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Thread: EvoHome - Optimizing

  1. #11
    Automated Home Legend paulockenden's Avatar
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    Smappee has a really good gas monitor, but it really needs to be used in conjunction with their electricity monitor.
    2019-01-18 09.17.47.jpg
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  2. #12
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    I think Evohome in poorly insulated houses doesn't always help with energy savings but may increase comfort levels. For instance, I have a customer who has a HR92s on all the rads including one in the porch near the cat flap. Although the house is well insulated the draft from the cat flat caused the HR92 to be constantly calling for heat during the night when the set back was too high (16oc) for that zone. I suspect that also during time periods when it's On it'll call for more heat than it needs, due to the heat losses of that particular zone.

    If you go back and think to a traditional system with one roomstat, in an older house that's poorly insulated if the roomstat was in a particular warm zone it would click off and so the rest of the house would, even though the rest might not be warm. It's not monitoring each room individually, so therefore not always calling for heat. Start monitoring each room individually like you do with HR92s you are going to create a greater demand across the system trying to keep each zone at the set points when heat losses are great, therefore increasing gas usage.

    I think the answer to get your gas usage down is you need to insulate more, more and then some more

  3. #13
    Automated Home Legend paulockenden's Avatar
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    That porch is why I wish the “Don’t call for heat” facility of the electric zones could be optionally used in radiator zones too. It would be ideal for situations like this.

    Without that, I can’t help thinking you might be better off deleting that zone and just using a conventional TRV instead.

  4. #14
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    Quote Originally Posted by mtmcgavock View Post
    I think Evohome in poorly insulated houses doesn't always help with energy savings but may increase comfort levels. For instance, I have a customer who has a HR92s on all the rads including one in the porch near the cat flap. Although the house is well insulated the draft from the cat flat caused the HR92 to be constantly calling for heat during the night when the set back was too high (16oc) for that zone. I suspect that also during time periods when it's On it'll call for more heat than it needs, due to the heat losses of that particular zone.
    I hear what you're saying, but then, that's a symptom of a poorly installed system surely? You could have these draughts anywhere and if the thermostat at the radiator is not relating to the overall room temperature then you should be buying a wall-mounted thermostat and hook that up to the zone. That, combined with analysing the problem with something like Domoticz should resolve the issue.

    Quote Originally Posted by mtmcgavock View Post
    If you go back and think to a traditional system with one roomstat, in an older house that's poorly insulated if the roomstat was in a particular warm zone it would click off and so the rest of the house would, even though the rest might not be warm. It's not monitoring each room individually, so therefore not always calling for heat. Start monitoring each room individually like you do with HR92s you are going to create a greater demand across the system trying to keep each zone at the set points when heat losses are great, therefore increasing gas usage.
    We have a couple of rooms that lose heat rapidly and the radiators are struggling to keep them at temperature in this chilly weather. The old system was completely ineffective though so it's a huge advancement being able to make it liveable in. I'm working on reducing set points to achievable temperatures but they do result in higher demand as expected.

    Quote Originally Posted by mtmcgavock View Post
    I think the answer to get your gas usage down is you need to insulate more, more and then some more
    Absolutely. Haven't really worked out how we're doing that yet, but more loft insulation will be a good starting point. There's false ceilings with voids above them in the upstairs, evidently due to previous owners having heating headaches. They've got probably 100-150mm of insulation at present but it's old and needs topped up. I'm cautious about restricting the airflow from the basement by using underfloor insulation as it could lead to damp problems. Similarly I don't want to stud walls as I want them to be able to breathe properly. It's going to be a long project, but at least now the house is warm

  5. #15
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    Quote Originally Posted by paulockenden View Post
    That porch is why I wish the “Don’t call for heat” facility of the electric zones could be optionally used in radiator zones too. It would be ideal for situations like this.

    Without that, I can’t help thinking you might be better off deleting that zone and just using a conventional TRV instead.
    I'm sure the cat likes it nice and warm with it's radiator bed, but yes that would be quite a good feature to do that. You are right though a traditional TRV would maybe be more suited to that situation but then you risk trading off comfort for efficiency. I suppose it depends which call you want to make. A room which was once cold is now warm, but at a cost.

