| Author |
Message |
Brian Elfert
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 7:52 pm: | |
I'm still looking for a shell, but I keep researching other things.
Does anyone actually keep the road air? The majority seem to say junk it.
One coach I looked at was a '95. It had modern A/C and heat. The A/C comes out through the luggage overheads normally, and with the the overheads gone, it just shoots out from the back of the bus. Ducting would be needed to circulate the air through the coach.
Am I just better off running the generator to power the roof air instead? Could the driver stay cool enough that way?
Brian Elfert |
JW Smythe (Jwsmythe)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 8:35 pm: | |
Myself, judging by the crap I found in the ducts, I'd say rip them out.
My decision was made easy by the fact that the A/C didn't work. I didn't like the idea of giving up all the space taken up by the ducts either.
A serious consideration was that I didn't want to leave the engine running all the time, just to have cooling. It seems like a bad idea, and probably unfriendly in campgrounds. |
David Hartley (Drdave)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 8:39 pm: | |
If you don't mind that 25 to 40 horsepower load on the engine and 3 mpg keep the road air.
Transits generally have about 100,000 btu of air conditioning at a substantial cost to operate and maintain. My MC9 had a/c but with the 25 hp being sucked from the engine plus the 140 amp power draw. along with probably $300 to $1000 per year to keep it going just didn't make sense to me.
Figure also that R134 prices are going out of sight like R12 did. Some buses ran R22 but it too will soon be $$$$$ ...
At 30 to 40 lbs per fill up.. Wow....
They all leak or develop problems eventually.
Put the money into a good diesel generator, insulation and either roof airs or basement airs..
They last longer and are easier to swap out when they die.... |
james dean boggs (Jd_boggs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 9:04 pm: | |
Where I live and where I travel, I can't afford to remove the road air because 2 roof airs at 30,000 BTU is simply not enough to keep me going when it's 120 outside. I removed the ducts and replaced them with 4" white drainage pipe and T's along the way. Also snapped in some heat outlet vents on the T's that work just great, no modifications needed. From here: http://dwincorp.com/index.php?cPath=54
Don't forget if you travel in the winter you still need a good heater so if you remove the road air keep the heat exchanger plumbed and the marine pump functional. Also don't remove the extra alternator that energizes the fan motors. You may need them later to run a 36 VDC inverter to run the roof airs.
just my .02 cents worth or $ 0.00000000675 inflation adjusted cents. |
WEC4104
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 9:11 pm: | |
Your question regarding the ability to keep the driver cool is crucial. Driving down the highway, into the sun, on a 90 degree day, the thermal load on the front of the bus is a VERY high percentage of the total needs.
The windshield glass is a greenhouse. If there are any air leaks in the front, the outside air is forced through them under pressure. It is a difficult place to add extra insulation, and then there is the convection action of a never ending supply of hot air blasting the front face.
On warm days the back facing vents on my roof unit are shut off so that maximum cooling is directed forward. If I were setting up a duct system I would heavily bias it toward front distribution. |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 9:49 pm: | |
Hello
DrDave, go easy, Brian is trying to make informed decisions.
The A/C load in a coach is typically 25 HP total, for compressor and alternator loads.
The fuel economy is not harmed that much. One of the early retrofits of Series 50 in an MC9 driven on a dedicated line run on the westcoast saw approximately 9 mpg with AC off and approximately 8 mpg with it on.
You will not notice any change in hill climbing power, AC on or off, so don't think that helps.
An MC 7,8,9 uses, give or take a few, 25 pounds of refrigerant, depending on type.
If you return to your coach after it has sat in a parking lot all day in the sun, the 80 000 BTU or more of cooling will be welcome to pull down the temp. Two roof airs may hold the temp in a coach, but it is the devil to get the coach pulled down with only 25 - 30 000 BTU.
If the AC is leaking gas, then the leaks need to be found, repaired and then they don't leak anymore.
Remember, bus converters end up with worn out buses from companies that were planning to get rid of them. It was cheaper to add gas than to repair the system in the last months of its commercial operation.
