What's the opinion. Keep it or remove it
If you are on a small budget, remove it except for front heater defroster. Down the road, it'll be costly to maintain. Unfortunately, older systems don't hold freon well and it'll be expensive to add it every year. I'm not even talking about relays, sensors, other components.Jmo.
I'd say keep it if it works or is easily repaired. Nothing will keep you as comfortable going down the road. There are those who automatically say pull it out, but I've had two buses with working factory a/c and it is nice. If the system was maintained it you're ahead of the game.
At least have a proper a/c shop give you a quote so you can make an informed decision.
Not to be rude, but have you done any reading on here?
There is a search function up there, experiment with keywords, everything that was ever known, has already been written about.
That's what's good about these good boards, BCM, BNO and BGM, unlike social media, you can find old stuff, and if it isn't accurate, others have corrected it.
It has been typed out dozens of times, the pros and cons.
Happy coaching!
Buswarrior
OTR air is expensive to keep going I have friend in Phoenix that has a charter co and tells me he budgets from 2 to 5 grand a year for maintaince but his Ac's work hard every day.fwiw a compressor can cost up to 5K for one,If is a 134A unit you are a head of the game to convert one over to 134A the cost one can buy another bus
Richard, your present coach was or is supposed to be in fantastic shape. What is the TOTAL amount of dollars have you spent on your otr ac and heat so far? Include the water circulation pump.How many hours could you run a generator to use your rooftops with the money you spent? Unfortunately, it'll take several years to see how yours will now hold up.
It still depends on petarm1's budget, short and long term.
There a lot of difference now with AC's since Richards was made you put 35 people in his bus and you would probably never knew there was a AC unit,takes a lot of BTU's to cool these 40 or 45 ft buses 12 ft tall with 55 passengers and the huge glass in front called windsheilds
I'm in for about $5,000 for the repairs - replacing compressor, recharging system with refrigerant, and work on circulating pump. The rest of the system appears to be in good shape and holding up nicely. That said, only time will tell.
Our first bus had a minor leak repaired and the system recharged. Total cost on that one was about $1200. The original OTR a/c compressor had been replaced at some time with the dual GM rotary compressor setup, which greatly simplified things.
I never said that maintaining the OTR a/c system was the least expensive way to go. My point is that it is the best way to keep comfortable while driving, and that if the system is working or repairable it's my preference.
Probably would be cheaper to run the generator and house a/c systems, but those a/c units are not designed to counter the sun pounding in from the windshield (which is normally covered while camping in summer). Also, in my case that would mean spending money to either update the generator or replace with something more reliable.
Regardless of whether the OTR a/c is pulled or not, it is my opinion that the OTR heat & defrost should be retained if possible. These things are really difficult to keep warm while in motion otherwise. At the least, the loop going to the defrost coil so that the windshield can be efficiently kept clear.
102D's have good OTR air starting out. Very likely 134, look on the side of the drier. 30lb cans of r134 are at least affordable. With a set of HF gages you can top it off yourself if it needs it, helping to keep the cost down. If it cools, I think you'd be crazy to throw that away. The main evaporator is 10 tons of A/C. That's two relatively large sized houses worth. Each of the overheads is 1-1/2 to 2 tons. The dash unit is 1-1/2 tons. At 12,000 btu per ton that's like having a dozen or more roof units. Personally I think those guys who just automatically say to tear it out are just jealous.
True, that much cooling capacity is going to cost more to maintain than, say a quarter as much would. And if it doesn't work, has no freon, and the belt is off the compressor then depending on your budget it may not be worth putting back to original. But even then you do have some pretty good building blocks to play with and a outdoor condenser unit in the basement can be used to advantage, driving the overhead and dash units.
Finally, there is no reason why it would not be possible to set up a compressor to run off shore power and operate the OTR system when parked. That will take a little ingenuity perhaps but you can believe me when I say that creative minds are at work on the concept and you can probably expect to see at least some progress over the next year.
So first assess. Make no decisions until you absolutely know the condition of the system. Also be aware that the compressor is nothing but a pump. If it leaks, all seals and gaskets are replaceable. If it has lost compression, it may be rebuildable. There's nothing magical about it.
Jim
Rebuilding a 05G Carrier is not a easy task and parts are expensive,there is more to the D systems that worrying about a compressor the condenser motors are almost 2 grand each for new ones,this guy is dealing with C that has a 6v92 power plant and the AC in the bus robs him of 15 to 18 HP with a 05G compressor hp he doesn't have to spare
Quote from: Jim Blackwood on May 20, 2019, 10:08:46 AM
There's nothing magical about it.
Nope. Nothing that a pile of Benjamins, a bunch of engineering and/or mechanical ability or resources and good luck over time can't conquer. There is a well traveled trail of system removal by private busnuts established for a reason. I am sure there are some who have ended up spending more on their AC system upkeep and/or salvage than the bus in the first place. That is a personal gamble. Tread carefully.