    Quote Originally Posted by Jemster View Post
    I hear what you're saying, but then, that's a symptom of a poorly installed system surely? You could have these draughts anywhere and if the thermostat at the radiator is not relating to the overall room temperature then you should be buying a wall-mounted thermostat and hook that up to the zone. That, combined with analysing the problem with something like Domoticz should resolve the issue.
    It depends how you look at it, it is a limitation of the HR92s with temperature sensing. But when you've got 12 zones, are you going to shell out £800+ in wall stats to cover each zone? Also the wall stat might not make much difference if the heat loss in the whole room is high.

    Quote Originally Posted by Jemster View Post
    Absolutely. Haven't really worked out how we're doing that yet, but more loft insulation will be a good starting point. There's false ceilings with voids above them in the upstairs, evidently due to previous owners having heating headaches. They've got probably 100-150mm of insulation at present but it's old and needs topped up. I'm cautious about restricting the airflow from the basement by using underfloor insulation as it could lead to damp problems. Similarly I don't want to stud walls as I want them to be able to breathe properly. It's going to be a long project, but at least now the house is warm
    Yes, you'll have to make a trade off for having comfort rather than efficiency for the time being. I've always seen Evohome as a benefit to comfort rather than energy savings, and if it saves you money along the way then great! But I think in some cases, particularly in cases where there's great heat loss I can be more costly.

  6. #16
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    Quote Originally Posted by Jemster View Post
    Yes the usage is high. Too high (it is metric so I'm glad to say it's your lower figure per day at the moment), but on the other hand, when I looked back at my bills for last year, the old house was using about 100kwh per day average in the winter quarter so half-again isn't ridiculous.
    Our middle of winter (below freezing outside) average usage is around 130kWh a day in gas so no that far off you, and our house is a 1930's detached bungalow with (poorly insulated) loft conversion, 2 bedrooms and various difficult to find and fix leaks and drafts in some rooms. So given the size of your house you're probably doing OK!
    I figured that if a room gets up to temperature 30 minutes early, surely the HR92s sense this and close off the radiator to just a trickle, so it's not like the heating is going to be full-on for that half an hour extra. I didn't want to introduce the extra variability of the optimal start until I got the usage reduced and the system set right (takes a while to tweak at 9 zones to a point where we're all happy).
    Yes, once the zone approaches and then reaches the set point the HR92 will reduce the radiator flow and heat demand sent to the controller, otherwise the room would keep sailing on past the set point...

    However the correct way to look at the situation is that heat loss from a house is proportional to the temperature differential between the inside and outside. The higher the temperature differential the more heat loss, the more heat loss, the more heat the boiler has to produce to maintain equilibrium of the inside temperatures and maintain the set points.

    Therefore the more time you spend with a higher temperature differential (higher set point) the more overall gas consumption. So if a room falls back to 15C naturally over night on a particular night and you want it to be up to 20C at 6am, if it gets to that temperature at 5am instead of 6am that's a whole extra hour where you have the additional heat loss of the higher internal temperature, thus more gas usage. So shaving off any unnecessary lead time should save gas.

    Got to say I also felt a little bit out-of-control until I got Domoticz up and running a couple of nights ago. Now I can see the temperature history, even if not the actual boiler demand. I turned on optimal start last night. It will be interesting to see how much it alters the usage (haha I'm guessing not at all, still be 15 units ) but EvoHome turning on the bedroom heating at 4:45 for a 6:30 wake-up this morning was a little excessive. A bit of adjustment is definitely required as that's 1hr 15m more than I'd previously been using to get a little heat to get up to.
    Yes, having full graphing is a lot better. I don't use Domoticz anymore but do still use Evohome-munin, as I prefer the style of the graphs, but otherwise it provides the same information. Not having the actual head demand is a sore point with many of us here though - the API does not provide heat demand information.

