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paul65k 09-21-2020 02:43 PM

Quote:

Originally Posted by glennwest (Post 5449692)
I have mini splits. But a 24X24 would not fit anywhere in mine. The standard wall mount did. Bedroom had to put a cassette.

We actually have a wall that is next to the refrigerator and room over/on the headboard that we will be modifying.:thumb:

cwk 10-22-2020 07:49 PM

Based on some of the suggestions received so far... :bow::bow::bow:


I have been researching mini-splits. A family member just installed a 24K BTU unit in his 1100 sqft shop building. I had a chance to visit last weekend and listen to it in person. There is not much to hear! :cool:

All that I can say is Wow! It is quiet.

This past year I replaced the front roof A/C in our coach with a new 15K heatpump. It is quieter than the original roof A/C. But is still loud. I had planned on adding ductwork to diffuse the sound of the rushing air, but DW and I can still hear the compressor on the roof.

I listened to that 24K mini-split. It was cool outside, so we turned the heat on and played with the fan speeds inside. Wow. This thing is quiet: both inside and outside.

So, based on what I have learned so far, a mini-split system is probably in our future.


But, I still have a few questions.

Last night, while researching vendors online for a two-zone system (up-front and bedroom), I found a vendor that had a special on a "2-zone system" which was actually a sale for buying two single zone systems.

One of the benefits is that the units are 120V, not 240V like the larger 2-zone systems. Our coach does not currently have 240V. The Onan generator is 120V. We could use two Victron Inverters to create 240V. But that would mean a lot of rewiring, etc. Another benefit supposedly is that the two separate units should be more energy efficient than one larger system.

Also, last night, I read a post here on iRV2 with a comment that two separate systems would be more efficient as well. (Thanks to hclarkx.) Talk about timing. Both discoveries made within hours of each other? Hmm... :whistling:

The trick is where to place the outside units on a Class A. I am thinking about one unit where the current propane tank is. And, the other unit where the current gas furnaces are located. Measurements need to be taken to be sure, but that is the direction at this point. (Thanks again to the iRV2 member that pointed me in the direction of the Bus Conversion videos.)


QUESTION: How much difference will a higher SEER rating mean to me?

The goal is to be able to run the mini-splits as much as possible on SOLAR and LifeP04 batteries.


One vendor has a 9K BTU unit at 17 SEER, another at 22.8 SEER, another at 23 SEER, another at 25 SEER, and even one at 30.5 SEER.

I even found a 6K BTU unit at 33 SEER. (How many BTU's does a coach bedroom need anyway? (No slides, bedroom accessed by a side-hallway instead of an open bathroom plan)


And, while I am asking, how many BTU's does the front end of the coach need? No slides, 38' DP, adding 1/2" foam insulation to the walls, single-pane windows.

Thanks to everyone who has commented. Our remodeling plan is now much better for it. :bow:

paul65k 10-24-2020 11:21 AM

1 Attachment(s)
I've already wired my dual Victron 24/3000s for 220 and we have a dedicated sub panel and wiring for the future outdoor unit which will be in the former battery compartment (Lithiums were moved inside) on our 36'DP.

I plan to install the LG system which has the unique "Picture frame: heads that I'll be able to mount without needing to re-work or lose cabinet space. The plan is to use a 9K unit in the bedroom and a 12K unit in the front of the coach. From everything I've read the Mini-Split puts out much more cooling from lower sized units than comparable rooftop units.

The specs for both units running is actually a little lower than a single rooftop unit which I can currently run with full sun and our 1600W of solar.

I just wouldn't be able to make room for 2 outdoor units and setting up the inverters for split phase was really not a big wiring deal

It will be interesting to see how :thumb:both out installations come out:thumb:

hclarkx 10-24-2020 02:23 PM

Some thoughts .....
 
My son is in the process of installing a 6K and a 9K on his older Class A. I'm planning a 9K on my 30' 5er. Final decisions are yet to be made, but we are looking at the cost of additional solar and battery versus higher efficiency mini splits. He has four 6K Mitsubishi SEER 33 units on his small LA area home. I have two multi-splits and two mini splits on my northern CA home.

