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Old 09-26-2012, 07:25 PM   #1
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Amp draw of appliances

Anyone know the average amp draw of the typical appliances in an Airstream?

Furnace
A/C
Water pump
Bath fan
Refrigerator running on 12v
Microwave
Hair dryer
Etc....
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Old 09-26-2012, 09:09 PM   #2
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Well a couple of them depends on what model is installed.

A/C stock 13,500 14-15 amp, more on start-up
15,000 17-18 amp
high efficiency 13,500 10-11 amp

microwave 8-14 amp

hair dryer 5-14 amp maybe more I don't know that much about them.

converter .5-5 amp depending on size of converter and charge in battery(s)
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Old 09-26-2012, 09:37 PM   #3
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Furnace 12 volts: 3.5 to 7.5 amps. Small (16000 btuh) newer ones 3.5; older larger ones (30,000 btuh) in the 7 to 8 amp range.

AC, 120 volts: In general, 13 to 15 amps, depending on temps, and rated output.

Water pump, 12 volts: 3 to 7 amps, depending on brand and flow rate.

Bath fan, 12 volts: 1 to 3 amps

Refrigerator, 12 volts: 1/2 amp more or less, depending on brand, some go as high as 1.5 amps but not common.

Microwave 120 volts: 10 to 13 amps

Hair dryer, 120 volts 6 to 12 amps, most are 6 to 8.

Remember amps are not the same as watts. Watts = volts times amps. Things that take 5 amps at 12 volts only take 60 watts where as 5 amps at 120 volts is 600 watts.
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Old 09-26-2012, 11:01 PM   #4
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Thanks Idroba. some comments: Amps = watts/ volts.

Fridge- Mine is 180 watts, so 180/120= 1.5 amps.

Microwave- 800 watts out, 1200 watts in, so 1200/120= 10 amps

Hair Dryer- 1500 watts, so 1,500/120= 12.5 amps

Thanks especially for your comment about energy consumption for the furnace fan on old versus new furnaces. I have an original furnace and it seems to take a lot of battery power to operate the fan. If I can cut the current usage in half, by replacing the furnace, I will probably do this because I do a lot of boondocking.

Dan
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Old 09-27-2012, 01:29 AM   #5
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Dan,

My new 16,000 btuh Suburban is enough to heat any smaller size AS in temps down to freezing easily. Who wants to be out much below freezing anyway...lol. I bet it would do your 31' with no problems too. Amp draw is 3.5. It is a bit noisy though. No ductwork, I just use it direct discharge. Air circulation is fine and not as much heat lost under the beds and cabinets. But that is with my 20' Argosy.

When I had my 310 motorhome I replaced my original 30,000 btuh furnace with a 24,000 and it would keep the thing warm down to below 20 F, and the fan took just over 4 amps as I recall. The original took over 7.
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Old 09-27-2012, 09:36 PM   #6
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idroba

Thanks for the feedback on the 16k furnace. I wonder if you can get a variable speed furnace to allow you to slow the speed down to reduce amp draw and the noise level.

But if by getting a new furnace, I can cut my amp draw in half, 3.5a vs. 7.0a, then it will be well worth it. I would also get spark ignition and the safety and reliability of a new furnace good for at least the next 20 years. Sounds like a no brainer- another item for the Airstream wish list.

Dan
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Old 09-27-2012, 10:31 PM   #7
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From our '91 34'er
.9 amps for the fridge .4 w/o defrost
.5 water heater startup, .25 in fault
Heater-6.5 fan, 7.8 running
Fantastic Vent-1.82 amps low, 2.5 med 3.4 high
kitchen sink dual tube lamp 2.4
1.9 stove fan

Some where I have the same stuff after swappin' for LED's
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Old 09-27-2012, 11:11 PM   #8
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Originally Posted by TouringDan View Post
idroba

Thanks for the feedback on the 16k furnace. I wonder if you can get a variable speed furnace to allow you to slow the speed down to reduce amp draw and the noise level.

But if by getting a new furnace, I can cut my amp draw in half, 3.5a vs. 7.0a, then it will be well worth it. I would also get spark ignition and the safety and reliability of a new furnace good for at least the next 20 years. Sounds like a no brainer- another item for the Airstream wish list.

Dan
Unfortunately the fan speed is determined by the amount of heat from the burner, you cannot reduce the speed and still get the heat out of the box. In addition the fan has a second wheel (blower) for the combustion air. If the fan speed were reduced, there would not be enough combustion air for the burner.

