Originally posted by bruce_miranda
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Specifically:
1) If you use the heating off action which without a hot water kit is the quick "everything off" action it actually leaves hot water following its normal schedule, EG on when scheduled to be on. This does make sense because the action is called "heating off", and it also makes sense that during the summer for example you might want to manually turn the heating off but you would still require hot water.
However there is no "heating + hot water off" quick action to let you quickly disable both heating and hot water when you are for example leaving the house for several hours (or days) during a time when heating and hot water would normally be scheduled on - eg a Saturday or Sunday.
So you actually have to choose the heating off quick action, and then go into hot water and do a manual permanent override to off for hot water to achieve this, which I would argue isn't obvious to a non technical user. Nor would remembering to separately cancel the hot water off override in addition to cancelling the heating off quick action.
This is symptomatic of the limitations of the quick actions in general though.
2) If the heating is on and you choose the "Day Off" quick action, both heating and hot water will switch to the (by default) Saturday schedule - I am using this right now as I'm off work for 2 weeks, and this works great.
However there is a major gotcha - if I were to turn the heating off with the heating off quick action, which I would probably do during the summer, the hot water returns to the current days schedule (Thursday) instead of the day off schedule. There is no way to turn off the heating and at the same time have the hot water continue to follow the day off schedule.
This is a quite inconsistent user experience IMHO. Because on the one hand if you turn off the heating on a normal day the hot water stays on and continues to follow the same schedule, however if you go from a day off schedule to heating off you may suddenly find your hot water has gone off as well if the different day's schedule would have your hot water off at the current time.
The workaround is after using the heating off quick action, if that results in your hot water going off as well (because you were previously on the day off quick action) is to set a timed manual override for the hot water to bring it back on again until your normal night time off temperature. This works OK but feels clumsy to me and wouldn't necessarily be obvious to a non technical user.
I've said it many times before, but the quick actions are the biggest weak point of the Evohome user interface as they are quite limited and inconsistent in their operation.
2. You can have a HW overrun, to dump the remain heat of the boiler into the cylinder, rather than just waste it. This feature tends not to be possible with a traditional clock, because it would simply shut off the valve when the time or thermostat has shut off.
Keep in mind though that for hot water overrun to work on the Evohome you must be using a 3x BDR91 configuration including a boiler relay or 2x BDR91 + OpenTherm. A 2x BDR91 configuration alone can't do hot water overrun any more than a standard timer can because the boiler is fired from the zone valve limit switch.
3. The HW kit temperature sensor is more finely manageable.
4. You can set a temperature differential settings, so if the HW is hot enough, but not up to the temp set, it won't bother firing the boiler unnecessarily.
I find my cylinder loses about 1 degree per hour so a 5 degree differential still means the boiler only reheats it once about every 5 hours if no hot water is used, and only takes about 5 minutes boiler run time to get it back from 45 to 50 degrees, so I'm fairly happy with that.
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