So, the accumulated experience has been that the AC needs repairs. Since you need another AC system for campground use, spending more money on the big coach system when you are spending all sorts of money on roof airs that on the face of it look like they'll do the job, and the rest of the conversion $$$$ adding up....
Easy to see why the coach HVAC gets a bad reputation and is popularly removed.
Up here in the frozen north, I am maintaining the coach heat, so keeping the AC working too isn't as big a deal as it would be if I had the option to tear out the ductwork.
happy coaching!
buswarrior |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 10:00 pm: | |
Brian - to add a little info - thermostatically controled OTR ACs unload the compressor by up to 2/3rds when the designated temp is attained - FWIW |
Matt (Hgtech)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 10:04 pm: | |
I've got to agree with WEC4104. The drivers area on these buses turns into a really hot greenhouse in the summer.
We decided to junk the bus air and aux bus air. The main reason was equipment failure (the A/C was dead - needed converted to something other than R12 and other work). We also didn't want to have to run the bus for A/C at $3 per gallon.
While we were at it we decided to remove the bus heat also. We did keep the plumbing for the driver heat as it gets really, really cold up there when going 70+ at 0F. We did this for a number of reasons:
1. We could remove all the duct work since we didn't have the heat or air.
2. We could remove the blowers
3. We could remove the heat and a/c cores from the bus (they were bolted together during an aftermarket mod someone did to our bus).
4. We could get rid of the large 350Amp alternator (less load on the engine).
Our decision is definately not for everyone. It did however let us take an estimated 2500+ lbs of weight out of the bus. We're currently using a number of 1,500 Watt floor heaters which work fairly well when stationary. As of right now, we're going to move to a roof heat pump setup before next winter.
We decided to go with roof units to save bay space. As our bus is being designed as a tour bus, I'm trying to save as much bay space as possible for gear.
As everyone on here says - Do it YOUR way . . .
Matt
1979 Silver Eagle Model 05 |
Greg Peterson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 10:13 pm: | |
When I first bought my bus the air worked great and I thought I would keep it for extra cooling of the front windshield area of the bus while I was driving over a hot highway.
I drove the bus down to Fred Hobe place and the bus air worked great even in the hot Florida weather.
Fred advised me to take the air out because as you have heard it is expensive to repair. My air system was new in 2000 and I thought since it is relatively new I would be ok. However, after 1-½ years the Freon seems to have leaked out. I talked to busted knuckle and he said that it is common to have to add Freon frequently on the charter buses.
I think I am now going to take it out since it is going to be expensive to maintain and adding the ductwork in my MCI is not simple and does mess up some of the conversion floor plan.
There are trade offs to everything but I think the experts like Fred are correct in not using the bus air.
This is my current opinion after being converted by practical experience.
Good luck finding a good bus and don’t rush into anything unless you’re sure it is right for you. |
Brian Elfert
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 11:05 pm: | |
Does A/C load really put enough load on the engine to drop mileage by 1 MPG? That is over a 10% drop in mileage!
My little TDI powered car does lose a fair amount of acceleration when the A/C is on, but MPG is about the same in the summer with AC on as winter with AC off. Of course, it is only a little 90 HP diesel.
The '95 coach I looked at had a little electronic pad near the drive that controlled heat and A/C. It displayed the current interior temperature. You then set the heat or A/C to the exact temperature you wanted.
The A/C in this '95 coach didn't work due to being flat on charge. The dealer was willing to charge it and get it working.
It sounds like it just isn't worth keeping both road air and roof top or basement A/C units.
The condensor on this particular coach took up 1/3 of a luggage bay. That 1/3 bay would be perfect for a generator it looks like.
Brian Elfert |
David Hartley (Drdave)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 11:12 pm: | |
Sorry, Didn't mean to upset..
I looked at my compressor, it said 25 hp on the tag.
The driver air situation is a tough one, I have heard of people keeping the drivers air system and putting a smaller sanden automotive compressor back on the engine and using an automotive condensor. a little replumbing of the lines to the front and all is cool again.
