Can I do all this with a new stat and ELK M1

[dpilati]

So I have an ELK M1 that has gotten very light automation use and I have 2 Carrier Infinity systems - one with one zone and the other with 2 zones. One system is dual fuel and both HPs are 2 stage. The NG furnace is 2 stage.
 
I just switched to a TOU-D rate where I get penalized for high peak demands. Because of this, I'd like some more control over the units. 
 
First, I'd like to keep the second stage of a/c from coming on during peak pricing. I do that now manually but I'd like it automated. This is fairly easy with the stats I have if I can ever find the wire for "utility saver". 
 
Second, I'd like to shut the a/c or heat down when the oven is run (and the solar is not generating). I could tap into the float switch but it isn't very elegant. 
 
Next - I'd love to do all this shutting down and fire up the NG furnace if needed (but I'm not sure this is really necessary)
 
Lastly, I'd really like to have more control over a/c run times. The Carrier gives a few options but I would like more control for both efficiency reasons and to be more gentle on the compressors. 
 
My understanding is the Carrier SAM is not only ridiculously expensive but doesn't even give that many control options but I would love to be proven wrong. 

 

[ano]

I had a contractor explore the Carrier Infinity because the SAM module can connect to an HAI controller, which I have. In that setup, you can control all the thermostats, but I'm not sure what you can do with an ELK. In any case, it is $900, and I understand they are discontinuing it soon, if they haven't already. Instead I went with four OmniStat2's and I'm very happy.  I'm on a peak rate as well, and with careful control, and pre-cooling I have cut 25% off my summer bills. I do some pretty sophisticated things like reading the temps inside and out and monitoring how often the AC units turn on and off so I don't overcool. I don't monitor the oven or microwaves, but I try to not use them during peak periods.
 
Anyway, there is a bunch you can do with the right setup.

 

[dpilati]

I'd love to hear how much control you have - basically can your automation just decide which stage to run in and when to shut off? And can it do it in a dual fuel setting? 
 
In AZ, I understand the demand interval is 1 hour, here it is 15 minutes. So a 15 minute microwave run with the toaster oven also running and both a/cs can really hit your peak. My peak so far this month was a 18 minute oven run when the a/c was running. 

 

[ano]

I have four OmniStat2's, two HVAC units, with one having three zones, so four thermostats total. 
 
In AZ, the peak is measured over an hour period, like you say, but only the maximum peak for the month matters. This is why at most i run the AC for 20 minutes per hour. This is why I say 5 or 10 minutes of microwave isn't likely going to exceed power from 20 minutes of AC, assuming both don't run the same hour.  A 15 minute window really seems a bit unfair, but the good news is, if you can spread-out your loads, you can benefit.
 
I can't control stage 1 vs. stage 2 AC on the Omnistat2 directly, but I can control this indirectly.  The thermostat is pretty advanced as it will use several factors to decide if its stage 1 or stage 2. It looks at the rate the temperature is dropping inside,  as well as the length of time, and the temp. difference between the set temp and actual temp. By default, if the inside temp is not more than 2 degrees away from the set temp., it won't use stage 2, and you can change that setting to 1 degree, or 3 degrees, or more.  So, if the set temp and actual temp are no more than 2 degrees apart, then no stage 2, and I can easily control the set temp.
 
Basically I precool the house in the morning, when rates are low, then once per hour the system will check room occupancy, check if the alarm is home or away, and check the temps at each thermostat to decide if it is going to run up to 20 minutes that hour.  In practice it only needs to run at the 5pm and 6pm hours if its over 105 outside.  One day it did run at 4pm, 5pm, and 6pm when it was 116 outside. 
 
My next plan is to decide how much to precool based on morning temps. As fall comes, its cooler in the morning, therefore the house doesn't need to be made as cool to keep the house cool until 7pm.  That is still a work-in-progress, but as it gets cooler, I'll start working on that.  I was thinking at having the system check the weather forecast everyday, but I think just looking at the outdoor temp at say 3am is just as good of an indicator.  When its still 95 at 3am, that means its going to be pretty hot the next day.

 

[tmbrown97]

When its still 95 at 3am...

:nono:  That's when I move...  I thought 85 as an overnight low was bad, but luckily that's only a couple days each summer...

 

[ano]

:nono:  That's when I move...  I thought 85 as an overnight low was bad, but luckily that's only a couple days each summer...

Our record was 96 degrees minimum, so its not 95 often, but often over 90, but still I bet my electric bill in the summer is lower than yours.  My off-peak electric rate is 4.4 cents/KWH, on-peak is 8.8 cents/KWH.

 

[tmbrown97]

Not to go too far OT, but I pulled this just the other day:  Note temps aren't Highs, they're Average for the day.

 

[ano]

Yup, not going to be moving to CA anytime soon. :wacko:
 
In my last bill I used 2933 KWH, and it averaged 91 degrees. (Typically my highest of the year.) My house is a bit under 3000Sqft. My bill was $244.

 

[BraveSirRobbin]

I'm may look more into 'pre-cooling' the air around the compressor with some basic 'swamp cooler' methodology next summer as the humidity is very low here (and the temps of course VERY high) in Las Vegas during the summer months.  My last few electric bills were killers!

