Maybe what you need is a variable speed system, or at least 2-speed condenser and variable speed fan coil unit that would be better equipped to handle humidity and give you longer run times at lower speeds.

I have my doubts that manual operation is either efficient or satisfies comfort levels.

Is your system variable speed? You didn’t say.

IMPO

SR

I'm a fellow homeowner, not an HVAC expert. Here's how I think it works, I may be wrong.

You're right that on the very hottest of days, a properly sized installation may struggle and be unable to reach your normal temperature even with continuous running. That's especially the case if it's been off and the interior temperature rises to a high level. There's not enough cooling ability to remove all the accumulated heat. But that's okay because you want that lower capacity and longer run times to remove humidity on more normal days, exactly as you describe. Long run times are fine.

Older analog thermostats typically had a temperature anticipator setting. When you removed the cover, there was a sliding switch used to set how many degrees or fractional degrees of variation from the set temperature would trigger an on cycle. If the anticipator was set to 1 degree and the thermostat set to 74 degrees, after 74 degrees was reached and the system turned on, it wouldn't come back on again until the stat sensed it was 74 + 1 or 75 degrees.

Newer digital thermostats don't have anticipator settings but rather have the cycle per hour setting option. I have two different Honeywell internet enabled digital thermometers in two different homes. In one home, the CPH can be set and I have it set at 2. In the other, the CPH is fixed at 3 and can't be changed. As I understand it, how it works is that the CPH sets the maximum number of runs. The one that I have set for 2, will run continuously until the set temperature is reached. Then it cycles off and waits 15 minutes before measuring whether an On can be triggered (2 cycles per hour means two ons and two offs, a total of 4, not less than 15 minutes 60/4 between the cycles). The one preset to 3 waits 10 minutes after off before measuring whether the variation (which I think is .5 degrees) requires an on cycle. 3 cycles per hour means 3 ons and 3 offs equals 60/6 or 10 minute minimum gap.

Anything more than 5 cycles per hour is for sure too many ons and offs.

If I have this wrong, I'll look forward to better information.

fsq, plenty of people who are out of the house during the day and have variable returning home times use what you've called "manual operation" rather than a fixed time setting for recovery from setback. It's a matter of not cooling or heating an empty home.

What doubts do you have about this common practice?

When the AC was replaced, we dropped from a 4 ton to a 3 ton single stage york condenser but still have a old two stage mercury stat. The furnace is a two stage infinity and that's the only appliance the anticipator will effect. The anticipator is not in the AC circuit.

Id love to have a stat with a 4 degree differential setting to force the AC to cycle only twice a day as Im ok with 4 degree swings.

Thanks for the info about the anticipator.

Is your analog thermostat able to control a 2 stage furnace? Is it able to effectively control the staging of the furnace? (I thought that required a proper and often same-brand thermostat to do that). If not your staging is controlled at best by a timer on the furnace that has no idea what stage is more appropriate when.

Lux makes thermostats which the temperature swing can be set up to 2.25 degrees.

I would be curious to know how your mercury thermostat operates the 2-stage Infinity furnace. Have you considered replacing it with an Infinity Controller?

Honestly, I didn't know there was a infinity stat. I'll look into that if it has adjustable differential. But as far as the heating mode.. My old mercury two stage stat does just fine controlling my infinity. Many times the furnace will idle along on low for hours at a time with nice quiet even heat, practically silent. It's the cooling mode and cycling I'm not happy with and I'm guessing any old programmable stat will give me the ability to set up two cycles per day.. If I program each day to run from 5 am to no later than 8 am. And then from 5:30 pm until the early morning when it reaches 70 degrees and then turn off until it maybe rises to 72.25.. Which might take hours of off time to warm up to 72.25..

In many instances communicating type systems have a legacy control option.

Analog T-stats also were able to control 2 stage systems.

2 mercury bulbs = 2 stage control.

The 20 something year old kid you'll likely hire has never seen one. Probably not the homeowners of this board either.

Thermostats these days... time of life is probably shorter than your underwear. Nearly everything is made in China and or Mexico.

That infinity stat is going to cost you $$$.

I am more in the camp of using the thermostat that your equipment was designed for, but the bigger problem in that is proprietary controls.

You're at the whims of the manufacturer. They stop making the control and if you don't have backwards legacy support... well you have to buy a new system?

Yeah, that day is probably coming....

This is the honeywell stat im using. I bought it because I heard of the short life the new electronic stats have. And I'm not thrilled I cant buy a electronic gadget to extend my run times, or a fake timed call for AC.. Sort of like the delay to restart the AC except in reverse.. Oh well.. I'll probably continue to run my stat like a on off switch.. Or give a new programmable a try. I see GoControl Z-Wave has a stat with 4 degrees of differential..

[url=https://servimg.com/view/14972252/118][img]https://i.servimg.com/u/f59/14/97/22/52/th/img_0812.jpg[/img][/url]

Re: Elmer J Fudd

‘Manual Operation’ was the term the OP used. While plenty of people use setbacks with heat pumps & AC - I do not. I believe it’s more efficient to let it run and maintain a constant temperature with the longest run times possible. I believe that this provides the greatest efficiency as the equipment has to run for quite some time to again achieve maximum COP on restart, as well as having to once again deal with both the latent cooling load and sensible cooling load in AC mode.

