Gas usage sensible?

[D_Hailsham]

It is rare for me to come home from school to find that the heating is still off and hasn't been tampered with, last month only once out of 31 days did the heating stay on Automatic.

And I thought the CM900 series was too complicated for the average female to fiddle with!

My Mum is at home during the day and she usually opens the windows at 1000 to ventilate the house and then switches the heating back on at 1200 @ 19.5C as usual.On very cold days she won't open windows and she will normally put the heating on at 1000.

If she has to go out she will lower the temp to 18C.

I don't see the point in lowering the temp to 16C if someone is home all day.

It so happen that one cold weekend we were out so the heating was left at 16C, we got back just before 1800 and the temperature had dropped to 17.0C which was comfortable for me but not anyone else.

You should have set the programmer to get the house up to temperature when you arrived home!

When you say that the CM900 is rarely left on Auto, do you mean that the slider switch has been moved to Manual or just that the temp has been changed using the two buttons? I would use all six daily settings, e.g. with one set for about mid-day and the other in the middle of the afternoon. Also, show your family how to put the temperature up/down by using the buttons. This way, if they drop/raise the temperature, it will automatically revert to your setting at the next time check.

You will use less gas if you try to keep the temperature constant during the day.

The attic has no door.

So heat from down stairs will rise and keep the attic warm during the day. Synchronise times and temperatures during the day. It does not matter if the attic is warmer at night.

The house usually gets to temperature quite quickly, do you think it would be more efficient setting the flow temperature even lower and waiting a little longer for the house to warm up?

No. If you do that, you will just reduce the radiator output even further. I think you are trying to do the boiler's job rather than letting it adjust temperature according to requirements; i.e high when the house is cold and lowering as the house warms up. I know there is a problem because your boiler is considerably oversized for the heating load - but that's the result of choosing a combi just for hot water requirements.

 

[David937]

Thanks for the reply.

So best option would we to close the attic hatch when I go to school and set the CM927 to switch on at 1200?

The main reason why I didn't tell them to use the arrows is because they would get too tempted to raise the temperature higher than normal even though we all cope fine with 19.5C.

So it is not worth lowering the temp when we go out?

 

[JohnD]

provide them with a fake controller that they can tinker with, and hide the real one.

 

[D_Hailsham]

The main reason why I didn't tell them to use the arrows is because they would get too tempted to raise the temperature higher than normal even though we all cope fine with 19.5C.

Did you know that you can set an upper temperature limit of 21C? Its Parameter 6:uL

The reason I suggested setting other temperature times during the day is that, if they do put the temperature up, it will automatically revert to your setting at the next set time. I f you want to have all day times set to 19.5C, that's no problem. You have five day settings to play with and one overnight!

So it is not worth lowering the temp when we go out?

I doubt it for short periods. In any case you can programme the CM927 to come on half an hour before you expect to get back. The possibilities are endless.

I thought you said you didn't have a door to the attic! Now you say you have a trap door. That's a better barrier than nothing!

 

[David937]

Yes I have already set the limit to 21C.

No I thought you meant a proper door like

Ok thanks for all your help D_Hailsham.

Well anyway an insulation chap/company is coming to survey some time.

 

[JoeMar]

David937

i think a big part of your problem is caused by the user messing around with the settings on the boiler too much.

why is the boiler range rated a 14kw? put the boiler back to it's full power and let it decide how much power it needs. According to Vaillant it is not necessary to range rate the boiler at all.

Why did you decide against a Vaillant controller? You are not getting the best out of the 937 using a 3rd Party controller. Should you had gone for a Vaillant controller with weather compensator (VRC430 or simillar) you wouldnt have the problem of manually changing the flow temperature everytime the weather changes.

Im definitely using a lot less gas this winter with the 937 than i did the previous year with the Baxi back boiler.

 

[David937]

Now I have learnt to leave the flow temperature set at 65C, it works very nicely like that.

It is better to range rate the boiler as an engineer on this forum told me.

I did not decide against a Vaillant controller, we originally had one but it is not compatible with multi zone systems.

Now I am told by my Dad that there is some kind of credit building up on the gas bill so the bills will go down apparently

 

[Deleted member 105431]

Where exactly do Vaillant state that their boilers should not be range rated?

They don't; it's bullsh1t.