to have hot water when the house is warm!
Combis need a permanent supply so they are in standby for hot water heating.

Depending on whether the boiler uses mains or 24V controls, you will either have to:

Mains voltage control:
Replace the T&E with a 3&E between stat and boiler (N, Perm L, Switched L), or
Supply the thermostat receiver with mains from the junction box and run an additional T&E between the boiler thermostat terminals and the COM and ZONE 1 ON.

24V control:
Supply the thermostat receiver with mains from the junction box and run an additional T&E between the boiler thermostat terminals and the COM and ZONE 1 ON.

So if you're not sure, running the separate cable for the control contacts works every time!

Simon.