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Author Topic: What do you think?  (Read 1743 times)
John316
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« on: April 21, 2009, 07:21:29 AM »

I need your input on this. First off, we have a MCI DL3, with a DD S60, and a Allison B500.

We are struggling with whether to take the OTR air out. That is a lot of space that we would gain if we removed the OTR air. We have five 15k Dometic, penguin roof airs that we run off of our 20kw generator (we are thinking about changing that generator out for two smaller gensets). Our OTR air, including the driver air, is not working right now. I am thinking that our coils are clogged. I haven't torn that down to see, but we have had everything else checked. 

Now, here is what I need from you all. How do you cool your coach as you run down the road? What about the driver, since he is pretty important, how do you cool him? What about leaving the air, and fixing our driver air. Is that the best way to cool the driver? Those of you who do use the original drivers air to cool the driver, how old is your bus?

For the down the road heat, we will be using out Aqua Hot, or similar equivalent.

We have thought about running some of the roof airs off of our house batteries and our two 4000 watt inverters. I don't know if that would be hard on the batteries to have the constant discharge on them, and then recharging them. Right now our roof airs are tied into the generator. So if we want air conditioning, right now, we have to run the genset.

What think do you all?

God bless,

John
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RichardEntrekin
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« Reply #1 on: April 21, 2009, 07:31:58 AM »

If you have roof airs and a 20Kw genset, then run the roof airs off the gennie by all means. I have a 20 kw gennie, and at full load it uses less than a gallon an hour of diesel.

If you want to run a couple of roof airs off the inverters, the house batteries alone won't do it, you will need to install a 250 amp or larger alternator to feed the power to the inverters.

If you add up the cost of retrofitting with anything other than what you already have, you will see that you can run that 20Kw gennie for a LONG time before you break even with a retrofit to do it a different way.

You still have the dash A/C question for the driver. I have an automotive compressor mounted on the S60 that drives a small system up front just for dash A/C

In Texas in the summer, it takes both roof air and dash air to keep the driver and passengers comfy. The roof air alone WILL NOT do the trick if there is sun coming in the windshield in the southern climes. 
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Richard Entrekin
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« Reply #2 on: April 21, 2009, 08:11:07 AM »

FWIW and I am not as experienced as many here but I have driven buses for a school district that had both types of systems and the buses with the engine driven compressors won hands down for  maintanance and noise. They retrofited non AC buses both ways to see which was best. The buses with the roof airs required four units to do the job, that could have been because the lack of insulation. Either way you go will work. I myself would stick with the engine driven compressor.
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Nick Badame Refrig/ACC
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« Reply #3 on: April 21, 2009, 09:59:27 AM »

Hi John,

I think you should get an estimate of what it is going to take to get your OTR A/C running up to par.

At that point, you will know what you have to spend and compair it to 2 smaller gen-sets... or bigger altinator, etc..

As everyone knows, I'm a big fan of OTR Air....

Good Luck
Nick-
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« Reply #4 on: April 21, 2009, 10:00:24 AM »

Most disable the the OEM OTR because it consumes a lot of power AND is spendy to repair AND it takes up space.  The consensus is that you need OTR from a engine coupled AC Compressor.  Maybe two.  But they are auto size.  You should be able to leave your dash AC and all the switches and ducts in place and just get6 your liquid freon from a different source...auto compressor.  The trick is, according to Nick, getting the condensor and compressor and evap units sized right.  Takes a AC man to do that.  Nick recommended a supplier named "Red Dot" for consulting and material sourcing.  I have gotten good advice from a reputable local shop in the past.  Their materials are a lot higher than I can get them for but tat is expected and sometimes I bite the bullet as payback for their help.

I think using the roof airs for OTR is a mistake  Keep that capability as a backup for the engine system....redundancy.

John

John
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« Reply #5 on: April 21, 2009, 05:39:25 PM »

I pulled all my OTR stuff out and made good use of that extra space, both in the engine room and the evaporator cavities.   I have a 12 kw genny and use 3 roof airs.  Mine are ducted and I have a Danhard blower at the front that draws lots of cfm from the ducts and dumps it on the driver and works very well.   Ducted may be more than you want to fool with.  If you run roof air unducted then you need some type of mounted fan behind the driver to draw as much air to the front as you can, otherwise you will be disappointed with your comfort.  It takes lots of cold air to cool all that glass up front.

