4 Curious Georges' 2001 Saf-T-Liner

[cadillackid]

this rocks!!!!! Lovin the fact you got both splits running!!! its pretty warm so the heat mode wont piull as much current as it will when its colder outside.. my units in high heat when its in the teens or 20s out are when they oull the most. as the comporessor and outdoor fan go max speed.. your compressors were never even close to 80% in the warm humid conditions experienced right now.. im assuming you guys have been wet like us.. that wet air is perfect for heating as the uniuts condense that water out on the outdoor coild which makes a LOT of heat easily.. thats a nice inverter.. is it a regular 12 volt to 120 volt inverter or is it one designed for solar and all that? just curious if it is something i should have in my setup.. I have a genny. though ive never used it much.. when my bus is on the alternator charges my batteries.. i dont have solar..
-Christopher

[sojourner]

Just got caught up with your build. Keep up the good work!! Lookin' and workin' good!!

[synestine]

I'm considering a fridge about that size for my project. Is yours AC? If so are you running it on the same inverter or a separate one? Are you planning on adding any additional insulation around the fridge (with consideration for the compressor and coils) or is that a bad idea? In my plans I want to minimize the duty cycle as much as possible.

Sent from my Nexus 7 using Tapatalk

[david.dgeorge07]

Originally Posted by synestine

I'm considering a fridge about that size for my project. Is yours AC? If so are you running it on the same inverter or a separate one? Are you planning on adding any additional insulation around the fridge (with consideration for the compressor and coils) or is that a bad idea? In my plans I want to minimize the duty cycle as much as possible.

Sent from my Nexus 7 using Tapatalk

Yes, AC. Had considered extra insulation a little, but not seriously. This one has no exposed coils so I’m not sure what parts would need to stay free and where to insulate.

[cadillackid]

Originally Posted by david.dgeorge07

Yes, AC. Had considered extra insulation a little, but not seriously. This one has no exposed coils so I’m not sure what parts would need to stay free and where to insulate.

without exposed coils it either is using the outer shell as its condensor or it has a fan that blows the heat out from underneath.. if it has the fan then you need to make sure you dont box that unit in too permantently as you need to be able to pull it out to clean the coils.. usually in the back on the bottom..

be sure to keep the inside of the bus withing the normal limits listed in the book for that frig.. residential fridges have a lower operating range of temperatures than RV frig's, if the bus get too hot inside the frig may just decide to turn off.. usually residential frig are good up to 95-100 ambient temp but no more than that. (if that).. RV frig's usually have higher temperature operating abilities.. . the books that came with it should tell you if you need clearance around it or not.
-Christopher

[Dave in Tucson]

Originally Posted by david.dgeorge07

Does this make any sense? I hope so...

Does to me, but I've always been a scrap paper Sketcher!

[david.dgeorge07]

Originally Posted by cadillackid

thats a nice inverter.. is it a regular 12 volt to 120 volt inverter or is it one designed for solar and all that? just curious if it is something i should have in my setup.. I have a genny. though ive never used it much.. when my bus is on the alternator charges my batteries.. i dont have solar..
-Christopher

It’s an inverter, charger, and automatic transfer switch. Not specifically for solar, but is a nice unit for any system where you would like to charge your house batteries any time you have shore power. Sort of like a UPS it automatically switches back and forth between mains and battery power as conditions dictate and is always either charging or discharging batteries. I think it charges at up to 80 amps and has a sophisticated trickle/batt maintenance program. 2500 W continuous, 7500 for 30 seconds. I don’t have much to compare it with, but like it a lot.

[david.dgeorge07]

Originally Posted by Dave in Tucson

Does to me, but I've always been a scrap paper Sketcher!

Glad I’m not the only one!

[Dave in Tucson]

Originally Posted by david.dgeorge07

Got one of the units up and running! I have to say they said that these units were quiet that is an understatement. It’s taking a lot of work to get to this point but I couldn’t be happier with how this unit is performing and how the install in general seems to be working out.

The unit is cooling very well and even has features that I didn’t realize in addition to being both heat and air conditioning it also has a dehumidifier mode that leaves the ambient temperature the same but removes the moisture from the air. It had not occurred to me that units like this might have that feature but I would see it as being highly desirable in a bus environment where you may have condensation issues.

I did a check to see how much power it was using and I’ll need to do further testing to see how much it uses in various conditions but a while it was running on its initial cool down it was using about 650 W.

I ran it off my house batteries alone for about 5 to 10 minutes and it ran without any issue.

On the other unit we are trying to figure out if there’s a problem with the unit or a problem with the technicians equipment. It holds a nitrogen charge just fine but it went from holding a 600 µm vacuum to not even getting below one atmosphere of pressure within the course of just a few minutes. It seems possible that the vacuum pump is just going out. He left it with the nitrogen charge about 200 psi and is going to come back this weekend and see if it’s still holding that charge. If it is still holding the charge then will use a different vacuum pump to evacuate the system and then that system should hopefully be ready to run.

The whole bus cools pretty effectively with the single unit but it is noticeably colder at one end of the bus then the other especially while the bus is parked on somewhat of an incline.

So, I was going to ask what brand and model split you were using, but after looking at that tiny (on my phone) pic, I see it's a Pioneer. What size is it? And where are you putting the outside unit?

[david.dgeorge07]

Originally Posted by Dave in Tucson

So, I was going to ask what brand and model split you were using, but after looking at that tiny (on my phone) pic, I see it's a Pioneer. What size is it? And where are you putting the outside unit?

12000 BTU / 1 ton 17 SEER. Look earlier in my thread for a probably overly detailed answer about outdoor units/placements. But generally this:

[david.dgeorge07]

Big milestone today. Finished the electrical. Will have to tidy up a few things, but 120 V and 12 V systems are fully installed and fully functional!

