Airport Power

I think you will have a hard time beating the $15 a month deal. A
generator would do it, but it's expensive and needs gas and
maintenance. The only other thing that makes sense is to run your own
power hookup to the power company. But find out what THEIR minimum is
first. If it were me, I'd pay the $15, or do without. Solar, battery
etc is all in the hobby area. Fine if you want to mess with it, but not
a cost effective solution.

"Kyle Boatright" writes:

Again, the problem is that a pre-heater and/or a trickle charger need hours
to do their thing. Trying to run either from a car ain't gonna cut it.

Yup, I sure did miss that. Let's find the "ain't gonna cut it" part.

125 watt heating element
inverter with 90% efficiency
Much better are available.
roughly 44 amp-hours available from regular 12V starter battery
A dual-purpose deep-cycle/starter battery would be much better.

125W / 90% = 139W = 12V * 11.6A
50 amp-hours / 11.6A = 3.5 hours to "discharge"

Hmmm...I'm still missing it. How many hours do you need to leave it
without starting the car? What are you doing at the airport all this
time?

And why would you run a trickle charger when you have a car available?

--kyler

"Kyler Laird" wrote in message
...
"Kyle Boatright" writes:

Again, the problem is that a pre-heater and/or a trickle charger need
hours
to do their thing. Trying to run either from a car ain't gonna cut it.

Yup, I sure did miss that. Let's find the "ain't gonna cut it" part.

125 watt heating element
inverter with 90% efficiency
Much better are available.
roughly 44 amp-hours available from regular 12V starter battery
A dual-purpose deep-cycle/starter battery would be much better.

125W / 90% = 139W = 12V * 11.6A
50 amp-hours / 11.6A = 3.5 hours to "discharge"

Hmmm...I'm still missing it. How many hours do you need to leave it
without starting the car? What are you doing at the airport all this
time?

I don't want to be at the airport for any lengthy period of time. That's why
I'm looking for a power solution in lieu of paying the "power guy" $180/yr
for a buck or two of electricity.

And why would you run a trickle charger when you have a car available?

Because jump starting an airplane isn't the most enjoyable thing in the
world. Cords, spinning props, etc. make it a process that could lead to a
dumb accident.

KB


--kyler

"Kyle Boatright" writes:

I don't want to be at the airport for any lengthy period of time.

That was my first question. ("You'd attend while using the drop cord,
right?") So the answer is "no." No problem. You could still buy a
deep cycle battery, charge it in your car and then pull it out to use in
the hangar. It should be able to run your 125W heater for several
hours.

Not quite as elegant but still a way to be independent of "the (power)
man."

And why would you run a trickle charger when you have a car available?

Because jump starting an airplane isn't the most enjoyable thing in the
world.

I don't have a problem with it. I just start the engine on the opposite
side of the nose from the charge port. Maybe it's your plane that's the
problem.

Cords, spinning props, etc. make it a process that could lead to a
dumb accident.

I still don't see how a "trickle charger" changes any of this. Do you
leave it on when you turn the prop? Then you still have "cords,
spinning props, etc." If not, then why would you leave a fast charger
(car) connected when you spin the prop?

Connect the car. Load and do your preflight. Put the car away. Start
the plane. What am I missing?

--kyler

I would hesitate to recommend solar panels and batteries for the
purpose of generating heat - but it is certainly do-able. Were I to
decide to go this route I would find some sort
of a DC heating element to use - thus avoiding the expense and
conversion loss of running an inverter. If your winter flying is
infrequent you could figure your recharge time to be a week or more,
and thus size your solar array accordingly (and save upfront cost in
the process). I have had great success with using solar battery
maintainers in my airplane and also in a seldom-used vehicle.

This past winter I tried a different approach to preheat. AC was
available - with a long extension cord - and I had a couple of the
"cube" style ceramic heaters laying around. I picked up a couple of
dryer duct flanges and duct taped these to the business ends of the
cubes. Then I took an 8' dryer hose, cut it in half and attached the
halves to the cubes.
Feeding the heat to the engine by way of the cowl flap openings, I let
this rig run for half an hour with temperatures in the 20s. I have no
idea what the engine temperature was after this treatment, but it did
start immediately - just like in warm weather. If no AC is available,
one could power heaters of this sort with an inverter in a car. It
would take
a large one - 3 KW or so for a pair running on high. It occurred to me
that a couple of
cheap ($10 at Walmart) hair dryers might do the job just as well (the
wattage is similar - about 1500) - but I haven't had the opportunity to
try it.