Saves having to worry about those 1 1/2 or 2 hp blower motors too. Now I am curious.. I wonder if I can belt drive a sanden from one of the old blower motors enough to just cool the drivers area? Might make a neat package unit for mounting in the spare tires compartment close to the driver.
I have to apologize in advance, I just had cancer surgery today on my right ear and they had to really hack out a chunk all the way down to the bone and do a skin graft. Besides the pain the pain killers are affecting my normally good behavior. So for the next few days I may be a little rancid at times but I will try to help where I can.
I will say however, Anyone who does welding without full protection to exposed skin should really think about the equipment. The UV is a sure way to hurt yourself. Always use a full face mask and not those goggles.
Dave.... |
Greg Peterson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 21, 2006 - 11:40 pm: | |
My 8v-92ta got 8.5 mpg on the way to Florida with the bus air on all the way.
I accurately measured this and even had my wife following me in a car that verified the mileage. At no time was I ever under any speed limit all the way there. I could not feel any difference by turning the air on or off. The 8v-92ta did not know it was even there. It pulled the ridge in Tennessee like a car. My wife called me on cell phone and said slow down I can’t keep up with you.
In my opinion on an 8v-92ta you don’t need to worry about the power loss. The main concern is the upkeep cost of the bus air system.
Good luck and thanks for your info on the Dina very enlightening. |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 12:20 am: | |
Oh, ok.... .02 cents...
The Welch system is worthwhile, since it can power the
driver's air also. (I haven't received the plans yet, but will
post 'em when I do) Welch System
I'm lucky, my bus had one... And yeah, it cools the bus from
super hot (Floriduh), to cool, within 1/4 hour.
With OE?
It's not the power loss, it's the refrigerant loss that's of
concern. Mine worked perfect (ice on the windows), until it
sat for a few months. The amount of r22 it needed, would
have cost me over $340... The two used (6 mo) roof airs
cost me $250 ea... Does it pay to have the OE system?
Most all converters take it out; there's a reason for that! |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 5:04 am: | |
"Does A/C load really put enough load on the engine to drop mileage by 1 MPG?"
A 2 stroke DD uses a galon an hour at normal ROM to produce 16hp.
A modern turboed intercooled aill run 20 or so.
Whatever adding a gal an hour does to your fuel bill , its the price of air cond.
FAST FRED |
Jon W.
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 9:31 am: | |
If you'll accept an opinion from a store bought conversion owner I strongly suggest keeping it.
First, lets dispense with some subjective issues. I can't tell the difference in my fuel mileage with it running and with it turned off. That comment is relative to an 8V92 or a Series 60. Second, the principle service item is the seal on the Carrier type compressor, and replacing the seal is something anybody with a modest collection of tools can do. If you switch it from R12 to 134-A you can pump it down and shut down the valves, replace the seal, add back in a can or two of 134-A (I'm oversimplifying a little here) and you are good for another 10 years or so.
Now as to the practical aspects, by having OTR air you are not using inverter capacity to run roof or Cruise airs. You are using that capacity to keep your house batteries charged while you drive. Or conversely, you are not running your genset to run your house AC units while your bus is running.
Additionally, OTR air keeps the whole coach comfortable while you drive. You may not care, but your wife or family wants to be comfortable no matter where they are as you drive. My wife would be very unhappy if we did not have OTR.
If you have a conversion, but drive it little, forget what I just said. OTR is only important if you rack up some miles.
Regardless of the choice, don't make a decision based on MPG, service issues, or saving space. They are not that big an issue. |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 11:33 am: | |
Damn, Jon-- you just took every argument for getting rid of the bus air and said they are all wrong! It must be because you bought a store-bought conversion (as you say) that someone else had the headache of incorporating into the interior. I, for one, removed a perfectly working OTR air system and used the room for installation a generator. And they *do* cause a load on a 6V92TA that is noticable and fuel thirsty. I use my inverter to run the front air while traveling, and start the generator if I need to run more than one air. My house batteries stay charged, and when I pull over for a break I can shut the main engine down while the generator keeps the bus cool. I bought the generator and inverter to use, not just for occassional boomdocking.