 

[ano]

I looked into that, but the results I saw weren't that great, plus you really want to be careful not to cover the condenser with minerals as that will definitely raise your costs.  
 
I don't know about LV rate plans, but with a few tricks and some automation, I've cut my summer rates by 25% (And its a few degrees hotter here.)

 

[dpilati]

I think if I don't get total control, it isn't worth the expense.
 
Without stage control, I can just only imagine the complexity of the rules which would have to include input from multiple sensors to fool the stat into stage 1 or stage 2.
 
Just last night, I had to put into stage 2 manually at 9 when off peak came into effect. It then stayed there all night with unneeded stage 2 runs and then off times when it would have just been better to revert to stage 1. What I want is stage 2 option from 9pm to 10pm. 
 
Since we have veered OT. My last year max bill was $150 for 5000 sqft in NC. Very little shade and 40 windows mostly facing East but a lot are West. 
 
This year, put in solar and went to Tou-D. Only really have 1 month bill and it was $50 but that includes some rebates from the utility company. But it also includes an EV. So yeah - not moving to CA or AZ anytime soon. 5.5 cents off, 6.6 cents on peak, demand charge $5.40 per kw during peak. First month peak was 4.3 kw and this month I have held to 2.9 so far for the first half. Last night, the toaster oven  came on with an a/c and the sun was off the collectors - I may have dipped into 3.1 kw. Normally I have the a/c off during dinner prep but I was also squeezing in some car charging so I had to shut the a/c off when it would have usually run.
 
My energy usage is wickedly slanted to off peak. Right now the car is charging and both a/cs are running - stage 1 only. If it is going to be cloudy, I'll fire up the hot water backup on the solar - I'll be chugging at over 10 kw. 

 

[ano]

If you have a good thermostat, it shouldn't keep it in stage 2 any longer than necessary. The OmniStat2 has three settings to control this.  I just let it do its thing and it works just like i would expect. In addition, unless you have the Trane XL20i compressor, which has dual compressors, chances are your stage 1 and stage 2 are not that far apart anyway. Typically stage 1 is 75-80% of stage 2. Not a great difference. The XL20i has two compressors so its 50% and 100%, because there is a several minute delay in changing from one stage to the other, its not well suited to AZ.
 
In addition, since the difference between stage 1 and stage 2 is nothing more than one thermostat lead connecting or not, it would be pretty trivial to have a home automation system fully control this. You could also open this lead during the day during high rates and it simply would never go into stage 2. Not really hard to do if its important to you.

 

[dpilati]

My stage 1 is 50% of stage 2. Carrier doesn't do anything simple regarding thermostat communications so I doubt there is a terminal to control stages. 
 
What I do know is turn on the utility curtailment which can force it to stay in stage 1. With a demand charge, just hopping into stage 2 for 10 minutes will up the charge. Downstairs I never need stage 2. Upstairs, I just need it to get the master down to 65 when it is still 80+ out. Stage 1 holds it there fine but I hate to keep it at 65 all day long.
 
There is way too little histeresis (sp?) in the Carrier stat. The stat will limit the cycles to 3 per hour but I'd prefer to be 1 per hour.

 

[tmbrown97]

unless you have the Trane XL20i compressor, which has dual compressors, chances are your stage 1 and stage 2 are not that far apart anyway. Typically stage 1 is 75-80% of stage 2. Not a great difference. The XL20i has two compressors so its 50% and 100%, because there is a several minute delay in changing from one stage to the other, its not well suited to AZ.

That's what I just put in here... Stage 1 is 2 Tons, and stage 2 is 5 tons... and that's the only unit for my 4K sq ft. house in northern california...  And the RCS thermostat won't kick down to stage 1 if it's close - it has to stay in stage 2 until it reaches set temp; and even if you change the temp to more than the Stage 2 threshold, it still goes into stage 1 for 5 minutes before it turns off, waits about a minute, then switches to the other compressor - this seems to be the RCS doing this though, not the Trane.
 
If the Carrier has that utility conservation mode, it'd be quite easy from any automation system to trigger that I'd think - have you read what it takes to activate it?

 

[dpilati]

Yes - the Carrier does have a way of triggering the utility conservation mode (I am still looking for the boards). What is challenging is that I basically live in stage 1 so I need a way to both go to zero and stage 1. My workaround involves triggering stage 1 using the utility conservation mode and then cutting the unit off using the sensor that detects water in the pan. I think I can get all this to work and do what I want. This demand charge is really challenging to get right but if you control it well, the $$ savings are worth the trouble. Just tonight the wife turned on the oven while the dryer was running - can't let that happen. I can see relays cutting off the elements on the dryer when needed but keeping it running so you don't have to restart it. You can also cycle the elements slower to keep the 15 minute average lower when run in peak times. 
 
In the end, it still doesn't get me longer cycles but that alone is not worth $800 in new stats. By forcing stage 1 and changing the temp frequently, I get long cycles. My worst short cycling can be taken care off with a dump zone of sorts where I cool the downstairs at night with the excess.