Front A/C while driving using SOLAR + ALTERNATOR

[NealC]

Kudos to C.Martin for his engineering of the system to drive with the front AC on SOLAR and not GEN. It's crazy hot and humid hear in the east with 100 deg temps. With Charlie's mod we use a 3 position switch near the circuit breaker panel in the 1/2 bath. I don't know if he's shared his design on the site yet but what we did was essentially add another breaker on the inverter side (20A I believe) to match the same amperage as the main bus side. The toggle switch ON/OFF/ON essentially allows you to choose where the power for the Air Conditioner is sourcing; Inverter or Main Bus.

What we do prior to driving is turn off the AC at the t-stat, go to the 3 way switch and switch to Inverter. Now turn on only the front AC (other AC's should be off as they are not powered). The inverter is now powering the front AC and when combined with the alternator it is sufficient, actually excess current required to support the demand, i.e. you can still charge but you will arrive fully charged per our 8 battery (FLA) config.

We installed the MicroAir EasyStart which is very easy to do. I had my first one done by an installer from the MicroAir web site, Charlie gave me the steps to do the rear AC on my own and I wish I had done the front one on my own, Charlie's plan was better in placement.

Anyways, it's very nice to have your T-STAT set to 73 (my preferred coach temp) and arrive cooled and not have to catch up on arrival. Keeps your critters (welcome and unwelcome) cool too.

Kudos to Charlie! If you have solar consider this great advantage awaiting you. I believe my front AC draws around 120-160 AMPS. I think the ALT will give you around 60 but Charlie can answer that better or someone else around here.

If you have a smaller solar array you can still benefit, you just have to watch your SOC to know when you can go no more. Do not do this without a ME-ARC/BMK setup, you need SOC.

[bruceisla]

Originally Posted by NealC

Kudos to C.Martin for his engineering of the system to drive with the front AC on SOLAR and not GEN. It's crazy hot and humid hear in the east with 100 deg temps. With Charlie's mod we use a 3 position switch near the circuit breaker panel in the 1/2 bath. I don't know if he's shared his design on the site yet but what we did was essentially add another breaker on the inverter side (20A I believe) to match the same amperage as the main bus side. The toggle switch ON/OFF/ON essentially allows you to choose where the power for the Air Conditioner is sourcing; Inverter or Main Bus.

What we do prior to driving is turn off the AC at the t-stat, go to the 3 way switch and switch to Inverter. Now turn on only the front AC (other AC's should be off as they are not powered). The inverter is now powering the front AC and when combined with the alternator it is sufficient, actually excess current required to support the demand, i.e. you can still charge but you will arrive fully charged per our 8 battery (FLA) config.

We installed the MicroAir EasyStart which is very easy to do. I had my first one done by an installer from the MicroAir web site, Charlie gave me the steps to do the rear AC on my own and I wish I had done the front one on my own, Charlie's plan was better in placement.

Anyways, it's very nice to have your T-STAT set to 73 (my preferred coach temp) and arrive cooled and not have to catch up on arrival. Keeps your critters (welcome and unwelcome) cool too.

Kudos to Charlie! If you have solar consider this great advantage awaiting you. I believe my front AC draws around 120-160 AMPS. I think the ALT will give you around 60 but Charlie can answer that better or someone else around here.

If you have a smaller solar array you can still benefit, you just have to watch your SOC to know when you can go no more. Do not do this without a ME-ARC/BMK setup, you need SOC.

We will assume a Pure Sine Wave Inverter. I run 2 (sometimes 3) A/C units plus reefer so I'll continue to run the genset. However, yourr method is a nice alternative for some folks.

[Ricci]

Hi - Just curious if the alternator supplied by Cummins is rated to run a constant load without overheating. It is possible that it can withstand it, but in general alternators for vehicles are not designed for long term heavy loads. When you look at commercial buses they generally use a different type of generator than what we have. Would a shortened life of an alternator outweigh the cost of diesel displaced?


Tom

[jharrell]

I can run my single 15,000 btu a/c off my inverter using alternator and solar as I also put a Micro air easytart on but as Ricci said not sure if my 175 amp alternator is really up to the continuous load, very hard to find continuous rating for them. I might upgrade my alternator one day to make sure it can handle the continuous load I don't like pushing it.

Instead I run my generator which is designed for the continuous load and with my Hybrid 3000 Magnum it still does load support VDC allowing the solar to contribute. I also replaced my combiner solenoid with a Blue Sea ACR unit with manual override so I can disconnect chassis and house when generator is on so the Magnum won't pull a bunch from the alternator too, just solar.

[Ricci]

Hi - I'd like to see someone of the folks with this set up place a remote temperature sensor on the alternator case to get a rough idea of what's going on back there. It sounds like a great idea but not at the expense of an alternator. I really hope it is feasible. I'd guess we are on the edge of lots of changes in how our RVs are powered, both electrically and propulsion wise.


Tom

[redbaron73]

Why pay $300 for a capacitor? Even the dometic version is only $45.00. I put the hard start kit on all my units to run 3 units on 30amp service. Works wonders.

[jharrell]

Originally Posted by redbaron73

Why pay $300 for a capacitor? Even the dometic version is only $45.00. I put the hard start kit on all my units to run 3 units on 30amp service. Works wonders.