And I have to add that the factory air did a poor job of keeping the driver's area cool-- I am much better off with my front roof air being ducted and aimed at the front. Good riddance to the complicated factory air and the problems it presents to keep for a conversion. One cooling system works fine for me!
--Geoff
'82 RTS AZ |
D. Tracy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 11:56 am: | |
I have a 1984 Eagle 10 that had a great working AC. I kept it for 5 years but it was too much $$$$$ to maintain. I sold it to Welch Industries and they took it all out. I had their dash air installed and it works great. I hardly ever use it here in the coooler weather. I kept the over the road heaters. They were great people to work with. |
Brian Elfert
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 12:45 pm: | |
I don't plan to do over 10,000 miles in any one year.
MPG is certainly a concern with fuel prices going nowhere but up.
Roof airs generally just work year after year in my experience. I don't have any experience with coach air over time, but a lot of people say to just junk it. I do know the coach I looked at had no charge and would need R134A at minimum to work again. If it would hold a charge for years, great, but I suspect it would be flat on charge every spring.
Brian Elfert |
WEC4104
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 1:52 pm: | |
Side stepping the question of whether to keep the road air, I'd like to address the comments on the MPG aspect.
In the discussions above, folks have noted the decrease in fuel economy when running the Road Air, pointing that out as a negative.
The fact of the matter is, if you want to cool your bus, you will be burning fuel no matter what system you have.
If the OTR air is scrapped in favor of roof units, it lightens the burden on the Detroit Diesel and you will get better mileage. BUT, how are you going to power the roof units? Most likely you will be running a generator that is burning diesel, gasoline, or LP. You are only taking the money out of a different pocket.
To really know whether you making out better or worse you would need to compare the efficiencies of each (and the relative fuel cost difference if it is not diesel), and that is beyond what I will get into here.
The only "free ride" would be to plug in at the campground, load up a massive set of batteries, and use them through an inverter on the road. But how much run time are you going to get from that?
I am thinking the OTR or not OTR question will be decided on factors other than fuel savings. |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 2:12 pm: | |
The fuel milage comparisons I have seen in the past (ignoring the present claims of no increase in fuel usage for OTR air) is that a diesel genset running a couple of roof airs will use 1/2 to 3/4 gallon of fuel per hour, while the bus OTR air uses 1-2 MPG. It takes 30-50HP to run an OTR air system, while an average diesel genset (8-12 kW)only uses a 16-24 HP engine running at less than full load. The OTR bus air system not only has to run the freon through the compressor and evaporator, but the bus alternator also has to power the big fans to distribute the cool air. There is a big difference in fuel savings. |
Matt (Hgtech)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 2:18 pm: | |
One of our primary decisions in junking the OTR air was fuel savings. When we calculated it out, our 8v71 burns between 2.5 and 3 gph at high idle which was required to run the a/c and not kill the batteries. Our genset runs 3 roof units plus anything else (laptops, cell phone charges, microwave, radio, etc.) at around .75 gph. That’s about two gallons per hour difference - which at current fuel prices works out to over $5 per hour savings. Keep in mind that our conversion is a tour bus and we spend a lot of time sitting in the bus at venues. When we ran the final totals, we saved enough by running off our genset during the day to pay out campsite fee at night. Obviously this wouldn't work out the same for everyone - but it did for us. Also, after removing the bus OTR systems (not just disconnecting them - but removing them) we are now getting about 9.5 mpg. We used to get about 7 when using the OTR a/c. That works out to be a tremendous savings when you travel 50,000+ per year. Just my experience - probably wouldn't be the same for everyone.
Matt
1979 Silver Eagle Model 05 |
Mark R. Obtinario (Cowlitzcoach)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 2:32 pm: | |
To dump or keep the OEM HVAC system, that is the question.
The answer pretty much is determined by how you are going to use the bus.
To me the answer is a no brainer--dump it!
As it has been pointed out, the duct work on an older motorcoach is so black and disgusting you wonder people aren't getting sick from all of the crud. The other part of all of the black crud in the duct work is it reduces the flow of air so much that the cold or hot that comes out is not adequate when the temp goes way up or way down.
