A little help understanding "Optimum Start".

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So our new up-to-date CH fitted in the summer took us back in time with a rotary thermostat (rather annoyingly the installers took away (and "lost") my Horstmann DRT so I couldn't reinstall it).

I got a good deal on a Honeywell CM907 and installed it this week. But I'm a little confused about "optimum start". The manual says:

What is Optimum Start?
Optimum Start is a program which ensures that the optimum temperature conditions are achieved at the required times. This is an Energy Efficiency feature that adjusts the start time of your heating system depending upon how cold it is. For example, on cold days your heating system will be started earlier to ensure that your home is warm when you get up (at the target temperature) and on warmer days the heating system will be started later to save energy. So, if the Optimum Start Feature is used, then the time / temperature settings which are entered into the thermostat should be set to when you want to be warm by and not when you want the heating system to start.

I have a constant background temperature of 16c and raise this to 19c during the early morning, mid afternoon and evening periods that we are home.

With the Hortsmann I set the 19c temp to start at 6am ready for us getting up at 6:30.

Does optimum start on the CM907 mean that I can set the 19c temp for 6:30 and the temp will be reached by 6:30 because the stat will call for heat at the right "start" time?
eg, if its 16c in the house then it might start it at 6am,
if its 17c in the house it might start it at 6:10,
and if its 18c in the house it might start at 6:20.

OR

Does optimum start need the external temperature sensor and so I cant use it anyway.
 
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Optimum start does what is stated.

But that will have little effect if you set at 16 C overnight as there is little increase needed.

But Weather Compensation control is better if you can use it to do the job!

Tony
 
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Optimum start does what is stated.

But that will have little effect if you set at 16 C overnight as there is little increase needed.

But Weather Compensation control is better if you can use it to do the job!

Tony

Or indeed both together. My system is performing admirably at the moment utilising both optimum start/stop at u individual room level and weather comp. I have a 4 degree setback temperature.

Mind you it is still quite mild outside. But then that's the point I I guess.
 
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Thanks for the replies.

I looked at the weather comp stats but didn't understand how weather comp works? Plus it wouldnt be easy to get a temp wire out to the outside world from the stat position (and I cant change that) and they were beyond my budget.

To be honest I wasn't looking for a stat that was as technical as the CM907, after all, the simple Hortsmann served me just right for the previous 2 years. But the price I got it for and the user display made it a lot better than the ones in my budget.

I'll set the optimum start up and see how it goes when the CH gets turned back on. We've gone from a 30 year old boiler and single rads that were apparently too small for the rooms, to a new Vailiant boiler and double rads with TRVs that are the right size (apparently). So no doubt it will be another learning curve to get the rooms and the house to the right temps.
 
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I assume these devices have a learning routine that adjusts future performance based on past warm up time, as there is no setting to tell the device how quickly one’s building heats up.
 
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I assume these devices have a learning routine that adjusts future performance based on past warm up time, as there is no setting to tell the device how quickly one’s building heats up.

Why could it not do that from its own built in temp measuring element?
 
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Every bill paying husband does. I did a non scientific test a while ago whereupon without telling the customer, after the first year of service I changed the offset by one or two degrees. The following year not a single subject had noticed a comfort change. And a good proportion noticed a saving in their gas.


Mind you they also had the running temperature of the boiler lowered 10 - 15 15 degrees at the same time.
 
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There is also a problem that when a new more efficient boiler is fitted many people will use it more so that the gas consumption increases!

I am still not sure if it is the "new toy" syndrome or they think its cheaper to run so they use it more!

Have to confess that I make more journeys in my 55 mpg car because they are cheaper!
 

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