Central AC Takes 5+ Minutes To Start Up After It's Been Off For Hours

D107

As part of a Con Ed Grid Rewards program on super hot days we turn off the central AC for four hours 4-8pm a few times a summer. When I go to turn the t-stat on again it takes five or more minutes to start up. I've heard that this could be a bad capacitor--never had this problem before. Some say if it cools when it comes on then there's no problem. AC works fine otherwise--if it's been routinely delaying on a t-stat call for cooling we'd never know unless we stood by the t-stat and saw the 'cooling' indicator blinking.

JUGHNE

Who controls the AC shutting off...you or them?
If Con ED has control they may be instigating a 5 Minute "delay on start".

Your tstat will probably do a 5 minute "delay on restart"....this protects your compressor from short cycling and trying to immediately restart and just humming and then kicking out on overload....tough on compressors. You may have heard your refrigerator do this if the power blinks while it is running.

Power company may want a delay on start when bringing many compressors back on line. Just 30 seconds difference between yours starting and then the neighbor's coming on line will save them a lot of demand charges.
That grid must be running on the edge of being overloaded, and the slower they can bring compressors back on line is to their benefit.

What benefits do you get out of this program?

D107

@Jughne It would be news to me if ConEd has any control over this--while we do have a smart meter I can't imagine how without my consent or some kind of added wiring or control they could do this. A third party sets this up with Con Ed. And on the last two occasions, I started back up late since I was busy and forgot (at 8:30pm and 9pm respectively) so it would not have been a time when a large number of people would be re-starting up their ACs. I control with my t-stat; there was no special wiring done for this program.

We are looking forward to seeing exactly how much we will be saving. Out of the 5 days we have done this we have been told we earned 100% of eligible savings by cutting our power by 1/3. We turn off our basement dehumidifier and the central AC to participate. So now I'm thinking if they did figure out a way to delay the AC, I could end up throwing away money on an AC service call looking for a problem capacitor that may not exist.

I dont' think this is a delay on start kind of situation--no short cycling here since the AC was off for four+ hours. I know that there is also a safety involved on shutting OFF the AC that delays that for a minute or so. if Con Ed is not involved can this be in fact a bad capacitor? I have contacted someone who knows the program well so he can likely tell me if Con Ed has the ability to do this.

JUGHNE

Do you have a WIFI tstat that was furnished by the power company?

D107

no wifi, just old style wired t-stat. So i guess no Con Ed control. So then should i get a service call for possibly bad capacitor?

mattmia2

What kind of t-stat is it specifically? Is it a mechanical t-stat or electronic?

D107

@mattmia2 Cheap nonprogrammable honeywell with digital screen. Will get model in the morning. Never had this happen before.

retiredguy

If we all are forced to go to electric cars be prepared to shut off your A/C for 23 hours a day. Replacing most of the coal, nat gas, or oil fired power plants and replacing them with solar and wind will have the same effect. These "morons" pushing for all electric cars and no coal, oil, or nat gas power plants need to get the heads out of their a*s. You need to buy an electric scooter while the congress and senators fly in their private jets and suburbans.

ChrisJ

When you say it takes 5 minutes to start up, do you mean the outdoor unit sits there silent for 5 minutes while the blower inside is running?

Or, are both silent for 5 minutes?
Or, is the blower running and the outdoor unit is attempting to start (buzzing over and over etc) for 5 minutes until it finally actually starts?

ChrisJ

retiredguy said:

If we all are forced to go to electric cars be prepared to shut off your A/C for 23 hours a day. Replacing most of the coal, nat gas, or oil fired power plants and replacing them with solar and wind will have the same effect. These "morons" pushing for all electric cars and no coal, oil, or nat gas power plants need to get the heads out of their a*s. You need to buy an electric scooter while the congress and senators fly in their private jets and suburbans.

Nice political rant, but unfortunately it didn't have anything to do with the thread.

