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Date Posted |
Forum
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RE: TPMS - Tire Pressure Increase
This week on our trip I took a look at tire pressure/temp. In the morning before starting one tire 63psi, 55F. After about 30 minutes of driving and outside temps up to 65F, that tire was at 78psi, and 90F. Other tires basically same pattern. Now the "sunny side" of the trailer had tire temps noticeably hotter, 10F or so. and higher pressure as well likely from heat absorption from the sun hitting the black tire.
Now if outside temps hit 90F, I would expect a slight increase in pressure, most of the pressure increase is due to friction induced heat.
Now, the other unkown is how accurate is the temp reading for a TPMS?? Is it measuring rim temp? air temp? or some combo.
And then factor in how dry the air in the tire is. If it is dry, boyles law works nice. if there is moistue (water) expecially if it condenses, pressure will bump up noticeably once it become a vapor. which is a strong function of temperature.
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ktmrfs
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09/12/23 10:43pm |
Travel Trailers
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RE: exterior solar plug
Be VERY VERY VERY carefull about the polarity of the plug!!!!!!!
In many cases it is REVERSED from the connection scheme on a battery tender charger!!! or many such extension cables.
It may seem like a stupid design, but it really isn't when one looks at which pin is hot and which is ground on a portable panel with the connector scheme.
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ktmrfs
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09/12/23 10:00pm |
Technology Corner
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RE: Calgon & Dawn treatment for waste tank sensors issues works!
The sensors that come in the tanks are actually electric probes that pock into the tanks. They get coated and then will not conduct the low voltage power that shows the level in the tanks in fractions. RV tank Sensors are electronic
strips that are stuck to the tank and give read-outs in % to a circuit board on the wall.
Just do a Google search. A little expensive but to me well worth it.
actually the factory sensors work the opposite of what you outlined. when they are not in contact with a liquid which provided a electrical path to ground they are off. Problem is if crud gets on the surface and on the sides of the tank there is a electrical path to ground even though they are not submerged. Hence the light up.
I agree the most foolproof solution is something like the sealevel system which I have, more accurate, zip troubles.
dishwasher detergent, vinegar, calgon seem to help keep the factory sensors working, dishwasher detergent has good grease cutting capabilities, better than clothes washer detergent. Vinegar is a mild acid which will help desolve crud on the sensor or tank walls, calgon softens the water and then keeps calcium etc. from building up on the tank walls.
But then the sealevel system doesn't care about any of that and it is easy to install. But not inexpensive,
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ktmrfs
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09/03/23 08:28pm |
Tech Issues
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RE: 12 volt transfer pump
shureflow revolution.
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ktmrfs
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09/03/23 08:20pm |
General RVing Issues
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RE: Unusual propane plumbing???
From description on etrailer.com:
"High-pressure regulator is designed for high-demand propane equipment, primarily used for dual-bottle psig setups with distant separation applications. Regulates 500,000 Btu/hr or 30 psig based on 100 psig inlet."
The red regulator reduces the pressure from tank pressure (100 psi) to 30 psi before sending it across your rv to the auto-switchover regulator which reduces the pressure further. It's for safety.
yup. every 5th wheel I've seen has this arrangement. Unlike a TT with the propane bottles external and very close together a 5th wheel has propane tanks seperated by a reasonable distance AND inside the trailer. So the high pressure regulator is a safety precaution.
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ktmrfs
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09/03/23 11:07am |
Tech Issues
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RE: Travel Trailer for Two
And Tow vehicle mfg generally assume max tongue weight of 10% while trailer mfg design for around 15% min tongue weight. See the problem?
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ktmrfs
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09/03/23 09:06am |
Travel Trailers
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RE: TPMS - Tire Pressure Increase
And pressure should be set with the tire(s) at ambient temperature, NEVER vent a hot tire thinking it is overinflated!!!
An increase in ambient temperature will increase pressure (PV=rT) V (volume is constant, so if T increases, so does P) And rolling resistance of the tires creates friction which increases temperature.
And yes 20-25% is possible, I usually see around 15%
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ktmrfs
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09/03/23 09:03am |
Travel Trailers
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RE: Travel Trailer for Two
you might look at the mini-winne offerings. They don't hit all your list of wants, but likely would be reasonable to pull with your colorado.
