honeywell evohome - is it doable setup

[phier]

Hello,
I know exact times when the power is off for these 40minutes. That's why i wanted to program it to set temp for example on 0C during these 40min intervals. There are I think 6x40min intervals during the day.

What internal sesnsor do you mean? I am bit confused, you mean BDR91?


Yeah I linked it via mobile app, so now the evo controller shows 21.5C , my two other thermometers 22.5C and app current 21.5C and target 21.5C ... that's odd.


thanks

[DanD]

Oh, I didn't realise that you already had some of the Evohome devices!

I think I may have misunderstood exactly what you wanted the Evohome system to do.

Here's what the Evohome system should be able to do for you:

• Allow each of the 3 zones within your home to operate their own programs with 6 changes in temperature setpoints per zone, per day.
• You mention putting 2 valves in each of your zones and I assume you mean adding HR92s TRVs to your radiators which function as both a temperature sensor and control the variable flow valve. These HR92s also allow you to change the room temperature directly by turning their control wheel and this temporarily overrides the program temperature. This will cause the BDR91 to send a signal to the boiler to heat, if it currently not heating.
• The Evohome system will learn how quickly your rooms heat up and cool down and try to optimise the use of your boiler to efficiently heat your zones. 'Optimum Start' and 'Optimum Stop' options also help to maintain the room temperatures by either heating the zone early to ensure that it quickly achieves a program increase in setpoint target, or switching off the heat to a zone early to efficiently achieve a program decrease in setpoint.

Here's what Evohome is unable to do:

• It isn't possible to program the controller to tell it that the boiler will not respond to requests for heat during certain times during the day. The BDR91 will still send a signal to the boiler for heat even if the boiler is unable to provide heat during the 40min intervals.

Apart from the limitation above, I think Evohome should be able to efficiently control your heating. I don't use the temperature sensor within the controller and each of my HR92s to measure the temperature of each zone (I use all 12 zones with 16 HR92s in my setup).


Dan

[phier]

Hi Dan,


I am not sure, during these 40min intervals... while demand on the heat will come to the controller ... it will just make it disoriented ... I assume ... that's why I was asking to setup whats apparently is not possible.



Yes, I was talking about HR92 valves. I thought valves are not showing current temp in the room. But it seems that control unit doesnt come with that much precise calibrated thermometer... right now it shows 22C but other 2 meters shows 22.7 and 22.4.

I am bit skeptic ... about whole system and thinking if danfoss would be better solution? if any.

[DanD]

I think the controller will work OK and the 40min periods won't cause it problems. It's a shame that the Evohome 6 setpoint daily limit isn't enough for your setup. I find the Evohome system works well and keeps my home at a comfortable temperature. You might need to try increasing the setpoint before the first 40min period if the temperature drops too far, but it should provide good control.

[phier]

well shame... there are these 40min intervals...

what's the point to increase before first 40min period... can't see it....


also wondering why temperature shown on control unit differs from other thermometers...

[gordonb3]

What internal sesnsor do you mean? I am bit confused, you mean BDR91?

No. The internal sensor of the boiler. As I see it, the boiler is meant to keep an amount of hot water, say 100 litres, that is within some temperature range. If the temperature drops below the threshold then the boiler will fire up and in your case this will apparently obey some time limits, or be subjected to a network operator controlled switch either inside or outside your home.

As stated this does not fall within the control of Evohome, nor should it. Evohome cannot predict when you will manually turn up the heat. It can also not predict when you will take a shower or run a bath. The boiler will thus need to hold enough hot water to match any of these needs at all times.

[DanD]

I was thinking that the room temperature might drop during some of the 40min periods so that you notice it feeling cooler. If this happens you could increase the setpoint by 0.5deg to keep the room at a more comfortable temperature. It may not be necessary though.

[phier]

I was thinking that the room temperature might drop during some of the 40min periods so that you notice it feeling cooler. If this happens you could increase the setpoint by 0.5deg to keep the room at a more comfortable temperature. It may not be necessary though.

yes but that doesnt solve the issue as this 40min intervals are 6 times per day... https://imgur.com/a/6d2Nd8J

first row means monday till thursday
2/ friday
3/ sat
4/ sun

[phier]

No. The internal sensor of the boiler. As I see it, the boiler is meant to keep an amount of hot water, say 100 litres, that is within some temperature range. If the temperature drops below the threshold then the boiler will fire up and in your case this will apparently obey some time limits, or be subjected to a network operator controlled switch either inside or outside your home.

As stated this does not fall within the control of Evohome, nor should it. Evohome cannot predict when you will manually turn up the heat. It can also not predict when you will take a shower or run a bath. The boiler will thus need to hold enough hot water to match any of these needs at all times.

Well and that's another issue... "electric boiler needs to hold enough hot water to match any need" that implies it has to run 24/7 and to be ready to provide heat once requested and valves opened. That electric boiler is powered off by its internal sensor once the water reaches specific temp, and if temp is colled down via radiators and falls down it has to be powered on by some control unit like Evo controller or some room thermostat stored in reference room. But I wanted zoned control so thats why I don't want to use thermostat placed in the one reference room.

Then there is another issue regarding those 40min intervals (https://imgur.com/a/6d2Nd8J) ... because evo will never know about this intervals it means it will let temp fall down and if required at specific moment try to send signal to BRD91 to power on boiler to heat up - but once the signal is sent and matches the 40min interval - no heating will be possible thus evo will get confused why it cant increase room temp in lets say 30min by 1C as it normally can so it will completely corrupt its internal fuzzy logic (thas my assumption). That's why I wanted somehow set more intervals per day and during these 6x40min set temp to let's say 15C.


Frankly there are zero Evo home specialists in country (czech republic)... they just sell units but you can't find any specialist/company that can install it and setup it correctly. That's why I was trying to ask people for help here ...


"
So here's the thing: I don't think you should try let Evohome control whether or not the boiler goes into a heating cycle for the simple reason that Evohome cannot predict any manual input you might perform in the next 1-40 minutes. You use Evohome in the secundary part of the system to control if, where and when the heat is deployed to any of the available radiators (or other heating devices) and thus how much heat is drawn from the boiler, which in turn determines whether or not it's internal sensor will cause it to switch on at the next available slot.
"

Well not really, the electric boiler I have work in the following fashion: once some control unit or external thermostat send a signal to it ... it will start to boil water and once it reaches specific tempreature it stops boiling water. If the temp of water inside the electric boiler falls down under some level nothing will happen - it will wait for another Power-on signal from control unit/thermostat. That's why I thought using BRD91 and evo controller I can power it on to increase temp inside the boiler per zone/while required.



Also, how can I query the actual temperature, as the mobile app shows the same number as on the controller?

thank you

[DanD]

Thanks for the additional info on how the 40min periods are spread throughout the day. I'd wrongly guessed that more of them would be grouped together near times if highest demand e.g evening. I think the Evohome system will cope OK with them. If the BDR91 requests heat during one of the off periods, it will continue to request heat until the end of the off period and the boiler starts. It will only stop asking for heat when the zones are comfortably close to their setpoints.