Pressure washer keeps tripping breaker

[beanflying]

110V @ 30A is not a defense for perpetrating a bad idea More Volts Less Amps please!

In Oz each state varies but we can hang 15A @ 240V off the end of 2.5mm sq on a domestic circuit or like in the case of my shack a lot more with a 4mm sq run and a sub board that will handle over 30A @ 240V. What size conductor  would you need on 110V and how much extra would it cost for a 40m run? 

[SilverSolder]

It was a bad decision made a long time ago...  we're stuck with it, sadly!  And you are right, it does use more copper for less power delivered.  Most of the time it all works OK but you run into the limitations real quick if you have portable electric radiators, kettles, etc., that you try to use.

US dryer outlets are actually 240V...  240V / 30A.  So you get > 7KW out of one of those! 

I have a long 30A extension cord that I use to run a welder and /or a 5KW fan heater in the garage.

[james_s]

Most US homes have at least one serious outlet:  the Dryer Outlet!   230V, 30A blows away even the UK's awesome 240V/13A outlets!   The only downside is that there is usually only one of those outlets in a house, so you need a long (and serious) extension cord...

Those with electric cook stoves often have a 50A 240V receptacle. It's also not uncommon to have a 240V 15 or 20A receptacle out in the garage for running things like air compressors and you occasionally see those indoors for large window AC units. I've noticed a lot of people in other parts of the world seem unaware that 240V is the standard voltage feeding houses in the US, it's just fed from a center-tapped transformer giving 120V from either side to neutral. The higher voltage is available for large loads that need it. In some ways it would be handy if everything was 240V however until recently that had significant disadvantages, 240V incandescent bulbs are quite a bit less efficient than 120V for the same wattage and 240V potential to neutral is arguably quite a bit more dangerous. Every system has advantages and disadvantages.

[SilverSolder]

Most US homes have at least one serious outlet:  the Dryer Outlet!   230V, 30A blows away even the UK's awesome 240V/13A outlets!   The only downside is that there is usually only one of those outlets in a house, so you need a long (and serious) extension cord...

Those with electric cook stoves often have a 50A 240V receptacle. It's also not uncommon to have a 240V 15 or 20A receptacle out in the garage for running things like air compressors and you occasionally see those indoors for large window AC units. I've noticed a lot of people in other parts of the world seem unaware that 240V is the standard voltage feeding houses in the US, it's just fed from a center-tapped transformer giving 120V from either side to neutral. The higher voltage is available for large loads that need it. In some ways it would be handy if everything was 240V however until recently that had significant disadvantages, 240V incandescent bulbs are quite a bit less efficient than 120V for the same wattage and 240V potential to neutral is arguably quite a bit more dangerous. Every system has advantages and disadvantages.

Yes, the center tapped transformer is a kind of cool idea in principle.  Half the outlets in the house are 180 degrees out of phase with the other half... not sure if this doesn't generate more EMI than having everything on one phase?

At least it does offer an easy opportunity to generate 240V, by suitably hacked extension cords connected to outlets that are on opposite phases!  (I'm pretty sure this is not approved...  but it does work!).

I wasn't aware that incandescent light bulbs have different efficiencies -  I though they were all somewhere in the "Terrible" category?

[beanflying]

Given the fairly widespread availability of 220V in houses it is surprising there hasn't been a push to migrate over time given most of the worlds population runs 200+V in particular as most home appliances are made offshore these days.

I will be good and not mention the Metric system either but it is good to see Liberia and Burma are moving toward using Metric 

[james_s]

I wasn't aware that incandescent light bulbs have different efficiencies -  I though they were all somewhere in the "Terrible" category?

Oh they're all terrible by modern standards, but until about 15 years ago there were not a lot of really good alternatives for domestic lighting so your option was terrible efficiency or even more terrible efficiency. Even today in 2019 incandescent lamps are still everywhere in homes, and they would be even more dominant still if not for regulations to phase them out. A 240V bulb needs to have a filament that is much longer and thinner so it draws half as much current, this results in thermal losses that are much higher.

Looking at a common UK 240V 100W "GLS" lamp the specs I find are 1320 lm and 13.2 lm/W. A standard USA 120V 100W "type A" incandescent lamp is 1600 lm so 16 lm/W, so almost 20% which is a pretty significant difference. There is an even greater difference with lower wattage lamps, IIRC a 240V 60W lamp is not much brighter than a 120V 40W lamp.

