Thermostat mode changes

[cmerlino]

Looking for some thoughts/suggestions/opinions on controlling thermostat modes.

Currently, I have 4 profiles setup (economy,comfort,night,morning) which control the heat and cool setpoints for all zones. We like the bedroom cool (ok, cold) at night, and warmer in the morning. The way I have it setup, however, we wind up running the AC at night and heat in the am all year 'round with the tstats set for auto mode. Obviously, not optimum. So - I added an exterior temperature sensor to the system, and was thinking of the following:

Every 4 hours, if outside temp < 60 mode = heat, if outside temp > 70 mode = cool, if outside temp between 62-68 mode = auto.

I left the 2 degree skip so that I don't get caught up in temp moving while the instruction executes, if it is in between, it will just leave the last mode set.

Here are the questions:
4 hours - kind of arbitrary - what do you all think?
2 degree skip - good idea?
Anyone already doing this (likely) - what do you do? How well is it working??
Anyone have any other suggestions? Glad to learn from more experienced minds!

BTW - Running ELK M1G controlling Omnistat RC-80B (4 zones) + ISY99, Insteon

THANKS!

 

[Desert_AIP]

I use occupancy modes.
Day/Off is my "Normal" mode
Night
Away
Vacation

I found this article interesting WRT setpoints and operating modes.
http://www.cs.virginia.edu/~stankovic/psfiles/sensys10-final169.pdf

I run my system in the "Auto" mode, so it automatically chooses heat or cool modes according to the setpoints and temps.
You can be comfortable at a wide range of temperatures. The more narrow the temperature range, the more your system will run.
I have wide ranges programmed into the Tstats. We also like it chilly to sleep.
I'm running an Omni Pro II and RC-2000 Tstats, but the principles should be similar.

Normal:
Upstairs HIGH SETPOINT 66
Upstairs LOW SETPOINT 77
Downstairs HIGH SETPOINT 68
Downstairs LOW SETPOINT 77
Night:
Upstairs HIGH SETPOINT 58
Upstairs LOW SETPOINT 72
Downstairs HIGH SETPOINT 60
Downstairs LOW SETPOINT 82
Away:
HEAT SETPOINT 58
COOL SETPOINT 90
Vacation:
HEAT SETPOINT 52
COOL SETPOINT 98
Outdoor Temperature:
LOW SETPOINT 64 HIGH SETPOINT 80

Instead of an "Every (time)" command I use the secure/not ready status of the Outdoor Temperature sensor.
So the HVAC won't run if the outdoor sensor is secure, between 64 and 80.
My system checks every 10 minutes. So if someone manually turns on a tstat and it isn't needed, the system will turn off the HVAC.
Also I monitor the windows. If any window is opened for more than 2 minutes, then the HVAC is shut off.
This condition is monitored every 5 minutes once active, until all windows are closed.

About an hour before we come home I have a warmup routine that bumps up the temprerature for an hour. Got that idea from the article above.

I have a "Wakeup" time programmed in that transitions from Night to Day mode to warm up the house when we get up.

I also have an electric wall heater in the Master Bath controlled by an RC-1000. It is set to come on about an hour prior to we wake up to warm up the Master Bath. It runs for 2 hours. But does not run in Away or Vacation modes.

 

[tmbrown97]

Personally I would always leave the unit on auto but just adjust the setpoints at certain times. What was the point of changing the modes?

You might also consider adding a fresh-air vent... so it can pull in cold outside air rather than having to run the A/C... that's on my list, so I don't have to manually open/close the windows every night to cool the place down.

 

[Desert_AIP]

The modes modify the setpoints. The system remains in Auto.

I like the fresh air vent idea. Would you do it with a fan? Wondering what you plan on using as a damper/penetration to the outside.

I run the HVAC fan every night at 1am for 30minutes regardless of whether it's running (or has been) or not to exchange the air in the house.

 

[tmbrown97]

When my current community was built, they offered a Fresh Air Vent as an upgrade option - I don't have it, but it seems about half the houses do. It's part of the HVAC - it's an additional intake that brings fresh air in from outside via a normal damper setup and a vent on the side of the house where the roof is higher. The RCS communicating zone controller also has an output for this.

The other popular option here is the whole house fan - people tend to get the homes as cold as they can overnight then seal them up to try to keep from using the HVAC during the day... then when they get home at night, they open all the windows and flush out the hot air real quick. All lovely perks of having some of the most expensive electricity in the country. Unfortunately there's people home 24/7 and it's a 4K sq ft house, so I get lovely $800 electric bills in july/august.

 

[Desert_AIP]

I need to look into this.
I really only need to vent the Master Bedroom at night.
It would be nice to tie it in to the Omni and automate it.

 

[cmerlino]

The fresh air vent sounds like a great idea. Looked into it when we built the house, but the budget ran out....
As for why to change modes, maybe this will help explain:

for the master bedroom:

Comfort - heat=66, cool=72
Economy - heat=64, cool=78
Night - heat=62, cool=66
Morning - heat=70, cool=74

So, what happens is, in the summer, we need the AC at night, but when the morning comes, we pay the gas company to heat the space that we just paid the electric company to cool (so we can shower without ice forming :blush: ). It would be ok to just have the AC go off in the AM, and let the house warm-up by itself.
In winter, the converse is true - no need to run the AC at night - the room will cool down on its own, but need heat in the AM

This could all be solved with Summer and Winter programs, but the catch is the few months in between where it could go either way. Hence, the mode changes. BTW - saw an ~20% decrease in utility bills when I put the existing program in place, just trying to tune it further....