His home 6K Mitsubishi units draw something like 315 Watts at full output which can exceed 6K if it's not too hot out. The cost is about double what a 120V Mr. Cool or Pioneer costs and the outdoor unit is heavier IIRC. As for cost, the SEER 33 Mitsubishi is about twice what a Mr. Cool or Pioneer (SEER 22) costs, roughly $1600 vs $800, enough to buy 800W of panels per mini split. Or 1600W total. One might need more battery though that depends largely where and when one camps (whether overnight A/C is needed). Since these units don't need 800W in the first place, going with SEER 22 and more solar seems like the answer. The Mitsubishi does have a turn-down ratio of 4:1 but some of the less coslty units do as well. Others are 3 to 1 but that may be enough since our RVs are not well insulated. They all seem to be quiet. I don't think failure from potholes is likely, but the less costly units are less costly to replace if that happens. And the 120V units don't need a 120-240 transformer or a 240V inverter.

Son has room for an outdoor unit next to his diesel in the back. Other one will probably go in the up-front generator compartment since the generator will be replaced with a 35# 1kW inverter generator for the rare occasion of days of too many days inclement weather.

When I get the 9K mini split on my 5er I'll use solar for winter heat to the extent the sun is good, with propane as backup. So far I have no power connector and my electrical panel is wired only to my inverter. Fridge is a Nova Kool RFU9000. 1000W of solar is ample. I'll add 600W for the 9K mini split. My 300 AH battery is sufficient for the times and places we camp (don't need all-night cooling from the A/C).

As for the BTU/Hr for the front end of the DP, my son is planning 9K for his 34' DP. That is based more on gut feeling and experience with mini splits in room sizes and such than a technical analysis. One could attempt a "manual J" heat gain analysis but it would be rough. The furniture along the walls and cabinets and such provide considerable insulation. Generally 9K is enough for up around 300 square feet in a home and should do fine with an 8x12 RV front end (100 square feet). A curtain mid cabin would somewhat confine the cooling if need be.

Do you have a spreadsheet program? I can send you a spreadsheet that will help in planning. It even models two different A/C units with different daily and seasonal usage patterns (cooling and heating). It helps calculate your current and future load if needed, takes into account where and when you camp, representative weather patterns (think multiple cloudy days), etc. etc. It will even help you size the auxiliary generator for the rare inclement weather need. And tell you how often you will use it (more battery and more solar equals less frequent use). PM me if you'd like to have the spreadsheet.

Have you looked at the Secor/Danfoss 12V fridges? Some are pretty fancy. Potentially save a lot of energy over a residential unit. My 9.1 cu ft (probably smaller than you would want .. there may be larger ones available) uses around 40 AH per day. I added considerable insulation to greatly reduce the energy use. It needs only about 50 AH of battery and 200 W of solar.

Give me a call if you wish ....... 916.426.6802.

hclarkx 10-24-2020 03:10 PM

Quote:

Originally Posted by cwk (Post 5445834)
OP here.


Floor Heat: Looking at a 120VAC mat system to be installed over the existing 3/4" marine plywood floor. Then, probably engineered wood, or some type of vinyl flooring (no carpet). DW is still in the interior design phase. I priced a 24V mat system from one supplier. The price was about 5K, just for the parts. I would be providing the labor, but I still thought this was high. 120VAC pricing appears to be much more reasonable.

Have you looked closer at this? I'm thinking that resistance heat uses 1 kW per kW of heat. A heatpump (COP=4) uses 1 kW to produce up around 4 kW of heat. So about 1/4 of the solar to produce the same heat.

jcussen 10-24-2020 03:19 PM

Actually resistance heat is about 5100 btus for about 15 amps at 120 volts. A rooftop heat pump will produce over 12000 btu's at the same amperage and voltage. I imagine a mini-split unit would be even more efficient.

hclarkx 10-24-2020 03:42 PM

Quote:

Originally Posted by jcussen (Post 5493389)
Actually resistance heat is about 5100 btus for about 15 amps at 120 volts. A rooftop heat pump will produce over 12000 btu's at the same amperage and voltage. I imagine a mini-split unit would be even more efficient.

