Smaller AC in bedroom?

[96 EVO]

Anyone with 3 heatpumps replace the bedroom unit with a lower BTU unit?

Our rig came with 15K-13.5K-15K Dometics. I don't need a 15K unit in the bedroom! I'm not hanging meat in there!

I was thinking maybe a 11K, which they advertise as 10 amp draw, which would give me a much better chance of being able to run two on a 30A shore connection.

[vito.a]

I have two 15K btu and one 13.5K btu Dometic Penguin A/C units.  I put the 13.5K unit on the bedroom and it works well. 

All these A/C units are connected by a duct that runs the full length of the motorhome.  I don't think I'd drop below a 13.5K unit as the duct over pressure from the two 15K units would over power it.  

Additionally, your electrical power draw challenge is during A/C startup, not running.  

[96 EVO]

2 minutes ago, vito.a said:

 

Additionally, your electrical power draw challenge is during A/C startup, not running.  

Na, I tried running a 15 and 13.5 together at home once and after an hour or so I was drawing 28A, and melting an extension plug.

[MyronTruex]

During the plague, I had to replace my 15K units with 13.5K units. I cannot tell the difference in cooling. I have done  some serious duct work and air flow improvements for sure. 

[96 EVO]

Myron, I can't tell the difference between 13.5 and 15K units either. That's output nor power draw!

[Tom Cherry]

Not quite sure what the objective is or the final solution.

• All three of the units are working now...? Confirm Please
• You want to replace NOW, the working 15K unit in the bedroom with a 11K unit....Heat PUMP, I assume? Confirm Please
• Therefore you will need to install the DUMB DOWN adapter or Controller (AC Board) and keep the OEM so that your 5 Button CCC MPX will work with the present control system.
• When one or more....of the OTHER TWO units FAILS...you will replace with the new CCC2 Penguins...and replace the Bedroom controller so that they all work off the CCC1 MPX system.

NOW a question...OR A THEORY...  Based on looking at YOUR 42 PDQ and MY 20 PDQ, the SHOWER SIDE has the DUCT WORK RUN BROKEN.  Hence the ROAD SIDE, where your Shower is, has the Bedroom Run Duct SHUT OFF at the wall (adjacent to the SHOWER.  THAT causes you to have the "Meat Locker effect in the Bedroom. 

Now, that also has a GOOD SIDE.  The Heat Pump in the Bedroom is WAY MORE efficient.  Not having the FULL Length duct work caused your Bedroom unit to run HOTTER...regardless of mode.  If you go up and pull the covers.  Use a Thermal (laser do) pyrometer.  Measure several points on the compressor and lines and such.  I can NOT remember the exact numbers...but the temps were at least 10...maybe 15 or more hotter in the REAR than in the FRONT.  PANICKED, was I, and Dometic said....NORMAL for a MONACO rig where they SHUT DOWN or closed ONE SIDE of the Full Length RUN. 

Will give you a LOT MORE Heat in HP mode....and you KNOW it overcools as it is.  I set my Bedroom about 2 or 3 degrees higher in cooling.  You HAVE THE LUXURY of 3 units.  So, you have 42.5 K in 42 Feet or about 1K per Foot.  Mine is way under that. I have 30K in 40 feet...or 0.75K per FOOT.  That is MARGINAL...

OK, from a THEORETICAL stand point.  The EMS is kicking or shutting OFF your Rear AC when you exceed the 30 Amp set point.  That is measured off the White Neutral.

If you really want to run BOTH AC's, then you need to rethink your Magnum setup.  When you are on 30 Amps...  turn DOWN the CHARGE PERCENTAGE (or whatever it is called) from 80% (which is where I run mine to keep from overworking the 15 YO Inverter.  Magnum sets it to a DEFAULT of 90%.  OK, on a NEW inverter....you can do 100%.  WHY?? All you are trying to do on 30 AMPS is "MAINTAIN".  One does NOT NEED 100%....  That only heats up the FET's and such and your Inverter runs WAY HOTTER....and HEAT is the death of them... PER MAGNUM.

SO, crank down the % Charge Rate to 30%.  Then, you SHOULD pull less current as the Magnum knows to SLOW DOWN..  