David
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JackConrad
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« Reply #6 on: April 22, 2009, 03:40:26 AM »

Our OEM Ac was not working when we purchased our bus.  we used a little different reasoning when making the decision about whether to keep the OEM AC. Of the total time we spend in the bus, the bus engine is running less than 5% of the time (that is the only time the OEM AC is functional). We could not justify the expense and lost space for something that could be used less than 5% of the time.  If we spent much more time driving and less time sitting, we might have kept the OEM AC.  Jack
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John316
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« Reply #7 on: April 23, 2009, 07:59:18 AM »

Okay guys, thanks for the replies.

First off, we have spent 5k on getting that running, so far. We have had a VERY reputable coach line shop doing the work on the AC (so we haven't gotten ripped off, these guys also know our DL3 very well, so they know what they are doing). The last thing to do, is to try cleaning the coils. Everything appears to work fine, except it just freezes up. We did a lot of other repairs, to try to get the system right. I am wondering if that AC is why Peter Pan sold the bus off. Could it be that they couldn't get the AC running, and decided to sell it then? I know that the AC is probably the most important item on a seated coach...

The idea of removing the OTR air is getting more and more appealing. That bay would be great for two banks of four batteries (we have four 8D deep cycle Trojan batteries now, and are going to add another four soon). That space would be perfect for those.

Any more input? This is a very tough decision!

God bless,

John
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« Reply #8 on: April 23, 2009, 08:51:55 AM »

John,

The coils freeze for two reasons:  First is that the evap isn't getting sufficient air flow to utilize all the freon that is being introduced to the evap.  My house unit froze up for this reason but it is cheap.  The auto systems are BETTER and if you choke off the air it shouldn't freeze up because the auto units have a temp sensor that limits how cold the air can be at the outlet of the evap unit.  When the output hits 40 degrees, or so, the expansion valve is closed till the air warms up enuf for more cooling to be needed.  Because auto units have such huge capacity and 3 or 4 speed fans, the evap must be really flexable and freeze resistant.

No matter how talented those bus mechs may be or how much their heart is in the right place, if they were HVAC guys they wouldn't be working as mechs.  HVAC pays a lot more and is far cleaner.  I take nothing away from the people you are working with, believe that.  BUT....there is always a "BUT", you need an HVAC guy that is auto system savvy....fresh look.  With $5K invested I would be bent on having an expert "fix" the thing once and for all.  $5K sounds like they might be Easter Egging the problem.  Get new help, qualified help, my friend. I ain't that guy!

John
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« Reply #9 on: April 23, 2009, 09:18:52 AM »

The causes I've experienced that caused evaporator freezing:
1- The pressure switch was bypassed (it was a used car that was low on freon, so the dealer 'fixed' it by bypassing the switch rather than adding a can of freon).
2- malfunctioning expansion valve.
3- low on freon.

If the system pressures are correct, I'd suspect the expansion valve system. . . . . A good hvac man should be able to cure your AC woes.
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John316
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« Reply #10 on: April 23, 2009, 10:54:09 AM »

Thanks for the help and advice thus far.

John, great post. I really appreciate it! I forgot to mention that they also replaced a ton of bad parts (I know that the parts were bad, not just a shotgun fix method). We will find another set of repair guys (like myself Roll Eyes, no really we will try to find a good AC guy).

Kyle, Thanks for the ideas. I will check them out. And I will see if we can find a good AC man. 

God bless,

John
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John316
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« Reply #11 on: April 23, 2009, 06:24:43 PM »

Thanks for the input guys.

That system will come out. We finally decided. We will cut our losses at 5k and call it quits. The evaporator was perfectly clean.

Now I think that Peter Pan sold the bus because the AC didn't work. Since the evaporator was clean, tells me that they tried cleaning it, among other things, to get it to work. I am going to take it out this summer.

Anybody here need parts (most of which are excellent condition) compressor, condenser, evaporator, the whole nine yards, everything is going (if you are interested PM me).

The other problem is we don't have a good AC man around. The guy that did the work on it, is a Arrow fleet manager. He seemed to know what he was doing, but he is stumped.

Oh, well. I can handle most of the other systems. Not AC, so it is going. If that fleet manager can't figure out what is going on, and I can't either, then we won't keep pouring money into it...

Thanks for the help guys, sorry for my rant.

God bless,

John
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