Air conditioner delay??

[dshogman]

two air conditioners function just fine except the front one starts up immediately and the rear one waits about a minute or two. Any thoughts, explanations, fixes?? I know, if it works, don't try to fix it. Just curious.
Thanks.

[Ted III]

Something is wrong with the front A/C. They should all have app. a 2 minute delay. If not the people that do not turn things off when they shut down would blow everything. This is a safety precaution to keep a large load back against their power source all at once.

[Cardsfan]

Both 13.5K units on the '98 I used have came on after starting the generator, and when the power kicks in, which takes about a minute. However, the two 15K heat pump units on my '07 delay about a minute after the power kicks in, so about two minutes total after starting the generator.

One problem I have with the triple slide unit is they placed the thermostat on the outside wall. I'm not sure if this is the reason, but the bedroom unit cycles regularly; however, the front unit never cycles until well after the sun goes down, and things outside start to cool off. It runs continuously on a sunny summer day. Also, on a hot day, the front a/c won't hold temperature. My '98 used to freeze us out. I even have solar screens on the windshield and pilot/co-pilot side windows.

[Old Rv'er]

We have a 40' with two 15K heat pumps I think. Anyway, we have the thermostat on the cabinet in the Kitchen, so we don't have the outer wall heating problem. But they put the heat/cold sensors on the ceiling, which seems wrong. The units never seemed to get cool enough, and so I started monitoring my incoming power. If the power drops off less than 110V, the units don't seem to have enough juice to operate correctly, usually just shut off the back unit until I get the front half cool. However if I use them both on generator, the units will work perfect. So last weekend we were at a different place and I checked the power and I had 122V on both legs, naturally I did not need to cool off. Better voltage equals better operation of the A/C units. I also read a little refresher on the A/C units and it said never run them when line voltages is less than 107V or higher than 130.

[wa8yxm]

Give us more info.. Is rig 50 amp or 30 amp.

If it's 30 amps. or if you have an Energy Management System and it THINKS you are on 30 amps... It may be causing the delay.

Also, if I were building an air conditioner with an electronic control system.. I would by design, put in a 3 minute dealy so that the compressor could not start till 3 minutes after the power came on... There are very good reasons for doing this (prevents "hot starts" where power is off, and then quickly on, and the compressor stalls due to the head pressure not yet bleeding off, very bad for the A/C)

Some of them.. do, indeed, have that delay built in.

[dshogman]

Posed the same question to Dometic customer service. Their response:
"... some manufacturers add a delay on the compressor so that to prevent short cycling. They may have added one to your second AC..." They suggest contacting our manufacturer. Well, that wont work.
Anyone have the same experience with their units? (50 amp).
Never really noticed it before. Just thinking, maybe it was done this way so that if you were to switch both airs on at once, the delay would keep them from both hitting the power at one time. Sort of makes sense to my limited electircal/mechanical experience.

[Ted III]

David Horn, I thought the question was in reference to the delay time in the starting of your Air conditioners. Is that what you wanted or did you want to discuss the performance of the A/C's as most people have responded with?
The delayed starting response is built into the A/C's and or/the thermostat(s) to protect the units. That is the way they are designed to operate unless they are extremely old units before this safety factor was built in.

[dshogman]

Ted, the question was about the delay of one and not the other.

[dgerstel]

I am quite sure that the delay is in the thermostat. The thermostat is powered by 12 volt. If it is left on and is calling for cooliing, with no 115 AC on, the delay will be finished and the AC's will start immediately when the 115 V. is supplied.

The location of the thermostat does not effect its operation, as the temperature sensors are remote located.

[Old Rv'er]

All, as an apex owner we have some kind of power management system I guess, as I can tailor my incoming amps via a screen on the silverleaf display. My coach is a 50 Amp incoming max amp coach, but if we only have 30 amps available I can change the incoming amount and the system will allow only some things to run. I have not tried to start both A/C units on 30 amps because I will blow something, but I rotate them letting the front one run for a while then shutting it off, and starting the rear unit.
As a side note, I cannot start the genset before I start the coach and have it continue to run, it will shut down once the main engine is started. I can however start the genset after the coach is started and it will continue to run. Yeah I am aware of the code 27 issue, but I have other things more important than that to worry about. I will get around to figuring what is up with that after I check the brake lines (see thread about break failure), check the steering bracket, and get my Hydro Hot to give me hot water, and figure out why my front air bags refuse to dump when leveling up. Those things are more important to me.

[takepride]

Duo-Therm controls the delay according to the OEM (and as per Dale).

The front unit delays the second unit's start (Master/Slave setup).

Programming only the rear unit will still have a delay, less than three minutes.

Programming both to start will have the front fan first, then front compressor, followed by rear fan and compressor.

Having thermostat "on" prior to having 120 volts available will bypass the delay (as per Dale) if the delay time is over.

Leaving the thermostat on while driving will allow you to start the generator from the dash and the AC's will start immediately (if the delay time is over).

The AC units can run on low or high fan if set to auto and the compressors cut in and out as called upon by the Duo-Therm.

The heat sensors are always in the wrong spot, doesn't matter which model or year. It's just an Alpine thing.


Magic things occasionally happen whereby they run as they prefer, in defiance of their design.