[RE-wrenches] To stack or not to stack? Off-grid 240V

Wed Oct 30 13:42:55 PDT 2013

Alan and all,

FYI, Magnum makes a 24V version of the 120/240VAC inverter, the MS4024PAE.

Brian Teitelbaum
AEE Solar

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan Sindelar
Sent: Wednesday, October 30, 2013 12:25 PM
To: Larry Crutcher, Starlight Solar Power Systems; RE-wrenches
Subject: Re: [RE-wrenches] To stack or not to stack? Off-grid 240V

Larry,
I didn't mention the MS4448PAE because Hilton had indicated that he was dealing with a 24V system and that Magnum model is 48V.

I don't think that the issues I see with lights flickering in my own home are related to either load or battery capacity. I have 1400 AH @24V of industrial cells in good condition with correct cables and installation, and the load that makes the most noticeable flicker is indeed the refrigerator, a small load. Not being an electrical engineer, I have assumed that it is related to the inverter's slow response to the poor power factor of the refrigerator's compressor, coupled with weak filtering in the electronics of some fluorescent ballasts.

That said, years ago when the first MS4024 came out, Phil Undercuffler of Outback, then still at Conergy, conducted an inverter shootout to test surge/capacities of Outback, Magnum, XW, and their older SW5548s using various power tools and other large loads. The Magnum impressed us with its ability to start loads well beyond expectation, but in doing so it allowed far more instantaneous measured voltage drop, to as low as 80 VAC, as I recall. At the bottom of this post is an excerpt from his emails of 8/19-20/08 with the results of that shootout.

There was one more issue with the Magnum, that I heard about from a customer for whom we'd installed an MS4448PAE: he told me that the crystal (?) used by Magnum to set frequency is not quite spot-on, such that he needs to reset electronic clocks, timers etc. every couple of months. He told me that he called Magnum tech support about this and they admitted that this was the case. I notice it too with the microwave clock, but am not as bothered by it, I guess (the customer is a retired professional mathematician). He told me that while he was otherwise quite pleased with the Magnum, had he known about this issue he would have rejected the Magnum for that reason alone.
Allan
Allan Sindelar
Allan at positiveenergysolar.com<mailto:Allan at positiveenergysolar.com>
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, Positive Energy, Inc.
A Certified B CorporationTM
3209 Richards Lane
Santa Fe, New Mexico 87507
505 424-1112 office 780-2738 cell
www.positiveenergysolar.com<http://www.positiveenergysolar.com/>
On 10/30/2013 12:19 PM, Larry Crutcher, Starlight Solar Power Systems wrote:
Hilton,

Magnum Energy also has a single 4400 VA model, the MS4448PAE, that operates 120/240 split phase. It can provide 8500 Watts for 5 seconds and 40 amps (line to line) for 100ms. This might start the 3HP motor load assuming it is 240 volt induction motor and not a capacitor start. Also assuming no other high loads are operating. See if you can find out (letter code on motor) or test for the LRA of the motor.

(Allan) Battery voltage dip is proportional to load/battery capacity. I install lots of Magnum product but I have not experienced voltage dip with large loads starting. Perhaps it was related to waveform and the CFL's. Magnum Energy products are designed and built in the uSA and have been the best and most reliable inverters that I have experienced so my vote is for Magnum.

Larry

On Oct 30, 2013, at 7:57 AM, Allan Sindelar <allan at positiveenergysolar.com<mailto:allan at positiveenergysolar.com>> wrote:

Hilton,
Kevin's comments are well taken. To add a bit:

Magnum are exceptionally easy to set up and program. The user interface is well designed. A few issues to be aware of from my experience:
- All of our Magnum-based off grid systems have been single inverter. At 4 kW, a single inverter may not be enough for that particular 3hp motor - best to CYA with the customer on the possible need for a stacked pair.
- Magnum allows a pretty wide voltage dip to accomplish surge capacity, so when the saw starts, expect lights to flicker. Our CF bulbs flicker when the refrigerator starts.

Our trial with Apollo a couple of years ago was probably the single most negative experience with an inverter manufacturer of my career. Kevin's comment that the most basic programming required hooking up to a computer is accurate. The computer must have their proprietary software installed, and the hookup was necessary even to initiate an equalize charge from an AC source. We have several warranty replacement and takeout units on a shelf here, from two installations (including in my own home) where the equipment was replaced after being unable to get it to work reliably. Ultimately, Apollo agreed in writing to reimburse us for the cost to replace their equipment with another brand. They never came through.

Allan
Allan Sindelar
Allan at positiveenergysolar.com<mailto:Allan at positiveenergysolar.com>
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, Positive Energy, Inc.
A Certified B CorporationTM
3209 Richards Lane
Santa Fe, New Mexico 87507
505 424-1112 office 780-2738 cell
www.positiveenergysolar.com<http://www.positiveenergysolar.com/>

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org> [mailto:re-wrenches-bounces at lists.re-wrenches.org]On Behalf Of Hilton Dier III
Sent: October 29, 2013 6:48 PM
To: re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>
Subject: [RE-wrenches] To stack or not to stack? Off-grid 240V
Hello Wrenches,

I have an off-grid client with a 24V system and an old Xantrex SW4024. He wants 240VAC capability with enough oomph for sometimes making a cut with his 3 hp table saw without starting the generator.