[david.dgeorge07]

OK so someone else help me out here. Last night after a mild day the temperature dropped quite significantly and hit the dewpoint early in the evening it was very humid and dew was everywhere. I was running my mini split heat pumps for in heat mode and began to notice areas in my wood ceiling where condensation was coming through from the ribs of the bus. Also in the portions of the bus where I have not gotten ceiling panels up yet the ribs of the bus we’re just hanging thick with water droplets. I decided to test the dehumidification mode on the minisplits and realized I didn’t know really how it worked. You can set the temperature still but not the fan speed. It never seems like it did much and the condensate lines stayed dry. I don’t know if this is just because the conditions were not very good for dehumidification or what. I ended up switching over to propane heat with the vented furnace that I’ve got to try to lower the humidity. Is this a situation you think I will encounter a lot, or just in high humidity situations? I’m trying to decide if I should pull down ceiling panels and try to add some thin insulation on the ribs of the bus to help not down condensation. I did not think that it would be able to condense right through the wood of my ceiling panels. I guess I just assumed that the wood would be enough of a buffer to keep that from happening.

[Twigg]

You are never going to eliminate condensation, not entirely, but you can mitigate the problem.

So condensation happens when the air is saturated and it meets a cold surface. At that surface the air can't hold as much water vapor as warmer air, and it settles out on the surface. This you already know

There are a number of ways to reduce it. One way is to increase the temperature inside so that the air can hold more moisture ... but you can't warm the frame up enough, so you have to isolate the inside from the outside.

This is why we insulate, and also why so many pretty-looking conversions are virtually uninhabitable because people insist on leaving in the OE walls and ceilings. Personally I think they are just being lazy and that's fine, it's their bus. But don't then ask for $30k on Facebook when you want to sell it.

Part of insulating is breaking any and all of the thermal bridges that you can, and it's difficult. You are correct in that the wood framing on the ribs does that at least in part. I prefer a layered approach, where the first layer is screwed to the ribs for a solid anchor, then subsequent layers are glued to the first. Thin strips of plywood works well. Every where a screw goes from inside to a rib, you have a problem. Adding a thin layer of insulation at that point would help, but mechanically it's difficult to achieve.

Second method is ventilation. The outside air is cooler and contains less moisture. Good ventilation helps although it does increase the heating bill. Ventilation is more important than trying to reduce the moisture with things like dehumidifiers. Those things cost a fortune to run and don't really do a great deal.

Third is preventing the moisture in the first place. You can't easily quit breathing, but takings a shower, cooking indoors and heating with open-flame propane, especially when humidity is high are all things you can try to avoid.

At many times of the year condensation isn't an issue. In very dry climates it isn't much of an issue, but there are just those times when all you can do is reduce it. Making sure the bus thoroughly dries out between times will help a lot.

There are those days when the inside of my workshop looks like it has flooded. This happens when the warm and moist outside air is warmer than the inside of the workshop. The entire shop sweats and can only be fixed by heating it. You can do the same with the bus. Get it warm inside and when the outside conditions improve you will drive all the moisture out.

Hope that helps. I know it isn't a solution, because there really isn't a solution, just steps you can take to reduce the issue. I'm sure others will have ideas too, and I'll be reading to learn some.

[david.dgeorge07]

Great info! I have isolated most screw thermal transfer via a wood block. Does anyone know if heat pump heat can add humidity? Maybe I have a blocked condensate drain so it is blowing moisture back in?

[cadillackid]

Originally Posted by david.dgeorge07

Great info! I have isolated most screw thermal transfer via a wood block. Does anyone know if heat pump heat can add humidity? Maybe I have a blocked condensate drain so it is blowing moisture back in?

heat pump heat does not add humidity except when it goes to defrost.. in defrost the minisplit, closes the air vent door, shuts off the fans and goes into A/C mode.. the outdoor coils are warmed by refrigerant being compressed and heat stored in the accumulator... the indoor coil will drop cold.. very cold.. ive seen my indoor coil go as cold as minus 5, that will create condensation in all but the dryest conditions... when the outdoor unit deforst cycle completes.. the unit returns to heat, warming the indoor coil.. any condensation which formed on that coil will be blown into the room. (usually minimal but if you were showering / cooking, or its snowing outside it could be a bit more).. you'll get a wet smell from the unit for the first minute or two until the condensation blows off..

now other thing.. if you in your testing were running the A/C, those coils get wet.. then you switch it over to heat.. you are going to blow that water into the room... once the coils are dry they will stay that way.. but any water in the pan that hasnt drained will need to evaporate as well..

most times in a Home you arent switching from heat to cool and cool to heat multiple times per day like in testing a new setup... im guessing in your bus on days where you heat you arent likely to A/C and vice versa unless you are very poorly insulated then I could see scenerios where you are switching back and forth in the same day which could easily cause condensation issues with left over water on the coils..

-Christopher

[david.dgeorge07]

Well this showed up today!

[david.dgeorge07]

I shot GoPro video tonight of both units turned off while driving so I could see how the fans would freewheel. I only got up to about 45 mph but fans didn’t do much at all and the units ran fine when testing while driving. More tests to come.

[Dave in Tucson]

Congratulations on the propane tank that's similar to what planning for my bus on the heat pump have you thought about putting some kind of windscreen in front of it

[Dave in Tucson]

Sorry about the punctuation in the last post. My phone is wierding out on me, and the only way it would let me post was by voice. Disabled now. When I looked at your outside unit post last night, I was wondering if you needed to protect it from the airstream. Apparently not?

[PNW_Steve]

David,

Thank you for taking the time and effort to document your progress. You are a trail blazer.

Many of us will be benefit from your thread!!

Thanks again.

S.