Adding a large capacitor to handle starting loads?? - Dutchmen Owners
Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×

Go Back   Dutchmen Owners > Dutchmen Technical | Towing, Maintenance and Repairs > Modifications and Upgrades
Click Here to Login
Reply
 
Thread Tools Display Modes
 
Old 01-06-2016, 03:38 PM   #1
Senior Member
 
Firstime RVer's Avatar
 
Join Date: Jan 2016
Location: allentown
Posts: 244
New Jersey
Adding a large capacitor to handle starting loads??

I added a KVAR capacitor system (650 micro farad/ 220V) to my house breaker box to " correct power factor" and "reduce energy consumption" some years ago.

I don't know if I ever realized any savings but I did discover that
after hurricane Sandy, my generator didn't struggle nearly as much when hit with the starting load of my well pump or microwave ..

My Aspen trail 1900RB has 30 Amp 110 V service and I was wondering if it would be a good idea to add a similar size capacitor to minimize the voltage drop during AC or Microwave starting.. I would plan to install it in parallel with the shoreline connection to my RV breaker box.. Are there any "sparkies" out there who would care to comment on whether this is a good idea and if so suggest what size capacitor I might use??
Its been over 45 years since I got my ME degree and just as long since I've done those calculations....

Pat
__________________

Firstime RVer is offline   Reply With Quote
Old 01-06-2016, 04:00 PM   #2
Senior Member
 
ewarnerusa's Avatar
 
Join Date: Dec 2011
Location: Helena, MT
Posts: 606
Montana
I don't know anything about adding a cap in parallel with a shoreline connection. But adding/replacing/upgrading a hard start capacitor to an air conditioner is a common modification for the RV. I have done it for mine and while I do think it helps my Yamaha 2400 generator start the A/C compressor, it is still marginal.
RV Air Conditioner Hard Start Capacitor | ModMyRV
Amazon link to SPP6 cap
There is debate on whether SPP6E or SPP6 is the more appropriate capacitor for this, but Supco told me that the SPP6 was the more appropriate cap. While also telling me they do not recommend this modification as it does not make a marginal situation less marginal. This size generator is still inadequate, even under the right circumstances, to reliably run a 13.5 kBtu A/C.
__________________

__________________
2012 Aspen Trail 2710BH | 470 watts of solar on the roof | 2x6V GC batteries | 1500 watt PSW inverter | Micro Air on A/C | so far strictly boondocking
ewarnerusa is offline   Reply With Quote
Old 01-06-2016, 04:42 PM   #3
Senior Member
 
Firstime RVer's Avatar
 
Join Date: Jan 2016
Location: allentown
Posts: 244
New Jersey
Thanks for the input.. Still a newbie here and doing my homework. I may be jumping the gun here a bit until we've had a chance for a shakedown trip. I read that the Dometic 13.5K BTU AC unit draws a lot of current on startup. Their manual recommends a minimum of a 3.5 KW Generator to handle the starting load, which translates to 29.16 amps. I was hoping to avoid turning everything off just to run the AC. It can get pretty hot and humid in our neck of the woods in July and August.


I just checked out your link and I'll definitely give the "hard start cap" a try. It would be the simplest solution.. Especially since you're able to start yours with a 2400 watt gen set.




I do plan on picking up a couple of Powerhorse inverter generators at Northern Tool for my no-hookup camping. Running them in parallel Delivers 3.6 K watts continuous and 4K surge watts. If the Capacitor doesn't work I would plan to run a separate line to the AC and install a switch to be able to run the ac from either the shoreline or Generator set.




It may be a while before my first shakedown trip but I will post my experiences when I do..
Thanks again
Pat
Firstime RVer is offline   Reply With Quote
Old 01-06-2016, 04:46 PM   #4
Senior Member
 
thompwil's Avatar
 
Join Date: Aug 2015
Location: Lancaster
Posts: 263
Pennsylvania
A capacitor in the starting circuit of an AC motor only shifts the phase of the current on motor start up. The current inrush will lead the voltage developed by 90 degrees in a purely capacitive circuit causing the rotor to spin. It does nothing else after that. Power factor is only an issue in industrial applications where there is mostly inductive loads such as motors. Even then it isn’t that big of a deal. At my employer before retirement, we had literally a thousand motors of all sizes from fractional to 1000 hp. Without power factor correction we were still near .94 power factor. My steel mill days we used power factor correction since we were pulling 60K amps per phase of pure inductive load on the furnaces. It was necessary then. Capacitors will store a DC charge, and will pass AC depending on frequency and capacitor rating. I can’t see how it would be of any benefit. But hey, what do I know?
__________________

