central heating optimiser

What do you mean by 'optimiser', and what have you looked at? What I recall was gizmos sold many many years ago to prevent (or reduce) boiler cycling, but this shouldn't occur with a properly designed system to current standards.

It has an internal and an external heat sensor.

You set the optimiser to reach a particular temp within the property.

You then set the timer. The system will then calculate (based on the temperature sensors) when the boiler needs to switch on and off.

The whole idea is that if you set the optimiser from, say, 6.00am to

On a warm morning the boiler might switch on at 5.30am to achieve this. On a very cold morning the boiler might have to switch on at

Similarly, if it is warm outside but initially cold in the house the boiler might be able to switch off the cycle completely at 7.30am. However, if it is still very cold outside it might wait until 8.00am.

We have an optimiser system fitted at work.

It means that you save gas and you know that the property will always be at the correct temp during the precise periods that you want the heating.

Graham

Honeywell CM67 with the optimisation function is what you need.

IMVHO I still debate there is any _significant_ benefit of having "optimum start" on a prog.stat, as the boiler burn time is going to be the same and the differernce between the heat being on(or off) for an extra 20 or 30 minutes isn't going to make much difference to the fuel savings, and the "heat leakage" of a relatively well insulated and draught free house isn't going to be the same as a 1970's commercial premisis (or whatever)

Just my take on it. FWIW

Weather compensation that adjusts the CH water temp depending on outside temp is great though.

At the moment my boiler is on about 6 hours of the day so a saving of 20-30 minutes a day is quite significant.

Rob

Totally and utterly wrong. Some Optimise on and off across all time zones selected. These really drop the fuel bills.

Over year it is. If it takes 45 minutes to heat your house from cold it could hold it off for 45 minutes. Those that optimise off, and on and off through the time zones you programme, are superb. Not cheap though.

I don't think it is quite as simple as that.

Let's say your boiler comes on 30 minutes earlier than it might need to were it controlled by "optimum start" that 30 minutes of heat is not just 30 minutes of "wasted" energy, it is energy being stored within the fabric of the building, so, come the 6th hour of the day, the thermostat(s) will have kicked the boiler off for much longer (throughout the day)thanks to the pre-heated walls etc therby regaining a very significant percentage of the initial additional "on" period.

Regardless of how long it is on for, the actual wasted energy is the energy "leakage" from the building which would be down to poor insulation and draughts, so a well insulated and draught free property wouldn't just "lose" 30 minutes of burned fuel.

Hence, to re-coup however many hundreds of pounds the complex controll hardware costs may take an exceptioanlly long time. Better off putting the money into additional insulation, argon filled triple glazed windows, heat recovery thingys etc.

(I'm sounding like DrEvil now!)

That's what I think anyway.

:¬)

A very good post, and very sensible, except that a Honeywell CM67 is only a few extra pounds for the optimisation function.

Read my earlier reply.

I am very suprised that you consider ther may be significant savings. Sou you say you want the evening temp to be held at 21 degrees untill

Well, I suppose if you were just pumping energy into an over ventilated un-insulated building then sure, 30 minutes of not heating the outside world would prove usefull, however if correctly insulated, heat loss would be minimal.

Accurately controlling on/off times of a boiler is nothing compared to corect insulation. If there are "significant" savings to be made by saving 30 or 60 minutes "boiler on" time then I would suggest a vast amount more would be saved by bringing insulation levels up to or beyond recommended spec.

But I'm sure you'll come back with another statement that re-writes the basic laws of physics.

But it's really ugly, and only has optimised start (first burn) IIRC which goes back to my point of being more of a gadget than anything else.

It optimises off as it optimises on. It has an end time and calculates the heat required to keep the system up to temp before the end time target. The better systems "learn" the heating system.

The point is not insulation. It is whether optimisation saves energy. In a superinsulated air-tight house its effect would be minimum compared to normal British crap house.

You are confused..and it's not even Friday.

Then buy a Landis & Staefa. Which I think is better.

The DCD optimises off and on on all time segments

If you want this level of sophistication cost and complexity are part of the territory. Opinions vary on this matter including the opinion of people I respect greatly. Costs of the Honeywell CM67 seem to be around £75 and people who have them seem happy that they are programmable with a reasonable ease relative to the complexity.

IMHO a simple programmable thermostat is about £30. Since the night time temperature will be maintained (at say 15C) the system only has to heat the house by a certain maximum amount in the morning.

More like £50

You opinion is lacking then. For £20 more you get far more, far more. Well worth it all around.

(I don't believe that) You are in the position that you have to _explain_ the operation of the heating controls to purchasers.

Even the simplest programmable stat is much too complex for some people.

If a "box" requires 10kWHrs of heat input to maintain its temperature getting it up to that temperature 30mins before it is required means that 5kWhrs of heat are lost. Yes, the box structure will also warm up but it is going to do that anyway, and release that heat later. That is not relevant, as what ever you do there is always going to be a

If you take the same box and reduce it's heat loss by insulation then the amount of heat lost is also reduced but it is still lost. It is up to people to decide if the savings from a complex control system or those from better insulation are best. Personally I'd go for both.

This is easier as all you do is punch in the occupation times, leaving out any warm up times.

I turned the optimising off on mine because it was cutting in far too soon. Otherwise the CM67 is IMHO simply brilliant, especially being able to use the Party button to hold the heating off for a hour or two if you are going out.

You can only save 25% by putting 25% less heat into a house. As the average difference across the heating season between internal and external temperatures is 10-12C this would translate to having your house 2-3C colder than it presently is. All the stuff about overshoots is junk science IMO: people set the thermostat to what they find comfortable, not a number.