The Efficient Home Forum

To tidy up the wiring of an Evohome installation, I wish to shorten the cable of an insertion sensor that is attached to a CS92 and inserted into an unvented cylinder.
I wish to shorten the cable to about 600mm as the excess looks unsightly.

Does anyone know of a technical reason why this would impact the performance of the sensor+CS92 or would this be a perfectly reasonable change?

Francis

If you shorten the cable, wont the device be too close to metallic objects? It is good practice to be 1m away from metallic objects and other evohome equipment in my experience.

I have installed two heating only Evohomes recently. Both work without problems.
However, I am coming to realise that installing hot water control introduces a lot of additional problems.
This is especially true when retrofitting Evohome to work with an existing S-plan or Y-plan where typically the wiring centre, and hence where one would ideally place BDR912 and CS92s, is in an airing cupboard that is largely filled with a metal cylinder.
The issue appears to be the reliability of the wifi connection to these devices if they are in close proximity with 1. each other, and 2. with other metal objects like the cylinder, expansion vessal and lots of pipework.

For those contemplating the addition of hot water control, i would suggest first investigating whether the BDR91s can be wired outside the airing cupboard.
Frankly I think it is generally impractical to site the CS92 transceiver outside the airing cupboard or to expect the installer to use the metre plus of sensor connector to site the transceiver a metre away from the cylinder when the cupboard wall is only centimetres away.
I haven't established whether or not the CS92 is a source of unreliability but if the set up I describe is problematic then I suggest this is an issue Honeywell need to address with a more robust solution for the CS92 at a minimum.

Returning to the specifics of my situation and question:
The existing cylinder is in an existing airing cupboard.
The wall of the airing cupboard is about 300mm away from the cylindert and the height of the cylinder from the pocket into which the thermostat sensor goes is about 1.2m above this. Hence there is little that can be done to placve the CS92 further away from the cylinder than about 300mm.
There is nothing that I can do about the constraints of the room and cylinder size.

The CS92 has been installed on said airing cupboard wall albeit biased towards the door.
The higher the CS92 is installed the closer it will get to the BDR91s that are also by necessity installed in the same airing cupboard because that is where the original controls are placed and there is limited scope for rewiring.

I am hoping that Evohome will cope with these real world issues.
If it can not, then I will need to reinstall the original CH & HW controls.

I have spaced things out as best I can but this means that I have about 300mm more sensor cable than I want.

My question is: Is the functionality of the sensor compromised by shortening the wire or not.

Thanks in anticipation for an answer on this.
Francis

Your reply re the optimal siting of the CS92 has made me think (shocking I know).

Maybe the ideal location for the CS92 would be much away from the cylinder higher in the airing cupboard or even outside the airing cupboard.

In both cases I would need to extend the sensor cable with a length of two-core flex.

In addition to answering the question:
Is the functionality of the sensor compromised by shortening the wire or not?

Please can anyone tell me if lengthening the sensor cable would compromise its functionality?

I have emailed Honeywell directly about the issue of the insertion sensor.
They tell me that it is OK to lengthen or shorten the cable.
This may be helpful for anyone looking to find a good position for their CS92.
Francis

Hi Francis,

The 'issues' you raise are well known by experienced installers of evohome and in the 1000's of systems we have sold and I have personally fitted myself, the RF issues you are talking about are not localised to evohome. The fact is RF communication of any product will interfere with the next should the two RF devices be within touching distance of each other.

You need to bear in mind what the evohome system is trying to do. The centralised controller is trying to 'listen' for each of the multiple RF devices it has bound to it. The controller sends out an RF pulse approximately every 4 minutes and then the RF devices on the system send an RF pulse back with their unique signature and information. If for any reason the information is scrambled or not received from the individual devices, evohome will continue to do what it was doing until the next 'pulse'.

There is certainly no difficulty with evohome installations but there must be thought given to the location of devices and location of the main evohome Controller.

Fail to prepare, prepare to fail was always one of my favourite quotes of my tutors while doing my engineering apprenticeship!

Thanks,

Richard