Central Heating Coming On

[steveyguk]

Hi,

I'll try and keep this brief.

Problem:- Central Heating coming on out of programed hours @ 04:00 in the morning. Time is set correctly.
Setup:- BOILER = Combi Instant 105E
Control:- Honeywell CM67RF (wireless) - checked comms all ok

1 to 7 (1 being Monday) Programed hours same everyday.

Programed Changes
1 06:00 19C
2 07:40 5C
3 -
4 -
5 16:00 19C
6 21:30 5C

Those of you who are familur with the control unit will know 1 to 7 is days, and 1 to 6 are programed changes throughout the day. I'm treating mine as an 'on and off' thus on at 6 and off at 07:40.

If this is wrong, or anyone knows why this happening I would very greatful for an answer.

 

[ollski]

Frost stat?

 

[steveyguk]

Frost stat? What is one of those, and where would I find it?

We have recently moved into our new home and I'm still getting to grips with the boiler etc.

Boiler is located in the loft.

 

[ollski]

From manual:
The frost protection mode is integral to the appliance and functions only with the selector switch, seeFig. 1xitem 20 in the domestic hot water and central heating position. If the system temperature falls below 5° C then the boiler will fire on its minimum setting until a flow temperature of 30° C is reached. Further protection can be incorporated by using a system frost thermostat.

It may be that you have an external frost stat which looks like a room stat near the boiler in the loft too.

 

[steveyguk]

I've looked and can't see a room stat in the loft nor where it was moved from before we moved in; therefore I can only conclude it's default behaviour is to fire up (like the manual states) when 5C is reached ( which I guess must be around 04:00 in the loft) until it senses 30C flow temp?

Arghh that's annoying.

 

[D_Hailsham]

Central Heating coming on out of programmed hours @ 04:00 in the morning. Time is set correctly.

Control:- Honeywell CM67RF (wireless)

1 to 7 (1 being Monday) Programmed hours same everyday.

1 06:00 19C

Do you have Optimization switched ON at the CM67? It's Parameter 15:Op.

 

[steveyguk]

Do you have Optimization switched ON at the CM67? It's Parameter 15:Op = Hmmmmm French Sorry no idea where I would check that.

 

[D_Hailsham]

Do you have Optimization switched ON at the CM67? It's Parameter 15:Op = Hmmmmm French Sorry no idea where I would check that.

Move the slider to the OFF position.
Press and hold INFO button and press PROG 3, 4 together.

The display will show: 1:CL

Press Prog 2 key

Display will show: 3:Ot

Press the "clock" + or - button to scroll through the parameters until you reach 15:Op.

If there is a 1 on the right, Optimization is ON; if a 0, it's off.

What's "Optimization", you ask?

Well, it's a clever way of turning the boiler on at the correct time, according to how cold it is.

With optimization OFF, you have to change the boiler on time manually if you think it's going to be very cold, so the house is warm enough when you get up.

With Optimization ON, you tell the controller the time you want the house to be up to the set temperature. e.g 1 = 19C @ 0700. The CM67 will automatically adjust the boiler on-time according to how warm/cold it is. The controller normally takes about one week to learn the characteristics of the house, i.e how quickly it cools down overnight.

 

[steveyguk]

Fantastic it was set to on. You star!! I've changed to 0. Thank you very much.

 

[D_Hailsham]

Fantastic it was set to on. You star!! I've changed to 0. Thank you very much.

Great that you have resolved the "problem", but Optimization is very useful - once you are used to it.

Your current morning schedule (On a 0600, Off at 0740) implies that you get up at about 0630 to 0700. But is the house actually up to 19C by then? Or does it only reach temperature just before you leave? I don't know, just suggesting that you could be wasting gas. Setting Optimisation On, with a time of 0645 (or whenever you get up) and a temperature of 19C, will ensure that the house is actually at 19C when you get up. You might even be able to have an earlier off time (assuming you leave home at 0740) if the house retains its heat.

The afternoon on time (1600) is more problematic as it's a bit of a grey area whether optimization works on any other time point apart from the first. If it does it would, logically work on 3 and 5 only as they would be the On times) If it does work, you would be able to set 5 to say 1700 (assuming that is when you get back home) and leave the stat to turn the boiler on at the appropriate time.