A variable gas input, variable fan speed output could be designed by some manufacturer, but the price and economics would kill the project rapidly.

Remember that a lower heat output furnace may run longer to heat the trailer. I believe there still is a lot of electrical savings with the lower output furnace based on my personal experience with many Suburban furnaces over the years.
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Old 09-28-2012, 07:32 AM   #9
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Thanks for the information everyone. I am at a 20amp site so these numbers really help.
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Old 09-28-2012, 12:01 PM   #10
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Thanks for the information everyone. I am at a 20amp site so these numbers really help.
Hang on. The 12 volt appliances (like the furnace) are using whatever amperage at 12 volts, so if it's using, say, 5 amps, it's 5*12=60 watts, which at 120 volts is only half an amp. Since you're worried about 20 amp 120 volt power, that half amp is what you should be concerned about.

Basically: If you're on a 20 amp circuit, you should be fine for everything but the air conditioning.
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Old 09-28-2012, 12:05 PM   #11
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Originally Posted by Skater View Post
Hang on. The 12 volt appliances (like the furnace) are using whatever amperage at 12 volts, so if it's using, say, 5 amps, it's 5*12=60 watts, which at 120 volts is only half an amp. Since you're worried about 20 amp 120 volt power, that half amp is what you should be concerned about.

Basically: If you're on a 20 amp circuit, you should be fine for everything but the air conditioning.
Yes, yes, he is right. Your original post did not say why you wanted the information. An Amp draw at 12 volts is only approximately the same as 1/10 amp at 120 volts.
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Old 09-28-2012, 05:40 PM   #12
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Originally Posted by idroba
Furnace 12 volts: 3.5 to 7.5 amps. Small (16000 btuh) newer ones 3.5; older larger ones (30,000 btuh) in the 7 to 8 amp range.

AC, 120 volts: In general, 13 to 15 amps, depending on temps, and rated output.

Water pump, 12 volts: 3 to 7 amps, depending on brand and flow rate.

Bath fan, 12 volts: 1 to 3 amps

Refrigerator, 12 volts: 1/2 amp more or less, depending on brand, some go as high as 1.5 amps but not common.

Microwave 120 volts: 10 to 13 amps

Hair dryer, 120 volts 6 to 12 amps, most are 6 to 8.

Remember amps are not the same as watts. Watts = volts times amps. Things that take 5 amps at 12 volts only take 60 watts where as 5 amps at 120 volts is 600 watts.


I think I understand the conversion to amps for 12volt, but I'm confused though as to when a 12volt appliance like the furnace would draw the full 3.5 - 7.5 amps?

So the draw (in terms of amps) when plugged into shore power would be much less for the furnace, but higher when boondocking? That is, when does the furnace draw the full 3.5 - 7.5 amps?
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Old 09-28-2012, 05:46 PM   #13
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Quote:
Originally Posted by Skater

Hang on. The 12 volt appliances (like the furnace) are using whatever amperage at 12 volts, so if it's using, say, 5 amps, it's 5*12=60 watts, which at 120 volts is only half an amp. Since you're worried about 20 amp 120 volt power, that half amp is what you should be concerned about.

Basically: If you're on a 20 amp circuit, you should be fine for everything but the air conditioning.
I've actually been able to run the A/C, but have been careful to not run any other appliances at the same time (eg, coffee pot). I've shut the A/C off and waited several minutes before turning it back on again. Is there a minimum time to wait so as not to hurt the compressor?
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Old 09-28-2012, 06:36 PM   #14
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Originally Posted by KYAirstream View Post
I think I understand the conversion to amps for 12volt, but I'm confused though as to when a 12volt appliance like the furnace would draw the full 3.5 - 7.5 amps?

So the draw (in terms of amps) when plugged into shore power would be much less for the furnace, but higher when boondocking? That is, when does the furnace draw the full 3.5 - 7.5 amps?
The furnace operates on 12 volts. At 3.5 to 7.5 amps amps that is roughly a 120 volt load of .35 to .75 amps. The converter/charger changes the 120 volt power to 12 volts but if you are concerned with the 120 volt power load in amps from the furnace via the converter/charger it is quite low. When boondocking, all the power would come from the battery, so it would be 3.5 to 7.5 amps, still at 12 volts.

If you have a single battery it may have a capacity of about 100 amp-hours, that is (for example) it could supply 1 amp for 100 hours, or 5 amps for 20 hours. You can probably see that a furnace, running on a single battery will run it down in a day or two, and that is not including the lights, pump etc.

Clear as mud?
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