Ecobee automatic vs manual staging on a two stage heatpump.

[EbS-P]

Hi all.

I am now one week living with a new ecobee thermostat. It’s controlling equipment just fine but it’s running different than I am used to.

I have a two stage heatpump. Installed by my hvac company when they replaced all my ducts. They used the automatic staging setting which uses an “algorithm” to control staging. It’s a black box and I can’t make out what it’s actually doing. To me it appears to be switching to second stage really too quickly. We kept the old 3 ton unit but upgraded the ductwork to 4 ton capacity. And I think the upped the blower speed too high. 450 cfm/ton.

I have the option to set up manual staging control. Should I do that or keep it in the automatic mode?

 

[fbelec]

if you don't like how it's working then get into the programming of the tstat and change it. i install those ecobee all the time. they are better that the nest.(sorry nest users) the ecobee has programming for room sensors and if you have a troublesome room to heat or cool the sensors almost take care of that. the customers that i install those for say that it solved their problem. i would change the first to second stage for a longer run on the first stage. if you are heating with it let do it's own thing so you'll heat and won't feel cold. most heat pump are controlled at the heatpump and not the tstat. i'm putting in ecoer brand units now and they have 40 different speeds for their units and the box that is doing the control is also the box that talks back to the company and tells them that something is wrong. i most cases the company and i or the guy installing it knows there is something wrong before the owner

 

[EbS-P]

Well I lived the last month in auto staging. I don’t like it. It calls second stage to soon then under shoots cooling set point. I disabled the room sensor to remove one variable. This spring has been much cooler than I remember the last couple years. So it could be that the learning algorithm just hasn’t had enough run time to get it down.

So I changed it to manual.


Setting seem straight forward. I set a longer than standard compressor off time of 600 seconds. Then I set .5 swing for first stage then a 1 degree swing temp for stage two with reverse staging. So once it’s back down to .5 degrees above set point it’s only calling stage one.

My thinking is the more time it spends in stage one the better. I need to go and change air handler settings back to standard instead of what trane calls “enhanced comfort”.

ecobee does not lock out dehumidifier once it gets a cooling call letting both run at the same time. I do not have pressure readings I’m just guessing that the dehumidifier static pressure can overcome the hvac blower static pressure. Did a quick experiment with fan on low and saw no difference with condensate volume produced while running fan and not.

Short summary I’m not in love with the ecobee. Maybe it will grow on me.

 

[ABMax24]

No I'm not in love with mine either, it has so much potential if they'd allow the consumer more options in the programming. I just want a function that when my rooms reach a certain temperature differential the furnace fan kicks in to circulate the air.

One thought, is your system actually more efficient in stage one? My furnace blower pulls 600 watts, if I had a 2 stage unit stage 1 would spend a lot of effort just removing the heat the blower creates.

 

[EbS-P]

No I'm not in love with mine either, it has so much potential if they'd allow the consumer more options in the programming. I just want a function that when my rooms reach a certain temperature differential the furnace fan kicks in to circulate the air.

One thought, is your system actually more efficient in stage one? My furnace blower pulls 600 watts, if I had a 2 stage unit stage 1 would spend a lot of effort just removing the heat the blower creates.

The seer data says stage 1 is the same as stage 2 but I have a variable speed fan. 900 cfm stage 1 and 1200 stage two with a fan ramp for both stages that runs lower speed for first 7 minutes.

But I assume the blower wastes more energy on high with higher static pressure. Seer 1 rating got to ignore this in the calculations now they can’t. Hence everything dropping.

I almost want to splice in a second thermostat to run the fan. Maybe outside ventilation too. Set the sensors up on the second tstat you could monitor 3 three rooms.

And I think recall the stage two delta only can be set using full degrees. But stage one delta can be set in increments of 0.5 degrees.

None of the will matter one lick come July. Ac comes on at 10am and won’t shut off until 11pm. It’s undersized.

And I miss the relay clicks in the old tstat. I have LEDS that I wanted to wire in so I could tell what stage it’s in but I can just just touch the screen now. But at least now I can lock out the heat strips.

 

[gthomas785]

But I assume the blower wastes more energy on high with higher static pressure.

I would think the opposite. Higher static pressure, decreased airflow, decreased power consumption.

Edit, nevermind I'm dumb. You were comparing to low speed not a lower SP on the same speed.

 

[EbS-P]

I degree delta for stage two was not enough. With the .5 degree delta for stage one that only allowed .5 degrees above set without calling stage two. I still have the basement air return blocked as we are still under construction, hanging drywall, now.

 

[EbS-P]

Well we have made through some hot weather. Couple days at or a bit over design temp. I am convinced even the main equipment manufacturers are programming their two stage thermostats wrong.

I have been able to keep my house cooled at design temp only running on stage 1. With a stage 2 delta T set at 2 degrees (stage two comes once once indoor temp is more than two degrees different that set point). Stage 1 runs a lot almost constantly from 2 pm -6pm.

That means I’m cooling my house with only 22k btus.

The house is much more uniform in temperature as the fan just keeps stirring it up. The basement never get more than 2 degrees colder than the upstairs.

The OEM Trane thermostat would only let stage 1 run for 7-10 Minutes before shutting off or calling stage 2.

One question I have is how long duration cycles on stage 1 affect equipment life. Everything I read says that starts are the equipment killers. Running at lower static pressure is more efficient. (Blower runs at 70 % of max).

The ECO automatic staging was not very good and kicked on stage two much too quickly. But if you only can control staging calls by whole degrees I can see many people not thinking a two degree delta is comfortable.

Right now this two stage equipment which has been around for nearly two decades I see as the best value for ducted systems. Just don’t rely on the stock thermostats to be configured well.

 

[gthomas785]

I agree staging is usually done wrong. Long cycles are good. Most equipment is designed to run continuously so don't worry about that. Starting a motor creates excess heat as well as magnetic stress in the windings, so the fewer starts the better. When the system is running the airflow keeps the fan motor cool and the refrigerant flow keeps the compressor cool. Not much else to worry about except bearings, and unless there is some kind of crazy vibration even those should not care about running all the time. Also more run time = more chance for moisture removal.

 

[EbS-P]

I agree staging is usually done wrong. Long cycles are good. Most equipment is designed to run continuously so don't worry about that. Starting a motor creates excess heat as well as magnetic stress in the windings, so the fewer starts the better. When the system is running the airflow keeps the fan motor cool and the refrigerant flow keeps the compressor cool. Not much else to worry about except bearings, and unless there is some kind of crazy vibration even those should not care about running all the time. Also more run time = more chance for moisture removal.

It’s all making more sense that I had humidity issues. 3000 sq ft (1/3 of it basement). Hot an humid climate. Low cooling loads, lots of people, lots of legs going in and out all day. I haven’t logged dehumidifier in time yet but it’s substantial even with AC on. I still need to air seal and add insulation to the attic

 

[EbS-P]

I finally logged into get eco bee data. For anyone who cares.

 

[fbelec]

look at your electric bill see what it is telling you