Hooked up to shore power but we keep losing power more and more often

[Bobtop46]

Fridge and water heater are both electric. Your reply is enormously helpful - we have three electric blankets we just got, so that may be it. Do you know the amps for fridge/water heater?

Fridge depends on size 2-3 amps while running, much more when starting up until temps come down, or after frequent/extended openings. More for 4 door model and varies with surrounding temps.
Water heater element is 1400W- 1500W and is either on or off, so 11.66 -12.5 Amps. This and the Converter are huge draws that you don't know when they are going to kick on. The water heater you can turn off the switch to control. The converter does it's own thing and kicks on when high power when needed. The converter also normally float discharges the battery, and supplies the RV with 12v power. Typical constant 12v loads are: 12v controls for water heater, 12v controls for fridge, LP gas detector, and AC/furnace thermostat. Variable 12v loads are lights and A/V speakers.

In your situation you can make a house rule, if electric blankets are on then water heater is off, and vice versa, if water heater is on then electric blankets are off. Don't try to control the converter if you are even able to. It is a sure way to dead batteries. Worse thing happens if you forget to turn on water heater is you have to wait to do dishes or take a shower, unless its bitter cold out and you freeze the tank, possible but unlikely while you're using the RV.

 

[Gary RV_Wizard]

I don't think you have a faulty breaker or outlet, though it is a possibility. However, your description suggests to me that you are experiencing periodic overloads. You mentioned several devices that have thermostats or intermittent power draw, e.g. electric blankets or pads, fridge, water heater, computer chargers, etc. With all these things switching on/off independently on each other, they are going occasionally coincide and could exceed your 30 amp, 3600 watt max capacity (1 amp @ 120v is about 120 watts). Others have given you some ballpark figures for amp or watt loads, so I think you can figure this out.

Modern devices mostly have low power draws, but they tend to get left on a lot, e.g. an electric blanket or pad gets forgotten or phones & computers left plugged in. Others are out-of-sight & out-of-mind, e.g. fridge is always on (200-300 watts pretty much non-stop), water heater cycles periodically to keep warm, etc.

 

[Ray-IN]

Fridge and water heater are both electric. Your reply is enormously helpful - we have three electric blankets we just got, so that may be it. Do you know the amps for fridge/water heater?

This should be informative:120 Volt AC RV Appliances And Their Estimated Current Draw

Keep in mind you have 30 Amps maximum. for continuous use 28 Amps should not trip out the main breaker.

 

[Gary RV_Wizard]

Keep in mind you have 30 Amps maximum. for continuous use 28 Amps should not trip out the main breaker.

Actually, a draw of 24+ amps for 30 minutes or more can often trip a 30A breaker. A sustained load of 80% of the peak rating is the performance standard set in the electrical codes for most equipment and installations. That's why you see complaints about a breaker trip 30-60 minutes after loads were added. It takes time, and the amount varies with a number of factors.

 

[Kirk]

Actually, a draw of 24+ amps for 30 minutes or more can often trip a 30A breaker. A sustained load of 80% of the peak rating is the performance standard set in the electrical codes for most equipment and installations.

The circuit breaker stated rating is actually a nominal number. They are designed with 3 trip ratings. There is a "long time" rating that is usually between 80-90% of the package rating or usually 24-27a will cause a trip if continuous, after 20 to 30 minutes. Then there is a "short time" trip point that is typically about 150% of rated current and triggers 2-3 minutes or so. The "instantaneous trip" the amount of current require to cause the circuit breaker to open immediately and that is typically on the order of 10X the breaker rating. These numbers are all very general and one would need to know exactly what circuit breaker we are talking about to determine the actual numbers. The inrush current of a starting motor will peak in a second or two and quickly trail off but a dead short will cause the breaker to open immediately. If you wish to know more about circuit breakers, I suggest this article.

How Circuit Breakers Work​

 

[Ray-IN]

Thanks for correcting my mistake Gary. I was thinking 80% and typed 28. Being old is inconvenient.

 

[Gary RV_Wizard]

Thanks for correcting my mistake Gary. I was thinking 80% and typed 28. Being old is inconvenient.

How well I know that!