Quote from: Jim Blackwood on May 20, 2019, 10:08:46 AM
Finally, there is no reason why it would not be possible to set up a compressor to run off shore power and operate the OTR system when parked. That will take a little ingenuity perhaps but you can believe me when I say that creative minds are at work on the concept and you can probably expect to see at least some progress over the next year.
Jim
I really like this idea, if the system is in good shape.
Hope to hear more along these lines.
Seb
Gonna keep mine going as long as I can or until I sell the bus which might be soon. Nothing like them if there working, freeze you to death. Also bought an Carrier O5G-Bus compressor last year to replace mine but found out all mine needed was as a seal. So I have one precharged with nitrogen sitting in the bus barn if needed. 8)(//)
The GM system using the rotary compressors seems simple compared to what I've seen installed in some MCI buses. Even the dual rotary compressor setup. Wonder if it would be possible to replace the Carrier units with the GM style compressors? Our 4106 had the dual setup and it worked great. Our current bus, the 4108, has just a single rotary compressor. Takes about 20 minutes to get the system fully running, but once it's going it keeps up quite well. I don't know the specs, but I'd suspect that the rotary GM compressors don't rob nearly as much power from the engine as the larger Carrier units.
I used my oth for 2.5 years and had to top it up once at about $300 but the next time I asked if they could top it up they said no as there was to many things that needed to be fixed or replaced . so then I removed all the parts . when it was working man could it cool down the coach fast ! and freeze you out if you left it on .
so if you do not need to I would leave it in if it works up until it starts costing you money . then remove it but think about what you are going to replace it with before it is to late or have to reinvent the wheel as to install on a finished converted coach
dave
Seb, the thinking at this point is that a pair of sealed rotary compressors with about a 5 ton seer 22 or better rating would handle the job and MIGHT be able to run on a combination of 50 amp shore line and genset, using both for drawdown and then just the shoreline to maintain. More analysis needed at this point, state of the art was seer 24 last time I looked.
As for the condenser and evap fans, switching those to VFD drive would enable variable speed by demand and conditions and also allow the use of less expensive motors if desired. Personally there is absolutely no way I'd ever even think of considering forking out 2 grand for one of those motors. Too many other good options.
Jim
Quote from: Sebulba on May 20, 2019, 01:04:36 PM
I really like this idea, if the system is in good shape.
Hope to hear more along these lines.
Seb
Not going to happen using the O5G Carrier taking 15 to 18 hp with a 18 hp motor on 3 phase 230 volts drawing 60 amps you would need a 15k generator just for AC,Jims idea may work but I wonder what will happen with all the valves and evaporators that used R22 like his DL
Thanks for all the input. Every little bit helps. And it was good that buswarrior thought not to be rude. And i did try to look at other threads
I would think that the horsepower required to run a compressor even at half the capacity of the factory unit, would require 50 amp shore power 30 amp at many campgrounds wont cut it. Add in also the current draw of the condenser fan, blower fans, and you are drawing some serious current.
Um, well first off my '96 DL uses r134, says so right there on the dryer.
Then secondly the Carrier compressor will be out of the circuit if the engine isn't running, otherwise why would I be looking at canister type sealed compressors?
Then thirdly, the efficiency of the Carrier pump has no bearing on amp draw. The only requirement is that there be enough amperage available to run the sealed compressors and that is entirely dependent on the Seer rating. So let's compare apples to apples. Most of the RV aircon units out there are probably seer 12 at best. So a 5 ton pump with a seer 24 rating is going to draw the same current as a 2-1/2 ton pump with a seer 12 rating. This is extremely important in determining current loads and is crucial in a high powered RV system.
Finally, the MCI OTR AC system uses TXV's. (Thermal expansion valves) this is an on-demand valve that regulates the introduction of liquid freon into the evaporator based on evaporator temperature. This means quite a lot of things actually, but one of those things is that it is possible to gain quite a lot of control over how much freon is dumped how quickly into the evaporator, and if your compressor(s) output is not quite up to full system capacity the possibility exists to still release freon at a slow enough rate to keep the liquid line full, which is required in order for the condenser to operate correctly.
It means basically de-rating the system while operating on shore power, but that only means that the condenser and evaporator become more efficient at doing their job.
The challenges are to minimize the plumbing changes, maximize cooling capacity, and remain within limits on power consumption. Done right, this system has the potential to be as good or better than any mini-split system, and still operate normally while underway.
Jim
Go for it!
Yeah, it isn't going to happen overnight, and before I evacuate my system I'll need to know exactly what changes need to be made and have all the hardware on hand, though it should be possible to start upgrading the blower and fan motors ahead of time. I'd estimate at least a year or two and realistically it might be wise to double that.
Jim
Quote from: Jim Blackwood on May 20, 2019, 03:56:33 PM
Um, well first off my '96 DL uses r134, says so right there on the dryer.
Then secondly the Carrier compressor will be out of the circuit if the engine isn't running, otherwise why would I be looking at canister type sealed compressors?
