programmable room stat to effect a move of the main controls

[smipx013]

Hi,

I have a unvented "system boiler" type heating with pumped water and heating (separately controllable). The main controller is on the first floor in the airing cupboard. I have looked into moving it to the downstairs utility room but the cost is proving to be prohibitive due to the flooring and wires required to effect the move.

I like to keep the heating on fairly stingy twice on/off settings and then press the boost button to give an extra hour of heat if it gets chilly. Its a real pain to have to go upstairs to do this (dark cupboard and generally too lazy ). I am only concerned with the heating side from this point of view - the hot water can be fixed to two on/off's per day and I rarely want to boost this.

I have considered the following as a solution:

In the hall downstairs I have a simple mechanical 2 wire room thermostat. I was thinking that if I got a programmable room thermostat with a boost button then I could install this in its place. I could then set it as normal with twice daily on/off's. I could then put the heating on "constant" on the upstairs timer (leaving the water on twice daily as before) and effectively use the room thermostat to control the heating part of the system from downstairs.

Is this a sensible plan? Are there any ramifications to doing it this way?

Thanks
Paul

 

[Charnwood]

Some programmable stats boost buttons go to the next time zone, not a 1 hour boost - the Honeywell CMT 901/907/921/927 range, for example.
If it has just entered a 6 hour time zone and you hit the boost button, it won't 'un-boost' until the end of the 6 hour zone.

 

[D_Hailsham]

Some programmable stats boost buttons go to the next time zone, not a 1 hour boost - the Honeywell CMT 901/907/921/927 range, for example.
If it has just entered a 6 hour time zone and you hit the boost button, it won't 'un-boost' until the end of the 6 hour zone.

I solved this by using all six time/temperature settings and spreading them evenly over the day (retired and at home all day). The temperature is the same all day. If some one decides to turn the temperature up, becasue they are feeling chilly, it wll revert to normal at the next setting, which will be within no more than four hours.

 

[smipx013]

Good point though - that is not what I want.

Having looked further I'm not actually certain there is a product that will do what I want. I want a boost for, say 1 hour and distinct on/off times rather than high/low times and on all the time (such as the TimeGuard TRT035 - http://www.timeguard.com/pdfs/0000/0691/TRT035_Instr.pdf)

Does such a thermostat exist I wonder?? If not then I guess I'll just have to rip up the floorboards



Cheers,
Paul

 

[D_Hailsham]

I want a boost for, say 1 hour and distinct on/off times rather than high/low times and on all the time

I am not aware of a programmer which does what you want. As for distinct on/off times, it is easy to achieve this by setting appropriate temperatures, e.g: off - 5°C; on - 20°C.

When the low temperature time is reached, e.g when you go to bed, the boiler will stay off until the morning on time, unless the temperature drops below 5°C, which will be very unusual in a well insulated house.

 

[smipx013]

Fair point D_Hailsham.

Do you know of a thermostat that will do a 1 hour boost of temperature rather than wait until the next change time though. A 4 hour boost is not what I would like ideally to have the following:

10pm to 7am - 10C (effectively off)
7am to 10am 21C
10am to 4pm 10C (effectively off)
4pm to 10pm 21C

Boost button - give 1 hour of 21C and then revert to program

Cheers,
Paul

 

[D_Hailsham]

You said that you have a 2-wire stat. Any programmer will require at least three wires: Live and Neutral (to power the programmer) and switched live to the boiler.

IF there is a third wire hidden behind it the existing stat you may be able to use it

I've just rechecked and the Honeywell Y9120H Sundial RF² Pack 1 has a one hour boost feature, but you will need three wires to the existing thermostat location.

The thermostat part communicates wirelessly with the programmer part, so you can locate the stat in a different place if you want to.

 

[smipx013]

Not all stats need 3 wires. I def have 2 (live and switched Neutral I believe.

Many are advertised as being suitable for 2 wire and 3 wire installations e.g.

http://www.plumbnation.co.uk/site/h...ostat/honeywell-dt90e-specification-guide.pdf

or

http://www.sangamodirect.co.uk/Sangamo-CHOICE-RSTAT3-Digital-Room-Thermostat-p/choice-rstat3.htm

 

[D_Hailsham]

Not all stats need 3 wires. I def have 2 (live and switched Neutral I believe.

Many are advertised as being suitable for 2 wire and 3 wire installations

1. The two wires will be live and switched live. Don't be misled by the fact that one wire is blue.

2. But you are wanting to install a programmer or programmable stat in the place of the existing stat. That requires a supply for the clock/electronics, i.e a live and neutral. You then need a switched live to the boiler/motorized valve. Three wires in total.

If you definitely have only two wires the only solution is a wireless programmable stat. The user control is battery operated and the receiver still needs a minimum of three wires, but it doesn't have to be installed in the same place as the old stat.

 

[Charnwood]

Neither of those are programmable. You would have to alter the temperature manually, therefore defeating the OPs object.

 

[D_Hailsham]

Neither of those are programmable. You would have to alter the temperature manually, therefore defeating the OPs object.

I know that, but I think the OP was just using them as examples of stats which could be used with two or three wires.

The obvious solution is a Honeywell CM927 with the receiver near the wiring centre.

 

[smipx013]

Hi all,

Yes they were just examples. I understand now about the need for a neutral on the electronic room stats. I curse the tw*t that put the timer in the airing cupboard and double curse him for fitting a 2 wire room stat.....

On the plus side I just fitted 14 ras-c2 's to replace a bunch of old honeywell trv' s several of which were not working well.

I used the old nuts and olives in all if them. Gave the olives a damn good clean with cloth and fine wire Wool, then a single wrap of ptfe and finally smeared the ptfe and threads with a little fernox lsx (that everyone here seems to revile) . Not a single drip or leak anywhere. Well chuffed but not so chuffed that I had to balance the system (as the honeywell ' s had the balancing within and subsequently all the lockshields were fully open) . The balancing took 4 hours :O. Doing the 14 valves (plus 3 tails and 2 lockshields plus lifting a towel rail by 1cm took 7 hours including full drain down, refill and bleed). Not bad for a non qualified diy-er.

 

[smipx013]

Hi,

Not wishing to flog a dead horse about a programmable 2 wire stat but is this one suitable: http://www.thermsaver.co.uk/media/pdf/controls/thermsave-celect-programmable-thermostat-guide.pdf

It's working from a battery so needs no power for the timer elements. It says it's 2 wire NO (normal open) and COM which I am hoping might be Live (com) and Switched Live.

Is this the case?

Cheers,
Paul

 

[D_Hailsham]

Yes, it will do the job and you are correct about the wiring.

The old programmer will need to have the CH set to permanently ON.