I'd experiment with that...  

Beyond that, and I have never had the need or the inclination to be TOTALLY Selfcontained and LIVE OFF THE GRID as well as NOT running the Genny.  I'd leave the AC's alone.  I'd spend the extra minute when I have to exist on 30 Amps cranking down the Magnum...and if that was NOT enough, I'd get rid of the crappy OEM solar. We have either 60 or 65 Watts...and it ain't NOWHERE near that (look at the controller)...60 Watts, in theory, gives you 5 Amps.  BUT, if you look at the Losses and such...a 60 probably only give a smidge, NEW, over 4 Amps.  Replace the old panel and add another one.  SAY 120 Amps.  You could THEN actually SHUT OFF the Charger (you can experiment right now...or set the Charge Rate to 10 or ZERO (if an option)...

You maintain your batteries.  The inverter doesn't PULL or use any power.  The incoming AC is being PASSED THROUGH the internal ATS. You give your old Charger a REST...It appreciates that and it runs COOLER.

That's my take.  We had one really "out there" member that added a 110 VAC Window Unit to his 06 Dynasty.  He HAD also added the SAME Intellitec 750 EMS like we have.  We THINK that is the ONLY Dynasty with the EMS....and NOT OEM.  SO, his solution.  He ran, while driving, the smaller window unit.  

Just a thought.  NOW....why NOT really go FAR OUT?  Replace the Bedroom.  Downgrade the rest.  That is a TOTAL of 38K...or you have 0.904 K per foot.  That is 21% MORE than the shorter TWO Foot SHORTER rigs..  If I had 20% MORE, I would be thrilled...and It would be comfortable.

SO...downsize....go ALL THE WAY..., you could EVEN downsize all of them to 13.5K and have 40.5 K or 0.964.  That would, with a reduced Charging Rate, I predict...even lay a small wager, solve your issue...

Things to think about.  

Your topic is interesting...but it involves just more than a "GUT FEEL" analysis and the idiosyncracies of the Monaco Ducting have to be taken into account...as well as whether you need the HP or the AC more or equally...BUT...the REAL solution.  Put the MH on a DIET...and turning down the Charging Rate is the simplest and most effective...

[Gary Cole]

The 15K and 13.5 K units could be using the same spec compressor. The rated capacity of an ac unit is a function several factors including evaporator and condenser size. I replaced one of my home heat pump compressors and noticed that Trane used the same size compressor on different rated models.

[96 EVO]

All 3 original unit's still working, just coming up with a plan for when the first one fails. Main objective would be to safely run 2 AC's on 30A shore.

It's been several years but pretty sure the time I ran two on my home 30A power, I had charging turned off, fridge on propane.

38 minutes ago, Gary Cole said:

The 15K and 13.5 K units could be using the same spec compressor. The rated capacity of an ac unit is a function several factors including evaporator and condenser size. I replaced one of my home heat pump compressors and noticed that Trane used the same size compressor on different rated models.

I'll have to look for that next time I have the covers off the 13.5 and one of the 15's at the same time.

Edited July 11 by 96 EVO

[CAT Stephen]

@96 EVO,

 

If your goal is to run two on a 30A shore connection, don't downsize your ACs.  Just install one (1) soft starter per AC:

- https://softstartusa.com/ssrv-product/

 

I am not affiliated with the company above.  But, I do own their soft starters for both of my ACs so that I can run both A/Cs on a 30A circuit with power to spare.

[amphi_sc]

One thing I do (plan B) to get by for a little bit longer on 30 amp during moderately warm days is TURN OFF the main breaker to the inverter sub-panel and thus run the entire house interior (TV, lights, fridge, etc) on the batteries-inverter sub-panel, and therefore all incoming 120v can be directed to the A/Cs.  Then at night, when it's cooler, I switch to one A/C and re-charge the batteries  overnight with the Magnum set to a 10 amp service (in fact I often have it set to 15 amp service most of the time anyway as the change in bulk/absorb current is minimal anyway). However when it gets really warm the sun heats up everything more and between the A/Cs drawing even more current as heat increases resistance and as the pedestal box also arms up from sun, it eventually exceeds the 30 amp breaker... and then plan C goes onto effect.  Plan B cutting the incoming current demand by one or two amps does make a difference in being able to keep two A/C's on ... and I may set thermostats so when 2nd starts to be needed more they both stay on so as to avoid the startup in-rush current of cycling.