I am looking at Apollo, Magnum, and Outback inverters. I'm most familiar with Outback. I have a couple of installations out there with stacked 3.6 kW Outbacks.

However, the Apollo marketing promises that their 3.2 kW inverter will start a 3 hp motor. Will it actually, and is this a good idea even if it can?

I'd appreciate hearing about your experiences with 240V Apollo units, stacked Magnums, and stacked Outbacks. I know from experience that the Outbacks require some hundreds of dollars of extra fittings and electronics to make a proper stacked installation. How about Magnum? Any comments on reliability?

Many Thanks,

Hilton

--

Hilton Dier III

Renewable Energy Design

Partner, Solar Gain LLC

453 East Hill Rd.

Middlesex, VT 05602

Unfortunately, there are no published specifications for voltage sag that I've ever seen, other than some manufacturer provided comparison curves used in various presentations.  Not exactly fair and unbiased, to be sure.  Admittedly, the equipment needed to gather this type of data is pretty spendy; not every wrench is going to have access to that type of hardware, so we're somewhat at the mercy of the manufacturers.

We had the opportunity here in our training room to play with the major products side-by-side this past fall, and looked specifically at voltage regulation when under surge loads.  We focused on voltage stability in unbalanced conditions - heavy surge loads on one phase, minimal loads on the other.  Voltage measurements were via two Fluke 87's in Min/Max mode, current via Techtronix digital scope, clamp meter input.  In short, the XW had the best voltage regulation and highest surge capability of the tested products, and the Magnum was impressive in its ability to start loads well beyond its rated capacity but your client better not be working on the computer when the well pump kicks on.

For this test we were looking primarily at how the inverters handled the
inrush current of a starting surge, and what affect that would have on
voltage regulation of both the loaded and unloaded phase.  I had heard
anecdotal tales of earlier split phase inverter designs allowing the
unloaded phase to spike wild under starting surges and we've all seen
real world problems with inverters dropping voltage to keep the current
up, so I wanted to see what would happen with the new XW and Magnum
products.  We also had the opportunity to have FX and SW products as a
reference comparison.

We used simple power strips in order to get all the loads to make a
coordinated starting spike, and all surge loads were on one phase.  We
locked the triggers in the on position, then turned on the power to all
the loads with the power strip switch.  Not high tech certainly, but
effective and kept us on time and within budget   We reached the
limits of the turkey timer circuit breakers in the power strips before
we reached the limits of the inverters or ran out of power tools.  In
future tests, I'll rig up a series of relays to allow us to push the
limits further.

The loads were standard contractor style equipment I hauled in from
home.
Chop saw -- Dewalt 12" compound miter saw, 15 amp 120v
Planer -- Delta 12" planer, 15 amp 120v Routers -- Porter Cable 690's, 11 amp 120v, 1-3/4 hp
Air compressor 1 -- Thomas T-30 pancake, 12.5 amp 120v, 1-1/4 hp
Air compressor 2 -- Rigid stacked hot-dog, 14 amp 120v, but probably the
second ugliest air compressor I've ever seen, from a starting surge POV.

There were also a baseline load on both legs of two electric heaters,
and we had two CF light bulbs for visual feedback -- it's one thing to
look at squiggles on a scope, but sometimes the best feedback is seeing
what is going to happen to the lights.
Now I'm kicking myself, because we didn't try the same conditions using
grid power.  Oh well, next time.

Battery bank was a single 48v string of 5 year old Surrette S460
batteries, with 4/0 cabling.

Phil Undercuffler
Director, Battery-based and Off-grid
Conergy Sales & Systems, Americas

Loaded phase

Unloaded phase

Loaded phase

Unloaded phase

Loaded phase

Unloaded phase

Loaded phase

Unloaded phase

XW6048

Dual VFX3648 OB Stacked

MS4448AE

Dual SW5548

Chopsaw alone

A peak

96 A

110 A

50 A

94 A

V max

122.4

123.2

124

127.2

128.8

132

124

124.8

V min

108.8

112.8

116

116

81.6

87.2

109.6

118.4

V Delta

13.6

10.4

8

11.2

47.2

44.8

2 Electric heaters (not metered), compressor, chopsaw, planer.
A peak

127 A

128 A

88.5 A

Overload shutdown

V max

124.8

132.8

124

129.6

144.8

142.4

V min

99.2

105.6

97.6

105.6

60.8

72

V Delta

25.6

27.2

26.4

24

84

70.4

2 Electric heaters (not metered), 2 compressors, 2 routers, chopsaw, planer.

A peak

133 A*

130 A*

93 A

Overload shutdown

V max

125.6

132.8

126.4

131.2

154.6

142.4

V min

96

103.2

92.8

102.4

59.2

70.4

V Delta

29.6

29.6

33.6

28.8

95.4

72
*Circuit breaker tripped
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20131030/09e3c275/attachment-0004.html>