Calling Electricians - amps, watts and volts.

[Beth]

Hi,

This is Beth's husband (aka 'YesDear' ).

We have a 1987 Fleetwood Bounder RV and I've just spent hours trying to sort out the aggregate power consumption of the two 1500/750-watt electric heaters (we disconnected the propane furnace and stove because Beth is allergic to propane, although the fridge is okay because there's no detectable odor from that), the microwave, the induction cook top (hotplate), our computers, and a Toshiba 40-inch LCD TV, plus a blu-ray player, as well as the fridge and the lights.

There's an air conditioning unit that seems to have it's own 20-amp breaker, but in the "charge sentinel" (breaker box), out of 30 amps there seems to be a 20-amp "portable appliances" breaker and a 15-amp "general purpose" breaker, as well as the "AC" breaker adding up to 55 amps instead of the 30 amps the RV manual says this rig has, so how does that work?

Obviously, we need to use these devices selectively, turning off some in order to use others etc.

Now, I already know that the fridge uses 300 watts, the microwave uses 700 watts, the "hotplate" uses up to 1500 watts, and each computer uses 90 watts.

The only constant is the fridge which runs all the time, and in Canada it's cold at night even in summertime, so we use one electric heater at 750 watts in the evening.

I can't figure out the difference between a kilowatt hour and a kilowatt, or find a conversion chart that will enlighten me, and I NEED TO KNOW how many watts my 40" LCD TV and blu-ray machine consume, and I can't find anything in watts, just kilowatts.

Can anyone help me out with any of this info?

Thanks in advance,

YesDear.
P.S. We'll never use the AC, so can I reroute the power for that (wherever it's coming from) to my other systems?

[RJC]

I was working on a house with a 50 Amp service last month. It has 120 V circuit breakers as follows, 2- 30 A; 4- 15 A; 4- 20 A. The 2 -30 A and 1- 20 A seemed to be capped off. However if we do the math as you did, than there is still a total of 120 Amps on a 50 amp service.

That’s not how it works. If the total draw exceeds the 30 Amp, on your RV, the 30 Amp breaker will trip, otherwise something will burn up if it does not trip. The issue is how much load you might have on any given circuit. If you can check where every outlet or load is for each circuit, then you can calculate how much load you can have on each circuit. You cannot exceed the breaker rating, i.e. 20 Amps on a 20 Amp breaker.

A 1500 watt heater at 120 volts is 1500/120 or 12 ½ amps, therefore no more than 7 ½ amps are left for the rest of that circuit. That’s why you want to check the loading on each circuit.

A kilowatt is a 1000 watts, and if you run a 1000 watt appliance for 1 hour you have consumed 1 kilowatt hour. The kilowatt value is relevant to consumption but you will convert the kilowatt rating to amps to determine what your circuit loading is. For instance a 1200 watt appliance on a 120 volt system is 10 amps. A toaster may be 1000 watts but it only is on for a few minutes. So it consumes only a fraction of a kilowatt hour.

Amperage is your concern and the condition of the breakers, if they do not trip as designed than something burns up.

[tm1439m]

Hi,

This is Beth's husband (aka 'YesDear' ).

We have a 1987 Fleetwood Bounder RV and I've just spent hours trying to sort out the aggregate power consumption of the two 1500/750-watt electric heaters (we disconnected the propane furnace and stove because Beth is allergic to propane, although the fridge is okay because there's no detectable odor from that), the microwave, the induction cook top (hotplate), our computers, and a Toshiba 40-inch LCD TV, plus a blu-ray player, as well as the fridge and the lights. When designing an electrical panel distribution you are allowed to DE-RATE the load as determined by codes. All circuits are not used to full capacity at all times so a lesser amperage is required to supply the panel than what the total added value of each circuit breaker in that system is. An example would be a home panel. Ours has 1-40a a/c, 1-60a heat, 1-30a water heater, 1-40a oven and 15-20a 120 volt circuits. That totals 470amps yet we only have a 200 amp service. The code allows you to lower the overall required service size based on the fact that you will never likely use everything all at once to full capacity.

There's an air conditioning unit that seems to have it's own 20-amp breaker, but in the "charge sentinel" (breaker box), out of 30 amps there seems to be a 20-amp "portable appliances" breaker and a 15-amp "general purpose" breaker, as well as the "AC" breaker adding up to 55 amps instead of the 30 amps the RV manual says this rig has, so how does that work?See above explanation.

Obviously, we need to use these devices selectively, turning off some in order to use others etc. I would just do whatever was normal and not worry about it unless a breaker tripped. Then determine where the problem lies. However adding two electric heaters (if both used to full capacity) would be a bit excessive for that small of a panel. We used a 1500/800/700 watt electric heater to heat about 1000 square feet for an entire winter years ago. It was a Delongi oil filled http://www.shopdelonghi.com/product_...ers%20delonghi you would be amazed at how well those things work.

Now, I already know that the fridge uses 300 watts, the microwave uses 700 watts, the "hotplate" uses up to 1500 watts, and each computer uses 90 watts.