YMMV 

[96 EVO]

I like the idea, but, wouldn't work for myself as they didn't give me an inverter sub-panel 🙁!

[jacwjames]

Prior to replacing both my Duotherm 13.5K BTU units I bought a remote camera do to a duct inspection.  I found 3 mouse holes and one duct seam that wasn't sealed.  Fixed all of those before installing the new 15K BTU Low Profile High Capacity Penguins. 

Proof is in the pudding, my wife was  plugged into a 30 amp service at a friends house in 95F temps in MI ~a month ago, no shade, and she was able to keep the coach cooled to 76F with one AC running.   I was able to help monitor via the MicroAir thermostat, I had set up alerts so when the inside temp got below 73F I'd get a notification. 

 

The previous owner of our coach rewired the rear AC.  put in an standard outlet for power supply and plug on the AC.  I suspect that he'd run an extension cord in through the window and run the rear AC on a 20 amp outlet.   So when I put in the new AC's I did the same thing to give me options.  Never know when I might need something like that. 

[amphi_sc]

I was thinking more about alternatives and creative solutions.  Similar to what Jim J has posted, I also have made some "modifications" to the standard factory wiring to help out in certain campground situations.  For example some CG pedestals have a 20a GFCI outlet along with a 30a.  While you can't use the cheater cords with a GFCI (And in general you really really really really need to understand potential overloading of the neutral wire with cheater cords) I have used that 20a GFCI to run an A/C (and BTW also load shared with the Aquahot via another Intelitec switching box typically used for the Washer and rear A/C) by completely isolating the circuit and switching via double pole center off properly rated switch.  (I ran a 12 gauge romex up to the "over the driver" electrical panels from behind the headlights.  The factory had a 2nd unused 14 gauge to the fridge area but 14 gauge is too small.)  However it should be noted some campgrounds power both the pedestal's 30 and 20 amp breakers from a common 30a breaker in their main home run box under the theory a camper is going to use one or the other.  Other CGs daisy chain pedestals, etc so you truly have a "box of chocolates" out there to deal with and may not know how the CG is wired.

Anyway, I was thinking about more options.  As the Penguins RATED draw is anywhere from 12.7a to 13.1a for the compressor PLUS 2.6a for the fan, the current for 2 units is really pushing a 30a breaker which will typically tolerate a slightly higher current for a limited period.  Just thinking about this theoretically here... First thought was perhaps a Magnum hybrid inverter instead of my MS2812 dual in dual out, but the hybrid would be more complex rewiring and seems to be single in single out ( https://www.magnum-dimensions.com/product-inverter/3000w-12vdc-pure-sine-hybrid-inverter-charger-msh-m-series ) So what about creating your own hybrid system of sorts for the 2nd A/C via the original inverter supplemented by a separate converter?  Could be cheaper and less re-wiring. i.e. in a two sub-panel setup such as mine and some other coaches ... flip off the 2 breakers to the Magnum 2812 so the batteries are running the normal coach loads and main panel is running 1 A/C, and also note the block heater receptacle also comes off that main panel. Install a properly rated double pole switch to toggle another A/C from the main panel powered by the pedestal to now coming from the sub-panel powered by the inverter.  The A/C load will draw down a battery bank but now suppose you use just a converter powered from the block heat receptacle to provide some simultaneous recharge.  Perhaps https://www.bestconverter.com/Boondocker-BD1265CL-65-Amp-4-Stage-ConverterCharger_p_671.html There are bigger converters but we want to keep the total pedestal load comfortably below 30a.  So fudging the 1 directly powered Penguin up to 17 amps if the voltage dropped to 110 and 85a DC @ 14.6 with 85% efficiency with a voltage drop could be about 10a from the block heater receptacle powering the converter... so maybe 27a pedestal draw. In my case I also have 600W of solar to also supplement the recharge. Perhaps should consider limiting the secondary converter to an absorb charge (lower non pulsed DC voltage) rather than bulk charging and soft start on the A/C to ease the inverter load. The Magnum 2812 will be working moderately hard some of the time but below the rated 2800w and peak 3900w spec.