[tooki]

Oh, my! That doesn't sound like fun checking all those things.

I didn't use a clamp meter per se, but I did use a Kill-A-Watt. Can't remember what the exact wattage was, but at one point, it started up using something like 1800 or 1900 watts. This was on a 15 amp circuit.

1900W at 115V is 16.5 amps.   The breaker is doing its job!   You would be better off running this washer on a 20A circuit.

A device with greater than 15A rated current draw isn’t allowed to use a regular NEMA5-15 plug.

The OP says “something like 1800 or 1900”, which means the device is intended to draw 15A (15A x 120V = 1800W).

With that said, a breaker is NOT supposed to trip at less than 1A overcurrent!! A small overload should not trip for a long time (using the thermal part of the circuit breaker), and the overload that causes immediate trip (using the electromagnetic part of the circuit breaker) is many, many times the nominal load. (It’s a common misconception that fuses and circuit breakers are supposed to blow the instant the current rating is exceeded even a little bit.)

So unless the circuit in question was already loaded with other loads, the 15A of this machine should not cause a trip at all, nor should the inrush current when it turns on.

[SilverSolder]

Oh, my! That doesn't sound like fun checking all those things.

I didn't use a clamp meter per se, but I did use a Kill-A-Watt. Can't remember what the exact wattage was, but at one point, it started up using something like 1800 or 1900 watts. This was on a 15 amp circuit.

1900W at 115V is 16.5 amps.   The breaker is doing its job!   You would be better off running this washer on a 20A circuit.

A device with greater than 15A rated current draw isn’t allowed to use a regular NEMA5-15 plug.

The OP says “something like 1800 or 1900”, which means the device is intended to draw 15A (15A x 120V = 1800W).

With that said, a breaker is NOT supposed to trip at less than 1A overcurrent!! A small overload should not trip for a long time (using the thermal part of the circuit breaker), and the overload that causes immediate trip (using the electromagnetic part of the circuit breaker) is many, many times the nominal load. (It’s a common misconception that fuses and circuit breakers are supposed to blow the instant the current rating is exceeded even a little bit.)

So unless the circuit in question was already loaded with other loads, the 15A of this machine should not cause a trip at all, nor should the inrush current when it turns on.

You are just at the edge of the permissible 10% overload at 16.5A and, in principle, the breaker should blow after a predefined time?

https://testguy.net/content/197-Characteristics-of-Circuit-Breaker-Trip-Curves-and-Coordination

I see what you mean about the device not being allowed to draw that much current.  If so, it may be faulty (and the breaker is still doing its job!).   There could also be other loads on the circuit.

Too many unknowns error in line 6, program terminating!

[tooki]

It’s not a 16.5A device. It’s 15A. The OP was unsure about whether it was 1800 or 1900W, but it cannot be more than 1800W nominal, or else it would have to come with a plug that doesn’t fit into a 15A receptacle. Given that the OP has tried it on multiple circuits, and that the appliance used to work just fine, it’s quite reasonable to assume that it is not simply a device that is too beefy for the circuit.

Remember also that you calculated the current by dividing the watts by 115V, but that’s wrong. North America has used 120V for many, many decades now, so 120V is what you need to be dividing by. Regardless, 1900W is a 5.5% overload of an 1800W circuit: a breaker should allow that condition indefinitely.

[james_s]

So unless the circuit in question was already loaded with other loads, the 15A of this machine should not cause a trip at all, nor should the inrush current when it turns on.

I think it's reasonable to assume that the circuit *is* loaded with other devices. In fact that could be why the pressure washer sometimes works and sometimes trips. Is there perhaps something like a refrigerator or freezer on the same circuit that occasionally cycles on?

[SilverSolder]

It’s not a 16.5A device. It’s 15A. The OP was unsure about whether it was 1800 or 1900W, but it cannot be more than 1800W nominal, or else it would have to come with a plug that doesn’t fit into a 15A receptacle. Given that the OP has tried it on multiple circuits, and that the appliance used to work just fine, it’s quite reasonable to assume that it is not simply a device that is too beefy for the circuit.

Remember also that you calculated the current by dividing the watts by 115V, but that’s wrong. North America has used 120V for many, many decades now, so 120V is what you need to be dividing by. Regardless, 1900W is a 5.5% overload of an 1800W circuit: a breaker should allow that condition indefinitely.

