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Old 10-12-11, 12:11 PM   #11
zick
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Ok, that makes sense. I was kind of surprised that your Sanyo could run on a single 20A breaker.

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Old 10-12-11, 08:49 PM   #12
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Quote:
Originally Posted by zick View Post
...I was kind of surprised that your Sanyo could run on a single 20A breaker.
Just putting this in here to make sure everybody knows...

The breaker for your HVAC device needs to be a bit less than the Locked Rotor Amps (AKA: LRA). This is the worst case scenario when the compressor's rotor is unable to turn, but still has FULL ELECTRICAL POWER applied. This situation MUST trip the breaker switch, or terrible things will happen.

The breaker also needs to be big enough to allow the HVAC equipment to run under full load.

The installation instructions will spell all of this out for you.

Unfortunately, this is one situation where you DO need to read the instructions.

This is very important.

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Old 10-12-11, 09:09 PM   #13
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Yeah, I looked at the rotor LRA number..



17.5 amps.. Which means you need a 15A breaker on this system..
But what's the deal with the Max and Min info on the lines right above the LRA?

And then much later you see this..



22.5A at 240v = 5.4 KW???? Dang! What's up with that?
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Old 10-13-11, 06:48 AM   #14
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Xringer; I see in one of your posts that you piggybacked your protector onto your mini-split's 20A breaker? Is this wise? By connecting to the load side of that breaker you may be cheating the rest of your home out of the surge protection if that breaker should trip for a bona fide reason. If, for instance, the utility voltage drops in the early stages of a storm (voltage goes down- current goes up), and the current goes up, and causes the breaker to trip, you may have no surge protection as the storm progresses.
I realize that may seem like an extreme situation, but that is the nature of the device.
The reason they suggest connecting to an unused (or new 15A 2P) breaker is that it is a safe way to connect to a live service, the breakers terminals are designed for smaller conductors, and you can make all your connections then flip the toggle on the breaker to put the suppressor into service.
Many manufacturers recomend installing the device as close to the utility conductors as possible, there are even encapsulated weatherproof models available, designed to be installed on the triplex at the top of your service mast, or within your meter base. These models require a disconnect/reconnect from the power company, so there is a bit more planning and expense involved.
I hope that this is helpful. Rob
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Old 10-13-11, 09:23 AM   #15
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IIRC, since the breakers were installed about 35 years ago, (goodbye fuses) we have never had one pop open.
And we do get a LOT of over-voltage.

IMHO, the inverter type mini-split power supply will not load down the 230ac line,
and try to pull in big surges of amps during voltage sags.

Motor power usage is controlled by two things.
A. Pulse frequency from the controller board. (Which has no power or RPM feed-back).
B. The voltage of the 230 AC line. (Connected to diodes to make DC).

In the case of (A), the controller has to get feed-back from the temperature
sensors in the system and/or orders from the remote control unit (via my thumb).
All of these inputs are way too slow to cause anything but a 'normal' change in current.

(B), A sudden drop in line voltage going to be buffered by
the charged capacitors in the DC power supply of the unit.
Any change in current draw will come after a time lag..
And, that change won't occur in microseconds, it will be slow and will be synchronous with the sine wave of 60hz AC supply.

Plus, I care a lot more about a mini-split not getting zapped,
than anything else we leave connected to the grid.
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Old 10-14-11, 06:06 AM   #16
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I wasn't questioning the abilities of your heat pump, rather, I was trying to illustrate the reasoning behind the manufacturers installation instructions.
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Old 10-14-11, 08:20 AM   #17
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I was responding to your idea that a drop in voltage would "causes the breaker to trip",
by over-explaining why that can't happen. (with the Sanyo).

The "manufacturers installation instructions" aren't too bad,
they tell you to cut the length of their long leads to the minimum needed.
And my 'guess' about using the 15A dual breaker is to limit the fire hazard,
in case the internals of the unit shorted out completely.
(Legal dept helped with that one)?

One minor problem with using a 15A breaker, is the coils in those breakers
will likely be resistive, because of the fast rise-time of power spikes.
(Due to the inductive reactance of the coil).
That would allow a fast spike on the buss to pass into your house wiring
during the time it was working it's way past the coils in the 15A breaker.

If you take a look at the back of a typical PC power supply's AC input,

You will see the best way to add protection to a device, is to connect
your protective parts directly to the AC line (and ground).
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Old 03-11-12, 12:08 PM   #18
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(voltage goes down- current goes up)


How?basic ohms law- if the potential difference goes down (incoming voltage decreases) then across a fixed resistive load the current and power across the load will decrease. Eg if you have 100volts across a 1 ohm load, then it will pull 100 amps. If you decreased the voltage to 50v, then across the same 1 ohm load, it will pull 50 amps. I=V/R .

The power quadruples when the voltage is doubled or the resistance halved. P=VI eg the same 100 volts at 100 amps will be 10000 watts. At 50 volts, and 50 amps, the power is 2500 watts.

If you lost a phase on a 3 phase supply, then the remaining 2 phases would overload at certain points in the 3 phase motors rotation. This would cause a breaker to trip.

I guess you are talking exclusively about inverter drive technology, not the old school stuff!
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Old 03-11-12, 01:00 PM   #19
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I think he was talking about what might happen during a storm..
http://ecorenovator.org/forum/lighti...html#post16672

That it might be possible for the line voltage coming into my house to drop down,
cause excessive current flow to my (reactive?) load, thus causing higher current
to trip the large circuit breaker I'm using to feed a Sanyo ASHP.
(Leaving the rest of my house wiring unprotected,
because the protection device is attached to the output of that large circuit breaker).


It seems like a very unlikely scenario.. But, since the Sanyos use modern
Inverter Technology, the current could increase (to maintain power),
as the voltage dropped..

However, now that I have installed precision 10A limiting,
low voltage/high current could cause the power to be completely disconnected from the Sanyos.
http://ecorenovator.org/forum/applia...r-limiter.html

A low line voltage (maybe under 220vac) while the Sanyo wanted to burn 2.4 KW,
could kick the current up to around 11A, shutting the system down for a while.

If we start getting a lot of Brown-Outs, I'll have to re-adjust to 11A.

~~~
One guy had his electrician buddy wire up a 240 drop for his mini-split and he mis-wired it for 120vac..
BUT, it still ran! But only in Cooling mode.. Even when he changed the control to heat mode..
I think maybe his 4-way valve wouldn't pull in on a mere 120vac..
http://ecorenovator.org/forum/geothe...html#post16160
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Old 12-31-12, 12:23 AM   #20
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I've recently installed some custom LED lighting. The other night I was sitting in my office during a pretty bad thunderstorm, and when lightning struck, the LED lights in my office actually came on for a second - which is very weird, because they were turned off at the switch!

There's also another fixture in the hallway, which was turned on at the time. It seems that the surge hasn't done any damage - they work just like they did before. It's possible that the transformers I use have built-in surge protection though - I've got the LED drivers built into my walls, and the light switches are just switching 12V.


Last edited by Daox; 12-31-12 at 07:57 AM..
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