Hot air coming in while moving and keeping cool

neoneddy · June 26, 2018, 07:31:39 AM

Well, if it's letting air out / sucking it out, it means it's sucking back in some place else.

In all honestly, foaming and insulation is good, I've done plenty, not as good as others, but I feel I've got a good start with how I made my ceiling and the 4" in the walls. Not a ton on the floor, I'll be adding that from the underside to keep headroom.

I noticed the biggest change when I started adding the cellular blinds and trapping the heat behind them. The sun heats up my windows and frames past 120 degrees, thats a lot of BTUs to have to cool. I opted to keep many of my windows, in hind sight I'd remove 2 more (1 each side for 6 total removed) .

This was made abundantly clear as I was pulling out a few days ago with shorts on and felt the sun directly hit my leg and I instantly thought heat was coming in through the floor again. Nope just radiant heat.

Anyway, my next steps are to add the black vinyl back to the tops of the windshields and a few other areas that are covered by other items anyway.

Dave5Cs · June 26, 2018, 07:33:04 AM

JC
I am with you on the abbreviations. They say some of the people now days don't even know how to read because of them and writing in schools has changed. There are some schools that no longer teach cursive writing.

solardude · June 26, 2018, 07:33:44 AM

Several years ago I looked up the specs of the OTR A/C, IIRC the original A/C is comparable to approximately 4-5 3bedroom residential house units. In other words the OTR unit is gigantic. I don?t think you could fit enough roof top units to even compete. Knowing that I still removed my OTR A/C as it was due for many maintenance items and cost/benefit was not worth it for me.
SD

luvrbus · June 26, 2018, 08:04:59 AM

I have 60,000 btu on my roof it does a good job in the AZ heat the draw back is I have to run the generator which is not bad but it cost $3.00 a hour to run the 20kw

luvrbus · June 26, 2018, 08:18:18 AM

Quote from: neoneddy on June 26, 2018, 07:31:39 AM
Well, if it's letting air out / sucking it out, it means it's sucking back in some place else.

In all honestly, foaming and insulation is good, I've done plenty, not as good as others, but I feel I've got a good start with how I made my ceiling and the 4" in the walls. Not a ton on the floor, I'll be adding that from the underside to keep headroom.

I noticed the biggest change when I started adding the cellular blinds and trapping the heat behind them. The sun heats up my windows and frames past 120 degrees, thats a lot of BTUs to have to cool. I opted to keep many of my windows, in hind sight I'd remove 2 more (1 each side for 6 total removed) .

This was made abundantly clear as I was pulling out a few days ago with shorts on and felt the sun directly hit my leg and I instantly thought heat was coming in through the floor again. Nope just radiant heat.

Anyway, my next steps are to add the black vinyl back to the tops of the windshields and a few other areas that are covered by other items anyway.

Shoot the frames on the windows you will be shocked at the heat transfer between the frames and the bus body.I am researching for a bond breaker for my Peninsula windows the off the shelf roll putty isn't cutting it and why do they paint a window frame black ?

neoneddy · June 26, 2018, 08:21:44 AM

@luvurbus Oh I did, it's what I meant, those areas can slow cook some meats on a rotisserie. I figured there was no way to keep them cool while in motion, so I need to trap the heat they generate as best I can. Kind of like how home roof systems work.

eagle19952 · June 26, 2018, 10:05:35 AM

Quote from: Branderson on June 26, 2018, 06:24:37 AM
Original Poster and Because

One needs a grand-daughter on speed dial for these items...

Jim Blackwood · June 26, 2018, 12:15:28 PM

I have studied fluid dynamics and do understand that fairly well, plus have a good bit of practical experience with it. The toll window makes sense as does the door when the bus is in motion but is the low inside pressure just an incidental then, rather than something planned? If so it would seem like a pretty simple thing to pressurize the coach slightly. How many places would there be for the air to leak out? Does the door generally leak air enough that all your cold air gets sucked right out? Sounds like a need for better seals but I can see how that might be difficult. You have a huge low pressure area behind the bus too and the wheelwells are generally low pressure areas. High pressure in front and forwards of any obstruction in the airstream.

I actually made one of those vent venturis out of PVC pipe adapters for my old S&S a decade and a half ago. Extended it up into the airstream too. But keeping water in the bowl was more effective. I think something more along the lines of the overhead exhaust diffusers on the newer transits might be adapted and get better results, maybe with an opening in the front. It'd take some experimentation. I haven't seen the commercial vent venturis. Positive pressure in the cabin would be even better, and might be usable to do the job when stationary.

Jim

DoubleEagle · June 26, 2018, 04:56:53 PM

The cool air does not get sucked out of a leaky front door, rather, hot air blows in under pressure. Any rusted out areas in the front along with pipe and wire passages, and leaky vents also allow air in. In many coaches in passenger service, the cooler air tends to go along the floor and gravitate to the rear. In an MC9, for instance, the driver could be sweating, but the passengers in the rear are complaining that it is too cold. (In the winter, the driver is cooler while the passengers in the rear are toasty). There is also the factor of the glass area in the front that lets in a lot of solar heating adding to the need for extra cooling. It is no wonder that many coaches had additional separate A/C's up front for the driver, and all of the A/C systems have fresh air inlets to improve air quality. The only way to keep a coach cool in all situations is to have excess capacity like the systems that came with the coaches originally, or for conversions, have five roof airs, or a combination of basement airs, or split units.

luvrbus · June 26, 2018, 05:53:30 PM

I am not down in the valley right now but in Scottsdale,it's 115 there today and my phone has rang non stop people with AC problems and the generator quitting.It is hard to explain to people in that kind of heat the amp draw will exceed 4 amps over the RLA (rated load amps) (for JC ) on a unit then x 3 units with a 7500 or 8000 watts generator and the amps falling off because of the heat.
I tell them turn 1 off,one guy told me no way it would be to hot inside you could not make him understand so I told him to find a place along the river with shade and park till the sun goes down because I cannot help you it is what it is with your setup

Jim Blackwood · June 26, 2018, 06:04:52 PM

Makes a lot of sense Walter.
OK, so here's just a thought. Since going down the road the air higher up should usually be a little cooler, how about a roof scoop in the rear that is configured to run through your A/C evaporator? Might not be the simplest thing to do but it's undoubtedly possible and with enough thought there might even be a simple way to manage it.

If that worked it should counter the pressure pushing air in at the front and reduce the flow from front to rear so it seems like it should help with that. Plus if it provided fresh air through the A/C when parked maybe it'd help with the bathroom vent too. Pure speculation on my part and you guys would know better than I do, but it seems like something worth a little thought.

Jim