A soft starter is not a hard start capacitor, the Micro-air reduces start surge much more by slowly ramping up compressor voltage and staggers blower start and compressor start. A hard start capacitor can actually increase start current.

You can run a RV ac off a 2000w inverter generator with a Micro-air

You can see a comparison of hard start draw and micro-air here:

https://www.youtube.com/watch?v=soP0uZFd0nQs

[redbaron73]

Wow, that makes sense. They are controlling the motor speed by adjusting the frequency of the 120 , ramping it up to 60hz....that is genius.

Ok, now I am sold, and will be buying a set of these.

[jcussen]

Originally Posted by redbaron73

Why pay $300 for a capacitor? Even the dometic version is only $45.00. I put the hard start kit on all my units to run 3 units on 30amp service. Works wonders.

You can run 3 roof air units on 30 amp service?

[redbaron73]

Originally Posted by jcussen

You can run 3 roof air units on 30 amp service?

Yes, but only with inverter assist. I have had many times where the power manager was shutting down and I couldn't figure out why. This was happening even with 2 units.

The reason above explains it. The large draw still happens, just very quickly. This mod will keep the spike from happening.

On 30amp, ems is preventing zone 3 from running while zones 1 and 2 run, so never do all 3 run on 30amp at same time, but they can cycle amongst themselves.

I keep bedroom at 68 and front 2 at 73. Once front reaches cool point, bedroom unit takes over.

[jharrell]

Originally Posted by jcussen

You can run 3 roof air units on 30 amp service?

Yes that seems far fetched, i have been debating adding a second A/C to my 30 amp coach and I might get away with it if I get a power saver unit and put a soft start on it my 15k unit draw around 15 amps running.

[redbaron73]

Originally Posted by jharrell

Yes that seems far fetched, i have been debating adding a second A/C to my 30 amp coach and I might get away with it if I get a power saver unit and put a soft start on it my 15k unit draw around 15 amps running.

Without inverter assist and ems, you cannot run these. Newmar provides both and that allows it to work as I described. It is more than just the capacitor, and now I am learning that the capacitor did not do anything to help.

[jcussen]

Originally Posted by jharrell

Yes that seems far fetched, i have been debating adding a second A/C to my 30 amp coach and I might get away with it if I get a power saver unit and put a soft start on it my 15k unit draw around 15 amps running.

Appears he has EMS which will not allow all three to run the same time.
I can run 2 on 30 amps. start rear unit and set at 60 f. and low speed fan. Then start front unit [with micro-air] set at 75 f.
Front will cycle on temp and rear runs continuously. Of course charger off, and fridge on propane. Do check the plug, mine was getting pretty warm and had to clean it up.

[richpatty]

Originally Posted by NealC

Kudos to C.Martin for his engineering of the system to drive with the front AC on SOLAR and not GEN. It's crazy hot and humid hear in the east with 100 deg temps. With Charlie's mod we use a 3 position switch near the circuit breaker panel in the 1/2 bath. I don't know if he's shared his design on the site yet but what we did was essentially add another breaker on the inverter side (20A I believe) to match the same amperage as the main bus side. The toggle switch ON/OFF/ON essentially allows you to choose where the power for the Air Conditioner is sourcing; Inverter or Main Bus.

What we do prior to driving is turn off the AC at the t-stat, go to the 3 way switch and switch to Inverter. Now turn on only the front AC (other AC's should be off as they are not powered). The inverter is now powering the front AC and when combined with the alternator it is sufficient, actually excess current urequired to support the demand, i.e. you can still chalrge but you will arrive fully charged per our 8 battery (FLA) config.

We installed the MicroAir EasyStart which is very easy to do. I had my first one done by an installer from the MicroAir web site, Charlie gave me the steps to do the rear AC on my own and I wish I had done the front one on my own, Charlie's plan was better in placement.

Anyways, it's very nice to have your T-STAT set to 73 (my preferred coach temp) and arrive cooled and not have to catch up on arrival. Keeps your critters (welcome and unwelcome) cool too.

Kudos to Charlie! If you have solar consider this great advantage awaiting you. I believe my front AC draws around 120-160 AMPS. I think the ALT will give you around 60 but Charlie can answer that better or someone else around here.

If you have a smaller solar array you can still benefit, you just have to watch your SOC to know when you can go no more. Do not do this without a ME-ARC/BMK setup, you need SOC.

As a another fellow student of Charlie, I also performed this modification and used it for the first time yesterday. Drove for three hours with the front AC on with no need for the generator. Between the solar (was a nice sunny day) and the engine alternator, the system kept up. You should arrive fully charged (especially if you left at 100% SOC). We even stopped for 20-30 minutes at a rest area for lunch and although the SOC started dropping (as you would expect) we were able to let the AC run without supplementing with the generator.

Bottom line, this is a pretty clever idea and it seems to work very well. You do need a Soft Start on the AC unit, but the rest is wiring and a few parts. And although Neal has more solar than I, it still worked just fine.

Thanks again to Charlie for all of his assistance with this mod and for his patience with my questions.

Thanks to Neal for putting together the details for everyone.