Then thirdly, the efficiency of the Carrier pump has no bearing on amp draw. The only requirement is that there be enough amperage available to run the sealed compressors and that is entirely dependent on the Seer rating. So let's compare apples to apples. Most of the RV aircon units out there are probably seer 12 at best. So a 5 ton pump with a seer 24 rating is going to draw the same current as a 2-1/2 ton pump with a seer 12 rating. This is extremely important in determining current loads and is crucial in a high powered RV system.
Finally, the MCI OTR AC system uses TXV's. (Thermal expansion valves) this is an on-demand valve that regulates the introduction of liquid freon into the evaporator based on evaporator temperature. This means quite a lot of things actually, but one of those things is that it is possible to gain quite a lot of control over how much freon is dumped how quickly into the evaporator, and if your compressor(s) output is not quite up to full system capacity the possibility exists to still release freon at a slow enough rate to keep the liquid line full, which is required in order for the condenser to operate correctly.
It means basically de-rating the system while operating on shore power, but that only means that the condenser and evaporator become more efficient at doing their job.
The challenges are to minimize the plumbing changes, maximize cooling capacity, and remain within limits on power consumption. Done right, this system has the potential to be as good or better than any mini-split system, and still operate normally while underway.
Jim
It has been changed the 1996 DL3 left MCI with R-22 pull the front evaporator cover and you can read R-22 only they don't work as good on R134 as they do R-22
Quote from: Jim Blackwood on May 20, 2019, 04:42:02 PM
Yeah, it isn't going to happen overnight, and before I evacuate my system I'll need to know exactly what changes need to be made and have all the hardware on hand, though it should be possible to start upgrading the blower and fan motors ahead of time. I'd estimate at least a year or two and realistically it might be wise to double that.
Jim
The condenser fans are huge they 53 amps @ 24 volt and the condenser is huge what and how would one replace those and keep the OTR air ?,I have seen it tried with 6 electric fans and it didn't work
I've had that experience with r134 conversions from r11, but then again I've also seen systems that seemed to work better. The AC on this bus works but just how well I won't get to find out until summer is in full swing. So far I'm pretty satisfied with it, though from the sight glasses it appears it could use a little more freon. Some of that may depend on whether or not they changed the compressor when they crossed over. I suspect that the very large capacity of the system would tend to cover up any shortfall. How that might affect cooling capacity vs amperage input I'm not sure at this point.
On the condenser I'm thinking that a basic 1/2 hp 3 phase motor is going to move enough air. Maybe I'm wrong but do you know what rpm those fans run? That'd give me what I need to find out I think. I can measure the pitch of the blades and with blade count maybe find an online calculator to help sort it out. With a VFD (variable frequency drive) those can be throttled back or overdriven based on demand and the current draw should be less. I can probably find a VFD that takes straight DC if it makes sense to do that, considering that the way they work is to input AC, convert it to DC internally and then output it as 3 phase AC. Might even be possible to run one on either/or, which would be good for OTR and shore. But finding those surplus could be a challenge. Might just be easier to access the internal buss.
As a rule 3 phase motors are pretty efficient, very available as surplus, and economical to buy. The availability of VFDs as surplus has declined as people began to learn they could use them to run 3 phase from split phase 220 but you still can find them occasionally, especially in the under 2hp range. I wish I'd bought a few more of them back when they were dirt cheap though as I'm using all of the ones I have in the shop. Anyway, I agree that slapping pancake fans on the condenser isn't going to do much. That thing is about 3 inches thick which means a lot of air resistance. You need a healthy pressure differential, something that a pancake isn't very good for. I'm not sure why they didn't use a squirrel cage but no doubt there was a reason. Maybe space constraints.
Jim
Richard do you know what kind of compressor you bus has? I would assume it's much cheaper than the 05g in the MCI.
Quote from: richard5933 on May 20, 2019, 01:41:53 PM
The GM system using the rotary compressors seems simple compared to what I've seen installed in some MCI buses. Even the dual rotary compressor setup. Wonder if it would be possible to replace the Carrier units with the GM style compressors? Our 4106 had the dual setup and it worked great. Our current bus, the 4108, has just a single rotary compressor. Takes about 20 minutes to get the system fully running, but once it's going it keeps up quite well. I don't know the specs, but I'd suspect that the rotary GM compressors don't rob nearly as much power from the engine as the larger Carrier units.
It is a GM A-6. Been used in millions of cars and trucks from 60s to the 90s. It has a capacity of about 42,000 btu's per single unit. Can be operated either rh or lh. Some 4905 used two in tandem in place of the big 3 cylinder. I wonder if you could use one, and kick in the other if needed. Are very reliable. Only repairs I've ever seen with them is the front seal leak and easily repaired with the few special tools required, and front clutch slip and burn from low oil, freon or improper cooling or overfill with refrigerant.
What he said.
Newer models are a bit more specific with right-hand and left-hand models, as well as a few differences depending on which oil they come pre-loaded with, but basically the same compressor that's been used for decades. Our bus could have had 2 of them mounted side-by-side using a manifold so they both pump the same refrigerant.
Seems like a much more simple and reliable system than the MCI setup.