Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-18-2020, 02:21 PM   #1
Guru
 
Steve91T's Avatar
 
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
What would cause an AC unit to drag the generator down?

Hey guys. So we have 3 reverse cycle AC units. All 3 work great on shore power but for some reason, lately, the aft unit will put a strain on the generator to the point where it’ll trip the breaker after a short time. I have played around with taking the load off so all it had to do was run that ac and it still does it. No problems while using heat. Plenty of water flow.

Again, it’s only while on the generator. With that one off, we can run the other two, water heater, battery charger and the microwave with no problems. Something doesn’t add up.

Inexpensive solutions only please...thank you
Steve91T is offline   Reply With Quote
Old 05-18-2020, 02:23 PM   #2
Guru
 
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft 381 Catalina
Join Date: Aug 2019
Posts: 7,554
Have you watched amperage draw for this unit both on shore power and generator? As well as confirmed generator output voltage and frequency (both at no load and under a moderate load)? If not, those are some good things to check that can narrow down what might be out of whack.
rslifkin is online now   Reply With Quote
Old 05-18-2020, 02:25 PM   #3
Guru
 
Alaskan Sea-Duction's Avatar
 
City: Inside Passage Summer/Columbia River Winter
Vessel Name: Alaskan Sea-Duction
Vessel Model: 1988 M/Y Camargue YachtFisher
Join Date: Jul 2012
Posts: 8,050
It sounds like your compressor is over loading the system maybe going bad.

The same happened to me with a NEW 12BTU Dometic unit. I had to install a "smart/Soft Start" unit to help the compressor initiate the start sequence.

https://www.dometic.com/en/pl/produc...t-iii-_-215771
Alaskan Sea-Duction is offline   Reply With Quote
Old 05-18-2020, 03:04 PM   #4
Technical Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
Steve you need to meter the volts and frequency when the suspect AC unit comes on. Normal genny volts are in the range of 115-125Vac, although some Westies like yours can be a bit sloppy with voltage control. Seen some lower, some higher.

Frequency should be about 61-63Hz unloaded. With a normal load should be about 60Hz. Starting a heavy load can drop to 57, but should recover to 60.

If either (or both) Vac and Hz are low, the AC unit will draw more amps, and that can make the difference between running and tripping.
Ski in NC is offline   Reply With Quote
Old 05-18-2020, 07:20 PM   #5
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,834
Do you have a ring style amp meter? In addition to the other suggestions, I would measure amp loads on shore power for the unit and for the compressor when it kicks in. If all 3 units are the same BTU, check the starting and running amps on all 3. A unit with a marginal compressor may start fine on shore because of additional available amps, but have trouble starting on the generator with less capacity. It would be good to identify or eliminate the air conditioner as the cause of the problem.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 05-18-2020, 09:36 PM   #6
Guru
 
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,186
Steve
New problem or always been that way?
sunchaser is offline   Reply With Quote
Old 05-19-2020, 12:40 AM   #7
Guru
 
catalinajack's Avatar
 
City: Edgewater, MD
Vessel Name: Catalina Jack
Vessel Model: Defever 44
Join Date: Nov 2011
Posts: 3,585
You didn't mention the size of your generator. We have two, a 12.5kw and a 7.7kw. The smaller generator will not run our three AC units simultaneously without tripping the breaker.
catalinajack is offline   Reply With Quote
Old 05-19-2020, 06:54 AM   #8
Guru
 
High Wire's Avatar
 
City: Cape May, NJ
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 4,965
Amp clamp. Do yourself a favor and buy the AC/DC amp scale meter. Until then we’re all guessing with you.
__________________
Archie
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May, NJ
High Wire is offline   Reply With Quote
Old 05-19-2020, 07:11 AM   #9
Guru
 
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft 381 Catalina
Join Date: Aug 2019
Posts: 7,554
Quote:
Originally Posted by catalinajack View Post
You didn't mention the size of your generator. We have two, a 12.5kw and a 7.7kw. The smaller generator will not run our three AC units simultaneously without tripping the breaker.
Depends on the AC units too. My 3 units (2x 10k and a 16k) run fine on my 6.5kw generator. It's a pretty heavy load for it, but still enough headroom for the water heater.
rslifkin is online now   Reply With Quote
Old 05-19-2020, 11:39 AM   #10
Guru
 
Steve91T's Avatar
 
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
Thanks everyone. We are in the car on our way to the boat right now. It’ll be later tonight once kids are asleep when I can take a look at it.

