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| Inverter Question [message #101499] |
Fri, 01 October 2010 15:10  |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
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Looking at a 120v refrig to replace my OEM Dometic which has the 120V heater element blown.
Will this inverter (1500 cont. 3000 surge) work properly, or do I need a Pure Sine wave?
Thanks
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: Inverter Question [message #101502 is a reply to message #101499] |
Fri, 01 October 2010 15:33  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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I run two 120V refrigerators and most will run just fine off a modified sine wave invertor much smaller than that. i would check the running consumption of the unit you are thinking about then multiply it by about 2.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Inverter Question [message #101557 is a reply to message #101523] |
Sat, 02 October 2010 07:06 |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
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Have not decided, there are a number of them at Lowes, Home Depot and Target for less than $250.00. Would like to get one that is Frost Free.
Will need some help in wiring the Inverter.
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: Inverter Question [message #101572 is a reply to message #101557] |
Sat, 02 October 2010 10:46 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
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| Oldngray wrote on Sat, 02 October 2010 05:06 |
Have not decided, there are a number of them at Lowes, Home Depot and Target for less than $250.00. Would like to get one that is Frost Free.
Will need some help in wiring the Inverter.
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look very carefully at the yellow energy tag on whatever you are considering. If you do any dry camping, you want the number to be as close to 270 kwh per year as possible, the lower the better. Some refrigerators, although small, are great energy hogs. Frost free are even worse, and I would not recommend them.
Also be sure that it has coils on the back, and not built into the sides of the refrigerator. Otherwise the heat will not get out of the unit if it is stuffed into the original 24" wide location.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] Inverter Question [message #101628 is a reply to message #101499] |
Sun, 03 October 2010 03:24 |
Douglas Norton
Messages: 191
Registered: April 2008
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Is a sign wave needed? http://www.donrowe.com/inverters/inverter_faq.html#modified
It is not needed according to the above link or according to several modified sign wave manufactures: "Voltec VTC1500 - The VTC1500 provides instant portable power for your car, truck, boat and RV. Able to handle small power tools and various appliances,
including vacuum cleaners, small refrigerators, TVs and more."
I may be a naysayer here; if so it is because I read several articles about the original GMC compressor powered fridge.
Your proposed set up should work well if not dry camping. While driving to a location with hookups, the generator should have no problem putting out the needed power for the inverter. Without alternator or generator/shore power support, I estimate a refrigerator will drain 2 golf cart batteries to below the recommended minimum (50%) in about 6 hours if the refrigerator draws an average of 10 amps and in 3 hours if it draws 20 amps (2 amps at 120 volts or 240 watts at any voltage). Duty cycle will impact usage but will be greatest near startup. My home energy efficient unit has a 40% duty cycle. A big advantage of having a compressor is a much faster startup than with a propane refrigerator.
A disadvantage of gas: while my gas frige made it 3 weeks on 7 gallons of propane on my last trip, very high Wyoming winds blew out my flame one day and the fridge warmed up in 12 hours. There was some spoilage and a mess.
Hope this helps. I have no doubt the 1500 watt inverter will do the job with capacity to spare.
--- On Fri, 10/1/10, Richard MacDonald <rm1936@gmail.com> wrote:
From: Richard MacDonald <rm1936@gmail.com>
Subject: [GMCnet] Inverter Question
To: gmclist@temp.gmcnet.org
Date: Friday, October 1, 2010, 1:10 PM
Looking at a 120v refrig to replace my OEM Dometic which has the 120V heater element blown.
Will this inverter (1500 cont. 3000 surge) work properly, or do I need a Pure Sine wave?
Thanks
--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
94 K2500 6.5 Turbo Diesel Silverado
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| Re: Inverter Question [message #101632 is a reply to message #101630] |
Sun, 03 October 2010 09:00 |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
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Definitely lower N load, however not sure 1100 is the right size.
Really appreciate all the input.
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: Inverter Question [message #101701 is a reply to message #101630] |
Sun, 03 October 2010 19:45 |
Dave Martin
Messages: 59
Registered: May 2010
Location: Ames Iowa Home Base
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| Dave Martin wrote on Sun, 03 October 2010 08:38 |
Check out http://www.invertersrus.com/powerbrightpw1100-12.html
No-load current is an important spec. Smaller is better.This one is good.
The 1100w powerbright unit shown in the link has a no-load current ofabout 0.16 amps while the 1575w Cobra unit draws about 0.6 amps, more than three times as much.
Dave in Florida
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I don't know that the 1100w unit I pointed to is appropriate for your purpose, but the web site is a good one. It lists a number of inverters and includes the no-load current, which is often very hard to find.
For planning purposes it is reasonable to assume the no-load current is being drawn whenever the inverter is on. A 0.16a no-load current will draw .16*24=3.8AH/day from your battery bank, while a .60a no-load current will draw 14.4AH/day, a considerable difference if you are dry-camping.
If you are not dry-camping for long times, but just using your inverter to keep the fridge etc running as you go from one plug-in to another, then no-load current doesn't matter much, even with an occasional layover of a few hours.
I think I'm good for a couple dry-camping days; electric fridge, oxygen concentrator, microwave occasionally, laptop, TV, some led lights, etc.
I would say a good way to chose an inverter would be to choose the one with the lowest no-load current and more capacity than needed to do the job.... the more capacity the better if the no-load current is the same. Avoid inverters with loud fans that run all the time.
