Basement A/C second compressor

Skipperphil · 09-17-2019, 02:13 PM

I'm reading up on 30 to 50 amp conversion on our 2001 Adventurer 32v. Kansas summer has many opportunities to need 50 amps. One thing I don't understand is why sometimes the second compressor kicks on and uses most all the 30 amps we have. I have looked at wiring diagrams but don't understand what I'm seeing.

At least I think it's the second compressor because the EMS panel shows 25 to 27 amps and the temperature of the air out of the vents is nearly 50 degrees.
If someone could help me understand this, I would appreciate it.

I have learned that wiring to the second compressor circuit is one thing that needs to changed in a 30 to 50 amp conversion.

Phil
2001 Adventurer 32v

BobC · 09-17-2019, 05:25 PM

Hopefully someone will post a better explanation than this, but here's a try:

Each compressor is on it's own circuit with it's own breaker. The amps drawn by each is higher when starting than when running. Starting both at the same time would draw more than 30 amps in total, therefore compressor #1 will start first, settle into the run mode and then compressor #2 will start if necessary (see below) and settle into the run mode.

When both are running, you will see that your amperage draw will be in the 20s. How much can vary from unit to unit and the accuracy of your power management system. It also will vary depending on the voltage being provided by your 30a service (more amps will be needed at 110v than at 120v, etc.). The total amps will also depend on what else is running at the time. If you're getting adequate cooling from compressor #1 alone, you can turn off the breaker to #2, giving you more "overhead" for other appliances. From what I see in the brochures, Winnebago moved to standard 50a service in 2003.

Here's an explanation of the starting and run cycles from the basement air's manual:

8. A TYPICAL COOLING CYCLE OF THE HEAT PUMP

Begins with a call from the wall thermostat for High or Low fan (customer choice).

Indoor fan starts on the selected speed.

Within a few seconds the thermostat will call for cooling.

Compressor 1 starts.

Outdoor fan starts 2 seconds later (Low Speed).

1 minute later the thermostat calls for second stage cool (subject to 2 degree temp. differential).

Compressor 2 starts, the outdoor fan goes off (subject to available 115 volt power supply).

Outdoor fan starts again 2 seconds later (High Speed).

Both systems operate to satisfy the thermostat.

Both compressors shut off at setpoint temperature.

When the thermostat calls for cooling again it will start by calling for stage one only.

If the heat pump is unable to keep up with the load, stage 2 will start again when the indoor temperature is 2 degrees above the setpoint.

You are correct with respect to the need to modify the basement air wiring when doing a 50a conversion. Here's a good thread on the 50a conversion: http://www.winnieowners.com/forums/f...mp-354924.html

You didn't mention if you have a generator or not. If you do, when running on the generator, your power management system isn't going to measure the total amps, just those relating to compressor #1 (and any other appliances), which can be confusing. This is because, when on generator power, compressor #2 is fed directly from a 20a breaker on the generator, bypassing the main panel's breaker and the power management sensor. The 30a generator breaker does feed the main panel. Your transfer switch manages this change in circuitry when you switch to generator power. The following thread addresses this and a number of issues relating to your questions:
http://www.winnieowners.com/forums/f...ps-135616.html

Also, here's a link to the basement air service manual, which can be very helpful:
http://bryantrv.com/docs2/docs/rvp/6535heatpump.pdf

I'm no expert so, if I've incorrectly described anything, hopefully someone will correct me.

Finally, be happy that both compressors are kicking in and you're getting 50 degree air. I'm having difficulty with compressor #2 not kicking in.

Skipperphil · 09-17-2019, 06:32 PM

Thanks,Bob for your response. A lot of information to process. I'll have to rely on friends with skills above my pay grade to interpret.

Hope my 50 degree air temperature claim is not too misleading. The test amounts to holding a small thermometer up to the duct for a few minutes. Not very scientific.

We do have a generator but didn't give it much thought since I'm focused on the differences between the 30 & 50 amp wiring diagrams. Thanks for pointing that out.