2015 Voltage 3305, Gone for Good !
2014 Ram 3500 dually, Aisin, Gone but not Forgotten.
2018 Winnebago Sunstar 32YE
thompwil is offline   Reply With Quote
Old 01-06-2016, 05:37 PM   #5
Senior Member
 
Join Date: Mar 2014
Location: Desert Hot Springs
Posts: 1,761
California
I installed the SPP6 on my & my sons RV A/C units. We both noticed how much quicker the compressors kicked on. We both have large enough generators so that isn't a problem. we did connect our portable 3100 Watt Champion up to see how it reacted. We could tell by the the way the engine loaded that the capacitor made a difference. As cheap as they are they can't hurt.
__________________
Mike
2002 42' Monaco Signature Triple Crown tow 2014 F-150
2014 Voltage V3605 Sold 5/3/17
2012 F-350 6.7l CC 4X4, Sold 10/10/17
DesertRat is offline   Reply With Quote
Old 01-06-2016, 06:20 PM   #6
Senior Member
 
thompwil's Avatar
 
Join Date: Aug 2015
Location: Lancaster
Posts: 263
Pennsylvania
I can see getting some improvement in starting an individual motor if the original starting capacitor was not sufficient. I cannot see any value in putting one across your incoming line. Basic capacitor theory states that, in this case, it will block DC and pass AC. If anything, based on its Fared rating, it will do nothing, or increase energy usage by allowing current to flow from phase to neutral. Power factor correction is also much more involved than simply putting a capacitor across the line. Even then, if you knew the original power factor so you could install the correctly tuned static VAR device, benefits gained in a residential application would be negligible. I can’t see it.
__________________

2015 Voltage 3305, Gone for Good !
2014 Ram 3500 dually, Aisin, Gone but not Forgotten.
2018 Winnebago Sunstar 32YE
thompwil is offline   Reply With Quote
Old 01-06-2016, 06:29 PM   #7
Senior Member
 
Firstime RVer's Avatar
 
Join Date: Jan 2016
Location: allentown
Posts: 244
New Jersey
Thanks for all your input..
Thompwil, I never expected power factor to be an issue in my home wiring and still have a hard time believing the KVAR unit represented any savings on my elec. bill. But I have to admit it really made a difference in how my generator accepted the inductive loads like my well pump when powering my home critical utilities after Sandy. I won't hesitate to admit that I just have a little knowledge which is a dangerous thing..


Think I'm going to see how things work and if necessary go with the starting capacitor first..


If it doesn't get me where I want to be, I found a neat transfer switch at the same site EWARNERUSA recommended Automatic Transfer Switch - PPL Motor Homes to automatically switch just the AC from shore power to my generator when power supplies are stretched to capacity..


I'll be posting the results most likely in the spring as I sort things out...


Thanks again and All the best.
Pat
Firstime RVer is offline   Reply With Quote
Old 01-06-2016, 08:35 PM   #8
Senior Member
 
Join Date: Nov 2015
Location: Ft. Pierce
Posts: 312
Florida
The power company has capacitors on their lines to maintain a power factor of 1. A power factor of one means the voltage and current are in phase and thus maximum efficiency is being achieved. If your incoming power is already corrected to 1 and you place a capacitor in the circuit, you are actually losing efficiency.

WHAT EVER YOU DO, DO NOT PLACE IT IN PARALLEL!!!! A 650 micro farad capacitor has about 0.25 ohms capacitive reactance to 60 hertz (Xc=2piFC). You will certainly pop a breaker and the capacitor may explode.

The bottom line is to leave things as they are.
Handyman is offline   Reply With Quote
Old 01-06-2016, 08:59 PM   #9
Senior Member
 
thompwil's Avatar
 
Join Date: Aug 2015
Location: Lancaster
Posts: 263
Pennsylvania
Quote:
Originally Posted by Handyman View Post

The bottom line is to leave things as they are.
Indeed !!
__________________

2015 Voltage 3305, Gone for Good !
2014 Ram 3500 dually, Aisin, Gone but not Forgotten.
2018 Winnebago Sunstar 32YE
thompwil is offline   Reply With Quote
Old 01-07-2016, 12:43 AM   #10
Senior Member
 
Firstime RVer's Avatar
 
Join Date: Jan 2016
Location: allentown
Posts: 244
New Jersey
Quote:
Originally Posted by Handyman View Post
The power company has capacitors on their lines to maintain a power factor of 1. A power factor of one means the voltage and current are in phase and thus maximum efficiency is being achieved. If your incoming power is already corrected to 1 and you place a capacitor in the circuit, you are actually losing efficiency.

