Air conditioning electrical power question

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JMyers1

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I am looking at building either a CH650 or 750 Cruzer. At KAPA here in centennial (Denver) it’s not unheard of to bake in line for takeoff for 30 minutes in 100 degree afternoon heat. I would like to put a zero breeze air conditioner in the baggage area, which requires 10 amps at 24V. I have not yet looked into plumbing the condensate drain and air exhaust but those seem easily solvable. It is a modest air conditioner but only weights 17lbs and the cabin is quite small in both of these airplanes.

I would like to use the vertical power VP-X, however it does not have any 20A breakers (it’s 14V so I need 20 amps), only up to 15A, but it does have two 10A breakers. My question is could I combine two 10a in place of one 20amp, or is that a bad idea?
 

TiPi

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Not a bad idea but not really advisable:(. Using 2 CBs in parallel could trip them on less than 20A. The sticky point is the resistance of each CB. The one with the lower resistance will take proportionally more current and potentially trigger with the load at normal level.
 

JMyers1

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Not a bad idea but not really advisable:(. Using 2 CBs in parallel could trip them on less than 20A. The sticky point is the resistance of each CB. The one with the lower resistance will take proportionally more current and potentially trigger with the load at normal level.
That makes sense I didn’t consider that. I was thinking if I the positives and negatives were tied together it would balance the load, assuming same gauge wires and good terminations, but the breaker itself could have a different resistance.

I suppose I could tweak it with a resistor? It is unlikely to be at exactly 20A so I presumably have a bit of wiggle room. Probably becoming too much of a science project at this point.
 
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Rhino

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Have you considered one of the cooler (ice chest) based models that use way less power? They don't cool as well as an air conditioning system, but I've seen reviews saying they do a good job of taking things down comfortably for short periods, like waiting in line for takeoff.


That's just one of the reviews I've seen. Aviation Consumer reviewed several not long ago, but I can't find that issue right now.

This is the one AvWeb chose:
 

Hot Wings

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Why not use their battery, or own of your own, as a stand alone system? Their web site says 5 hour run time.
Makes removal for winter weight savings easier too.
 

wsimpso1

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Significant and common errors in sizing electrical safety gear:
We size the breaker or fuse to protect the wiring, not the device. See what wiring is specified to run the gadget, and that dictates the fuse or circuit breaker;
That should usually cover both steady state and starting loads, but you can also check that the circuit protection equipment is sufficient to prevent nuisance tripping.
 

Derswede

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I have been looking at low voltage air conditioners as part of a solar office build. One interesting unit is this one:

They have a 24V version, too. When I get my retirement office built, I am planning to use solar power to run this during summer months. 10A is not too hard to achieve with a solar panel system. And, at 12 lbs, can be put most anywhere. Plumbing it in for me is not hard, and I would think that a solid package panel inside the baggage compartment would support it rather well. It is only about 1,500 BTU, but an aircraft cabin is not that large, so this may be usable.

Derswede
 

TFF

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I would ask if they could upgrade the box. AC is great when it works. Airplane AC seems to rarely work. A friend just had one burn up on the new Citation he flys, and I use to be working on them all the time during summer. I would expect if you need 20A, you probably need capacity of 30A for the circuit. You could always spend 30 minutes in the car driving to Erie instead.
 

Dan Thomas

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That makes sense I didn’t consider that. I was thinking if I the positives and negatives were tied together it would balance the load, assuming same gauge wires and good terminations, but the breaker itself could have a different resistance.

I suppose I could tweak it with a resistor? It is unlikely to be at exactly 20A so I presumably have a bit of wiggle room. Probably becoming too much of a science project at this point.
No fooling with resistors and stuff to tweak anything. Paralleling breakers will just result in frustration, and you have to size the wire big enough to handle the 20 amps anyway, so install a 25 or 30-amp breaker.

Any resistor capable of handling 10 amps is going to be big and will get hot. That makes location and mounting an issue. And to get some small adjustment in current you need fractional resistances. By the time you finish messing with it all you've spent ten times the time and money that would have been spent doing it right in the first place.
 

Rhino

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I would ask if they could upgrade the box. AC is great when it works. Airplane AC seems to rarely work. A friend just had one burn up on the new Citation he flys, and I use to be working on them all the time during summer. I would expect if you need 20A, you probably need capacity of 30A for the circuit. You could always spend 30 minutes in the car driving to Erie instead.
Or Centennial. Depends on where you live. My brother used to fly out of Centennial, and he seemed to like it.
 

Daleandee

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I understand the desire for AC! I have a Sonex which is known by some of us as an "E-Z bake oven" once you close the canopy.

Some builder/pilots have added a canopy standoff that holds the canopy slightly open to allow the prop to blow breeze into the cockpit while sitting in the heat. It helps but 100º air being blown at you just gives the "blast furnace" effect. There have been a few Sonex accidents and scares from the canopy coming open in flight (or trying to) for various reasons so I've stayed away from anything that holds the canopy partially open. I do have dual vents that are fed by NACA type inlets on each side and they give some air while idling on the ground but hot is still hot.

All that to say that if you come up with a great solution I'd really appreciate knowing about it. For now I really try to limit my exposure to such situations and stay hydrated while flying.
 

