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Thread: What water and overnight set-back temperatures do you use?

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  1. #1
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    Default What water and overnight set-back temperatures do you use?

    The title says it all, really.

    What temperature do you have your DHW cylinder set to? Are you using open vent, sealed or pressurised?

    What temperature do you have your CH overnight set-back set to?
    Last edited by dty; 9th February 2017 at 10:58 PM.

  2. #2
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    Quote Originally Posted by dty View Post
    The title says it all, really.

    What temperature do you have your DHW cylinder set to? Are you using open vent, sealed or pressurised?

    What temperature do you have your overnight set-back set to?
    I have an unvented OSO 250l cylinder. My HW is set to 62C with a differential of 7C. Through experiment, I have found that this temperature range suits an old thermostatic shower. HW is timed to come on at 0700-0900 and 1630 - 2000. During the summer, with a gas hob, I use about 1 cubic metre of gas a day.

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    Thanks HenGus. I've just clarified the second question, which was about CH, not DHW.

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    I'm using over 25 cubic metres a day at the moment! You can see why I'm interested in this stuff!

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    I have a Megaflow 250L unvented cylinder and set DHW at 60C with a differential of 5C. All my CH temps are set at 10C for overnight operation (mean spirited) unless we have very young or very old family visitors, then I run overnight at 15C to 18C. I do not use Optimisation. Hope that is of use.
    Last edited by killa47; 10th February 2017 at 01:44 PM.

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    Quote Originally Posted by dty View Post
    The title says it all, really.

    What temperature do you have your DHW cylinder set to? Are you using open vent, sealed or pressurised?
    Open vent 100 litre cylinder - I did have it set to 50 for a long time but increased it to 55 about a month ago as I couldn't quite run a full bath without temporarily turning the temperature up, and I find 60 far too hot from a tap, to the point of scalding. 55 seems a good compromise that isn't quite scalding but can fill the bath well. I have the differential set to 5 degrees.
    What temperature do you have your CH overnight set-back set to?
    All rooms except the bedroom are set back to 5 degrees at night. The bedroom is scheduled to 17 through the night mainly for our 10 month old son.

    I learnt the hard way in the first winter I had evohome that only setting the downstairs rooms back to say 12 or 14 degrees resulted in a lot of gas being burnt needlessly through the night and my costs actually went up not down!

    Likewise when the house is vacant during the work day every room is scheduled to 5 degrees, and I let optimal start figure out when to turn things back on again so things are warmed up for the time that people start arriving home.
    Quote Originally Posted by dty View Post
    I'm using over 25 cubic metres a day at the moment! You can see why I'm interested in this stuff!
    How many kWh in 25 cubic metres ?
    Last edited by DBMandrake; 10th February 2017 at 01:26 PM.

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    Further observations on our system.

    I found 10C works out ok for overnights temps except when outside temps are at or close to frost levels. I used to monitor whether any zones were triggering the boiler overnight when set at 10C (our house rooms are 10ft tall. outside double skin brick walls uninsulated) but have only seen this happen once or twice - so I temporarily dropped the setpoint.

    A word of warning leaving some rooms at 5C or even 10C - We came home one day and spotted condensation water on the dining room internal windows behind the curtains, causing some mould on the lining. I have since increased the temp in that room (rarely used) up to 16C to maintain a lukewarm temp to minimise condensation.
    Last edited by killa47; 10th February 2017 at 02:05 PM.

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    I have all our rads set to 10c overnight. I have opt on for start and off. I have never had heating on overnight, even when my son was born. (S'pose it was the way I was brought up).
    We also had a PIV installed when we moved to this house - best thing we ever did. Now we never get any condensation on the windows.

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    Quote Originally Posted by DBMandrake View Post
    How many kWh in 25 cubic metres ?
    I'm averaging about 300kWh a day at the moment.

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    Thanks for the input everyone.

    I'm in a large 1950s house. We have recently had a fair bit of work done on insulation (including CWI) but the house still seems to lose heat quite quickly (old aluminium framed windows with 10mm double glazed units won't be helping, I'm sure). I've been using 15C overnight, but I'm having long warm-up temperatures in the morning, maxing out our 30kW boiler for over an hour.

    My heating engineer (who is EXCELLENT, if you're reading this! ) suggested moving the DHW heat-up earlier, which I did, and I can see the morning spike not stressing the boiler quite so much now (although the noise of the boiler coming on at 5:30 is another matter...)

    His next suggestion was to keep the house warmer overnight, and suggested 18C. Again, that has obviously had a beneficial impact on the gas usage first thing in the morning, but at the cost of overnight gas usage!

    So I'm just trying to get a sense of whether 18C overnight, and ranging from there up to 21C during the day depending on occupancy and time of day is decadent, normal, or somewhere in between.

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