WHAT EVER YOU DO, DO NOT PLACE IT IN PARALLEL!!!! A 650 micro farad capacitor has about 0.25 ohms capacitive reactance to 60 hertz (Xc=2piFC). You will certainly pop a breaker and the capacitor may explode.

The bottom line is to leave things as they are.
Wow, I'm glad I asked!!
Certainly not my forte..


Thanks
Pat
Firstime RVer is offline   Reply With Quote
Old 01-07-2016, 05:41 AM   #11
Senior Member
 
hddecker's Avatar
 
Join Date: Jul 2013
Location: kamloops
Posts: 2,152
British Columbia
My head hurts!

Pat,

I have a 3kw Yamaha and it has no problem kicking the A/C on. The only thing that it can't do your me is run the A/C and another high draw at the same time, being as I only have a 20A receptacle on the generator.

I agree leave everything alone, until you get your set up together.

Another little ditty, "If it ain't broke, don't break it."

I get so mad whem I do that!

Jim
hddecker is offline   Reply With Quote
Old 01-07-2016, 12:50 PM   #12
Senior Member
 
Firstime RVer's Avatar
 
Join Date: Jan 2016
Location: allentown
Posts: 244
New Jersey
What can I say... Been there done that and got the T shirt!!
Broke it when it didn't need to be fixed!!!
Guess I've been getting carried away with anticipation.. Cant wait
for our first adventure and want to be prepared.. Spring seems a long way off.
Having said that.. The good advice here certainly has helped me avoid a
major faux pas..
Pat
Firstime RVer is offline   Reply With Quote
Old 03-05-2016, 01:11 PM   #13
Senior Member
 
HudsonFrog's Avatar
 
Join Date: Feb 2016
Location: Hudson
Posts: 102
Quebec
Quote:
Originally Posted by Firstime RVer View Post
Thanks for the input.. Still a newbie here and doing my homework. I may be jumping the gun here a bit until we've had a chance for a shakedown trip. I read that the Dometic 13.5K BTU AC unit draws a lot of current on startup. Their manual recommends a minimum of a 3.5 KW Generator to handle the starting load, which translates to 29.16 amps. I was hoping to avoid turning everything off just to run the AC. It can get pretty hot and humid in our neck of the woods in July and August.


I just checked out your link and I'll definitely give the "hard start cap" a try. It would be the simplest solution.. Especially since you're able to start yours with a 2400 watt gen set.




I do plan on picking up a couple of Powerhorse inverter generators at Northern Tool for my no-hookup camping. Running them in parallel Delivers 3.6 K watts continuous and 4K surge watts. If the Capacitor doesn't work I would plan to run a separate line to the AC and install a switch to be able to run the ac from either the shoreline or Generator set.




It may be a while before my first shakedown trip but I will post my experiences when I do..
Thanks again
Pat
One thing we commonly forget is that the 12V converter demands a lot of power to charge empty batteries. It's always good to start generator and wait for 10-15 mins to ensure the batteries are demanding a bit less from the converter. Or you can also switch off the converter breaker to start the AC and turn it back on after it runs.
HudsonFrog is offline   Reply With Quote
Old 03-05-2016, 10:38 PM   #14
Member
 
Join Date: Oct 2015
Location: Middletown
Posts: 39
Pennsylvania
Quote:
Originally Posted by hddecker View Post
I have a 3kw Yamaha and it has no problem kicking the A/C on. The only thing that it can't do your me is run the A/C and another high draw at the same time, being as I only have a 20A receptacle on the generator.
I also have the Yamaha 3000 SEB inverter unit, bought in 2008. Generator had no issues with the 13.5 Dometic A/C on my old travel trailer but as stated above had to turn off high draw appliances when starting the A/C. I like that it dips into the electric start battery if needed for extra power, and very quiet. It is now a home backup for the last 4 years, but has never given 1 bit of trouble.
__________________

__________________
2016 Voltage 3970 Full Body Paint (Earth tone/Burgundy)
2014 RAM 3500 Laramie Longhorn, 6.7, AISIN, 4.10
2012 Can-Am RT Limited, Lava Bronze
President, Susquehanna Valley Chapter Shelby Dodge Auto Club (SDAC)
Denviola is offline   Reply With Quote
Reply

Thread Tools
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


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Dutchmen RV or any of its affiliates. This is an independent, unofficial site.


All times are GMT. The time now is 01:23 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright 2020 Social Knowledge, LLC All Rights Reserved.
×