Run 24/7 or use Leave/Return?

Discussion in 'General Discussions' started by RegularCraig, Jan 3, 2014.

  1. RegularCraig

    RegularCraig New Member

    Hi. Just had a new geothermal system installed in my one-floor, 3 bedroom home built in the 60s.

    I have a fairly generic question: Is it more efficient to leave the thermostat on one temperature 24/7 (say, 69 degrees), or use Wake/Leave/Return/Sleep programming to drop the temperature when I'm away at work and sleeping? For 'Leave' and 'Sleep' I'd set it to 63ish.
    I live in New England where winters hit 0 degrees on occasion. I would think it's easier for the system to maintain a set temperature than to work hard bringing the house back up from 63 to 69. Am I wrong?

    Thanks in advance for any insights.
     
  2. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Set it and forget it. Geo is great to maintain temps, it usually is not designed to bring in the extra capacity to rev it up and down.
     
    RegularCraig likes this.
  3. moey

    moey Member

    Maybe in the spring and fall when its in the 40s and you can quickly recover. It was -22f last night had I turned it back it probably would have taken 5 hours ( no electric coil ) to recover.
     
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  4. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    Set it and forget it. I feel bad telling that to the customer, but a majority on the jobs I start up for the guys I actually disable the "programmable" t-stat and select the non-programmable option.
     
    RegularCraig likes this.
  5. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I am set and forget before I got into Geo, but years of hydronics taught me that is the best with a "slow and steady wins the race.", system.

    Mark
     
  6. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    A 6 degree swing would activate auxiliary heat in almost every instance, so you would pay 4 times the KWH to recover vs maintaining temperature.
     
    RegularCraig likes this.
  7. hardchines

    hardchines Member Forum Leader

    I do not think it is as simple an answer as you might think! Lots of facts missing, Short answer is when unit not running , bill not getting bigger, unit runs less at lower temp. set point!

    Questions :
    Does your geo handle holding a good temp(70F) easily or does it struggle?
    Does your house recover fast from a lower temp. quickly?
    Do you get up in the AM and go to work, or are you home all day?
    Does your system need and use auxiliary heat to recover at a reasonable (acceptable) rate.
    Is your cost of electricity high or cheap in your area?

    Here is my personal method, you fill in your check list and come up what is best for you.

    My Geo holds my home at 72 with outside temp at 0F, with units cycling on low /first stage, no aux heat like today (2F)!
    My system recovers at a very acceptable rate for me.
    I leave my house at 7:30 AM in the morning returning around 5 PM!
    I do not have or need aux heat, wish I had it for an emergency but did not plan for it!
    New York is known for its very cheap........... air, everything else is as high as it gets in this country, including electric!

    I have home POWER METERS, it cost me 30% + to maintain a constant temp,OR using the set backs I save 30%, your choice!

    My example;
    SLEEP starts at 9:00pm set at 65, bed time 10:00 stays warm that long.
    WAKE starts at 5:30AM get up at 6:30, runs on second stage for 1.5 hours, air temp plenty warm, not trying to heat up furniture etc..
    LEAVE starts at 7:00AM set to 65.
    RETURN starts at 4:00 runs on second stage till 70 F is reached between 5 and 5:30.
    If you are a person of habit or repeat route-an its easy to setup a program that works for you, if you are retired and are in and out etc. etc. then a simple leave it on may be best.

    P.S. units run less on set-back, maybe units last longer as a result of this!
    Hope this helps. Mark R.
     
    RegularCraig likes this.
  8. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Above is an example of a grossly oversized system. A right sized unit most often would not benefit from 5* temp swings.
     
  9. hardchines

    hardchines Member Forum Leader

    I built my home 25 years ago, the heating system was designed by a large reputable local shop, I paid for the design and did the work myself.
    I had two, 2 ton central air units one up split one down split with oil boiler providing hot water to heat radiator in each air handler and hot water storage tank, large all metal duct work, supply and return(by me), down stairs was marginal at best for the AC season , conditioning 1800 sq ft down and 1400 up, heat was great.

