I need help with an electric issue.

[Dom]

This post extends off of this thread: https://www.reef2reef.com/threads/a...iple-issues-in-my-tank.1091454/#post-13208215

The equipment rack for my tank has two circuits.

The first circuit (a mounted power strip) plugs directly into the utility (wall) and is where I plug in all non-mission critical equipment in the event of a power failure. On this strip, you will find display lights, utility lights, and dosing pumps.

The second circuit has battery backup for mission critical equipment: main return pump, power heads and skimmer.

​

This circuit begins with a new GFI outlet. From there, it goes to a 15 amp auto transfer switch. On one side of the switch is utility power, and on the other side, a deep cycle lead-acid battery with a 500watt inverter connected.​

​

Here's the issue; when I pull the plug from the GFI to test the backup, it switches over as it should. But then within a few minutes, the breaker on the battery trips. When I plug back in to utility, everything comes back on as it should. Then I can reset the breaker on the battery.​

​

I thought the issue may be the ATS, but still tripped the battery breaker when I plugged the circuit directly into the inverter.​

​

The inverter is rated at 500 watts, and KILL-O-WATT reports that the circuit is drawing 172 watts.​

​

I have the same inverter which is rated at 1000watts. Does it make sense to try a different inverter? At this point, I feel it is the inverter or something with the battery bank.

Feeling a bit lost with this one and am calling on members with electrical background/experience to help set me in the right direction.

Thank you,
Dom

​

​

​

​

​

​

​

 

[Reefering1]

Try the bigger inverter...

 

[Dom]

Try the bigger inverter...

I will. But if it works, what does that tell us? I'm only drawing 172 watts from a 500 watt inverter, so it isn't that the inverter is under powered. I would conclude that there is something wrong with the inverter.

 

[Reefering1]

Draw/ send a schematic of how you have it wired...

 

[Dom]

Draw/ send a schematic of how you have it wired...

Working on it.

 

[Dom]

I know... amateur. But I think it gives a clear idea.

 

[Reefering1]

So the inverter is on and ready at all times? Or turns on one power fails?

 

[ThisIsTheWay]

What size (Amp rating) is the battery breaker?

Watts = Amps * Volts
Watts/Volts = Amps

172W at 120V is ~1.43A (172/120 = 1.43)
172W at 12V is 14.33A (172/12 = 14.33)

It sounds like the 172W of power you're pulling from the battery through the inverter is juuusst enough to blow a 15A circuit breaker if there are fluctuations or a little power loss from going through the transformer.

I could be totally off but based on what I know that's my first suspect.

EDIT:
If this is the issue, then a larger inverter won't solve your problem. The issue it sounds like is when you go from 120V down to 12V your amperage goes up a lot for the same watt output (ohms law). In this case you'd be close to 15A of current between the battery and inverter.

 

[Dom]

So the inverter is on and ready at all times? Or turns on one power fails?

Inverter is on at all times.

 

[Reefering1]

Inverter is on at all times.

Did it come with instructions specifying wire size and fuse amperage?

 

[Dom]

What size (Amp rating) is the battery breaker?

Watts = Amps * Volts
Watts/Volts = Amps

172W at 120V is ~1.43A (172/120 = 1.43)
172W at 12V is 14.33A (172/12 = 14.33)

It sounds like the 172W of power you're pulling from the battery through the inverter is juuusst enough to blow a 15A circuit breaker if there are fluctuations or a little power loss from going through the transformer.

I could be totally off but based on what I know that's my first suspect.

EDIT:
If this is the issue, then a larger inverter won't solve your problem. The issue it sounds like is when you go from 120V down to 12V your amperage goes up a lot for the same watt output (ohms law). In this case you'd be close to 15A of current between the battery and inverter.

Missed that. The battery breaker is 10 amp. I purchased it by mistake, fully intending to match the 15 amps of the ATS and GFI. I didn't think it would be a big issue, until I just saw the math. I suppose I could bypass the breaker as a test and then get a larger breaker to install.

I think this may be the answer as the amperage pulled is close to exceeding the breaker (if it were 15 amps). I've had this configuration for a few years without issue, although, the pair of Nero5s were added to the circuit after building the battery backup.

 

[Dom]

Did it come with instructions specifying wire size and fuse amperage?

This is the inverter. I don't recall what the wire size and fuse amperage recommendations were.

Amazon product

 

[ThisIsTheWay]

Ah, yeah, I just looked up the Nero 5s and the online spec is up to 30W per Nero 5 so adding 2 is quite a big jump in power demand for that circuit. If you have them on some sort of sine wave/pulse mode that might explain why the breaker doesn't trip right away.
If you have an amp clamp you could always measure the amperage, though I admit it's not a common tool to have.

 

[Reefering1]

This is the inverter. I don't recall what the wire size and fuse amperage recommendations were.

Amazon product

Dead link. Copy title of product

 

[Idech]

Dead link. Copy title of product

It works for me.

 

[Dom]

Dead link. Copy title of product

Try this:

Amazon product

 

[jsmkmavity]

172 watts at 12 volts in 14.3 amps. As a breaker ages from tripping it gets weaker and trips easier. You should be15% below rating for continuous use. All these issues add up to your problem. The battery when new and fully charged should be 13.2-13.5 volts which will drop the amps a bit but as it ages the voltage will drop. Another thing to consider is when a lead acid battery gets older it takes a lot more charging to maintain and that causes it to release a lot of caustic and harmful gas. It should be outside or actively vented to outside. If in the same space as the charger, inverter, outlets and other connections or switches/relays that gas will corrode those things causing more problems. I have learned this myself the hard way and hope this info can help others.

 

[jsmkmavity]

One other thing to look at is the rating on the inverter. They have 2 different ratings for "continuous" and "peak". Usually continuous rating is half of the peak rating, making your 500 watt inverter a 250 watt continuous use inverter which is your type of usage.

 

[Reefering1]

Try this:

Amazon product

 

[Dom]

I believe you, I just don't understand why this suddenly started happening.

Bestek 500 watt