CH Controls

[Truman]

I've had a couple of quotes now for a combi boiler to replace my open vented set up and the heating engineers seem to be at a loss as to why I want a hard wired traditional simple thermostat and a hard wired single channel programmer to control my heating. They just want to fit a wireless or wired programmable thermostat. At the minute I have an old sunvic roomstat and a drayton 2 channel programmer and I'm happy with this set up but need to replace these parts when I get a combi.

My beef with wireless or wired "programmable thermostats" is that there's no simple On or Off function as I understand it, you have to set the temp really low (e.g. 14 degrees) if you want the programmer to turn the heating off. I much prefer a simple on/off/timed, even if that is perhaps a bit less efficient than maintaining a more constant temperature in the house. I could perhaps understand a programmable roomstat being used in conjunction with a separate programmer but they seem to be just fitted on their own as the sole control.

Can anyone either recommend a programmable thermostat with On/off/timed functions, if such a thing exists? If not, a good one channel programmer that could be used with most combi boilers? I'm looking for digital rather than a mechanical style one.

 

[Chalked]

Honeywell has an off.
​Honeywell CM901 Room Thermostat | Thermostats | NoLinkingToThis

 

[Truman]

Yes, so it does, I'd forgotten about that one. I remember now the reason I didn't like it was how it cycles the boiler as it approaches target temp. TPI or chrono proportional control I believe it's called. Unnecessary as far as I'm concerned, I just want a simple programmer and separate roomstat!

 

[Ray Stafford]

If that is what you want, just remind the installer that you are the customer, and as you are paying the bill you want things done your way.

An ACL Drayton LP111 and/or the boiler manufacturers entry level clock and a basic roomstat still work as well as they did 20 years ago. If the wiring already exists for the roomstat, its a piece of cake.

 

[Truman]

Cheers Ray. The roomstat wiring is already in place - I have an old Sunvic TLX 2259 at the minute which I think has 4 core cable, so all I want is a newer less ugly roomstat! I think the problem for the installer is more the programmer - both the wiring and where to put it, as it can't go where the existing 2 channel programmer is at the minute due to where the boiler is being located. Does the programmer need to be near to the spur for the boiler, or can it be wired anywhere in the house?

At the minute I have the spur, then a couple of inches above that is the programmer, then a couple of inches above that is the boiler. I don't know how it's all wired, but I do know with a combi there'll be no space immediately next to the boiler for the programmer.

 

[Truman]

Looks like I'll need mains voltage switching controls, so that rules the LP111/LP711 out, as they're volt free.
Does anyone know of any other mains voltage timeswitches/programmers?

 

[AWheating]

why not fit the timer inside the boiler? i think ray suggested this in an earlier post.

 

[heliotrope]

Looks like I'll need mains voltage switching controls, so that rules the LP111/LP711 out, as they're volt free.
Does anyone know of any other mains voltage timeswitches/programmers?

Volt free contacts just means that that they do not produce any voltage but will carry mains voltage.

It is the same as a light switch in that you feed a voltage in (from your boiler in this case) around time
control or thermostat etc and back to boiler to fire it up.

The LP111/LP711 would be suitable.

 

[Truman]

heliotrope thanks for the info but I still can't understand the difference. Some boilers state volt free switching, some state mains voltage switching, and likewise some timeswitches say they are volt free, others say mains voltage.
The boiler I'm looking at requires 240v mains voltage switching but are you saying a timer with volt free switching would be compatible?

 

[stevetheplumber]

volt free means there is no internal mains feed within the programmer the mains live and neutral run into the programmer purely to run the motor that drives the clock or actually the electronics that run the clock nowadays
at the set times the clock makes and breaks the switch between two or more terminals they can be fed any voltage you need within the limits of the switch gear this means the clock can switch 12 / 24/110 or 240 circuits

 

[Truman]

Ok so you're saying that if the boiler requires mains voltage switching, then either a mains voltage timer or a volt free timeswitch can be used?

 

[Truman]

Ok having looked into this further, the boiler in question does not generate voltage, hence why it needs mains voltage switching going to it from the timer. I'm guessing this is the opposite of a boiler that generates mains voltage which then links to a volt free timer.

In other words, if you have got a mains feed going from the boiler to the timer, then the timer can be volt free as it does not need to generate any voltage.
Conversely, if the boiler does not generate any voltage then it needs mains voltage switching to come from the timer to it? And a mains voltage timer is therefore needed.

Or have i confused myself?!

 

[doitmyself]

Ok having looked into this further, the boiler in question does not generate voltage

It would help if we knew which boiler you were talking about.