    After 20 years of use a lightning bolt toasted both AC condensing units (literally) as well as my well pump.
    I decided to replace AC with geo , I replaced the up unit with 2 ton and the down unit with 3 ton 2 stage so on stage one, 30 btu instead of 24 as before, not a massive change.

    So my AC works great and the extra 6000 btus made the lower floor work as good as the upper floor and both units are better then the old Goodmans from 1987.
    My heat is what it is, I sized to replace my AC units based on 25 years of living in the house I built, I did not even know if the heat output of the Geo units were going to cut it, but felt with the total of 60,000 btus it should work out and has.

    I kept my oil system completely intact and ready to run with the flip of a switch and a couple of valve changes, I shut down my oil on January 10 2007(08) and have never tuned it on again,

    I believe my total cost to install my high end GEO equipment was around 8K total, not bad for "grossly over sized units", my ROI was met after 2.7 years!

    Not sure how I could have made my new units grossly smaller and had good AC.

    I have read this forum for years, the overwhelming complaint from end users is always the same,
    My house is cold!
    My units run 100% of the time and my house is cold!
    My auxiliary heat is on all the time and my house is cold!

    Joe Hardin my electric cost .22 cents per KWH, I will bet it is just a little more then yours, ask my power company if you get a discount for heat use or high volume consumption, they will laugh till they cry!

    In closing; I am heating a total of 3200 sq ft, at 70-72F in the north east, preheating my domestic hot water to 106 degrees (average) and doing it on 4.5 tons of heat pumps that do not run all the time in 0 degree weather! My house is as well insulated as most new construction, but that said, I have 18 foot ceilings in a 35 foot long living room, 6 large skylights and 4 sets of sliding glass doors, not to mention a finished basement that is kept at 65 by the same units .

    If every one had such a "grossly over-sized system" this forum would go dormant as the people footing the bill for their geo units would be warm and happy!

    Happy New Year!
     
  10. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    You needn't take offense. In this modern era (vs designs in the Carter administration) most systems are closed loop with much more added cost/additional ton. This is why modern designs focus first on envelope improvement and judicious use of auxiliary heat.
    A modern closed loop system (in heating dominated climate) that boasts no auxiliary usage is often 2 tons (or in a 5 to system-grossly) oversized. In my A.O. systems in first stage at 2 F would be as well.

    further systems with designed in aux will activate auxiliary in as little as 5 minutes or as little as 2* temp boost. At your electric rates that might be $2.22/hr twice a day X's 30 days. Not a 30% savings!

    You took it upon yourself to dispute the opinion of multiple pros with what is likely very poor advice unless O.P. has a designer who hasn't evolved in decades or a home that is cooling dominated. Therefore it is necessary to point out that your system is grossly oversized for the heat load.
     
  11. hardchines

    hardchines Member Forum Leader

    "You needn't take offense", MY OPTION K.M.A.!

    "You took it upon yourself to dispute the opinion of multiple pros with what is likely very poor advice unless"
    One measurement is worth more then ten expert opinions, my facts as stated above are based on measurements. Again K.M.A.!

    2.22 x2=4.44x60 =266.40 increase in my electric bill, good deal!
     
    Last edited: Jan 8, 2014
  12. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Yes we get that it works for you. I'm simply explaining why. Setbacks in smaller swings also worked for Dwayne and Bill though both have mitigating circumstances (Dwayne has a generously sized loop field and Bill is in cooling dominated climate).......based on actual measurments.
    I've also had clients who fell into old propane setback strategies and our monitoring systems quickly emailed us about abundant expensive auxiliary use......based on actual monitoring and measurement.

    So when you choose to dispute the opinion/advice of multiple pros, it bears explanation so that O.P. can weigh the viability of your advice. When you choose to be offended by facts, that does not require me to kiss anything.

    i choose not to be offended by your rude behavior because i understand you seem to think I'm criticizing your system or you personnally. If you take a deep breath however and learn what i long since have- that systems and designs vary wildly. then you don't mind explanation of why, when something works somewhere, it may not be true elswhere.
     