Another point was made about the greenhouse effect of the windshields.
I have driven motorcoaches made by all of the major manufactures including an MCI E4500, Prevost H3-45, Van Hool T2140, and Setra 215. On a hot day, driving into the sun, none of the coaches that I have driven had adequate ventilation to keep the driver as comfortable as the passengers.
Another point is the cost of maintaining the OEM HVAC system.
Many others have touched on the costs relative to maintaining the system so I won't join the chorus and add my two cents worth. All I know is in my experience, no matter how well you maintain the systems and no matter how often you are running the systems, they always seem to need more juice. And with the price of the juice getting so dear the cost of some roof top mounted A/C units start to look very attractive, even in a seated coach.
Would I keep the hot water piping in place to run the front heat and defroster? Yes. Would I scrap the rest of the HVAC system if the bus was no longer seated? You betcha!
Again, it all depends upon how you are going to be using the coach. But unless you are running a seated coach I see no good reason to keep the OEM HVAC system intact.
Mark O. |
Brian Elfert
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 2:35 pm: | |
I did some quick calculations on fuel MPG when using a generator full time to run AC.
At 70 MPH, the coach gets 9 MPG. The coach would use 7.8 gallons an hour. A 8KW generator uses .5 gallons per hours approximately to run two roof airs. The total usage per hour is 8.3 gallons per hour with the generator. Total MPG drops to 8.45 MPG when using the generator.
(9 MPG is based on what someone told me a '95 coach I was looking at should get.)
Brian Elfert |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 2:46 pm: | |
The best thing is that when you get to a rest stop or a temporary parking place you can leave the genset running for very little cost while maintaining full electrical service if needed. Also you can have A/C in the evening or nite time. All this without running the main engine.
Richard |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 22, 2006 - 5:41 pm: | |
To verify my prior statement - see below
http://www.transportaircon.carrier.com/details/0,2806,CLI1_DIV8_ETI264,00.html
I think some people are getting confused about compressor HP and btu/hrs - let me see if I can confuse it more -
The btu's you are discussing are "cooling capacity" btu's - not the number of btu/hr or HP needed to drive the compressor
Using 1 HP = 2540 btu/hr
Then taking a "cooling capacity" of 76,200 btu/hr (6+ tons)
You first have to figure the "coefficient of performance" - this is the efficiency attained in actual 'cooling' by a particular refrigeration system - late model compressors are capable of achieving a factor of up to 3
A cooling capacity of 76,200 btu/hr with a "coefficient of performance" factor of 3 would require 25,400 btu/hr or 10 HP
Furthermore a compressor which unloads to 33% after the initial 'cool down' would only require 3.3 HP
*** DISCLAIMER (yes, this is for newer efficiency units operating at 100% efficiency - I am not commenting on the take it out/ leave it in discussion - only trying to clarify the actual loads placed on the mill - and yes I know the motors add more load via the alternator - but the COMPRESSOR ITSELF is more accurately a 5-15 HP load plus any inefficiencies in a 9 ton system) |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 23, 2006 - 6:09 am: | |
The usual hassle with factory road airs is maint and leaks.
When a 30lb tank of F 12 was $25 bucks it was no big deal to add a 5 lb shot every few weeks and keep cool.
For folks with the incentive , and courage , Propane is an even better refrigerant than the F12 was.And is still relativly cheap.
It needs to go thru an Ansul T flow drier while being installed , as some is not too clean.
Caviat Emptor.
FAST FRED |
bobm
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 23, 2006 - 11:34 am: | |
In my 4104 I kept part of the original air. I run a commercial fridge compressor with the generator engine instead of the pony engine. my generator engine is a 2-53 and is pretty good on fuel. I have other ancillary equip run by the 2-53, hydraulic pump, alternator, air compressor and a 15 kw generator. this keeps the 2-53 under load at all times even if I am not pulling a lot of electricity |
Jarlaxle
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 24, 2006 - 6:41 pm: | |
Anyone who charges any air conditioning system with propane (or anything else flammable) should be horsewhipped to death. |
Jon W.