The only constant is the fridge which runs all the time, and in Canada it's cold at night even in summertime, so we use one electric heater at 750 watts in the evening.

I can't figure out the difference between a kilowatt hour and a kilowatt( described in an earlier post), or find a conversion chart that will enlighten me, and I NEED TO KNOW how many watts my 40" LCD TV and blu-ray machine consume, and I can't find anything in watts, just kilowatts. kilo = 1000 so 1 kilowatt = 1000 watts.
examples: 1.2 kilowatts is the same as 1.2x1000 watts or 1200 watts. 0.89 kilowatts is the same as 0.89x1000watts or 890 watts.

Can anyone help me out with any of this info?

Thanks in advance,

YesDear.
P.S. We'll never use the AC, so can I reroute the power for that (wherever it's coming from) to my other systems? Not an RV expert but you could electrically speaking however if you are only using 750 watts for heat then it does not seem you should have any problems with your current setup. The heat and a/c should not be running at the same time. Just a thought, could your current A/C unit be replaced with an equal size heat-A/C unit to supply all your needs?

...

[WFK]

Yesdear, understand that breakers are fire prevention devices that protect the wiring from them to a load or outlet.
15 Amp breakers will have a thinner wire running from them than 30A breakers.
The whole game of proctection is one of current (and power) all of which are INSTANT values (meaning they can change within seconds.)
You pay for power use for use over time (technically: real power intergrated over time). You could say "average" if you are less technical.....
This entire consideration also applies when you select a generator.

[Dennis Olson]

Further, understand that the power distribution system will not allow your on-board circuits to draw more than the the rated amperage for your coach. Trying to "re-route" anything would be very complex and expensive in an RV. I asked similar questions of the service facility that I employed to do all the repairs on my Fleetwood Southwind before I lived in it. You CAN "re-route", but you can also buy a newer RV, which may, in the end, actually be a cheaper alternative. Think I'm kidding? I'm not....

[scubasteve]

As long as you can run what you need to run when you need to run it without popping individual breakers at the panel, the main breaker on the coach, or the main breaker at the power outlet... you are good to go. This is really the only way to "test".

[Southernboy]

Some good advice on this.

I would just like to add that *** circuit breakers do not always trip ***

A circuit should never exceed 80% of the circuit breaker rating, loading a circuit to the point of tripping is never a good way to determine your load...buy or borrow an ammeter, or have an electrician check out your loading for you. Or invest in some good smoke detectors, they don't always work either.

Be safe, if in doubt....don't.

SB

[Double_A]

Appliances are suppose to have labels advising the user of their power requirements. Problem is those labels are not always easily visible. One solution, buy yourself a $25 "Kill-o-Watt" meter that goes in between the appliance and the outlet. Unplug the appliance from the outlet, plug the meter in the outlet and then plug the appliance into the meter's outlet. The meter will show you on it's digital display the voltage, amps and kilowatts the appliance is using. (Read meter's instructions as this unit has some limitations for example, does not work on 220/240V and some very high Amp draw appliances)

[Dobbin]

And a Kill-o-Watt meter will tell you at a push of a button kilowatt (or watts) at that moment and kilowatt-hour (which is the measure of the actual energy you've used over time.)

You can use the kwhr reading (which starts at zero and continuously totalizes) to figure your actual cost to run that appliance during the time period in question.

One thing not mentioned is that the refrigerator may be 300 watts, but that only when it's actually refrigerating. When it's quiet and the door shut it may use nothing.

Most refrigerator compressors are sized so they run only about 20-30 percent of the time to cover heat gain through the walls of the fridge. This so they have an excess of capacity for those days when you bring in a whole bunch of warm veggies from the garden or store and put them en-masse into the non-freezer section. The machine will run continuously for a couple of hours until everything is cooled off - and then go back to "normal" (i.e. covering only the heat gain through the walls of the refrigerator.)

Big drawer in the bottom for carrots. Yum!

Sorry. I digress.

Dobbin

[KenGin31]

I like to throw in the wire gauge. The standerd wireing for a 20 amp circuit is 12-2. 15amp is 14-2. If the wire gauge is to small you could have a fire problem.

[Beth]

Thanks for all the input gentlemen; I appreciate it.

I already knew that 1000 watts = 1 kilowatt; what I didn't (and still don't) know is how to figure out the wattage used by my 40" LCD TV and blu-ray machine etc, as consumption is only given in kilowatt hours.

I don't care about kilowatt hours in terms of usage since I'm always at an RV campground (well, nearly always), and I understand what a kilowatt hour is. What I don't understand is how to calculate the wattage of an appliance (or whatever) based on the number of kilowatt hours it uses in a year. That's the info the manufacturers give in their specs, which isn't useful for my purposes, as I'm not concerned with saving $$$ (I pay the same fee at the RV site regardless of what I use); I'm concerned about blowing the system or causing a fire, which wouldn't be healthy in an RV loaded with gasoline and propane.

