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Topic: How many watts does you coach draw? (Read 887 times) previous topic - next topic
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How many watts does you coach draw?

Yahoo Message Number: 13818
Here is a simple measurement when you are connected to shore power at a metered RV site.

Measure the time in seconds for one full revolution of the disk in meter (most meters have a disk, otherwise stop here).

Look for the Kh number on the meter. Very likely it is 7.2

Calculate:

Watts = 3600 times Kh divided by the time in seconds for one full revolution of the disk.

Watts = 3600 * Kh / seconds

Measurements I found:

TVs off, Refrig on Gas, Water heater off, Charger OFF, 2 computers ON, LCD Monitor ON, Datastorm ON, WiFi ON, misc clocks ON = 282 watts. Turn on three TVs (2 tube and 1 13" LCD), the load increases to 424 watts. Add my 2600 lights of christmas decorations to the above, it jumps to 1739 watts.
Herb

Merry Christmas
Allure 2002 #30690

Christmas at Emerald Desert
www.suncitykid.com/albums/200411emeralddesert/dsc06461.jpg (copy whole URL)

Re: How many watts does you coach draw?

Reply #1 –
Yahoo Message Number: 13820
Hi Herb,

This line begs for a question:

Look for the Kh number on the meter. Very likely it is 7.2

Why do I need to know this?

I did like the calculation - saves reading the meter every hour.
Fred Kovol

Re: How many watts does you coach draw?

Reply #2 –
Yahoo Message Number: 13830
The Kh number is found on the face of the meter (mine is located to the right of and slightly below the disk). The number is used in the calculation. It provides the relationship between the disk RPM (or should I say Seconds per revolution) and the average watts being consumed during the timed period.

The forumula is:

Watts = 3600 * Kh / seconds

If the Kh is 7.2, then the formula reads

Watts = 3600 * 7.2 / seconds, or simply

Watts = 26920 / seconds

where seconds is the time it takes for the disk to make one complete revolution.

If it were to take 20.3 seconds for a revolution, then:

Watts = 3600 * 7.2 / 20.3 or 1277 watts or 1.3 KiloWatt
If that same load continued for one hour, then the power consumption would be 1.3 KiloWattHour. At 10 cents per KWH, that would be 13 cents.

The above would represent about a 16% load if it was being generated on a 8KW generator.

Now, go, turn everything on, and see how fast it spins and how many watts your can rig draw. You might have to time and average 10 revolutions .

More than you wanted to know, but maybe of further use to other members.

You are right, it certainly beats reading the meter every hour, and is much more accurate.
Herb

Quote from: fredkovol

Re: How many watts does you coach draw?

Reply #3 –
Yahoo Message Number: 13835
Hi Herb,

I looked at my bill and the 7.2 is not used in calculating kwh usage; the 7.2 is on the dial plate at the far right as you pointed out.
Fred Kovol

Re: How many watts does you coach draw?

Reply #4 –
Yahoo Message Number: 13836
The 7.2 is built into the gears in the meter to properly translate the disk revolutions to KWH reading (5 dials or 5 digits) on the meter. With 7.2 Kh, the disk needs to make 138.88 revolutions to log one KWH.

If a meter had a kH of 1.0, then the meter disk would need to make 1000 revolutions to log one KWH on the meter.

The Kh number never appears on your electric bill, all internal to the meter.
Herb

Allure 2002 #30690

Quote from: fredkovol
Hi Herb,

I looked at my bill and the 7.2 is not used in calculating kwh

usage;