Fair point, but it still seems to me that we would need a more accurate measurement of the specific conditions to answer the question as scientifically as you are attempting to do.

For example:  the long extension cord would mean a lot less than 115V arrives at the pressure washer.  This could mean the motor could have trouble spinning up against the mechanical resistance of the pump to begin creating counter-EMF, and all the while it would be drawing a higher start-up current for an extended time, blowing the breaker which is already marginal for this device.

The OP stated that the problem was reduced when using a shorter cord...

[mansaxel]

110V @ 30A is not a defense for perpetrating a bad idea More Volts Less Amps please!

In Oz each state varies but we can hang 15A @ 240V off the end of 2.5mm sq on a domestic circuit or like in the case of my shack a lot more with a 4mm sq run and a sub board that will handle over 30A @ 240V.

16A on 230V is quite nice.



But wait! It gets better:



There is no substitute for three-phase. Over 10KW from one outlet. Domestic. (Pic is from inside my garage) And that from a 5g2.5mm² cable. This particular outlet is driving a drill press (there are no capacitors in that drill press, but only the most beautiful electric motor ever designed, the three-phase induction motor) but it is actually put there in preparation for the heavy-duty stick welder I'm going to buy once I find someone wanting to part with it cheaply..

[SilverSolder]

[...]
There is no substitute for three-phase. Over 10KW from one outlet. Domestic. (Pic is from inside my garage) And that from a 5g2.5mm² cable. This particular outlet is driving a drill press (there are no capacitors in that drill press, but only the most beautiful electric motor ever designed, the three-phase induction motor) but it is actually put there in preparation for the heavy-duty stick welder I'm going to buy once I find someone wanting to part with it cheaply..

A real Viking wall outlet! - doubles as a charge point for an e-Longboat?   

[james_s]

I've always been envious of those who can get 3 phase power at home, outside of some agricultural situations that has never really been a thing here

Of course these days I suppose it doesn't matter so much, I run 3 phase motors at home easily using a VFD, the variable speed makes that worthwhile even if I already had 3 phase power.

[Hogwild]

So, what's my next troubleshooting step? Measure the current at startup again with the Kill-A-Watt? Test something else?

[james_s]

I would monitor the running current, and then figure out what else is on the same circuit. The startup surge should normally not be an issue.

[Hogwild]

Turns out...wait for it...my furnace may be on the same circuit.

Yes, I know how idiotic that is, but I didn't design the house, and to be fair, it's a 61-year-old house, so I doubt they were anticipating stereo gear, let alone power washers. Of course, these problems could have been minimized if they'd even labelled circuits in the breaker boxes. Will do some more research and post back. I guess I may have to resort to turning off the furnace while I'm pressure washing?

[james_s]

Or find a different circuit to connect it to. This is not really uncommon at all, what I would do is spend a couple hours to go through and determine what circuit *everything* is on and put it all in a spreadsheet then print up a list to tape in the cover of the panel. If your panel happens to be reasonably near where you use the pressure washer you could even install a dedicated receptacle on its own circuit.

I have one of these that has been very handy for this https://www.amazon.com/Klein-Tools-ET300-Electrical-Standard/dp/B003LHJSY8

Once you take the time to do this once, it saves you a lot of time in the long run.

[SilverSolder]

The furnace and fan uses about 10A - 12A here...  and is powered via its own separate 15A circuit.

Old houses can become a real spaghetti zone as new things are added, sometimes hard to anticipate by succeeding generations of electricians...

The house I'm in now is only around 35 years old, and I've still had to redistribute various loads across the breakers to avoid regular breaker failures (i.e. tripping even though the load is technically OK).  Whatever the specification says, if a breaker runs hot and close to its limit all the time, it eventually starts misbehaving (compared to surrounding breakers of the same make, model, and manufacturing batch that are not loaded as hard)...

You can see it with an IR camera, a heavily loaded breaker lights up like a supernova in the middle of the board!

[Hogwild]

The suggestion of using another outlet was one I already thought of, but the closest outlets are all...you guessed it...far enough away that I need an extension cord. Maybe the addition of an extension cord will be fine on a circuit with less load. I will try that on a circuit with less load, but not likely until next spring when it's warm enough to try using the washer. I don't want to risk damaging it.

Thanks everyone.

[james_s]

An extension cord is not a problem provided it is sufficiently heavy to carry the load.

Your other options are install another outlet on its own circuit, or locate and shut off any other loads on the existing circuit while you are using the pressure washer.