HVACNUT

If "cool" is blinking on the thermostat display, that is a built in time delay to prevent short cycling the compressor as @JUGHNE mentioned. 
Why its going into a delay by merely turning the A/C back on, I don't know but I guess is a default in the thermostat. 
What brand and model is the thermostat. 
The issue is in no way related to a capacitor.

D107

@ChrisJ both outdoor and indoor units seem to be off. I could check again to see if the outside unit is buzzing trying to start. I could switch out t-stat as one test.

ChrisJ

D107 said:

@ChrisJ both outdoor and indoor units seem to be off. I could check again to see if the outside unit is buzzing trying to start. I could switch out t-stat as one test.

If both are off, I'd go with everyone else, that's it's just the thermostat waiting it's 5 minutes.
It's sometimes not necessary, but it's only 5 minutes and it could save the equipment under the right conditions.

It's certainly easier on compressors, even ones that can restart immediately.

GW

What Chris said, if the stat is blinking during that 5 minutes, it’s the stat. 

D107

@HVACNUT @ChrisJ The T-stat is Honeywell RTH221B 1021. I put it in about 5 years ago, no issues. In the past whenever I switched it to 'cool' ––after being off for days––and it was warm enough for a call for cooling, it would go on immediately as you'd expect. This is new. Simple possibilities: t-stat switch dirty or worn? T-stat malfunction? What y'all seem to be saying is that if when it's on it's cooling correctly with both units on--yes it does––then there's no capacitor issue. I mentioned capacitor because when I first googled the problem to see if there was a simple answer online, one resident with a similar problem received this answer:

"There is probably an old capacitor in the electronics which dried out over the time and now takes a long time to gain the necessary power load. If you are familiar with electronics you can 1 check yourself for capacitors which looks bloated or otherwise funny and replace them." The resident replied: "Yes, i wound up replacing all two capacitors and relay and problem seems resolved. I also learned previous owner or AC person installed a hard start capacitor which I removed when I installed the two new ones and relay. Seems good as new now."

Of course, I will leave it to pros to deal with capacitors if that turns out to be an issue. For now I'll probably open up the T-stat, clean the switch, and make sure all the wire connections are tight and battery strong.

pecmsg

You need to find out HOW Con Ed is controlling your equipment!

D107

@pecmsg Ha, yes that was the first answer I received here. It did occur to me that even though the t-stat is not wifi or installed by them, that with a smart meter it might be possible for them to set up some kind of delay for any big load coming on. But I'll just look at the low-hanging fruit first.

ChrisJ

pecmsg said:

You need to find out HOW Con Ed is controlling your equipment!

D107 said:

@pecmsg Ha, yes that was the first answer I received here. It did occur to me that even though the t-stat is not wifi or installed by them, that with a smart meter it might be possible for them to set up some kind of delay for any big load coming on. But I'll just look at the low-hanging fruit first.

Literally every digital thermostat I've used had a 5 minute delay when switching modes.

I'm thinking you just never noticed it before.

I'm also confused why 5 minutes is something worth troubleshooting and trying to "fix" ?
It's 5 minutes, not 3 hours.


Now if the system isn't cooling properly, that's a whole other subject, but generally split systems etc aren't setup to pull an entire house down fast. It's simply not going to happen especially if it's hot and humid in the structure and outside. If it's hot inside, and cool outside (80 inside, 60 outside for example) that can make it even worse as most systems will behave undercharged due to the metering device underfeeding.

pecmsg

D107 said:

@pecmsg Ha, yes that was the first answer I received here. It did occur to me that even though the t-stat is not wifi or installed by them, that with a smart meter it might be possible for them to set up some kind of delay for any big load coming on. But I'll just look at the low-hanging fruit first.

LILCO used to put a box near the indoor unit that shut it down. We replaced many that failed!

No it wont be in the meter.

