air conditioning / ac on batteries, generator to maintain charge

[Dockhead]

Originally Posted by xluke

Hello,
I was wondering if it is at all advisable to run a 16kbtu air conditioner from a large inverter while using a generator to keep the charge on the batteries (would only be one 130ampH battery) topped off. I have a 2kwatt generator that is unable to handle the surge of the generator, but also have an inverter that can handle the load, so this seemed like a reasonable approach. I'm concerned about killing the deep cycles, but perhaps this is not too much of an issue.

Anyone have any experience / suggestions about this?
Thanks!

It's a perfectly reasonable approach if the inverter has capacity adequate to cover the startup surge (most of them will support a much larger load for a short period of time, than their rated power), and if your batteries have enough power to cover the shortfall (doesn't take much for just a couple of seconds of load).

An even better approach is to use a charger/inverter which has a power boost feature -- which will pass through AC power but supplement this with inverter power when needed to make up short-term deficits. Mastervolt and Victron make these. I have a Victron Multiplus in my boat and it works a treat for this purpose. I don't have air conditioning, but I can easily pop breakers on 16 amp shore power circuits if I don't use this feature. I set the current limit on the Victron and it will not allow the electrical system to take more than that from shore power (or generator). It will invert power if someone, for example, switches on an electric kettle which on top of other loads exceeds shore power capacity. Works great. Would be perfect for air conditioning startup loads like in your case.

[sdowney717]

Here is the 5-2-1 three wire start assist you can buy and install yourself.

5-2-1 Compressor Saver CSRU2 Hard Start Capacitor 854046521353 | eBay

a 3 wire assist is better than 2 wire due to nature of the device which breaks the start circuit. EMF from the start winding of compressor provides power which takes the start capacitor out of the circuit when it has started running.

this guy shows why a 3 wire is better than the 2 wire.

Hard Start Test! Not all Hard Start Kits are the same! - YouTube

IF you already have a potential relay and start capacitor from factory, then the 2 wire start assist will work better than the video suggests. I have found that once the compressor has started turning a minute that it restarts on marginal power ok if it already has a start capacitor and potential relay.
But to be sure the three wire one which offers instant restarts is the better one to get.

Apparently not all factory AC heat pumps have a start capacitor with potential relay when new. They used to have it but eliminated these parts to save money!
521 Compressor Saver - Residential Installation Video - YouTube

[sdowney717]

Good info on the potential starting relay and capacitors.
HVACReducation.net's Tech Tips: THE POTENTIAL STARTING RELAY

A discussion on why spp6 may be better than spp6E if using a generator.
Motorhome Magazine Open Roads Forum: Tech Issues: Another Supco SPP6E Question with Coleman

Dometic responds on this forum about start kits.
http://www.sailnet.com/forums/gear-m...tioning-3.html

Supco products list
http://www.supco.com/images/09%20rel...hardstarts.pdf