EMS' Time Delay for A/C Compressor Setting

[ROC-REQS]

I just purchased a Progressive Industries EMS-HW50C and was looking to see what I should set the EMS' time delay for A/C Compressor to (i.e., to 15 seconds or 136 seconds).

I contacted Jayco to see if the A/C units include a compressor delay as installed from the factory.

Here's what there response was:
"The only delay for the compressors in our normal system setups would be in the wall thermostat. There would be a 3 minute on break time delay when the thermostat stops the call for cooling. If their question is due to installing an energy management system, I believe they are trying to figure out if they need to set it to 15 seconds, or 136 seconds. If this is the case, they will always want to set it to the 136 second setting, as there would be no fool-proof way of keeping the compressor from short cycling."

So it seems like the safest EMS time delay for A/C Compressor setting is 136 seconds.

Also, I confirmed with PI that L1 & T1 Black wire connections are associated with Line 1 information presented on the display and L3 & T3 Red wire connections are associated with Line 2 information presented on the display.

However, the way Jayco wired up Leg 1 and Leg 2 at the Power Center is that the Red wire connects to Leg 1 50A Breaker and the Black wire connects to Leg 2 50A Breaker. See the pictures attached (i.e., 50A breaker on left is Leg 1 and 50A breaker on Right is Leg 2).

So, when I install the EMS unit I plan to connect the Black wire output from the EMS to Leg 1 50A breaker (i.e., 50A breaker on left) and the Red wire output from the EMS to Leg 2 50A breaker (i.e., 50A breaker on Right).

This way the Power Center labeling (i.e., Leg 1 & Leg 2) will be consistent with the EMS Display information wrt Line 1 and Line 2.

Thought I would share this with those that are considering or have installed an EMS.

[LiftedAWDAstro]

We set our 30 hard wired EMS for the 136 second delay.

[SkyBound]

Yep, same. Also another benefit is that when on generator power, it lets my generator warm up for 2 minutes once I hit the remote start before a load is applied. Win win.

[mjlaupp]

I have my EMS delay set to 15 seconds. I used to have it set to 136 seconds but after several times sitting in the dark for the delay period after all the rest of the campground is back to normal I went to the short delay. I am depending on the 3 minute delay hardwired into the Colman Mach digital thermostats to protect the compressors from short cycling.

If I did not have the digital thermostats then I would utilize the 136 second delay in the EMS.

When the the EMS restores power to the RV, the A/C circulation fan starts immediately and the compressor starts after the 3 minute thermostat delay. I don't see how the additional EMS 136 second delay would provide any additional protection.

I do like the idea of using the EMS 136 second delay for remote start generator loading.

[ROC-REQS]

Originally Posted by mjlaupp

...When the the EMS restores power to the RV, the A/C circulation fan starts immediately and the compressor starts after the 3 minute thermostat delay. I don't see how the additional EMS 136 second delay would provide any additional protection. ...

You're digital T-Stat runs of DC power. So if you only lose AC power, your T-Stat is still getting power from the RV Battery. Therefore, when AC power is restored, you won't get the 3 minute delay at the T-Stat because it never lost power.

So, if the A/C was running when you had a short intermittent AC power failure, the T-Stat would command the A/C to run immediately when power is restored and you could get into an overload condition.

The 3 minute delay at the T-Stat is to protect from toggling the A/C on & off rapidly at the T-Stat.

A simple test to confirm this would be:
Test 1. Run your A/C for a little bit, turn the T-Stat A/C off and then A/C back on, there'll be ~3 min delay before the A/C compressor comes back on.

Test 2. Run your A/C for a little bit, then turn AC power off (by either toggling the breaker in the control panel or at the power post) then turn AC power back on. The A/C compressor will come back on as soon as AC power is turned back on.
Caution on Test 2, DO NOT do this if the A/C has been running a long time.
Only do it when the A/C hasn't been run and DO NOT have the A/C running long before cycling A/C power. Only run the A/C a short time, 30 sec to less then 1 minute before cycling A/C power so the A/C unit doesn't achieve full pressurization.

[Jblack]

I use 136 seconds also just to be safe. I also have a residential frig and did not know if its compressor needed the extra time also.

[ROC-REQS]

Originally Posted by ROC-REQS

...
Test 2. Run your A/C for a little bit, then turn AC power off (by either toggling the breaker in the control panel or at the power post) then turn AC power back on. The A/C compressor will come back on as soon as AC power is turned back on. ...

I forgot to add for the results of Test 2 that if you A/C compressor is delayed in coming on after restoring AC power (i.e., delayed for ~2min), then your A/C has an internal compressor delay kit as part of it's components and a 15 second delay on the EMS is ok.

Sorry about that.

[ROC-REQS]

Originally Posted by Jblack

I use 136 seconds also just to be safe. I also have a residential frig and did not know if its compressor needed the extra time also.

That's a good question wrt impacts on residential frig. I don't know the answer, but you've peeked my curiosity.

[ROC-REQS]

Originally Posted by Jblack

I use 136 seconds also just to be safe. I also have a residential frig and did not know if its compressor needed the extra time also.

I check with a friend in the industry and he said a residential frig could have the same issue as A/C units.

He indicated that some frig's come with compressor delays but others do not.

So it depends on if the residential frig has a built in compressor delay.
If it does, it's not a problem.
If it doesn't, the 136 seconds EMS delay will help protect your residential frig also.