    Regarding the bedroom, was it actually up to the set point too soon though ? If it was, it should adjust its start time by about 15 minutes per day (assuming prevailing room/weather conditions are similar) until it hits the target. If it's a long way out like say an hour, that can take several days to adapt. I'd give optimal start at least a week to learn the characteristics of your rooms before giving up on it, and compare your daily graphs to see if it is making an adjustment on the start time.
    Of course, in my constant battle, the weather keeps getting colder. Makes it hard to tell if I'm making a difference by tweaking or not. So far, from Domoticz, I've identified the overnight 15 degrees wasn't low enough to stop the heating kicking in at 3am for some rooms. I've corrected that one. Similarly in the late mornings it was also running pretty much pointlessly. I can also see one bedroom that's unable to reach its set-point, new radiator required and some insulation I think. Hopefully in the next week I'll get the usage down.
    Graphs certainly reveal a lot about your house. A room that is unable to reach the set point is particularly important with Evohome. With a regular system, as long as that room wasn't the one with the thermostat all that would really happen is that room would fail to get to the temperature you were aiming for. But with Evohome because every zone can call for heat, that one zone that is a couple of degrees short of it's set point will keep calling for 100% demand from the boiler in a vain effort to get to the set point. Which means constant high flow temperature from the boiler. Certainly not ideal. In the meantime until you can do something about it you're probably best to just schedule it a bit colder to a temperature it can manage to reach.
    It's amazing such data isn't readily available direct from the controller. I don't know how anybody could possibly work these things out in any other way on anything other than the simplest installation. Many thanks to all who've helped me out here!
    Yes, lack of integrated graphing is a bit of a sore point with Evohome. We've been clamouring for it on here for years now and so far no movement from Honeywell. Some competitors like Tado even show graphs on the iPhone app complete with heat demand...

  7. #17
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    I use a battery powered TRV called a Honeywell Homexpert. It has a digital sensor/readout and you can set a limited number of schedules on it.
    It sits on the radiator on a downstairs cloakroom which I want reasonably warm but don't wish it to call for heat on it's own. When the rest of the system calls for heat the radiator warms if below the set temperature. (In response to Paul above).

  8. #18
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    Looks like optimisation is going to take time to adjust. This morning most zones are up to temperature between 30 and 60 minutes early. A couple are correct though so hopefully the rest will learn in.

    Checked the gas meter last night after having reduced on times overnight and mornings... guess what... 15 per day.

    Doesn’t make any difference what I do. Usage is the same. Bet if I turned it off it’d still be 15, I don’t get that at all. Even if I wasn’t thinking of money, I don’t get why usage isn’t varying.

    Quick additional question - what about boiler temperature and pump speed? What’s optimal for EvoHome given that it will modulate the boiler and the amount of radiators being distributed to is constantly changing? The plumber left the speed at max for the pump, is it just a suck-it-and-see thing? I know the drop should be 20 degrees between send and return for condensing but my IR thermometer doesn’t like pipes

  9. #19
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    Quote Originally Posted by peterf View Post
    I use a battery powered TRV called a Honeywell Homexpert. It has a digital sensor/readout and you can set a limited number of schedules on it.
    It sits on the radiator on a downstairs cloakroom which I want reasonably warm but don't wish it to call for heat on it's own. When the rest of the system calls for heat the radiator warms if below the set temperature. (In response to Paul above).
    I use Peglar Terrier i30s for the same thing. It's still not ideal though. For example, I have them set to 12C during the working day. But if I have a day off, and put Evohome in day off mode, they don't know about it. Or if we're away, or whatever.

    Also, no frost protection, although I realise that's a slim risk as some other part of the system is likely to be calling for heat if my cloakroom is down at 5C.

  10. #20
    Automated Home Legend paulockenden's Avatar
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    Yup. We need something that can be controlled via Evohome schedules and overrides but which doesn’t call for heat. It would be an easy thing to do in the controller. If only they’d implemented the electric zone in a more flexible way. They could have just left things as they were before but with a 'don’t call for heat' flag in the zone parameters. That would have been far more flexible than the way it was done.

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