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 25, 2006 - 8:07 am: | |
That lets out normal refrigerants and refrigerant oils. |
David (Davidinwilmnc)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 25, 2006 - 11:46 am: | |
How much propane is normally used in a refrigerant system? I doubt the explosive potential of it is nowhere near that of the 30 gallons of gasoline in my truck, or the many gallons of LP used for RV heating, cooking, water heating, etc. |
Jon W.
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 25, 2006 - 4:53 pm: | |
In a full bus AC system the amount of refrigerant may be as much as 24 pounds. For some reason the biggest argument that arises against the use of propane based refrigerants always seems to be the flamability or explosive characteristics. The reality is that the typical product for that purpose has a flash point greatly in excess of the freon it replaces.
There is more BTU content in the engine crankcase.
There are more vehicles running up and down the road today with propane tanks sitting in a bay or on the front of a travel trailer frame to worry about than there are vehicles with drop in hydrocarbon substitutes for R12.
Break out the horsewhips for those folks. |
truthhunter@shaw.ca
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 25, 2006 - 6:55 pm: | |
I understood that R12 was non-flammable, but would catalyze into deadly phoshegene gas (CN nerve gas agent, I can't quite remember that stuff ) if was combined in a propane flame.
I had given a little thought to propane drop in retrofits, as I had not read of a lot of propane-drop-in-refrigerant-in-Air Conditioning- retrofit in fire/accident reports. One speculation that comes to mind when trying to guess at the danger factor is that the cold side of the AC {that is in direct contact with the interior space}is the LOW PRESSURE side and therefor is less likely to be the first part of the system to leak; perhaps this is why few interior retrofits have been reported to blow up like a propane bomb so fare. I also do not know how common propane retro fits are either. A propane/CO leak detector (that we should have if propane is used for any use ) would I assume detect the leak well before it reached the level were the narrow margin of density (the combustion ratio of Air to Propane is between 2.4% & 9.5%. homogeneously mixed ) could be ignited.
Is 134A or R22 flammable?
I also noted from those carrier specs that a system converted to 134A would require less hp (x .674 if I recall from last years study) to operate and a corresponding drop in the BTU "heat transfer" ability. I may be wrong, perhaps someone can correct me here. I had this thought in mind when considering if it was possible to re-powering my OEM 5F30 AC compressor (at slower speeds/reduced capacity with one or two of the 3 cylinders unloaded)with a electric motor and/or my 24 VDC surplus military generator set
There was also a different rate factor for R22 in performance and hp, but not sure if this is a wise retrofit as it has not only getting very expensive but it is on the unobtainium hit list for 2010 with the ozone depleting substance regulations (seems to be yet another ineffective environmental make believe show, unfortunately) |
David (Davidinwilmnc)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 26, 2006 - 10:56 am: | |
I recall reading about propane used in small quantities with R134a in A/C systems. I can't remember the exact wording, but I believe it lowered the high pressure some... enough to make the 134 act similar to (but a bit better than) R12. I guess the point was that the system wasn't full of propane, but maybe a few ounces. This was in an auto system, so the amounts were much smaller than in a bus. I'll have to go back and see if I can find the link to make sure I'm remembering this correctly. |
truthhunter@shaw.ca
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 26, 2006 - 12:51 pm: | |
I think I have my answer on 134a flammability, according to several drop in HC replacement vendors, it is highly flammable and can sustain it's own combustion in air and combustion does produces "some" chlorine gas as a byproduct. They claimed 134a is far more of a combustion risk than there hydrocarbon based replacement mixtures, but were vague on hard facts.
I also found 406a and FR12 being marketed as drop in (or near drop in,) replacements for R12 systems. The 406a operates at lower pressures and higher efficiency than R12 and much higher efficiency and much lower pressure than than 134a.
Has anyone attempted or looked into converting there MC-8 or even a MC-9 AC carrier system to R22 or tried R22 drop-in replacements like FR22 that are claimed to be more efficient and are much cheaper than R22? |