 

[Gary RV_Wizard]

The circuit breaker stated rating is actually a nominal number. They are designed with 3 trip ratings. There is a "long time" rating that is usually between 80-90% of the package rating or usually 24-27a will cause a trip if continuous, after 20 to 30 minutes. Then there is a "short time" trip point that is typically about 150% of rated current and triggers 2-3 minutes or so. The "instantaneous trip" the amount of current require to cause the circuit breaker to open immediately and that is typically on the order of 10X the breaker rating. These numbers are all very general and one would need to know exactly what circuit breaker we are talking about to determine the actual numbers. The inrush current of a starting motor will peak in a second or two and quickly trail off but a dead short will cause the breaker to open immediately. If you wish to know more about circuit breakers, I suggest this article.

That's an excellent but concise explanation. A key point is that individual breaker models can vary quite a bit as long as they meet the minimum performance standards, so there is little value in debating specific amp tripping points. Just be aware that a 15A breaker doesn't always & only trip at exactly 15A.

 

[WILDEBILL308]

It will be interesting to see what the outcome is.
Bill

 

[dwdanby]

It will be interesting to see what the outcome is.
Bill

I so appreciate all the advice, I will be posting once we learn more. At the moment, an electrician is coming to check shore power, and has the gizmo to see what amperage our devices are drawing.

 

[WILDEBILL308]

Something no one mentioned is it could be low voltage as well as a hi load. Low voltage creates heat. I won't plug in without my Surge Guard. https://www.amazon.com/dp/B07BNWJVKX?psc=1&ref=ppx_yo2ov_dt_b_product_details
Bill

 

[John From Detroit]

Something no one mentioned is it could be low voltage as well as a hi load. Low voltage creates heat. I won't plug in without my Surge Guard. https://www.amazon.com/dp/B07BNWJVKX?psc=1&ref=ppx_yo2ov_dt_b_product_details
Bill

Actually .. Low voltage does not create heat. That which creates heat (Resistance) creates low voltage.. This is why it's important to keep the blades on your plug bright copper not dull black.
Heat is created by current through resistance.. Now to some extent lower voltage may cause some things (your converter, Anything motor driven and anything with a regulated power supply like your computer, phone, tv, and so on) will draw more current. but the water heater (Big ticket item) Fridge (medium ticket item)_ and other resistive loads.. Well generally less current (Though it is NOT a linier ratio)
A Kill--a-watt multi-meter helps for stuff you plug in to figure this kind of stuff out but the math if you try to do it otherwise gets interesting.

 

[Kirk]

Actually .. Low voltage does not create heat.

It can if we are talking about an alternating current motor. Since they base speed on frequency, when voltage drops they draw more current, just to opposite of what happens with a resistance load and the will overheat if voltage drops too far. But I agree with most of what John has said. All modern electrical equipment has a designed voltage range that it works best and too high or too low is nearly always a bad thing. The supply to your shore power plug should be 120V, +/- 10% or between 108V and 132V.

 

[Larry N.]

It can if we are talking about an alternating current motor.

I think John's point was that it's not the low voltage itself that causes it, but rather the extra current the motor draws as a reaction to that low voltage. But that's a technicality that isn't, in itself visible -- just the results of both "actions" are visible. From a practical standpoint you're definitely correct, Kirk.

 

[Bobtop46]

Something no one mentioned is it could be low voltage as well as a hi load. Low voltage creates heat. I won't plug in without my Surge Guard. https://www.amazon.com/dp/B07BNWJVKX?psc=1&ref=ppx_yo2ov_dt_b_product_details
Bill

This is a good point as lower voltage increases the amps. 1500w divided by 120v = 12.5 amps, where 1500w divided by 110v = 13.6 amps. This alone could drive the OP's amp draw up 4-5 amps.

 

[John From Detroit]

It can if we are talking about an alternating current motor. Since they base speed on frequency, when voltage drops they draw more current, just to opposite of what happens with a resistance load and the will overheat if voltage drops too far.

And that is exactly what I said. it is CURRENT that makes the heat
And anything motor driven will draw more current at lower voltage
Also switching power supplies will draw more current (Those are the most common now days) Transformer supplies.. it's a tad more complex.
Even on DC motors lower voltage = more current by the way.

 

[Ray-IN]

Even on DC motors lower voltage = more current by the way.

Yup, that's why some people who try to get the last breath out of a starting battery usually wind up also replacing the starter in the near future. A good battery voltage drops to ~ 10.8VDC when the starter is engaged, never measured a weak battery for that.