What the heck do I do with this?

[WoodenBoat]

Dave, I am in the process of  converting a 1998 H3-41.

You picked a nice rig to convert.

You know? Everyone has told me that I have chosen a good bus. But honestly, I didn't go looking specifically for a Prevost. I found it completely by chance! I was actually searching for a BlueBird All American RE because this was a bus I was very familiar with when I used to drive the kids back and forth to school. I loved my BB even though it was a pusher and have been sentimental over it. When it comes to driving for a school system, wheel base on buses has a lot of do with how the drivers like them. The All American RE does not like to turn around in cul-de-sacs and I had one on my route that I did have to do a three pointer. But I liked the pusher. It was smoother riding and a lot of quieter. The front engined Blue Birds are .... well calling them loud is like calling Dolly Parton a little chesty. And if you find a front engined Thomas, you not only have loud but you have gazzilions of rattles and banging around.

So I was asking around about Blue Birds and someone said he knew where there was a bus that was like a Greyhound and if I bought it I could get like a brand new dog for the side of it and everything. One thing led to another and now I have a Prevost and I'm trying to remember what the Blue Bird even looks like.

My wife loves the washer and dryer.

Wow, we think a lot alike because I've been planning where to put my washer and dryer too.

I would love to know what part of the country you live in. If you were anywhere close enough to me, it would be worth it to me to hop in the truck and come look at your bus. There is so much here that I need to learn.

[bandsaw]

Dave, I live in Oregon. I have benefitted from being close to several motorhome factories. Just keep removing fasteners the overhead racks will come out. I may go to Idaho this summer.  We should connect off of this  board.  Take care, Bandsaw. 

[WoodenBoat]

Yeah, Oregon is a down the road a fur piece.  Probably not going to make that in the next few days.

[bobofthenorth]

But running down the road, it will be Prevost all the way.

I think you are right about the build quality.  Ours was a 1981.  I hit a bear with it one night. Not a big bear but it was definitely a bear.  He pushed the bumper back enough that the door would only open far enough that the slim passengers could get out.  Once I moved the bumper back on its slotted holes there was no other visible damage.  Another time we were heading south on I5 north of Seattle.  There was about 4 inches of wet slimy slush on the road.  The guy in the lane beside me started fishtailing when he was about even with the ticket window.  I almost made it out without him hitting me.  The last time I looked in my mirror he was broadside in the lane  heading toward me with a truck coming at him broadside further back.  He hit hard enough to knock items off the shelves and I expect the car was totaled, not by me alone but totaled nonetheless.  I had to replace the oil bath cap on the tag axle and a piece of stainless trim. 

[Jim Blackwood]

Lake Barkley, KY huh? Well hi there neighbor. (Almost)

Jim

[bandsaw]

Dave, you need to check on a rear suspension recall. If your bus is early 1998 (before W2249) there was a recall to strengthen the rear frame.  The serial number is from memory.

Thanks, Bandsaw

[WoodenBoat]

Thank you for that. I will check.

My rig is W2115.

Lake Barkley, KY huh? Well hi there neighbor. (Almost)

Hey, we're both east of the Mississippi river... right? I mean, I think that counts. LOL

[WoodenBoat]

Still... no one has told me what a "mini-split" is. 

[chessie4905]

A mini-split is like a house ac, where the condenser is mounted outside and evaporator is mounted in the house. In your case, the condenser is mounted in the bay, and evaporator are mounted in the inside of coach. Called mini because the systems are much smaller than used in a house system.In a car, the condenser is mounted in front of the radiator and the evaporator is mounted in the dashboard.

[richard5933]

Still... no one has told me what a "mini-split" is. 

A mini-split is a type of a/c seen in residential and commercial installations, and in basic terms it's built as if you took a really large window a/c unit and split the compressor and evaporator functions into two separate locations instead of all inside of one box.

Unlike a traditional a/c system with the compressor and coil outside, air handler in the attic, and ducting running through the building, a mini-split system has a smaller compressor & coil outside which is connected to one or more head units inside the building through a small set of copper lines. There is no ducting in a mini-split system - the only thing that gets run inside the building is the copper line set. This makes them great for retrofit applications or for adding a/c to a remote area of a building where ducting is no practical. These are very common in parts of Europe and in the mid-east for retrofitting a/c to multi-story buildings.