I haven't looked at rooftop heatpumps lately, but early on they didn't seem worthwhile. And in my case I needed the roof space for solar. I've been without A/C for six years ... but being retired, I can avoid hot places.

15 x 120 is about 1800 Watts (ignoring power factor). Even a low-end 9K mini split needs well less than half of that (around 700W I think). A pair of 6K Mitsubishi SEER 33 at 315 Watts would provide 12,000 BTU/Hr for 630 Watts.

It's surprising that mini split heat pumps haven't gained more favor among the RV manufacturers. Or in new homes for that matter. My daughter bought an expensive new home recently and heat pumps were not an option. I converted my 47 year-old house to heat pumps and am heating and cooling for considerably less than the 10 year old SEER 14 package unit needed for just cooling (we are not in snow country, but do see low 20's in January).

jcussen 10-24-2020 04:03 PM

Quote:

Originally Posted by hclarkx (Post 5493406)
I haven't looked at rooftop heatpumps lately, but early on they didn't seem worthwhile. And in my case I needed the roof space for solar. I've been without A/C for six years ... but being retired, I can avoid hot places.

15 x 120 is about 1800 Watts (ignoring power factor). Even a low-end 9K mini split needs well less than half of that (around 700W I think). A pair of 6K Mitsubishi SEER 33 at 315 Watts would provide 12,000 BTU/Hr for 630 Watts.

It's surprising that mini split heat pumps haven't gained more favor among the RV manufacturers. Or in new homes for that matter. My daughter bought an expensive new home recently and heat pumps were not an option. I converted my 47 year-old house to heat pumps and am heating and cooling for considerably less than the 10 year old SEER 14 package unit needed for just cooling (we are not in snow country, but do see low 20's in January).

Actually they are getting more efficient in heat pump mode, this one puts out 15000 btu's.
https://www.recpro.com/rv-air-condit...P6cCBoCkCwQAvD

But agree none approaches the efficiency of a mini-split. Problem with motorhomes, no really good place to put the compressor/condenser unit without using up a lot of bay space.

hclarkx 10-26-2020 12:21 PM

Quote:

Originally Posted by Rocketman3 (Post 5437319)
For the 12 v side, I was think of putting one marine battery lead acid battery. Then using a 48v or 24v to 12 volt converter to run all the 12 v stuff. If my 12 v draw was more than the converter could handle - it would pull down the 12v battery a little. This way I keep the emergency battery assist to start the chassis engine.

I think this is a good idea. The power system in my Volt does exactly this ... albeit from a much higher voltage main battery. Some heavy 12V loads like tank heaters would probably dip into the battery. And you'd have the 12V battery to manage 12V loads for a few days should the DC-DC converter conk out.

Krbjmpr 10-27-2020 12:14 AM

Quote:

Originally Posted by hclarkx (Post 5496244)
I think this is a good idea. The power system in my Volt does exactly this ... albeit from a much higher voltage main battery. Some heavy 12V loads like tank heaters would probably dip into the battery. And you'd have the 12V battery to manage 12V loads for a few days should the DC-DC converter conk out.




As stated, and I know it wasn't your idea but Rocketman, I think this is a terrible idea.


We all consider our basic battery system to be 12v, but when everything is working as it should, voltage is actually 13.8-ish on converter and 14.2-ish off the alternator.


The DC-DC XXvolt to 12v converter (Buck Regulator) is going to put out 12volts and a few tenths. This won't be enough to keep the aux battery charged. 12.6v (or 12.8, I forget) is full charge voltage on a battery at rest. 12v on a battery at rest is dead (20% I think). You need a converter that is capable of at least 13.2 (lead acid float voltage) and at least enough current capacity to run loads & charge battery. Personally, I would start at 50Amps. This is going to require a fairly exotic DC-DC Converter. They do exist, but mostly for electric golf cart market whose owners are running electric beer coolers, lighting, power steering (not kidding), and of course a heckuva sound system to listen to on way to next hole.