D107

@ChrisJ You're right, ordinarily I wouldn't care about a 5 minute delay. Perhaps it was that first Google batch of answers that seemed to say that something could be heating up while the outside unit delays 'to gain the necessary power load" or the HO's report of success after replacing the capacitor. But I know you guys know your AC, so I'm relieved there's no serious problem here. (I am very cognizant of changes in operation, and after the unit has been off for hours and a call for cooling is clear, there has never been a delay in over 20 years with various t-stats. You switch on T-Stat from off to on and within one second you could hear the unit rumbling on. )

However with outside temps so hot, perhaps that affects some kind of internal compressor safety t-stat OR Con Ed lowered the voltage--which it in fact did yesterday but not supposedly exactly in our area. (This 3-ton Bryant central AC is 30 years old.)

The only delays I've seen in the past are if I turn the unit off while it's running, it will wait a minute or two to actually shut off. And I assume it would initiate a delay if someone tried to start it up too soon after a cycle.

JUGHNE

If power company is controlling your outside AC unit there has to be some form of interlink between them and your outside AC.
If you do not have the WIFI then there might be a small control box outside installed by them. But they most certainly would have contacted you before installing it.

Years ago power companies tried load shedding in this manner, but IIUC most of the system was abandoned. Often causing a service call from HVAC company to make the outside unit run as the failed little "black box" would keep AC off.
Homeowner didn't recall having the box installed or the previous owner had it installed. IIRC, the signal was sent over the power grid on a "piggyback" carrier.

The smart meter is how they would know when you kept your AC off and how long.

You could go outside when you experience this 5 minute delay on start and listen to the AC unit. Perhaps only the outdoor fan might run and the compressor is trying to start by humming......click....hum...click and eventually does start.......That could then be a weak compressor capacitor.

Does the inside fan start almost immediately even with the phantom 5 minute delay?
Some have a delay to start indoor fan.
If not then I would guess the tstat is at fault.

Also there may be a 1-2 minute inside fan delay to shut off when tstat is satisfied.
That may be the delay to shut off you think you experience, the outside unit does shut down as tstat shuts off, but furnace keeps inside fan on a few minutes.

D107

@JUGHNE Attaching photos of a box next to the compressor. Unit was installed in 1992, years before we moved here. Looks like just an emergency shutoff box. (Cutler-Hammer DPU222UR) See photos. No Con-Ed connection as far as we know, and again never had this issue before.

JUGHNE

That box is simply the 240 volt disconnect for the AC.
The little control box would be connected to the low voltage 24 volt circuit.
That is a small cable usually run with the lineset, often hidden with the lineset.

The few I have seen were mounted on the wall and not inside the AC unit itself.
If you pull out the disconnect plug on the wall, then there would be no power inside the AC unit. You could safely remove the corner cover of the AC where the power enters. There should be 1 or 2 capacitors and a large relay contactor.
You could post a couple of pictures here.

D107

@JUGHNE These are photos from 2017. Service record indicates 2013 Turbo 200 capacitor installed. So it's possible that or the smaller one needs replacement. No harm in having some overdue annual maintenance, but given the skyrocketing costs of the refrigerant, if they have to pump any in perhaps best to wait until price comes down, if it ever does.

To answer your other question, no when this re-start is delayed, the inside air handles is also silent. I can check outside unit on a call for cooling if I'm around and also switch out t-Stat with another one I have lying around just to eliminate the obvious.

EBEBRATT-Ed

I would say it's a delay in the stat like others have mentioned. If it was a capacitor it probably wouldn't start at all by now

HVACNUT

What's all the hubbub, bub? You're overthinking. At most it's a new glitch in the thermostat but not really a problem. Try removing the batteries or 24v for 10 minutes. See if it reverts back to normal. 
The condenser fan motor is a Rescue replacement. 
It doesn't look like the electric supplier is specifically controlling your system. There's typically announcements of mass brownouts.

mattmia2

If you are sure that there was no delay before with that same t-stat after turning the system to off then to cool several hours later then the issue is the t-stat. The batteries in the thermostat that remembers its state are bad so it doesn't know if the system was not just on when you turn it back to cool from off so it delays the cooling call. Is the clock keeping correct time?