Nice thing is the version my brother has addresses a couple of small trailer issues I didn't like
1) there is a couch AND a dinette. dinette is in the slideout. means one has a nice seating other than the dinette seats
2) It has a queen bed. Now the queen bed is a murphy bed behind the couch, couch flips forward, murphy bed drops down, So you don't end up with a Jacknife bed.
Shower is very nice, walk in actually slightly larger than the shower in our outback.
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ktmrfs
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09/02/23 03:41pm |
Travel Trailers
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RE: Educated guess !
Or S.W.A.G. !
With a 12V LiFePO4 200Ah battery bank and a "typical" inverter and no solar, how many hours of use can I expect running only a 11,000BTU-13,000 BTU A/C before the inverter shuts down ?
Assume a 24' TT and outside temperature about 85° and inside set to 75°.
*********************
So for a baseline, I’ll provide my own brand real world estimating method, though without concurrent harvest…My 11k btu Coleman typically uses 90-95a depending on ambient temperatures…
Since you’ve suggested an ambient of 85df this means only a 10 degree difference which is fairly easy to resolve, but which can be impacted by region and humidity…. Since you mentioned ‘inverter’ and the possibility of a 13kbtu air conditioner, I’d assume a 3kw inverter (most likely a PSW pass-thru inverter-charger type)…I’d also recommend a soft-start to limit start-up voltage sag, along with robust battery cables to reduce voltage drop feeding the inverter (I use 0004 AWG, for about 6-7’ R/T to inverter)…
Since you’ll be running an air conditioner, you’ll want to pick an inverter with a high surge rating ‘and’ duration - cheaper inverters are often rated at a high wattage, but of a lower surge duration…Recall that old adage, get what you pay for!!
Also consider duty cycle - for thumbnail calc’s, I generally use a compressor-run duty cycle of about 60%, though for the first hour’s initial cool-down I’d plan on 80%- this method with the fan on low speed continuous operation…
Since you’re using lithium, you’ll want to consider a battery’s continuous amperage and surge rating (often 1C and 2C respectively), and it’s allowable time duration spec while in a surge condition…
Now you’ll want to decide on your initial SOC and your acceptable DOD floor, this will tell you how much power your willing to commit to the air conditioner…
So hypothetically speaking, let’s say (assuming a full 200a/h charge…) you have 120a/h available for air conditioner usage before arriving at an acceptable lower battery limit of say 30% SOC meaning a reasonable 60amp/hrs being held back in reserve…
Now, back to duty cycle: Let’s assume a 13k btu air conditioner uses about 12amps AC (TBD… this, a combination of both compressor and fan running amps…due to various parasitics, and to be conservative I’ll skip the fine tuning of this math…). We can convert this to DC by using a multiple of 10, thus 12amps AC = 120 amps DC (as measured via metering…)
(Note, compressor amperage gradually increases a bit once at the early to mid 90 degree weather).
So, starting out at 200a/hrs x first hour at 80% duty cycle at 120a DC = 96a/hrs consumed, with 104a/hrs remaining, yet only about 44 remaining available amp hours to the target SOC of 30% (of original 200a/hrs)…
Beyond this initial cooldown period, lets assume a 60% duty cycle per air conditioner run hour, thus 72a/hrs per hour of operation…
So it’s relatively easy to see how you can extend air conditioner run times, and optimize next morning’s all important battery recovery times (e.g. non-air conditioning hours) with concurrent solar harvest…For this calculation, it’s important to consider the 4-5 ‘peak harvest hours’ and beyond, and what is a relatively rapid re-charge characteristic of LiFePo4 batteries…JMO
3 tons
for us the issue would be the duty cycle. Ours is a large trailer and to get it cooled down even if the inside temp is say 85 will take several hours of run time to get it to the mid 70's. That's assuming an outside temp of around 85. Once outside temps are in the 90's that AC need to run 3-4 hours for much effect.
Now on my small trailer (14ft cargo) with a coleman 9K BTU AC an hour cools the trailer down even in the high 90's outside, so it would make practical sense. and it only draws about 9A, another big advantage.
I wish I could cool my trailer down enough in less than an hour to have a 80% duty cycle!! The disadvantage of larger trailers, 30Ft double slides. Even a 24ft seems like it would be unlikely to do enough cooling in less than an hour even at 100% duty cycle.