Krbjmpr 10-27-2020 12:32 AM

Not as exotic as I thought...


48 to 13.8 @ 30Amps $35.60

https://www.amazon.com/Converter-Reg...8vdc+Converter


24 to 13.8 @ 40Amps $31.99

https://www.amazon.com/Automatic-Con...8vdc+Converter


Wish these were available a few years ago. I Had to use a chain of 6v (6.5v) *isolated* converters to individually charge a battery bank consisting of (8) GC2 in series. Even then, I couldn't equalize without use of a generator.


Using the above converters, I would definitely be implementing this If I had a 24/36/48v battery bank. Lack of converters is the *only* reason why I am not using my Ancient but very reliable 5Kw Heart Interface sinewave inverter and a 36v battery bank. That will change as soon as I get battery box welded up, cables made, etc. when it warms up next Spring.

richard5933 10-27-2020 07:57 AM

Quote:

Originally Posted by Krbjmpr (Post 5497116)
Not as exotic as I thought...

...

24 to 13.8 @ 40Amps $31.99

https://www.amazon.com/Automatic-Con...8vdc+Converter

....


I used four of these to update the four circuits feeding my 12v headlights from a 24v chassis battery system. From the factory they used a resistor bank to drop the voltage, which resulted in the headlights having varying outputs as the engine speed changed.

These converters put out a constant 13.8v which is the ideal voltage for most 12v appliances used in the auto industry. Since most RV house batteries charge at this (or nearly this) voltage, it is a good voltage to use for running RV house systems.

I've driven many miles using these to power the headlights, which are on all the time, and there have been no problems. I could have used converters with lower capacity, but went with these to help keep the heat buildup down. I mounted them on a piece of 1/8" aluminum sheet which has an air gap under it to provide a way for heat to escape.

Ponobill 10-27-2020 09:24 AM

Some good solutions here, but i took a different course. In my motor home conversion all the house loads are supported with a 24V bus with local 12V converters to suit the load. Small converters are cheap and reliable, but mostly cheap. The only 12V battery I have is the engine battery and a lithium booster that floats on the AC system. The booster is just a portable unit that is removable if I need to give someone else a boost. I can engage it from the driver's seat with a toggle switch that closes a relay.



using 24V as the bus means the bus current is half, so the wiring doesn't need to be heavy. In retrospect I wished I'd done 48V, though the converters would be harder to come by. I have some small ones with adjustable output that are good to 3A output. I've been running them in a test rig for three months driving a full 13.5V 40W load 24/7. They barely get warm. I have larger converters up to 150W. I bought them mostly on Aliexpress, since they all come from China anyway.

Krbjmpr 10-27-2020 09:29 AM

Quote:

Originally Posted by richard5933 (Post 5497288)
I used four of these to update the four circuits feeding my 12v headlights from a 24v chassis battery system. From the factory they used a resistor bank to drop the voltage, which resulted in the headlights having varying outputs as the engine speed changed.

These converters put out a constant 13.8v which is the ideal voltage for most 12v appliances used in the auto industry. Since most RV house batteries charge at this (or nearly this) voltage, it is a good voltage to use for running RV house systems.

I've driven many miles using these to power the headlights, which are on all the time, and there have been no problems. I could have used converters with lower capacity, but went with these to help keep the heat buildup down. I mounted them on a piece of 1/8" aluminum sheet which has an air gap under it to provide a way for heat to escape.


Do you have the ability to measure current in and current out? I use several 12 > 6 and then 6 > 12 converters to feed my electronics (router, BR burner, drives, anything with 12v wallwart). This allows me to switch to 6vdc LIFE for extended outrages. I also use 12 > 24 for my winega rd WC3000 booster. I am seeing about an 80%, rated draw, to 90%, light load. I don't have anything that could pad a converter with a 55/60w continuous draw.


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