Any one using a DC Thermal SA12-2000 Heater?
- Thread starter KMG
- Start date
Haf-E
Expedition Leader
Junk. The link I found says 220 watts and 3600 but/hr...
But that doesn't make any sense as 1000 watts = 3414 but/hr so 220 watts would give 750 but/hr for a resistance (non heat pump) type heater. That's a very small amount of heat - won't do much in a van at all.
Seems fishy to me...
But that doesn't make any sense as 1000 watts = 3414 but/hr so 220 watts would give 750 but/hr for a resistance (non heat pump) type heater. That's a very small amount of heat - won't do much in a van at all.
Seems fishy to me...
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Mwilliamshs
Explorer
You're assuming 100% efficiency? The following is copied from the DC Thermal Catalog
SA12-2000 12 Volt Brushless Cab Heater
This is our smallest 12 volt heater. Designed for very small equipment or systems that can not handle over 20 amps on the electrical system.
Heater Dimensions: 6”x 5” X 4”
12 Volt, 220 Watts [18.33 amps] 3,674 BTU’s
Brushless 50,000 Hour Ball Bearing Fan
10,000 Hour DC Thermal ©RuCar Vacuum Sealed Elements.
Case Construction: T5052 Aluminum.
Wired Entirely with GXL Wire
Thermally Protected
HIGH, OFF, and LOW setting.
Comes complete with mounting hardware, mounting bracket, fuse, fuse holder, electrical connector ends, and detailed instructions
ONE YEAR Parts AND Labor Warranty
Brushless Fan Measurements:
Bearing: Ball
Voltage: 12
Current: 0.30 [amps?]
Power: 3.60 [watts?]
RPM: 3,900
CFM: 52
Pressure: 6.731
Noise @ 1 meter: 40db
So I believe that their unit runs on 12 volts and that it consumes 18.33 amps because these things are easily measurable and that they designed it to do both, hence claims of "designed for 12 volt systems producing ~20 amps". I also believe the brushless fan they use consumes .30 amps because others can be found that perform similarly. That being said, I can calculate 18.33 (total amps) - .30 (fan amps) = 18 amps for the heating element(s). That 0.03 is not worth sweating over. [pun]
So the element(s) runs on 18 amps @ 12 volts = 216 watts (which is darn close to the 220 watt claimed by the manufactuer, huh?) Now if you take a smallish wire/resistor/element and push 18 amps of current through it, it'll get hot. That heat will be radiated out into the air but not quickly. To speed up the heating process, you can move the air around with a fan and conduct that radiating heat with the air as a conductor. This will heat things up more quickly, but less efficiently with regard to electricity because now you're also running an electric fan in addition to the element(s). This is how the heater in question puts out 3,674 btu on only 220w of electricity.
So not necessarily "junk" just misunderstood by those with a calculator and only half the textbook.
That being said, I think it'd be a handy little item for instant heat rather than waiting for the engine to warm up or to supplement other heat sources, but likely wouldn't keep anything as big as an Econoline van warm in anything less than mild weather despite most any rational level of insulation.
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Mwilliamshs
Explorer
2,200 watts is over 7,500 btus. Voltage doesn't matter, watts = power no matter the source. Maybe that blowdryer on medium or low would be close? A kill-a-watt meter is handy for such things.
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I found a forum post where someone was using the SD12-4000 model in a VW Karmann Ghia convertible and seemed satisfied. That is a much smaller vehicle than you're talking about, though it is a convertible. The Samba.
There are also reviews on Amazon.
I don't understand how the company is getting their BTU numbers. The physics of it don't work unless I'm missing something major (like a tiny heat pump...). As Haf-E mentioned there are ~3.413 BTU's per watt, so at 220 watts that gives you 750 BTU's.
Have you looked into gas fired coolant heaters, propane heat, etc.? I know those options aren't the cheapest but electric heat would require a pretty massive battery bank.
There are also reviews on Amazon.
I don't understand how the company is getting their BTU numbers. The physics of it don't work unless I'm missing something major (like a tiny heat pump...). As Haf-E mentioned there are ~3.413 BTU's per watt, so at 220 watts that gives you 750 BTU's.
Have you looked into gas fired coolant heaters, propane heat, etc.? I know those options aren't the cheapest but electric heat would require a pretty massive battery bank.
Mwilliamshs
Explorer
Forced-air cabin heaters have btu ratings based not on the power they consume (which would be in watts, as derived by amps and volts as demonstrated in my previous post), but on the heat they put out, which is multiplied by the air they move. Imagine how poorly your A/C would work without a fan. Now think about what its btu rating would be.
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One watt in = 3.413 BTU/hr of heat out. That is fixed relationship because resistive heating is ~100% efficient. So if you have a 100 watt electric heater it is capable of producing 341.3 BTU/hr. That's it, no more. Adding a fan will not increase it's ability to produce more heat (other than the minute amount of heat produced by the fan).
A fan will help move that heat through the space, but it doesn't increase the efficiency of the heating element.
If you don't believe me go look at some heaters at a place like Northern Tool and take a random electric heater (forced air or otherwise) and multiply the rated watts by 3.413 and see if you can find one that doesn't match the manufacturers BTU rating.
A fan will help move that heat through the space, but it doesn't increase the efficiency of the heating element.
If you don't believe me go look at some heaters at a place like Northern Tool and take a random electric heater (forced air or otherwise) and multiply the rated watts by 3.413 and see if you can find one that doesn't match the manufacturers BTU rating.
Mwilliamshs
Explorer
I agree with what you're saying for home heaters. The calcs are different for the cabin heaters I've spec'd on aviation and mining equipment and include change-of-air rates. The ratings there more accurately compare the heat experienced whereas the "power in = btu available" work well for heat produced.