David Johnson

On 4 Jul 2006 21:04:12 -0700, wrote:

I would hesitate to recommend solar panels and batteries for the
purpose of generating heat - but it is certainly do-able. Were I to
decide to go this route I would find some sort
of a DC heating element to use - thus avoiding the expense and
conversion loss of running an inverter.

For a building, I would definitely agree. For an a/c block heater, though,
one's choices are more limited. And 125W is a fairly modest load.

The issue, though, is whether the OP wants to jury-rig a heater for his
a/c, that might be only usable with a DC supply, versus perhaps he has
something already installed, which can be used at other airports, with an
AC source.

He'd really have to do some cost comparisons to determine the most useful
and economical method.

Since he already has a heater, the question would be whether purchasing or
fabricating a second heater, which would only be used in his hangar, and a
controller to avoid overcharging his a/c battery (he already has a charger)
would be more or less expensive than a small inverter and perhaps slightly
more panel than might be required without an inverter.

I still think that the economics would favor a few bucks a month to his
neighbor, and a long extension cord :-).
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

writes:

Were I to
decide to go this route I would find some sort
of a DC heating element

What kind of heating element *doesn't* work on DC?

--kyler

On Wed, 5 Jul 2006 08:06:44 -0400, Kyler Laird
wrote:

writes:

Were I to
decide to go this route I would find some sort
of a DC heating element

What kind of heating element *doesn't* work on DC?

--kyler

Obviously, any resistive load will heat up if you put DC voltage to it.

But now you've got me thinking.

What are the design considerations for converting a heating element that
has been designed to function on 120VAC to 12VDC?

For example, I have a TANIS system in my a/c which draws about 375W @
120VAC.

It consists of four heated intake bolts, and a heated oil screen. It works
very well and heats the entire engine to 75-100°F on below zero F days
(with a cover).

I'd guess, as a minimum, I'd have to rewire everything to handle ten times
the current, depending on whether or not the 120V wiring is oversized, or
not. That might (or might not) add sufficient weight to have to do a new
W&B (A&P and logbook entry required). Obviously have to change the
connectors, too. How simple would it be to attach the larger wire to the
bolts and engine oil screen?

Will the heating elements handle a continuous (DC) as opposed to an
intermittent (AC) current? Or will I need some kind of
controller/thermostat?

I'd also want to retain the ability to run on AC, so I'd need some kind of
additional connector -- probably paralleled with the AC connector.

What about the AC neutral/ground? If that gets upset in the rewiring, I'll
wind up blowing GFCI breakers when I use AC.

??
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Ron Rosenfeld writes:

Obviously, any resistive load will heat up if you put DC voltage to it.

But now you've got me thinking.

What are the design considerations for converting a heating element that
has been designed to function on 120VAC to 12VDC?

Note that I wasn't suggesting using 12VDC. I was thinking in terms of
an equivalent voltage DC. That would not require any changes to your
installed system.

I'm really not even suggesting using DC; I was just pointing out that
the heating elements can handle it. Nine 12V batteries in series should
give approximately the equivalent power to a resistive load as 120VAC.
It could be done but it'd be a pain.

I think you'd be happier using a special-purpose (cheap,
high-efficiency) inverter on a single 12V battery. You could have a
noisy 400 Hz inverter and it would be perfectly fine for your heating
elements.

....or you could just buy a decent general-purpose inverter and use it
for powering a video projector for late-night drive-in movies at the
hangar when the weather is nice.

--kyler

Ron Rosenfeld wrote:
: What are the design considerations for converting a heating element that
: has been designed to function on 120VAC to 12VDC?

: For example, I have a TANIS system in my a/c which draws about 375W @
: 120VAC.

You wouldn't convert it. You'd just hook it up to ~125 VDC. It will work
great. You may have trouble if it has an electronic thermostat (SCR/TRIAC)
because these require the reversals of the AC voltage to stop conducting
(you can turn on a TRIAC with DC across it, but you have to interrupt
the current flowing to shut it off).
--
Aaron C.