Compressors run best when continually run as there are fewer in-rushes of high current and temperature changes due to unnecessary startups as well as the restarting of the oil return cycle of the lubricant suspended within the refrigerant that is life and death to a compressor. Current inrush also holds true for fan coil units - especially those with ECM blower motors that are very expensive to replace.

Like cars, light bulbs and many other electro-mechanical things most failures happen at startup - not while running. I personally do not use setbacks for time of day or any other reason - ever. That includes winter holidays; if we’re gone for a month, the t-stat setting remains at the same setting as if we were still at home.

Our system is geothermal. It’s cheaper to run it than repair it.

YMMV

IMPO

SR

This device would power the yellow ac wire 600 seconds after the stat was satisfied. I wish it was a longer "True Off Delay", like 6000 seconds or 100 minutes.. But it looks like you can order whatever time you want.

http://www.airotronics.com/AOTpdfs/trueoff/Airotronics-TGMT.pdf

I bought it because I heard of the short life the new electronic stats have.

This might be true for the $29 thermostat you can buy on Amazon. But if you invest in a quality thermostat like the Honeywell Focus Pro then it should outlive your HVAC equipment. Honeywell doesn't support a temperature differential setting. But it does have a compressor cycle rate setting. The default is 3, but you can reduce it down to 1 cycle per hour. You may also be able to achieve the 4 degree temperature swings by programming additional set back settings when you are home.

My father, who was an HVAC engineer back in the day, used to say "keep it cool; running the AC continuously cools down not only the air, but the walls, the furniture, etc. and it is actually more comfortable than coming into a house which was hot all day long, with cold air blowing in. You can actually use a higher set point." In addition, I think it keeps the humidity lower.

"I believe it’s more efficient to let it run and maintain a constant temperature with the longest run times possible."

This is true of many heat pump systems to an extent because recovery from setbacks (as in heating mode) is very slow. It's not true of systems most people have, that's why setback thermostats are so common and why the utilities (who are usually mandated to promote energy saving practices) encourage they be used. With heat pump heating, setback recovery usually triggers the supplemental heating system

fsq, you're sometimes like the person who has a hammer and sees all around as being nails. You've said you work in the ground source heat pump business and you push it to the exclusion of other things. You live in Quebec where winter temperatures are extreme and electricity is lower cost than in much of the US. That profile is one few people who visit this forum have in common with you

Excluding newer multistage equipment that most people don't have, conventional non-ground source HVAC equipment is the norm in the US and elsewhere. Such systems cycle on and off and last 15-20 years or more, depending on where located. . Your comment " It’s cheaper to run it than repair it" applies very few systems.

mtvhike, your father knew what he was talking about, of course, but I think the paraphrased comment is misleading.

Interiors heat up or cool down mostly because of temperature differences between indoors and outdoors. (Also, direct sun). The heat or cold passes through windows, ceilings, floors and walls. On a hot day, walls are warmer than the inside.

Setbacks save energy and costs, that's uncontroversial. Where and when it's real hot (or cold), it's reasonable to set the temperature at a threshhold temperature (outside of the normal temp used when occupied) so that the empty structure doesn't get too extreme. Otherwise, keeping a set temperature during the unoccupied times can be very expensive and is wasteful.

Look no further than commercial buildings, where the HVAC systems are turned off overnight and on weekends. If it were better or more efficient to keep them on, that would be the practice.

Re: mtvhike

Your father was right. You can actually use a higher set point because the latent cooling load (humidity) has been addressed through longer continuous run times. We feel more comfortable at higher temperatures because skin moisture evaporation is enhanced at lower relative humidity levels - even if temperature is higher. Cold and clammy doesn’t do it; it’s still uncomfortable.

The best equipment would be variable speed compressor and fan coil that would drop down in speed and run at longer at lower capacities using less energy while addressing humidity and maintaining a constant temperature. The slower the air moves over the evaporator coil (dwell time) the more humidity is wrung out of the air at greater efficiency. High air flow over the evaporator coil reintroduces moisture back into the air as it doesn’t have a chance to drop out and be collected as condensate.

Geothermal evaporators (or condensers, depending on the mode of operation) are generally different from that of air-source heat pump evaporators in that the geo heat pump condensers are wider or thicker, allowing for greater dwell times (air flow over or through the coil) at any given air flows than air-source heat pumps or air-conditioner. This is a benefit for either mode, heating or cooling but especially cooling due to enhanced moisture removal (latent cooling).

IMPO

SR

This might be true for the $29 thermostat you can buy on Amazon. But if you invest in a quality thermostat like the Honeywell Focus Pro then it should outlive your HVAC equipment.

This is incorrect. They all use cheap components made in china and last a average of 10 years. Sometimes malfunctioning to the point of running both the heat and AC at the same time, or the condenser without the furnace. If they used hermetically sealed components, they would last longer but no one does.

My mercury stat will out last me..

Can anyone verify that the component I posted above will extend my AC run times?

http://www.airotronics.com/AOTpdfs/trueoff/Airotronics-TGMT.pdf