  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    "2.22 x2=4.44x60 =266.40 increase in my electric bill, good deal!"

    I just saw your edit. You are having trouble with your math it would either be 2.22X60 or 4.44X30. This would be artificial auxiliary requirements placed on the system by your set back strategies (if geo were not significantly oversized and auxiliary was not designed out). This would be on top of the geo running for an hour and a half (so recovery would take 5 times the energy for an hour+).

    Not sure everyone would consider this a "good deal", particularly if temp could be maintained for less energy.

    Since I'm at my desk instead of my handheld now, I'll address a couple of other comments you made:

    "I do not think it is as simple an answer as you might think! Lots of facts missing"

    Yes facts were missing and I tried to provide some facts that explain why set-backs work for you.

    "Short answer is when unit not running , bill not getting bigger, unit runs less at lower temp. set point! "

    Unit runs less at lower set point, unit runs more when large temperature swing is called for.

    "P.S. units run less on set-back, maybe units last longer as a result of this!"

    Your set back strategy is similar to a teenager driving: lock the brakes up at the stop sign and then floor it when you are ready to go. A less agressive set back strategy, or no set backs, would be more like the mature driver who (knowing the stop sign is coming) coasts up to it and gently brakes, then slowly accelerates once ready to go.
    Which car do you suppose has less stress on it?

    "If every one had such a "grossly over-sized system" this forum would go dormant as the people footing the bill for their geo units would be warm and happy!"

    So you are suggesting that everyone should have a system sized to avoid auxiliary heat? You might easily add $5,000+ to the cost of a closed loop system in my AO to save less than $100/year. Of course those that buy the grossly oversized systems from my un-evolved competitors might be ignorantly warm and happy (cause they never have to use auxiliary). My customers are educated warm and happy because they spent so much less on their system that their return on investment is years quicker (in spite of incidental auxiliary use).
    Further we can demonstrate that use of a larger compressor all the time to avoid modesty use of auxiliary can actually make system more expensive to run (if grossly oversized).

    Remember, many people pay closer to retail for closed loop systems. While there is nothing wrong with your system for you (8K total, nice!) it is not great advice for your neighbors Who might pay 3-4K more for each additional ton (as you point out NY is expensive).


    "this forum would go dormant....."
    Not sure if you noticed what this website is really dedicated to......no matter as long as there is an abundance of bad advice, people will need help sorting things out.

    H.A.N.D. (have a nice day)
     
    Last edited: Jan 9, 2014
  14. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    The above few post, having typed, with both posters, over years, may have been PWI.

    Mark
     
  15. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    "The above few post, having typed, with both posters, over years, may have been PWI."

    Perhaps someone was when they offered a 5F set back schedule and hinted foul language. I certainly was not when suggesting the strategy offered would seldom be a good one.
     
  16. RegularCraig

    RegularCraig New Member

    Thank you for the replies folks! Definitely learned from it.
     
  17. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Craig I would suggest if you want to try set-back strategies, combine it with monitoring so that you are able to tell if you are helping or hurting your bill. Something that can show you which stages are activated and ensure you don't employ auxiliary heat when you don't want to.
    I like the Ecobee stats, but many other choices are out there.
    j
     
  18. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    The above system is grossly oversized, one has to understand that the energy it saves by letting the house cool down within a few hours is similar than the one it needs to heat it up again a few hours later. Plus the lack of comfort when the cold objects radiate coldness….brrrrr.

    Correctly sized, your hot water using the DSH would be around 130F due to less cycling. Plus your heatpumps would last longer, due to lesser cycling. Short cycling units are less efficient, due to the compressor having to built up the pressure many times more. The geo system's motto should be "lean but mean". An oversized system costs much more upfront, requires larger infrastructure (loops, pumps, ducts etc) and usually runs less efficient, besides lesser comfort.

    Just because it works fine for you, you might not have have much comparison how good it could actually be if sized correctly.
     

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