In a bus installation, the compressor & coil unit is installed in a bay. The copper line set is run up into the interior where the head unit is hung to supply cooled air. Here is a video of a guy installing his in a 4106: https://www.youtube.com/watch?v=GvdIe0AkXV8

Our bus has a custom made mini-split using commonly available commercial refrigeration parts. The system used would commonly be found in a walk-in cooler, with the compressor in the basement and the head unit in the cooler.

We have something similar to this in our bay: https://www.webstaurantstore.com/randell-rf-con1404-condensing-unit/HPRFCON1404.html?utm_source=Google&utm_medium=cpc&utm_campaign=GoogleShopping&gclid=CjwKCAiA2fjjBRAjEiwAuewS_f777JGug6NhGff9AwYuWcy-cXfOOnSuotI0WHOReMDuvYt7xDyaJxoCiiQQAvD_BwE

We also have an evaporator coil and squirrel fan inside the bus, built into a cabinet so that all that shows is the output vent. The evaporator is connected to the compressor unit down below with a copper line set. Works like a champ.

[robertglines1]

I'm running two 9000btu and 1 ea12000 in front above driver.  A little oner kill but all running pull 22 amps.  Bob

[buswarrior]

"Overkill" is another way of saying "faster pull down when heat soaked"

Nobody ever complains of too much HVAC, but lots of others spend time being uncomfortable...

Happy coaching!
Buswarrior

[Jim Blackwood]

It all works the same, just a different way of balancing out the system components. One of the big advantages of a mini-split is that you buy it fully charged (the freon is in the compressor/condenser unit) so you can install the lines, leak check, draw a vacuum, open a couple of valves and switch on the power. Quick and easy(er). But, if you can do all that you are already pretty well equipped to do whatever else is required for a custom system. And despite what professionals would have you believe with their charts and formulas, it ain't rocket science.

So, a few things to be mindful of are, that perfectly matched system components are fine but imperfectly matched still works too and perfectly matched to do what exactly? For instance, a bigger condenser always increases system capacity but it also can create a longer delay in getting cool air out. Maybe not objectionably longer though. The compressor has to be big enough to keep a ready supply of liquid to the expansion valve(s) under full load. The expansion valve should be big enough to make full use of the evaporator (less than that is ok but wasteful of space) but not so big as to freeze up the evaporator. The receiver/drier should be big enough to allow practically all of the freon to accumulate as a liquid between there and the condenser, but the larger it is the longer it takes for the system to cool down.

So with those tidbits of information, the following conclusions are perfectly valid: The expansion valve(s) (TXV) determines the cooling capacity of the system. The evaporator should be at least big enough for the txv and can be larger (less likely to freeze up if it is). The compressor should be able to handle at least as much flow as the TXV(s), for the condenser generally bigger is better as long as you have the room, and the accumulator should be big enough. (subtract the volume of the liquid lines and about 1/3 of the condenser from total system liquid volume.

Now you can go shopping for components. Want a 3 ton system? (12K btu per ton) Select a compressor to handle it, then TXV(s), evaps, condenser, dryer, lay out the system and install. Same if 5 ton.

Bear in mind, all compressors are not equal. Look at seer ratings. The seer is a measure of how much power is required to achieve a measured level of cooling, you can find exact numbers, but what's relevant here is that if the seer number doubles the power usage is cut in half. Seer numbers have gone up by a factor of at least 3 and maybe 4 in the last few decades. So an old seer 7 system like the one on my shop will use 3 times as much power as one of the brand new seer 21 or 22 systems. In other words, maybe 60 amps instead of 20. Big, major difference there.

Now some of that is in system design but most of it is in the compressor. For the most part fans are fans but you can see where the new variable speed fans came from, an effort to boost the seer rating. The rest of the system is passive so that leaves the compressor as the one big element determining system efficiency so choose wisely.

But sometimes practicality trumps efficiency. So for instance, if you found a way to drive the bus OTR compressor with an efficient electric motor you might find it practical to do so even if you could do better in terms of efficiency by plumbing in a sealed compressor from a household outside unit.

Jim

[WoodenBoat]

Thanks guys for explaining things. I've got a lot to learn and I'm having fun doing it. This is a great forum.