Question about wire size

[Chewwi]

I have a question! I see that older GD trailers had a 50 amp breaker for the hydraulic pump and now have an 80amp breaker. So if the hydraulic pump draws 80 plus amps, why didn’t the old 50 amp breaker blow all the time and for that matter, why doesn’t the 80amp breaker blow if the draw is 80 plus?

The breaker is sized to protect the circuit, not the load. If breaker is 80 Amps, the circuit must be designed to safely supply 80 Amps. That doesn’t mean the pump is 80 Amps. A 50 Amps pump will work just fine on an 80 Amp circuit.

[riverdrifter1]

The breaker is sized to protect the circuit, not the load. If breaker is 80 Amps, the circuit must be designed to safely supply 80 Amps. That doesn’t mean the pump is 80 Amps. A 50 Amps pump will work just fine on an 80 Amp circuit.

I was questioning SolarPoweredRV reply at the beginning of this thread when he said that the hydraulic pump draws 80+ amps. I understand that the hydraulic pump should not normally draw much more than 50 amps. In that case, if I locate the batteries 10-12 feet from the pump I don’t really have any reason to worry about the batteries being close to the pump and why not place them in a heated,place.

[Chewwi]

I’m just confused on how much current the hydraulic pump really draws.

You could contact either GD or Lippert regarding what it is supposed to draw or get a clamp on Ammeter and measure its current draw.

[CoChris]

I have a question! I see that older GD trailers had a 50 amp breaker for the hydraulic pump and now have an 80amp breaker. So if the hydraulic pump draws 80 plus amps, why didn’t the old 50 amp breaker blow all the time and for that matter, why doesn’t the 80amp breaker blow if the draw is 80 plus?

Many factor/aspects come into play here. Part of the story;

1) The current draw will depend on a number of factors. Some of which are temp, where in the stroke are you measuring the current, is anything external effecting the slide(s), are you talking instantaneous or average (over how long a period?) current, etc.
2) Circuit breakers have a time and current factor as to when they trip. They do NOT trip at exactly xx Amps for a picosecond. They will go over their rated current and not trip for a certain amount of time. The further over rated current, the sorter time it will take to trip. For example (these are made up numbers -and see the next 2 points) a 50A breaker may support 55A for 3 minutes but only support 60A for 1 min or 80 A for 10 seconds.
3) The stock circuit breakers are very cheap devices. Quality, consistency, reliability and life are all poor.
4) Circuit breakers "wear out". Cheap ones wear out fairly quickly. Each time it trips, it degrades (wears out) a little. When they wear out, they tend to trip at a lower current/shorter time.

On our Solitude 310GK (hydraulic jacks and main slides) I typically see 60+ amp draw (warm weather) over most of the cycle but the start and end can be 20+ amps higher (but for a short period of time). In cold weather (the hydraulic fluid is thicker) is see much higher (over 90A) current draw.

Chris

[Chewwi]

Many factor/aspects come into play here. Part of the story;

1) The current draw will depend on a number of factors. Some of which are temp, where in the stroke are you measuring the current, is anything external effecting the slide(s), are you talking instantaneous or average (over how long a period?) current, etc.
2) Circuit breakers have a time and current factor as to when they trip. They do NOT trip at exactly xx Amps for a picosecond. They will go over their rated current and not trip for a certain amount of time. The further over rated current, the sorter time it will take to trip. For example (these are made up numbers -and see the next 2 points) a 50A breaker may support 55A for 3 minutes but only support 60A for 1 min or 80 A for 10 seconds.
3) The stock circuit breakers are very cheap devices. Quality, consistency, reliability and life are all poor.
4) Circuit breakers "wear out". Cheap ones wear out fairly quickly. Each time it trips, it degrades (wears out) a little. When they wear out, they tend to trip at a lower current/shorter time.

On our Solitude 310GK (hydraulic jacks and main slides) I typically see 60+ amp draw (warm weather) over most of the cycle but the start and end can be 20+ amps higher (but for a short period of time). In cold weather (the hydraulic fluid is thicker) is see much higher (over 90A) current draw.

Chris

Recognizing that hydraulic demand varies significantly with the load and hydraulic fluid viscosity, shouldn’t the circuit still be designed to supply it’s WORST LIKELY LOAD without relying on the time delay of the thermal trip?

