Fitting room thermostat

[GrahameS]

Hi folks
Just joined & my first post.
My gas CH = GlowWorm Hideaway + ACL LP241 programmer
All rooms have TRVs but there is no room thermostat.
I want to have frost protection when away for a few weeks in the winter
What is the easiest/cheapest way to do this?
I'm thinking about a wireless roomstat.
Can I put this into my current system or just get new combined unit e.g. Honeywell CMT921?

 

[45yearsagasman]

You must describe the type of system ie Yplan or S plan to get the correct guide to wiring in your new stat.

 

[D_Hailsham]

My gas CH = GlowWorm Hideaway + ACL LP241 programmer
All rooms have TRVs but there is no room thermostat.
I want to have frost protection when away for a few weeks in the winter
What is the easiest/cheapest way to do this?
I'm thinking about a wireless roomstat.
Can I put this into my current system or just get new combined unit e.g. Honeywell CMT921?

If you install a room thermostat, you will have to set the TRV in the same room to Max.

You can add a wireless stat, e.g Honeywell DT92E to the existing system. If you use a CM921, you would still need to keep the LP241 to control the hot water.

Another option is the Honeywell Sundial RF² Pack 2. This would replace the LP241 and has a linked wireless room stat.

Personally I would opt for the CM921 or 927

CMT921 and CM921 are the same product. CMT refers to the control unit on its own CM to the control and the relay box.

Are any of your pipes in an unheated space, e.g the loft? If so, you should have a pipe stat and frost stat to prevent them freezing up. The frost control in a thermostat only operates if the heated part of the house gets too cold.

 

[GrahameS]

Thanks guys
I think I'm out of my depth already
But maybe I can learn enough to have a sensible conversation with an electrician!

How would I tell if I had Y or S-plan
The loft is full of pipework and I've had a quick look around
Is this where a frost thermostat would be? There is nothing obvious near the pump etc
Is this (if I have not got one already) all I need to add for frost protection when we are away?
The TRVs can be set to * but I'm not sure I trust them as some of them seem to stick even at normal settings

 

[D_Hailsham]

But maybe I can learn enough to have a sensible conversation with an electrician!

Hang in there and you will learn enough to do the job properly yourself.

How would I tell if I had Y or S-plan

A Y plan will have one valve, as in left pic; S Plan has two valves, as in right pic. The valves will normally be near the pump or hot water cylinder

View media item 5946View media item 11762

 

[GrahameS]

Thanks D_H
Eventually found it
The attic is a maze of pipes and wires
It says on the box -Honeywell Sundial Y Plan V4073A1039

 

[ajrobb]

May I suggest posting some pictures of your attic (or is it a loft)? Preferably showing pipes and/or insulation. Also a picture of your sticking TRVs might get some tips on servicing them.

 

[GrahameS]

The attic/loft/garret whatever was previously converted to extra bedroom space. It has very limited headroom, little spaces to squeeze past chimneys etc and no natural light
It will be impossible to take wide pictures showing large segments of the layout
The pipework is mostly covered in black foam sleeves.
The TRVs stick until I take them off and waggle the little pin!

 

[D_Hailsham]

Eventually found it
The attic is a maze of pipes and wires
It says on the box -Honeywell Sundial Y Plan V4073A1039

Was the valve in the attic? If so, you definitely need a frost stat and pipe stat to prevent the pipes in the loft freezing. As I said earlier the frost setting on a wall stat only stops the rooms in the house from freezing.

Here's the wiring diagram for the frost/pipe stat (Click image to enlarge.):

View media item 27048
The frost stat closes when the temperature drops below the set value (say 5C); the pipe stat opens when the water temperature rises above, say, 25C.