[RE-wrenches] phase issues with SB8000US

Tue Aug 31 07:32:00 PDT 2010

Nik,

It's been a few years since I've seen this... I have seen several cases of
plug-in UPS and "surge protector" power-strips that were incompatible with
the inverter. The symptoms were "tripping" and "singing". These were
straight up incompatible and would "trip" or "sing" any time the inverter
was running at any power level over about 1000 watts. There weren't any
unrelated loads associated with the issues. Changing to any other model
solved the problem. If these are plug-in models, I suggest taking a
replacement with you and seeing if that trips under the same conditions.

Beyond that:

You say their UPS systems are "tripping". 

Some background diagnostic info:
Is the PV tied into the same distribution panel that the UPS and air handler
are?
How many UPS units are there?
120V or 240V?
Is/are this/these local to each workstation or is/are this/these backing up
one or more distribution circuits?
How many of them are "tripping"?
If these are local units, are the "tripping" units all on the same circuit
or phase out of the distribution panel?
What do you mean "tripping"? (i.e. Local UPS "beeps" and picks up the
workstation or ?) 
How long does the "trip" last? (i.e. Just until the air handler motor is up
to speed or ?)

I'm guessing that these are workstation units. If the inverter is not
dropping out, I suspect it is fine.

If it's not an "incompatible" UPS issue, the air handler may be the source
of the problem. Could be a failing capacitor or the motor might be dragging
& spiking the neutral. They may have a bad breaker or bus on the air handler
circuit, or a problem in the neutral. Neutral issues can be caused by a host
of things. These things can be on the load circuit or in the feeder/bus.
Undersized, loose connections, shared with other circuits.... I would make
sure the air handler has a dedicated neutral.

Another thing to look at is the relationship of the UPS circuit(s) to each
other and the air handler circuit. If multiple UPS units are on the same
circuit and these are on the same phase as the air handler, switch one or
the other to the other phase and try it. If there happen to be two circuits
feeding the UPS units, and these circuits share a neutral, tell the
electrical engineer in charge that they need dedicated neutrals. If there
are multiple 120V circuits sharing a neutral AND they happen to be on the
same phase, switch one breaker to the opposite phase and then pull a
dedicated neutral and charge them for it. An EE will argue that it's totally
fine to share neutrals, but trust me, it's not. (The cheap-ass practice of
sharing neutrals for multiple 120V circuits is complete BS. In circuits with
inductive loads that don't have good filtering, this creates harmonic
distortion.)

Good luck and let us know what you find out.

Matt Lafferty

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Richard L
Ratico
Sent: Tuesday, August 31, 2010 4:45 AM
To: re-wrenches at lists.re-wrenches.org
Subject: Re: [RE-wrenches] phase issues with SB8000US

Hi Nik,

Some questions:

Is this a 3 phase service?

Details on the UPS; brand, kVA, age?

Breaker sizes for the circuit(s) supplying the UPS and fan?

Details on the air conditioning system and fan. Are they powered through the
UPS?

Dick Ratico
Solarwind Electric

--- You wrote:
Wrenchers,

We installed our first SunnyBoy 8000 this month. The customer (happens to be
electrical engineer) is complaining that their computer UPS systems are
tripping whenever the air conditioner (with 120V fan) comes on. This didn't
happen before commissioning the solar system and it doesn't happen when the
inverter is disconnected. So, of course, they suspect the inverter is the
culprit. The theory being that the inverter itself is going out of phase
when one of the legs is loaded down momentarily.

So far, SMA tech support is not agreeing. They are blaming the problem on
the unbalanced loads and/or the UPS systems. Their latest solution is to
move the UPS systems to the other leg. Not surprisingly, the customer is not
impressed with this game of Kick the Can Down the Road.

The inverter does not drop the grid, nor display any error codes when this
happens. This is a 200A, 240V service. The 120V fan draws about 10A
continuously, 40A surge.

Anybody else with similar experiences? Suggestions?

Thanks
Nik

--
Nicholas Ponzio
NABCEP Certified Solar PV Installer

Building Energy
1570 South Brownell Road
Williston, VT 05495
t: 802-859-3384 x15
f: 802-658-3982
c: 802-365-1973
http://www.BuildingEnergyVT.com
_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out participant bios:
www.members.re-wrenches.org
--- end of quote ---
_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out participant bios:
www.members.re-wrenches.org