[CoChris]

Recognizing that hydraulic demand varies significantly with the load and hydraulic fluid viscosity, shouldn’t the circuit still be designed to supply it’s WORST LIKELY LOAD without relying on the time delay of the thermal trip?

Yes, but that costs money. I replaced the sock 50A CB which I could by for a little over $5 retail for an 80A (which is what Lippert recommends) that cost $25 retail and have had no further problems. These are built as cheaply as they can be. Especially if it is not something "easily seen" and used as a sales aid.

Chris

[Chewwi]

Yes, but that costs money. I replaced the sock 50A CB which I could by for a little over $5 retail for an 80A (which is what Lippert recommends) that cost $25 retail and have had no further problems. These are built as cheaply as they can be. Especially if it is not something "easily seen" and used as a sales aid.

Chris

Since you recognize they are “built as cheaply as they can,” do you believe the circuit originally supplied with a 50A breaker is going to be protected with the 80A breaker?

[CoChris]

Since you recognize they are “built as cheaply as they can,” do you believe the circuit originally supplied with a 50A breaker is going to be protected with the 80A breaker?

If you are asking "is the original wire (size) adequate for an 80A circuit breaker" my answer is it depends. The way I see it, there are two primary limitations based on wire size. Voltage drop and temperature (for the insulation). Increasing the wire size will always lower the voltage drop for a given current. For me, the factory 6 gauge wire from the battery to the hydraulic pump worked OK, but I increased it to 4 gauge as it was "better" (lower voltage drop). Note: This is a very short run, so the voltage drop was not a lot to begin with. As for temperature, this again has a time factor. 6 gauge wire with standard insulation will not handle 90 amp for a long period of time (the insulation will get to hot and can lose is physical strength (i.e. short)). However, it will handle the heat generated for a short period of time. Think of how an electric toaster actually toasts your bread. The hydraulic pump only runs for a short period of time and I am personally fine with that.

Hope this helps you understand some of my thoughts behind it.

Chris

[wjpatter]

https://www.bluesea.com/files/resour...on_chartlg.jpg
When I look at this chart, and consider that the converter is a 55 amp one, just a rough estimate of the converter to the front battery compartment round trip is about 20’. It looks like 6 wire isn’t enough and at least 4 or 2 should be used. That would probably keep the fuse from tripping. There is a BB video of hooking the converter directly to the battery bank and they show it without a fuse. I assume if you abandoned the 6 wire and ran a set of bigger wires from the converter direct to the batteries the internal fuse in the converter and the battery management system in the batteries would be adequate protection.

If I remember right, if you run 2 wires in parallel, you get a combined gauge half the size of each wire. The math gets more complicated if the wire sizes are different. Most fuses trip based on thermal caused by the current so if the fuse is tripping, the current going through it exceeds it's rating. If you change the setup, wire size and change the current draw, you need to resize your fuse to match your new configuration.

[Chewwi]

If you are asking "is the original wire (size) adequate for an 80A circuit breaker" my answer is it depends. The way I see it, there are two primary limitations based on wire size. Voltage drop and temperature (for the insulation). Increasing the wire size will always lower the voltage drop for a given current. For me, the factory 6 gauge wire from the battery to the hydraulic pump worked OK, but I increased it to 4 gauge as it was "better" (lower voltage drop). Note: This is a very short run, so the voltage drop was not a lot to begin with. As for temperature, this again has a time factor. 6 gauge wire with standard insulation will not handle 90 amp for a long period of time (the insulation will get to hot and can lose is physical strength (i.e. short)). However, it will handle the heat generated for a short period of time. Think of how an electric toaster actually toasts your bread. The hydraulic pump only runs for a short period of time and I am personally fine with that.

Hope this helps you understand some of my thoughts behind it.

Chris

Chris,

Thank you for the explanation but it was not necessary. I too am a retired electrical engineer and a licensed PE with over 35 years of experience with large industrial facilities.

Your initial reply in this topic indicated you had replaced the 50A breaker with an 80A breaker but did not mentioned you had also replaced the 6AWG conductor with 4AWG.

Based on what I think I know, the original circuit with 50A breaker and 6AWG conductor was properly protected (assuming copper vs aluminum) but inadequately designed for its application. This resulted in excessive nuisance breaker trips. The modifed circuit solves the breaker tripping issue but with an 80A breaker and 4AWG conductor results in less than adequate circuit protection.