I'd use the web site indicated to narrow the search based no-load current and other specs important for your application.
Dave
Some inverters have very low no-load current, in essence they don't turn themselves on until they sense a demand. The few I've seen were costly.
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| Re: Inverter Question [message #101886 is a reply to message #101499] |
Tue, 05 October 2010 13:57 |
Erv Troyer
Messages: 125
Registered: February 2004
Location: Lagrange, IN
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| Richard McDonald wrote on Fri, 01 October 2010 15:10 |
Looking at a 120v refrig to replace my OEM Dometic which has the 120V heater element blown.
Will this inverter (1500 cont. 3000 surge) work properly, or do I need a Pure Sine wave?
Thanks
|
I went through this upgrade last year, and I chose the Frigidaire FRT045GB, which is a double door model.
I posted a set of pictures on the GMC Photo Site:
http://www.gmcmhphotos.com/photos/showgallery.php?cat=5264
The inverter/charger I have is a Trace Engineering 2000 watt with modified square wave output, which was in the GMC when we bought it. After the refer was installed I did some testing, and found that the the AC amp draw at the refer was more than double when running from the inverter source. I used a true-RMS meter, so I'm sure that was accurate. Your inverter may do better than this, but if it is modified square wave I doubt it. A true sine wave inverter would surely do better, but still less efficient than running from line power.
For any one running a refrigerator, microwave, ar any other appliance from an inverter, you should keep in mind that it will ALWAYS RUN FROM THE INVERTER, even when you have the coach plugged in. This means that the appliance will ALWAYS see that modified square wave, along with any problems this may (or may not) cause.
I would recommend that you set up your inverter supplied circuits so they can be switched to line power whenever it is available. This can be done by:
1. installing a double-pole double-throw switch to manually switch power sources. Simple method, least expensive.
2. installing an automatic switchover box which will switch to line power automatically whenever it is available. More expensive, but automatic.
3. instead of using a separate inverter and converter/charger, use a combination inverter/charger. All of these that I have seen have a built in switchover relay that will switch all AC loads to line power whenever it is available. Most expensive, but the best solution, in my opinion.
By the way, we really like that Frigidaire refrigerator, and would not go back to to the propane unit. It cools MUCH faster, and has a better interior design. It cost us $267, which includes a 3 year warranty - if it quits we can buy a new one for $30. That cost is considerably less than it would cost just to repair the old Dometic, and about 1/4 the cost of a new Dometic or Norcold.
This refer has the condenser (hot side) within the walls of the unit, so I made sure I had at least 2 inches at each side, and left the top of the compartment open for ventilation. I closed off the sidewall and roof vent openings, as they are no longer needed.
And that is just what I did - may not be the right solution for everyone.
Erv Troyer Lagrange, IN
74 Sequoia
reo43@aol.com
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| Re: Inverter Question [message #101898 is a reply to message #101499] |
Tue, 05 October 2010 15:06 |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
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Thanks Erv, that really looks nice, at first I thought it would be much larger (capacity) but see that it is about the same size as my original RM66.
Have not made up my mind what to do yet, still debating on getting the RM66 fixed or replacing.
Would be a lot less expensive to repair and save the rest towards my wanted TBI.
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: Inverter Question [message #103482 is a reply to message #101886] |
Tue, 19 October 2010 15:08 |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
Karma: 0
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Erv,
I replaced my Dometic with a Fridgidaire 4.4 cu ft single door. I had issues with the Dbl door as I have the Dry bath Model and not enuf depth in the top an bottom of the cabinet. It is the same size just a single door and not self defrosting.
I should have followed Dave Martins advice about Inverters though.
The Cobra is way too loud and I intend to return it and get something with fans that are not so loud.
He also made a good point about current draw which I did not really pick up until too late. I do like the way your ref looks. Something about dbl doors, Dan Myers (sp) also has the same as yours only in black.
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: Inverter Question [message #103498 is a reply to message #101499] |
Tue, 19 October 2010 17:03 |
Gail Marks Cruiser
Messages: 125
Registered: August 2009
Location: Gold Coast, Australia
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G'day,
Erv wrote in his post,
"For any one running a refrigerator, microwave, ar any other appliance from an inverter, you should keep in mind that it will ALWAYS RUN FROM THE INVERTER, even when you have the coach plugged in. This means that the appliance will ALWAYS see that modified square wave, along with any problems this may (or may not) cause."
I haven't heard of any Trace units working like this. I have had 3 Trace/Xantrex, inverter/chargers, using modified square wave and all of them have transfered shore power directly to all appliances when plugged in.
It is part of the automated switching system so that when it senses suitable shore power, it automaticaly shuts down the inverter, turns into a 3stage battery charger, using shore power to run the motorhome.They have their own circuit breakers to protect the battery charger and the power out-put, whether mains or inverted.
It also does the reverse when un-plugging. Many years ago had some idiot unplug our motorhome in a campground, whilst Gail was using the computer and the Girls were watching videos. If I hadn't seen the lights on the Trace change I wouldn't have noticed the change in power supply, it was that quick!
The pure sine wave models have dropped in price, to the point that they are all I would look at now. The only real difference I have ever noticed between a good Modified Square wave and Sine wave is with electric motors e.g. The smoothness of a power drill running at low r.p.m's.
I am always willing to be corrected, I have already learnt so much from the wise members of this site.
Mark Bennett
Gail & Mark's Cruiser
Gold Coast, Australia.
Motorhoming Lifestyle.com
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