Here’s what I do know. The hertz on the generator do drop lower than 60 and will stay there while the aft compressor is running. So I wonder if the compressor has bad bearings or something causing an excess load. It’s not just a initial start up.

This is a new problem. We used to be able to run 2 of the 3 and the rest of the boat with no problem. We still can run the entire boat and forward and middle ac’s. Just not the aft.

I have a digital multimeter onboard. What exactly do I need to test with it?

Tonight I’ll mess with it and give more info. Maybe tomorrow I’ll fire the generator and take videos of what’s going on.

Thanks everyone!
Steve91T is offline   Reply With Quote
Old 05-19-2020, 01:21 PM   #11
Guru
 
High Wire's Avatar
 
City: Cape May, NJ
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 4,965
This might help:
https://youtu.be/zr4Ow1JT9jU
__________________
Archie
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May, NJ
High Wire is offline   Reply With Quote
Old 05-19-2020, 05:13 PM   #12
Senior Member
 
DrissZougari's Avatar
 
City: (Cypress Landing) Chocowinity, NC
Vessel Name: BZ interlude
Vessel Model: MS390
Join Date: Mar 2019
Posts: 243
you will need to borrow/buy a clamp on meter and make a homemade cable to give you access the wires (Hot, Neutral, Ground) inside your shore power cable. The clamp on meter should go on the Hot (Black wire) then turn one ACs one at time to measure their current draw (make sure you are on the active shore power if you have two of them).
DrissZougari is offline   Reply With Quote
Old 05-19-2020, 07:08 PM   #13
Guru
 
Steve91T's Avatar
 
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
Hey guys. Real quick we just got to the boat. We cranked all 3 ac’s in shore power and the rear ran for a while then tripped at the compressor. I fired up the generator, turned all 3 ac’s off and then recorded the gauges while my wife turned on the aft ac. It takes a huge huge when it kicks on but then has a massive draw that seems to get worse over minutes. I had her turn it off and let the generator recover. Then I flipped on the central AC and it had very little load. The. My wife turned on the v birth ac. With both the V birth and central AC, the load still way less than with just the aft.

So back to shore power I turned on the aft ac. The compressor turned on and was blowing cold. But it got hot as shit within minutes. I turned it off and informed my wife that we will be sleeping in the v birth tonight.

I called topsies and that’s about when she realized she forgot to bring wine. Might be a long night.
Steve91T is offline   Reply With Quote
Old 05-19-2020, 07:16 PM   #14
Guru
 
Steve91T's Avatar
 
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
Here are some pics for now. I’ll have to edit my 5 minute video of my kids going nuts while I try to get the gauges while the ac kicks on.

Unloaded (mostly)

Aft ac on

Suspy ac

As always...inexpensive solutions only please.
Attached Thumbnails
8320B066-032A-4B03-AA6E-DACA572FD30B.jpg   26A1C333-1687-4E8A-A6F3-E33D2CF70BE9.jpg   4A464C99-0013-4499-995D-A4A11AFBA783.jpg  
Steve91T is offline   Reply With Quote
Old 05-19-2020, 07:59 PM   #15
Technical Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
So it even tripped the breaker on shore power?
Ski in NC is offline   Reply With Quote
Old 05-19-2020, 07:59 PM   #16
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,189
Sounds like you are going to be buying a new A/C for the aft cabin...
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
Comodave is online now   Reply With Quote
Old 05-19-2020, 08:37 PM   #17
Guru
 
Steve91T's Avatar
 
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
Quote:
Originally Posted by Ski in NC View Post
So it even tripped the breaker on shore power?
Yes
Steve91T is offline   Reply With Quote
Old 05-19-2020, 08:38 PM   #18
Guru
 
Steve91T's Avatar
 
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
Quote:
Originally Posted by Comodave View Post
Sounds like you are going to be buying a new A/C for the aft cabin...
I said....inexpensive solutions only. No stating the obvious.
Steve91T is offline   Reply With Quote
Old 05-19-2020, 09:26 PM   #19
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,189
That is the inexpensive solution, the expense solution is to have a mechanic come to the boat and do the replacement and charge you double for what it will cost you to do it yourself.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
Comodave is online now   Reply With Quote
Old 05-19-2020, 11:02 PM   #20
Technical Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
Can your meter test capacitance, or microfarads? A crappy capacitor can cause all sorts of grief with a refrigeration machine. A good meter has that setting and a capacitor can be tested for zero bucks. If it is not in spec you are looking at ten or twenty bucks.
Ski in NC is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 07:51 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012