(The Kill-O-Watt meter sounds like a neat gizmo, but I'd like to be able to calculate wattage prior to purchasing appliances etc.)

tm1439m: We used a 1500/800/700 watt electric heater to heat about 1000 square feet for an entire winter years ago. It was a Delongi oil filled http://www.shopdelonghi.com/product_...ers%20delonghi you would be amazed at how well those things work.

Interesting, and thanks. Our HomeBasix heaters work very well, but it's not that cold here at the moment (rarely below freezing). Our RV is only 224 sq ft (1,568 cubic feet), so less than a quarter of the area you heated. I have a couple of questions, if you don't mind. Were you heating an RV, and how cold was the outside temp? Canada is brutal in winter and we're only allowed to spend six months a year in the Southern US.

Thanks again to all for your responses.

DENNIS: I'd like to join TB as myself, but like Beth (naturally) I only have a Google e-mail addy since we travel all the time and it's the easiest way to monitor my mail. Any suggestions?

TIA

YesDear.

[Dennis Olson]

Send Deena in GA a PM and explain it. She does registrations. We do make exceptions from time to time.

For calculations, just remember "the magic pie".

P=IE , where P (power in watts) = I (current in amps) times E (voltage)

Simple

[Dobbin]

HARD to believe there isn't a label on the TV indicating Watts. I think it's a Nat'l Electrical Code requirement or something. NEMA. National Electrical Manufacturer's Association.

One could look online using the manufacturer's name and model number. I bet it's listed there.

Dobbin
Gentle-being.

[Dobbin]

A Coby 40" LCD over at Best Buy uses 210Watts. 298 kwhr/yr.

That means according to their standard you watch the TV 1419 hours in a year. 3.88 hours per day.

I don't think Owner watches his TV 3.88 hours per week! But he's busy.

Dobbin

[Double_A]

HARD to believe there isn't a label on the TV indicating Watts. I think it's a Nat'l Electrical Code requirement or something. NEMA. National Electrical Manufacturer's Association.

One could look online using the manufacturer's name and model number. I bet it's listed there.

Dobbin
Gentle-being.

Agreed it has to be there somewhere. Agreed again to google model number and see what you can find.

[Dobbin]

I looked up the Toshiba 42" machine (currently available) and it lists only kwhr/yr. This may be because a lot of TVs now have "instant on" feature which is a small but steady load which keeps the TV "warmed up" and you push a button and the pix is THERE. So the TV might use 5watts just sitting there no pix, but 150 watts while it's in operation.

This is the so called "hidden loads" that the solar panel/offgrid folks fight all the time. A lot of appliances now are "hidden load." And for a solar setup a hidden load can amount to a LARGE load over time - and just for an added but not necessary convenience.

Dobbin

[tm1439m]

.....................................

Interesting, and thanks. Our HomeBasix heaters work very well, but it's not that cold here at the moment (rarely below freezing). Our RV is only 224 sq ft (1,568 cubic feet), so less than a quarter of the area you heated. I have a couple of questions, if you don't mind. Were you heating an RV, and how cold was the outside temp? Canada is brutal in winter and we're only allowed to spend six months a year in the Southern US.

.........................................

We were in a duplex in South Carolina. It was about 28 years ago and we had just gotten married a year or so before. It was poorly insulated but we did not get as cold here as you do in Canada. We see temps down in the teens at night in the colder months. It was cool in the house in the morning, maybe around 60 or even a little cooler during the coldest days. It always got warmer by the time we got home from work during the day. I would think with the size you are talking you could keep warm with one of these heaters.

The unit I posted was not the one we used but similar. Ours had 3 temp settings. It is safe and you can actually touch it when it is at its hottest setting without getting burnt although it is hot. We still use it occasionally and it still works great.

I think this one is closer to ours. http://www.fingerhut.com/product/del...4Eg1dw&ctid=69

[WFK]

Beth,
you go on the internet feed it the exact type number of the appliance you are considering and add "specs" to that.
You will get what you want.

[Beth]

Thank you, Joe, Tim, and everyone else who's helped here.

I think it's safe to assume (I know, I know, ass-u-me and all that) that my 40" Toshiba won't use any more watts than the 42" model, which uses 150w, according to Joe, and that seems likely to me. We won't be leaving ours plugged in (we can't), so it'll just have to 'warm up' when we need it. (We don't watch TV per se, but we're movie buffs and have insanely busy days, so watching a movie at night is to us what comfort food is to some other people. It helps us through; what can I say?)

WFK: I tried all the Google searches I could think of prior to bothering the good folks on TB. The only information given for the TV we want is in kilowatt hours, period, and yes, I searched using the model number etc and asked for specs and everything under the sun. Beth swears that there's nothing the collective mind power of the membership on TB cannot answer, and over the years I've come to agree with her. I have my areas of expertise but I'm not an electrician, although I'm learning more than I want to in order to look after our RV, which is in almost constant use at the moment and we can't see that changing in..., well we can't see that changing!

Dennis: thank you; I'll do that.

Cheers!

YesDear.