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ktmrfs
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09/01/23 06:17pm |
Tech Issues
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RE: Tires
Inflating to max load will cover anything you put in it but loading to the max sidewall pressure when not needed will result in a lot of bouncing being that most trailers do not have shocks to stop that.
Inflating to max trailer load if your anywhere near that actual load (from what I've seen, many are at or even above that load given the marginal load capacity of trailers) gives you ZERO margin on tire capacity. Loose a few psi over time and your overloaded.
And don't assume that tire load = (GVW/4)!!! If your going to go on actual tire load, you need to determine ACTUAL load on each tire, which means getting weights on each tire individually.
Better to inflate to cover some % over actual max load, just like cars and trucks do.
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ktmrfs
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09/01/23 02:00pm |
Travel Trailers
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RE: Educated guess !
swag....
Googling, I see that a 13000btu RV AC draws about 13amps at 120v. If your 12v battery is providing this through an inverter, it will be drawing roughly 130amps from the battery. There are also inefficiencies running through your inverter that will probably result in 5-10% more amps needed. So my swag/guesstimate is that your AC will be drawing ~140amps from your battery. Assuming your battery can handle this and that all wiring is adequately sized to reduce voltage drop/etc, it looks like your battery will power your AC for about 1hr 20 minutes. This assumes that your battery was fully charged and you aren't drawing significant power running anything else.
Summary: Not long at all. Use a generator to run your AC
Good luck!
Chris
And I don't know about lithium batteries, but lead acid AH capacity is rated with a 24Hr draw, a 2Hr rating is noticeably less
Couple that with what the max long term current rating is on the lithium battery, it may be less than the current draw of the AC
And then even lithium batteries can't be drawn down to 0 SOC, add that factor in
Then what voltage will the inverter shut down at? may reduce run time even further.
And all this is assuming the inverter can even start the AC
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ktmrfs
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09/01/23 12:21pm |
Tech Issues
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RE: Tires
Unless they say "always inflate to xx psi" on the sidewall then go to the tire manufacturers site and find their inflation chart for the tires. 8000 max divided by four is 2000 pounds on each tire so that is the load that you need the psi for. If it does say "inflate to xx psi" on the sidewall then that is the only number you need.
really need to inflate ABOVE the actual load.
Look at your other vehicle tire psi and you will find that the recomended inflation pressure is noticeably above the max rated load of the vehicle or each axle.
And many of the ST tire mfg recomend inflating to max psi unless that is way above the actual tire load. I have LRE endurance on my trailers and I use the max pressure, can't tell the difference between that and lower pressure and the still wear evenly.
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ktmrfs
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09/01/23 09:02am |
Travel Trailers
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RE: Proper Power Receptacle For Home?
All you need is the 50A line and the 50A and 30A receptacles can be run off that. I am not up on the code for that but it may require you to change the receptacles and breakers when you change to a 50A RV.
TT 50A is a 240V/50A 4 wire circuit with two 120V/50A legs, two hot, one neutral one ground.
30A is a 30A/120V 3 wire one hot, one neutral, one ground.
If you plan to eventually go 50A, have the system wired to support both. A 50A/240V 4 wire from the main breaker box feeding the "trailer box". That box will be like what you see in campgrounds with one 50A/240V breaker and usually 2 120V breakers, a 30A feeding a 30A RV outlet a 20A/120V feeding a 20A duplex outlet and a 50A/240V breaker feeding the 50A outlet.
Note: The trailer will use the 50A 240V as TWO 120V/50A circuits, I don't know of any trailer that actually have any 240V appliances, although it would be possible to do.
Just make sure the don't wire the 30A as a 240V circuit!!!
https://www.homedepot.com/p/GE-RV-Panel-with-50-Amp-and-30-AMP-RV-Receptacles-and-a-20-Amp-GFCI-Receptacle-GE1LU532SS/203393689
Or just install a 50A circuit and use a 50-30 dogbone, Later if you decide you want a 30A outlet it can be added
Don't start with 30A, you'll basically redo everything going to 50A.
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ktmrfs
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08/26/23 07:48pm |
General RVing Issues
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RE: RV Power Cord FIRE!!!
I've found that the combo of a 30A RV cord, 30A to 15A adapter and extension cord is a BAD combination. many of the 30A/15A adapters have very weak contacts on the 30A side which will loose tension against the 30A blades pretty easy. = overheating= weaker contacts= trouble. And the heat affects not only the adapter, but the nice copper high heat conductivity to the 30A plug assy. Not a good combo.
