Force under floor heating on before wake up

[marcuslee]

Hi All,

HVAC control'ed relay for UFH (under floor heating) trigger.

Also dynamically generated HVAC menu configured.

What's the best way to config the system to start the UFH say at 6am, if the temp outside is xx degrees?

Is the best way in to get this working, whilst fitting in with how it's all setup, to setup:
Event Scheduler > [New event] > HVAC object > Action Function > HVAC object's Force Heating change state (is it value =1)?

Cheers,

Marcus

[Karam]

If its conditional on temperature and time then you should probably use a Macro triggered by the scheduler. The Macro can then implement the IF temperature < xx degrees condition. But I'm not really sure that the use of the Force Heating change state directive will always work as planned (depends on how the HVAC is set up) because this is a kind of toggle action as 'change state' implies. In other words upon receiving this command Cortex evaluates the present state of heating and based on this decides what it should do in order to force the heating on. For example the heating could be 'off' (logically off) because the HVAC has been asked to be off, or it could be 'off' (not heating) because the temperature is already above the set point. If the reason it is not presently heating at 6am is because the HVAC is in off mode at that time then probably this method will work in the sense that the change state should always take it to on, but if it finds the temperature already above the setpoint then it will introduce a temporary offset to the setpoint to take it about 0.5C above the present tempearture.

[marcuslee]

If its conditional on temperature and time then you should probably use a Macro triggered by the scheduler. The Macro can then implement the IF temperature < xx degrees condition.

But I'm not really sure that the use of the Force Heating change state directive will always work as planned (depends on how the HVAC is set up) because this is a kind of toggle action as 'change state' implies. In other words upon receiving this command Cortex evaluates the present state of heating and based on this decides what it should do in order to force the heating on. For example the heating could be 'off' (logically off) because the HVAC has been asked to be off, or it could be 'off' (not heating) because the temperature is already above the set point.

If the reason it is not presently heating at 6am is because the HVAC is in off mode at that time then probably this method will work in the sense that the change state should always take it to on, but if it finds the temperature already above the setpoint then it will introduce a temporary offset to the setpoint to take it about 0.5C above the present tempearture.

Thanks for reply Karam.

I chose this action based on HVAC Object, Dynamic UDM's 'Force heat on' action.

If I do use this, just to check, it sets a new set point 0.5 above current temp, and this stays in affect until midnight reset back to Profile set points?

Also I take it 'Force heat off' does the opposite, ie set the set point to 0.5 under the current temp?

[Karam]

What Cortex chooses to do in order to force heating on (or off) depends on the state of various other directives acting upon the HVAC at that time. If you go to your HVAC object, click on more connections and in that menu click on the help button you will be taken to the relevant help section and just about at the end of this you will find the logic described. If your set up is such that the various tests are always passed and the only remaining method is to increase the setpoint then perhaps you can rely on this as being the action. The temporary setpoint change will be automatically removed at the next profile change (if nothing else removes it before then).

Perhaps a more fundamental question is why you are doing things this way? By this I mean say you have the heating following a profile at all times (never switching HVAC OFF). So even overnight there is a set point to follow albeit this can be quite low and on warmer nights is never reached before you get up. On cooler nights it could be reached earlier in the night at which point the heating will come on to keep it at that set point. If that is the control approach then you can make a further more deterministic adjustment by using the scheduler and IF THEN Macro to temporarily adust the setpoint upwards on colder nights - in other words implementing your own time period based outside temperature compensation. The same criteria for subsequent auto removal of adjsutment would apply.

[marcuslee]

What Cortex chooses to do in order to force heating on (or off) depends on the state of various other directives acting upon the HVAC at that time. If you go to your HVAC object, click on more connections and in that menu click on the help button you will be taken to the relevant help section and just about at the end of this you will find the logic described. If your set up is such that the various tests are always passed and the only remaining method is to increase the setpoint then perhaps you can rely on this as being the action. The temporary setpoint change will be automatically removed at the next profile change (if nothing else removes it before then).

Hi Karam,

Thanks for the help file pointer. I had read it before, I just forgot that indeed that's where the logic info is.

Oddly, none of the dynamic menu options are listed under the connections (should they)?

