Originally posted by Kevin
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How "smart" is the hot water system
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Just like the heating, you should be able to state for example "At 7am I want the hot water to be 55C". So this means the boiler needs to fire up at say 6.45am to get it to 55C by 7am. In the scenario of someone getting up early, the temp in the tank would be lower as a result, and so the boiler may need to come on at 6.35am instead. Sounds pretty simple to implement. I thought that was the purpose of the hot water probe to allow this optimisation, but all it shows me is the water temp - the cylinder's own thermostat can just be set to the temp I want the water to be without needing the probe.
If I just set the water to come on an hour earlier, then you have up to an hour longer to maintain that temperature for, wasting energy. Admittedly, a well insulated water tank will not lose much heat over an hour, but for those with the external circulating system (such as jonstatt above) to provide quicker hot water to remote taps, then this could be a significant saving over time.
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Originally posted by top brake View PostThanks for your feedback Kevin, what would you like the system to do in this scenario?
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Originally posted by G4RHL View PostPerhaps an override such that if the hot water drops below a certain temperature then the boiler puts it right? In Kevin's case if someone gets up early and the tank goes cold or below a pre-set temperature the system senses that has happened, checks when hot water may next be needed and goes into action at the relevant time. Optimisation itself may be a hit and miss affair for some of us.
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Originally posted by G4RHL View PostPerhaps an override such that if the hot water drops below a certain temperature then the boiler puts it right?
Or am I being silly?
P.
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Originally posted by davidaj View PostIf you have reasonably stable conditions then optimisation should be able to work accurately. If you have wildly varying conditions then optimisation will be unable to calculate when to switch on correctly, and so may not always work for you for room heating. However, hot water is typically the former, reasonably stable, so optimisation should work well for this. You'd hope someone who is installing evohome would also address the more fundamental efficiency measures of good insulation.
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Originally posted by paulockenden View PostBut that's exactly what happens when the h/w is switched on. So aren't you really just arguing to switch it on a bit earlier?
Or am I being silly?
P.
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Originally posted by G4RHL View PostI have "reasonably stable conditions" but optimisation is a waste for me. It comes on far too early. E.g in the winter months it takes 15 minutes max to get a room comfortable and around 30 minutes to get it up to the site temperature but optimisation in my case had the boiler firing up 60 minutes before the designated time. I have switched it off. If the heating comes on at 06:30 and I am getting up at that time, fine.
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Originally posted by top brake View PostThanks for your feedback Kevin, what would you like the system to do in this scenario?
Even then there is still the possibility that an optimised start for heating couldn't achieve its temperature goal, if the HW and CH goal times were set too close. To avoid this the system would presumably have to calculate two stacked optimised start times, one for the HW that allowed sufficient time afterwards for the CH to bring rooms up to temperature. This may, or may not be practical, or problematic in ways I haven't considered but the intention is certainly desireable for those with a hot water priority system.
My current (Potterton / Siemens) system doesn't offer optimised start for heating i.e. I just set a time at which the CH starts, and I have no separate HW timer control at all. What it does do is calculate the optimised start time for HW ensuring it is up to temperature just before that heating time is due to commence. So having optimised start on heating will be a new and attractive benefit but if the HW priority compromises that I'm losing some features I already have.
Back in this forum because I'm considering which smart system to choose but I'm now wondering about compatibility with only one heat request signal available on my boiler. I'm thinking I can common the two demand signals (HW & CH) from evoHome but I need to think that through a bit more as the boiler uses its own resistive temp sensor on the HW to decide when it's satisfied and to switch from HW to CH mode. I'm not sure I can intervene here easily.... I can however enforce which circuits the heat output flows through though and even force both simultaneously. That's rather brute force and the flow temperature the boiler chooses is based on the mode it thinks it is in e.g. using a higher flow temperature and applying weather compensation to CH only.
Obviously more thought needed .. and maybe even a different boiler would make things easier. I've always been interested in an Opentherm solution. A well qualified evoHome installer has done a site survey and said everything is do-able though.
K
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Originally posted by davidaj View PostWell you either have more unstable conditions than you think, or a fault with your install, or a bug in the device and optimisation is not optimally implemented. Turning it off removes a major energy saving feature of the product. I see you've raised this long ago in another thread, and appears Honeywell think it's your fault. Sounds to me like it's not your fault and the optimisation algorithms need improving. Most people don't carry out the in-depth analysis that others on this forum have, so not enough evidence to prove this.
I tried optimisation. Set it to come on no more than 60 minutes before the desired time but found it seemed to come on 60 minutes before that time regardless. To be fair not exactly so, sometimes it was 50 minutes. Optimisation never learned what it is supposed to do - the time it takes to warm up the zone. It ignored it.
Optimisation at night was a little better but even then it would switch off about an hour before the set off time which was not always good. As it seems optimisation is doing the same as a person setting an on time ahead of when he wants heat to allow for a warm up it begs the question whether it is worth it when you can adjust your settings to do the same. In my case I don't need to worry about the temperature being up to set point when I get up, it is quite acceptable for it all to come on the same time I get up. Less wastage that way anyway.
The installation seems to be fine. Am pleased with it. I still feel less gas is being used now I am zoned but will know better after a 12 month period. I find it useful if away for a few days some distance from home to be able to override the custom off setting on my way back. Not much of a concern this time of the year though.
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