Many thanks for taking the time to reply.

I'll share my experience when I get into the conversion process.

Phil
2001 Adventurer 32v
Topeka, Kansas

BobC · 09-17-2019, 06:52 PM

Quote:

Originally Posted by Skipperphil

Hope my 50 degree air temperature claim is not too misleading. The test amounts to holding a small thermometer up to the duct for a few minutes. Not very scientific.

Phil
2001 Adventurer 32v
Topeka, Kansas

Pretty much as scientific as how most HVAC techs are going to do it, although they may use an infrared thermometer. The service manual may give some info on acceptable ranges but that sounds pretty good to me.

Good luck, and, if you're not well versed in interpreting and reading 120v circuitry, getting some experienced help is the way to go.

A 50a conversion is on my to-do list for sometime in the future.

Ttowntoehead · 09-23-2019, 04:43 AM

I have a 1995 Vectra with basement air that had not been serviced in 10 years. Started having cooling issue and went to Flint Hills RV in Wichita. I heard on this forum forum that they worked on basement air and was not disappointed. Tech found spot where duct had separated and was allowing hot air in return. I highly recommend them if you decide you need help. Plus the company that makes the units is in Wichita.

NeilV · 09-23-2019, 06:42 AM

On a 2001 they are usually wired so that the second compressor does not come on unless the room temperature is 2 or 3 degrees warmer than the thermostats set point so in moderate weather the second compressor may not get called. Even the "Pros" mess up on wiring the basement air coaches as the staging of the compressors and how they are wired for a 30 or 50 amp service confuses many. Considerations have to be made at the generator, transfer switch, Basement Air Unit and main panel to keep it all straight. Many really mess up on the generator wiring since most come with the split 50 amp generator with on 30 amp main breaker and a second 20 amp breaker with no real provision for 220 volts.

To use 50 amps of course you need to be staying at campgrounds that have a 50 amp service most of which charge a premium for their availability. I found that less than 1/3 of the campgrounds in my price range have 50 amp services and most that did charged extra for the sites that have them.

Even where I live in Florida with effective temps well over 100 degrees I have not found the need for a 50 amp service even with the larger 35U however I do have thermal pane glass and put insulators in my roof vents and over my front windshield and always deploy my awning.

Jim_HiTek · 09-23-2019, 08:47 AM

Something you might consider is the age and whether or not your basement air has been serviced. If it's never been serviced, it could probably use a good maintenance service. If the caps have weakened or gone bad, or if the motor bushings need lube, or if the pillow block bearings on the fan shafts are gummed up from age, those things could all conspire to make the system draw more current.

My basement air (50 amp rig) use to draw very near 30 amp when running on a 30 amp supply with only one compressor running...until I serviced it. Now it only takes 17 amp to run one compressor and 24 amp for two.

Servicing a basement air can be quite involved and when I did mine early this year, I wrote up an article about it. Maybe doing a service will help your system run more efficiently. Check it out: Coleman 2-ton Heat Pump

BobC · 09-23-2019, 09:26 AM

Great write-up, Jim. Maybe you can stop by the next time you're in the Sacramento area and do mine.

Jim_HiTek · 09-23-2019, 09:35 AM

Quote:

Originally Posted by BobC

Great write-up, Jim. Maybe you can stop by the next time you're in the Sacramento area and do mine.

Hah! Don't think I've ever stopped in Sacramento...always just passed through. Not sure it's a real place.

OR, you could join me at Preferred RV Park in Pahrump, NV and I'll help. I'll be there from Oct. 7th to probably Nov. 16th. I even have 2 pillow block ball bearings for sale.

BobC · 09-23-2019, 09:47 AM

Jim-

You should stop sometime, the Sacramento/SF Bay Delta area is a great place to explore with quite a few RV park options. It pretty much covers Stockton, north to Sacramento west from I-5 to SF. Have fun in NV. I had rotator cuff surgery so we're sticking pretty close to home right now and the next couple of months.

PM me about the pillow blocks.