In reality it is probably just better to just run the generator or get a true 50a site when it gets hot.  But in theory would something like this work?  I would think one would also have to consider the battery voltage drop supplying that many watts to the inverter.

Idle minds wander... a solution in search of a problem ...

Edited July 13 by amphi_sc

[MyronTruex]

Sorry it this has been covered.

With the Intellitec system on my 2008, it watches the current over a three hour period and if it gets close to the 30 amps over that period it will start shedding, and basically limiting you to about 24 amps before shedding.

I like  the idea of running the inverter if needed during the day to reduce the demand, even if only 2-3 amps. 

When I compared my 13.5 unit draw to my then 15K unit there was a few amps difference. I'm  running two 13.5's now and with the ductwork and Kool Air components and now our MCD shades we are staying quite comfortable here in Central Fl. 

[jacwjames]

Back story

In 2021 while on a trip my generator would not run, I was driving back home from a long trip so I could be by driving to keep house batteries up.  I have a residential refer so had to watch power.  I did some trouble shooting on the road and found the generator would stay running if I shut off power to main power panel turning off the 50 amp breaker.  So I thought it had something to do with the inverter.  When I got home I did some checking, ohm readings etc on the inverter 120 volt circuits, called Trace support line and the person I talked to said "your inverter is bad" and it has to be replaced and gave me all the info on what I'd need.  On a whim I contacted a shop near Nashville that does Trace repairs, explained what happened, what readings I had >>>> he said "nothing wrong with the inverter, your problem is downstream".  He gave me some tips on troubleshooting.  So put inverter back in and followed his steps, I shut off all breakers and turned on the 50, then other breakers on circuits not tied to inverter, turn on the two 30 amp breakers feeding inverter so far so good, all stayed on.  Then one by one I turned on each breaker in the sub panel, finally when I flipped on the breaker for the bedroom outlets the generator died.  Funny that it was fine on shore power, the generator much have been sensing a slight problem in the circuit.  So I dove into the circuit and found I had a short in the ceiling, I think mice got it.  Had to rewire circuit to make everything work.

 

So I decided that I wanted to add a smaller backup inverter.  Year's ago while Yahoo Groups a member Bill G posted on how he installed a second inverter as a backup and also to improving charging while running generator.  See attached

So I did something similar, I installed a 1000W PSW inverter in the old TV cabinet in the bedroom.  I used the Block heater circuit off main panel, but I wanted to still be able to use it so put an outlet in the cabinet going to the block heater and a plug on the wire coming form main panel.  Then a plug going to the inverter.  On the inverter I used a power strip I could plug in the power going to the refrigerator and other small loads.  And if I want I can use it to help charge the batteries.

2nd inverter from Yahoo Monacoers.docx

[Robert92867]

I like the 11k BTU unit in my bedroom.  It's a lot quieter than the 13K in the front.

[96 EVO]

31 minutes ago, Robert92867 said:

I like the 11k BTU unit in my bedroom.  It's a lot quieter than the 13K in the front.

Do you know if it 'really' only draws 10A in real life operation?

[Robert92867]

In 110 degree heat it pulled 12A, last week in Nevada.  That is the original 2002 unit.

[96 EVO]

2 hours ago, Robert92867 said:

In 110 degree heat it pulled 12A, last week in Nevada.  That is the original 2002 unit.

Thanks!

My 15K unit's are pulling about 15A after running a couple of hours, and that's on gen power, where the power supply isn't dropping below 116V.

{edit} My bad... I got my amp reading while I was on 30A shore power with voltage about 112V. I have no way of reading individual amp draw while on my 10KW generator!

Edited July 18 by 96 EVO

[DBRV.0]

On 7/17/2024 at 8:30 PM, 96 EVO said:

I have no way of reading individual amp draw

Do you have an AC amp meter?  Personally, if I only had one, I would select a UNI-T because of size and features.  They are not expensive and very popular.  Clamp it on a wire, such as what might be available behind the interior air intake screen.  Another location choice would be to remove the metal breaker box panel and clamp onto the circuit breaker wire there if the AC is the only load on that circuit.  Of course, if curious, it can also be used to check amps coming out of the generator, say, for analysis info.

