Power Consumption/Requirements for fifth wheel

[John Berger]

How can I estimate how much total power would be required to run appliances and lights on my fifth wheel? I know there is a formula to do this, but I can't remember what it is?



Also, how can I determine the draw on power when my A/C initially starts? What about once it's running. I'd like to make up a list to keep handy when I'm dry camping.

 

[Jumbo Jet]

If your RV was like mine, it came with a specification sheet for every appliance and option added.



Add the numbers up from those.



A good amp probe could help you with the A/C startup.

 

[klenger]

There are two considerations.



One is the DC draw, which is just the sum of all the DC currents for the appliances in use. One way to keep track of these loads is to calculate how many amps an appliance uses times the hours it will be used. The result is the amp-hours for that appliance. Add up all the amp-hours for all the appliances, and you then you can estimate how long the battery will hold up based on it's amp-hour capacity. Try not to discharge the battery below 40-50% of it's total capacity.



For AC appliances, you need to add up the watts used for all the appliances. If you are using a generator, make sure that your total load is less than the continuous output power in watts of the generator. If you are using an inverter, a good rule of thumb is that the DC draw for the inverter is about 10 times the AC current for the appliances on the inverter. You can calculate the AC current draw by dividing the watts required by 115 (watts = amps * volts, amps = watts / volts, volts = watts / amps).



It is very hard to determine the starting current for an A/C unit as the startup current is dependent on a lot of factors including temperature, freon pressure, etc. , and the surge is for such a short period of time that it is difficult to measure with simple electrical meters. Also, generator specs usually do not call out short term over-current capacity. The two options to make sure the generator is big enough is either to try a generator before you buy it, or make sure that you buy more than you need.



See the RV link in my sig for info on RV electrical systems and generator installations.



Good luck.

 

[John Berger]

If your RV was like mine, it came with a specification sheet for every appliance and option added.



Add the numbers up from those.



A good amp probe could help you with the A/C startup.

I bought it used. Didn't see anything like that on board or with the manual package. And there were alot of manuals.