Also regarding automatic removal, I think it was yourself or Viv who let me know, if nothing changes to cause a profile change, the temp setting will only remain in affect until midnight.

(it was in answer to my query of if I choose not to use Occupied or Non Occupied and just have non occupied and everything set to run 24/7 to maintain a set temp, and what would happen if I used a temp set point change, wouldn't it remain in affect forever).

Perhaps a more fundamental question is why you are doing things this way? By this I mean say you have the heating following a profile at all times (never switching HVAC OFF). So even overnight there is a set point to follow albeit this can be quite low and on warmer nights is never reached before you get up. On cooler nights it could be reached earlier in the night at which point the heating will come on to keep it at that set point. If that is the control approach then you can make a further more deterministic adjustment by using the scheduler and IF THEN Macro to temporarily adust the setpoint upwards on colder nights - in other words implementing your own time period based outside temperature compensation. The same criteria for subsequent auto removal of adjsutment would apply.

In this case, it wasn't for anything to do with room temperature. It was simply so the babies crawling don't have a cool/cold tiles to crawl on ie we have situations where the room is perfectly fine at say 24/25 degrees, but the tiles are deemed to cold for them.

Also in regards to how to automoate, I think conceivable approach is to leave things completely manual. See how people get on using the system manually (ie when they would put the heating on at what times of day, what the temp is outside, etc), profiling the data, then build the automation rules based on that?

Certainly this later approach might be one to use if one was to roll out systems for other people/houses etc, where it's difficult to know other people's tastes, and how the house you're automating for, is?



However back to the original question, sounds like it's easier to leave HVAC object setup as it should logically be, and then just do a Event Scheduling and direct manipulation of of the zone valve to quick inject a bit of heat into the UFH concrete slab morning before everyone's up, and mid evening just before they return..?

[marcuslee]

However back to the original question, sounds like it's easier to leave HVAC object setup as it should logically be, and then just do a Event Scheduling and direct manipulation of of the zone valve to quick inject a bit of heat into the UFH concrete slab morning before everyone's up, and mid evening just before they return..?

I'll reply to my question on this part. Obviously not easier to do a direct zone valve manipulation, but simply to change HVAC object, set point profile, to something really high for the room for the 6am to 7am, just to have it come on!

[JonS]

I'll reply to my question on this part. Obviously not easier to do a direct zone valve manipulation, but simply to change HVAC object, set point profile, to something really high for the room for the 6am to 7am, just to have it come on!

This is what I do...
Unoccupied profiles are low over night, but because UFH is so slow to react in the hours before we are likely to get up, the unoccupied profile steps up to be close to the occupied level and then steps down again. So on a really cold night the heating in the downstairs rooms comes on earlier and it is up to temp when we get down stairs.
I also have low occupied profile overnight so if the cat jumps on a table etc the heating isn't wasted on his comfort - he has a loverly fur coat afterall!
HTH

[marcuslee]

This is what I do...
Unoccupied profiles are low over night, but because UFH is so slow to react in the hours before we are likely to get up, the unoccupied profile steps up to be close to the occupied level and then steps down again. So on a really cold night the heating in the downstairs rooms comes on earlier and it is up to temp when we get down stairs.
I also have low occupied profile overnight so if the cat jumps on a table etc the heating isn't wasted on his comfort - he has a loverly fur coat afterall!
HTH

Nice thinking, thanks Jon. Will consider using this when we switched to having true Occupied and Not Occupied status in operation.

Cheers,

Marcus

[Karam]

If your HVAC is in an operational mode 24/7 (by which I mean set to automatic or heating rather than off) then you can trigger the 'Heating Increase Temperature' input. This will then cause Cortex to adjust the setpoint to 0.5C above the present measured temperature and so trigger heating demand. This, like other user offsets, is of a temporary nature and will be cleared back to the usual profile upon next change in profile OR midnight (its either of those two which clears temporary offsets). You can add refinements using the scheduler and macro such that it only tries to do this at certain times, conditional upon outside temperature and whether it is already heating. On the other hand maybe we should introduce separate force heating on/off inputs but I haven't thought that one through so don't quote me :-)