[96 EVO]

28 minutes ago, DBRV.0 said:

Do you have an AC amp meter?  Personally, if I only had one, I would select a UNI-T because of size and features.  They are not expensive and very popular.  Clamp it on a wire, such as what might be available behind the interior air intake screen.  Another location choice would be to remove the metal breaker box panel and clamp onto the circuit breaker wire there if the AC is the only load on that circuit.  Of course, if curious, it can also be used to check amps coming out of the generator, say, for analysis info.

I guess I should have said, "I have no 'easy' way of reading the amp draws on gen power", as in glancing at my EMS panel 😁!

I have that very DVM in the coach!

[DBRV.0]

23 hours ago, 96 EVO said:

as in glancing at my EMS panel

Sounds like you might want to search for "amp meter for generator".  There are multiple choices.

[Tom Cherry]

51 minutes ago, DBRV.0 said:

Sounds like you might want to search for "amp meter for generator".  There are multiple choices.

YES and NO.  Specifically, in order to measure the AMPS of each line of the Generator...and that is the 120 VAC TWO line Onan 7.5/8.0 or the 240 VAC Onan 10.12.5....you have to get to the GENERATOR line or the Cable (Romex #6 - THREE conductors and GROUND).  It can be done on the Generator SIDE, but you would have to have UNHOOK it from the ATS.  THEN find a place, near the ATS that you can install a Plastic Junction box.  You strip back the Romex jacket and use strain relief connectors.  The Romex is fed into the J-Box (plastic) and then each of the coils below are slid one.  One of RED and the other on BLACK. Then you need a short section of Plastic flex conduit...called SEALTITE or what is being used as the "Conduit" for the incoming Romex into the ATS.  Then you run the Coil leads up and into wherever you want to mount the gauges.

Here is a cheapie....but the concept is the same...

2 Pieces AC Current Voltage Amperage Power Energy Panel Meter LCD Digital Display Ammeter Voltmeter Multimeter with Split Core Current Transformer CT AC 80-260V 100A Multi-Function Power Monitor

This one DOES have the separating coil or current rings....so it would work....see the last comment.

NOW, I did not see any of the "cheapies" on Amazon that were designed for our environment.  I like to see the power on my CONTROL PANEL (inverter remote and such).

THERE are some on Amazon that would work....not ideally suited for me...but would do the trick.

If you pulled OFF the main panel cover...then the two HOT Leads are exposed.  If you found a meter (BUY two) that has the CLIP on or spring apart COIL or Current Tap, then you could snap that around each lead, hopefully have enough wire so that the remotes could be mounted BELOW (I THINK the 50 Amp is bottom fed). Then, you could install the meters and snake the meter leads through a little Dremel tool notch. The one from Amazon should work.  NO CUTTING or such.

Then, regardless of source...AC or GENNY, you have a direct lead.  My Progressive HW50C has internal current taps. The Digital remote display has three screens that toggle or go through their cycle every 5 seconds or so.  So I get REAL time telemetrey on each leg and the overall system and any error coded.

That's the SIMPLEST.  NOW there are kits that are specifically made for power reading in a commercial application.  $500 is the minimum I saw...

Hope this helps... 

[96 EVO]

Yeah, I'm certainly not $500 curious what my amp draw is with a 10KW generator running!

[Tom Cherry]

3 hours ago, 96 EVO said:

Yeah, I'm certainly not $500 curious what my amp draw is with a 10KW generator running!

GEE, BEN, I thought you would find that a bargain.  LOL. 

However, the $35 Amazon really looks like it would work if you can find a place to mount or put the meters.  Knowing your Main Panel, the #6 leads are easy to snap the Torodol coils or rings or taps on.  Then a little notch, from a file would clear the small wire.  

It is actually pretty neat.  I use my HW50C display all the time....but don't worry about the Genny as I never exceed the 70 Amps on the EMS, as that is the max for the neutral, which is what that is measuring.  The technology and implementation is really simple....once I started googling.

Let us know if you add one.  Pictures are always nice...