how to wire a room stat to an existing programmer(grasslin)

sandpaper · 16 Jan 2009

Hi Folks,
I wonder if any one out there can help me.
House i bought a few months back was only fitted with trv's, so i ordered a wireless room stat (solus st 300 rf) which arrived yesterday. Although im certainly no electrical masterclass (i have fitted new light switches and fittings troughout the house straight forward stuff) i have to admit i have no idea how to wire the room stat up.
The programmer is Grasslin Towercron QM2 im not 100% on my system is it Y plan? etc. Its a sealed system im i right in thinking it must be fully pumped. The programmer will let me select HW only but not CH only.Although even if i select HW only the rads are still coming on discovered the motorised valve dosnt work (will replace this in the summer when i need it and have the money).
Should i wire the st300 between the pump and the Qm2 or should be wired to the valve (2 port).
If i could afford to get some in to do this i would but ive just been made redundant and im trying to save money.
If anyone out there can help id be very grateful.

Thanks in advance

sandpaper · 16 Jan 2009

Forgot to mention its a riello rd3 oil burner.

Cheers

mogget · 16 Jan 2009

Do you have a tendency to be slightly 'abrasive'?

The switch on the receiver goes in series with the CH switch on the programmer.

Live / neutral to electrical supply.

According to the website, remove the link on the receiver.

Hope that helps.

sandpaper · 16 Jan 2009

Sorry,

Trying to keep an eye on my 2 year old at the same time as i was writing the post, puntiation was all over the place. Oh and far too much coffee.

My goodness is it really that simple, feel kinda stupid now.

Thanks a million.

mogget · 16 Jan 2009

sandpaper said:
Sorry,

My goodness is it really that simple, feel kinda stupid now.

Don't worry about it - which is the more stupid?

1) Asking on a forum because you don't know how to do it, or

2) Blundering on despite not knowing how to to it, possibly blowing your new stat, or worse, the boiler!

BTW it's your username that made me giggle - just couldn't resist!

sandpaper · 16 Jan 2009

Guess i am a bit rough

So i take it this is a volt free application?
Im going to have a go at this in the next few minutes.
So does that mean the room stat will turn of the boiler directly? This would be brilliant.
Just to be on the safe side the connection marked n.o or switched live on the receiver, is what runs back to the boiler, and il use a small piece of wire to run from the programmer to com (volt free feed) is this right?

Thanks alot

sandpaper · 16 Jan 2009

Okay i have taken the back plate of the programmer live and neutral is there (1-2) 2 and 3 are not wired up and 3(HW) has 1 red wire i assume this is for the valve and then 4(CH) has two red wires, is this for the boiler and pump? Do the two of them go into the reciever/stat connectin marked n.o or volt free feed?

mogget · 16 Jan 2009

sandpaper said:
Okay i have taken the back plate of the programmer live and neutral is there (1-2) 2 and 3 are not wired up and 3(HW) has 1 red wire i assume this is for the valve and then 4(CH) has two red wires, is this for the boiler and pump? Do the two of them go into the reciever/stat connectin marked n.o or volt free feed?

I'm not sure how your system is wired, but if the programmer turns the heating off, so will the thermostat.

If you've got space, put the two red wires into a connection block.

Then add a new piece of twin and earth between the programmer and the stat receiver.

One wire will go from programmer terminal 4, to com on the receiver.

The other, back from the receiver (probably marked NO) to the connection block with the two red wires in.

This means that the switches on both the programmer and the thermostat must make, for the CH to switch on.

You are correct that in this instance it's a 'volt free' application. It's the easiest way to do it

sandpaper · 16 Jan 2009

No Worries
Im doing it now,luckily i have a spare block lying around.
i take it this will make it a little tidier

mogget · 16 Jan 2009

sandpaper said:
No Worries
i take it this will make it a little tidier

Yes, it will be neater, which is always nice. It will also make it easier to comprehend if you need to do something else on it in the future. I don't know about you but I usually forget what I did, a few months down the line!

Strictly speaking the 'neutral' wire should have some brown sleeving on it, because it's actually a switched live - but it will work without it

bhm1712 · 17 Jan 2009

if you cant get central heating on, on its own, surely that would indicate that you dont have a fully pumped system? and that you have a gravity hot water and pumped central heating?

if that is the case, then the room stat will only control the pump, and basically acts as an on/off switch for the pump.

mogget · 17 Jan 2009

bhm1712 said:
if you cant get central heating on, on its own, surely that would indicate that you dont have a fully pumped system? and that you have a gravity hot water and pumped central heating?

if that is the case, then the room stat will only control the pump, and basically acts as an on/off switch for the pump.

The system as it stands has a programmer for heating and hot water, if it's a gravity HW / pumped CH, the programmer will ensure that whenever heating is called for, the boiler will fire for hot water too.

The thermostat if wired as I described will not affect the functioning of the system, apart from turning the CH pump off when the temperature in the room is high enough. As the switch in the receiver duplicates the function of the CH switch in the programmer, there will be no change, as far as the rest of the system sees it. It will work just as it did before, apart from having some degree of temperature control.

To convert the system to independent control, the programmer would need to be switched to independent operation, and a relay fitted in order to supply a switched live to the boiler when CH (only) was called for. A cylinder stat could then be fitted and the boiler would then have a proper interlock. The only exception being that the hot water circuit would be active whenever CH is called for - the temperature of the water in the cylinder may rise above the stat setpoint in this case.

sandpaper · 17 Jan 2009

Mogget,

What can say, disaster last night. Wired up everything last night stood back and took pride at my neat wiring job(like all men do), swithed on the power and, nothing happened. The light on the reciever indicating power was not lit. Double checked the connections (L-N) wich i had wired in parralel to the timer they all looked fine, moved the unit around( i had not fixed it to the back plate yet, wanted to check it worked first) and the light came on briefly and then there was a spark and smell of burning. Closer inspection indicated that the copper screw holding had come loose from the pcb board in side the reciever, i figure either i was a bit to hard on the screw holding while fixing in the wire or it was faulty from the start. The thing is im sure i would have noticed it was loose when i originally screwed in the wire, the strange thing is that when i turned on the power originally although the reciever switch did not light up, the boiler kicked in anyway and kept going even after the spark. If the reciever was not operating surely the switch didnt work the connection wasn't completing the circuit.
What can i say im gutted, ive emailed the supplier on the off chance he will replace it but i doubt he will, oh well £40 down the drain but im not giving up.
Thanks again for all your help. do you reckon the reciever was faulty from the start?

mogget · 17 Jan 2009

I couldn't say for sure without seeing it, but connection blocks shouldn't fall off PCBs! They don't need doing up hugely tightly, but certainly shouldn't be loose.

I'm assuming that you didn't forget to take the link wire off for volt-free switching, probably the best thing is to try a replacement and be very careful as it sounds like the terminals are a bit fragile. Hopefully it hasn't taken anything else with it.

sandpaper · 17 Jan 2009

don't worry didnt forget to take of the link wire.

Thankfully existing system is fine, although i dnt understand how heating was still working while i still had the blown reciever hooked up to it

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

how to wire a room stat to an existing programmer(grasslin)

Similar threads