If I'm going from a 30A plug to extension cord I use one of the short "dogbones" that has a real 30A receptical on one end and a stout 15A blade on the other end with about 12" of wire in between
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ktmrfs
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08/26/23 05:10pm |
General RVing Issues
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RE: Black Ants in outdoor kitchen
I believe Ortho makes a spray called Home Defense. Might check the label.
Have you tried the home remedy from borax and sugar as a paste, placed on paper squares.
Ken
or use terro liquid ant bait. basically borax maybe with some sugar as well. Borax kills many ants and the track it back to the nest.
Works fantastic on the small "sugar" ants we get in the spring. see a few, put out a bait trap, pretty quick they come out in force creating a congo line back to home, and few hours later all gone and dead.
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ktmrfs
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08/25/23 02:56pm |
Travel Trailers
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RE: Does AC Softstart void Warranty?
Here's the problem with soft start caps; If the original cap dies while the AC is running, rather than stopping like it normally would the AC will continue to run on the new cap and destroy the compressor.
Ones I've installed have a thermistor or other cutout on the soft start connection so it opens after a short period of time, and only leaves the run cap in the circuit. Or the motor may have a centrifical switch that keeps the start cap out of the circuit once the motor gets up to speed. I've seen both schemes on motors with a start and run cap.
In fact my current coleman =AC units have start and run caps installed from the factory. Same as an aftermarket, the start cap drops out of the circuit after startup and won't be energized again till a stop and then start occurrs.
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ktmrfs
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08/25/23 11:34am |
Tech Issues
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RE: Micro Air Easy Start 364-XP installation
My understanding of the THEORY OF OPERATION of the Easy Start, once the A/C is running, it has no impact on the operation !
Call Micro Air and see what the say.
that's almost correct. The micro-air is a START aid, not something that reduces running current, it doesn't.
BUT The easy start does in some way try to detect a power source overload that could affect the AC. If it thinks the circuit is overloaded it will drop the AC for a few minutes and then start up again.
I've experienced this when I was using my honda 2000 at high altitude to run the coleman AC. That 2000 was maxed out, above continous rated power and into the short term power limit, and instead of having the honda drop into it's overload the micro air would shut off the ac for a short period of time, honda would idle down, then about 5 minutes later ac would start up again, The mico air manual talks about how it handles what it thinks is an overload.
BTW, once I switched to a honda 2200 the high alitude problem went away.. the extra 200VA and the 25% larger motor saves the day. Mostly the larger engine.
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ktmrfs
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08/25/23 09:11am |
Tech Issues
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RE: 100w panels
I will agree that high altitude and/or a breeze is a benefit. First you may get solar radiation in w/sq meter above the standard reference due to the altitude. Next any breeze helps keep temperatures down. And usually high altitude= lower temperatures.
So, while I've never seen output> rated, I will change my opinion and say it is possible. not likely to occur very often, but is possible.
Also years ago, like when I bought my panels there were rated under ideal conditions. Solar engery 1000W/sq meter, cell temp 77F, 500ft altitude.
Since then the NOCT rating has been used as well which is more realistic. (Normal operating conditions and temperature) It assumes 800W/sq meter, 500ft altitude and 68F AIR temperature and a 2mph wind. Note the use of AIR temperature NOT cell temperature.
so using NOCT I can see panels oeak reading exceeding the rating on a nice sunny cool day with a nice breeze especially at high altitude as long as they are aimed within reason. I wouldn't expect that reading to last for very much of the day.
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ktmrfs
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08/24/23 10:40am |
General RVing Issues
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RE: add another MPPT
not sure about the controller the OP has, but midnite solar "kid" controllers are designed to be paralleled if needed. Two can be set up with one as master the other as slave. if you have more than two, they can be "daisy chained" with one as master and it passes info to the next in line, that one passes info to the next in line etc.
I have two kids, master is the roof solar setup, slave is for the portable panels. works great.
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ktmrfs
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08/24/23 10:26am |
Tech Issues
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RE: hauling capability
also there may be a sticker in the glovebox listing max camper weight.
Just don't listen to a camper sales guy, cuz his answer will be "your truck will handle this no problem"
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ktmrfs
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08/23/23 04:44pm |
Tow Vehicles
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