JMyers1

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Not sure there would be room in a Sonex, but here's the install I have planned for the Zenith:

Zero Breeze AC (small portable rv air conditioner) is a good fit because it is a small unit, both physically (17lbs) and in current draw (240watts max). It requires 10 amps at 24 volts, a drain, and an exhaust for the hot air and optionally a cooling inlet if you don't want negative pressure in your cabin. It's about 20 inches long and 10 inches wide and tall. It is a 2,300 btu unit, which does not sound like a lot, but it is similar to what would be coming out of one vent of a car AC system. If you point this at your face, that's a huge change from a fan (or propeller) blowing 90 or 100 degree air in your face. We are not trying to cool down a large car, just a small space for two people, and it doesn't need to be ice cold. I just don't want to sweat through my shirt by the time I start the takeoff roll.

The other nice thing about it is it is self-contained, so you can simply unplug the power, drain, and exhaust duct and put it in the hangar for the winter. It even has a handle. I plan to put a small strap through the handle to make sure it doesn't move in turbulence.

This will fit nicely in the CH650 in the center of the baggage area, with the vent nicely position between the two seats and the intake right below. Combined with a tinted canopy and sun shades my hope is this will work pretty well. I do not have the plans yet, but I think there is some room under that baggage shelf to possibly recess it a little bit. There is a good bit of room left over for an overnight bag or backpack, and the CH650 has wing lockers that are fairly roomy and can hold 25lbs each.
 

JMyers1

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Why not use their battery, or own of your own, as a stand alone system? Their web site says 5 hour run time.
Makes removal for winter weight savings easier too.
I might do that, however the battery is relatively bulky and requires charging. Not sure which is the lesser evil. If you put it on max, I think the runtime is closer to 2.5 hours. Still a good amount.

Another consideration is I have to tilt the front of the unit up because the condensate drain is in the back (unless I can modify it), so it becomes rather tall at that point.
 

JMyers1

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No fooling with resistors and stuff to tweak anything. Paralleling breakers will just result in frustration, and you have to size the wire big enough to handle the 20 amps anyway, so install a 25 or 30-amp breaker.

Any resistor capable of handling 10 amps is going to be big and will get hot. That makes location and mounting an issue. And to get some small adjustment in current you need fractional resistances. By the time you finish messing with it all you've spent ten times the time and money that would have been spent doing it right in the first place.
Thanks I agree this is not a good idea. I will either just use the zero breeze battery or wire a separate old fashioned CB and ammeter.
 

rv7charlie

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Handiest site I found showing automotive a/c btus
Just the insulation in a typical car's cabin would weigh a significant percentage of a CH650's empty weight. No insulation; many more btus needed. Bubble canopy in the sun; many times many more btus needed. In little airplanes, a little weight can eat up a really large percentage of useful load...

TiPi is absolutely correct about paralleling CBs; don't go there. While you're not going there, do your homework on failure modes effects analysis on any all-in-one electrical panel you may be considering. Some of them have single-point-of-failure modes that can take out the entire system. Not a big deal if you're running mags/carb in a day-VFR plane, but if you're electrically dependent in any way, analyze intelligently and carefully, or find someone who can do it for you.
 

Rhino

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I am looking at building either a CH650 or 750 Cruzer....
Out of curiosity, have you sat in them both, with another person? Difference between night and day.
 

JMyers1

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Out of curiosity, have you sat in them both, with another person? Difference between night and day.
I haven’t, I am going to the September Zenith build workshop to sit it them both. I was at airventure for Friday only and was trying to decide between a tail wheel and tri gear RV-14, I decided that’s too much airplane after sleeping on it. I walked right by the Zenith tent. Oops. I did talk to Nick Otterback about his Lightning and came away impressed with both him and his airplane. The cabin width I think was just too narrow as much as I liked the plane. If I was a bit smaller I think that airplane with the new engine is great.

The 750 is very slow, but I am planning on building this with my father as much as he can help and he has a very bad back, so if he cannot get into/out of the 650 I will probably go with the 750. I am partners in a C340 for trips so I don’t really need the speed but two digit air speeds are a whole nother level of slow.
 

Rhino

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The 650 is a great plane, but it's a really tight fit for two people. The 750 has waaaaay more interior room. The bubble canopy on the 650 makes it a greenhouse, so you should keep that in mind if heat is a concern. You can crack the canopy during taxi, but you can keep the doors on the 750 completely open, which is way better. I have problems with heat, and that's the primary reason I chose the 750 over the 650, even though the lower speed didn't really appeal to me either. Mine is a STOL because the Cruzer didn't exist yet when I bought my kit. The other primary reason was the space. But sitting in them is the right thing to do. That's how I finally made up my mind. I'm hoping to be there next month too, so maybe we'll see each other.
 

rdj

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Not a direct answer to the OP question, but perhaps of interest -- what I plan to install in my 650 for cooling is this:

Van's Vent Kit

I forget where I came across the idea (these forums? the Zenith list perhaps?) but a few other folks have mentioned that it does a much better job of sucking prop blast into the cockpit than the standard NACA ducts on the fuselage.
 

JMyers1

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Not a direct answer to the OP question, but perhaps of interest -- what I plan to install in my 650 for cooling is this:

Van's Vent Kit

I forget where I came across the idea (these forums? the Zenith list perhaps?) but a few other folks have mentioned that it does a much better job of sucking prop blast into the cockpit than the standard NACA ducts on the fuselage.
I noticed the RV-12 has these, it looked like an updated design. It hadn't occured to me I could simply buy those. Good thought.
 
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