You should replace those burned terminals to the contactor in the condenser or possibly the contactor itself depending on why they are burned.

Might be easier to just set a program that turns the setpoint up enough that it won't turn on during the higher rate time period and back down when the period is over.

GW

If both are “silent”, it’s not the outdoor unit 

JUGHNE

I agree with GW. The tstat calls for both of these items to come on.
IIWM, I would try another tstat. In any event you want one with the 5 minute delay to restart.

If your AC contactor looked like that 4 years ago, I would say you need a new one.
The lower push on connectors are not the best method, under a screw or a "box lug" design is better, IMO.

And the price of R-22 gas will most likely never go down.
It is a commodity that is priced at whatever the holder wants.
(Think of it as water in the desert).

And then the price is often bumped up more to encourage the homeowner to change out the system rather than add 1-2 lbs of R-22 possibly each season.

30 years is a pretty good life for an AC.

Rest assured that your next system will not last that long.

mattmia2

If i am reading the instructions for that t-stat correctly it has aaa batteries in it as backup. It likely uses those when it is set to "off" to run the clock and remember when the system last ran so I think the batteries are dead.

D107

FWIW I checked the batteries, they measured borderline, I replaced them, and the next time I turned on the AC a few days later, it started right up. I'll keep my eye on it, but likely MattMia2 and HVACnut nailed it. I think this T-stat may be completely powered by battery without any low voltage, don't know. Guess I could check by trying to run system without batteries. Thanks to all for comments. It wasn't a major problem to begin with, but even for an apparently simple problem in the future I will come to this site first rather than just Googling the issue. The first site I got on had a lot of speculation, pointing to potentially more serious issues which got me a bit over-concerned.

mattmia2

I suspect that when you have the switch set to heat or cool it runs off the control transformer for whichever one is selected but if it is set to off it doesn't have the circuitry to pull power from one or the other depending on which has power so it just runs off of battery.

ChrisJ

mattmia2 said:

I suspect that when you have the switch set to heat or cool it runs off the control transformer for whichever one is selected but if it is set to off it doesn't have the circuitry to pull power from one or the other depending on which has power so it just runs off of battery.

The Honeywell's I believe, at least most of them run from the cool connection's power, always.
The higher end Prestige you can pick, or even do a totally independent supply.

D107

This t-stat is only connected to AC; two wire only. My heating t-stats are separate, all two-wire, so I believe therefore, battery only. Original controls installed at least 30 years ago. Perhaps with AC, two wire could connect to Low Voltage electric.

JUGHNE

The simple HW tstats (5000 series) I have in my house have a small electromechanical switch inside, when calling for cooling you hear a double click.
One for the AC relay and one for fan relay.
So if on battery power only, apparently with marginal charge, the battery had to slowly come alive to power both switches, thus....possibly....your 5 minute start delay.

If possible it is always good to have the common (third) wire at the tstat.

Well, we got almost 2 pages out of a dead battery discussion.

ChrisJ

JUGHNE said:

The simple HW tstats (5000 series) I have in my house have a small electromechanical switch inside, when calling for cooling you hear a double click.
One for the AC relay and one for fan relay.
So if on battery power only, apparently with marginal charge, the battery had to slowly come alive to power both switches, thus....possibly....your 5 minute start delay.

If possible it is always good to have the common (third) wire at the tstat.

Well, we got almost 2 pages out of a dead battery discussion.

Worse case, it kept traffic on the forum which is beneficial in the end.

JUGHNE

But wait!... there is more... the HW 5000 has a test function at the end of the installer's instructions.
You can use this method and actually hear the relays click on and off.
With batteries you can program and test with it off the wall.