Easiest solution to provide generator "boost" for HVAC peak inrush

[time2roll]

You would think there would be a market for a portable generator booster which could plug into any generator output and serve as a passthrough unit until such time as a short term boost is needed. Then, an included battery/inverter combo could provide the boost and then return to charge/passthrough mode. I bet this would sell like hotcakes.

Need to be more than a milk-crate build. More like a battery wagon

 

[solar8484]

You would think there would be a market for a portable generator booster which could plug into any generator output and serve as a passthrough unit until such time as a short term boost is needed. Then, an included battery/inverter combo could provide the boost and then return to charge/passthrough mode. I bet this would sell like hotcakes.

And cost $100

 

[solar8484]

I heard these are selling like hotcakes ...

9500 Watt SUPER QUIET Inverter Generator with CO SECURE Technology

Amazing deals on this 9500W Co Secure Inverter Generator at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[Browse]

I heard these are selling like hotcakes ...

9500 Watt SUPER QUIET Inverter Generator with CO SECURE Technology

Amazing deals on this 9500W Co Secure Inverter Generator at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

Running two generators in parallel is a possibility but there are numerous drawbacks. Excess noise, excess fuel...most of which is being wasted except when the AC cycles on. A battery inverter generator for parallel usage with a gas inverter generator would be the most efficient, especially if you could have a set point to activate battery "boost". I don't think the battery or the inverter would have to be excessive in size if used for a second or two.

 

[solar8484]

Running two generators in parallel is a possibility but there are numerous drawbacks. Excess noise, excess fuel...most of which is being wasted except when the AC cycles on. A battery inverter generator for parallel usage with a gas inverter generator would be the most efficient, especially if you could have a set point to activate battery "boost". I don't think the battery or the inverter would have to be excessive in size if used for a second or two.

There are definitely tradeoffs with generators. The battery/inverter booster you want already exists as others have pointed out. Cotek and Victron sell inverters that have the generator power assist function you want. So, I assume the issue is cost? Since you just need the battery/inverter to provide short surge power then you may be able to get away with an undersized battery bank at lower cost but the total cost is likely still more than a generator of equal power capacity. How much is avoiding the generator noise and fuel waste worth to you?

 

[Browse]

Cost is an issue in principle since a second unit in parallel (or for boost) wouldn't be used much unless the weather required it. I suppose you could look at it as extra "insurance" cost...or having a backup generator in case the primary unit failed. I could buy a second Honda and not use it unless it was needed, but that is another $5k just sitting around in the garage. At least they have good resale value though.

The Victron Multiplus looks like it would be just as (if not more) expensive since I'd require 2 units for split phase, plus a large battery to provide the boost current.

I suppose I could also consider paralleling a smaller Honda like this guy did but I don't think Honda advises it and it could potentially be bad for the inverter module:

 

[psycaz]

The resale on the Honda’s seem to be great.

If going second generator to run parallel, just make sure you buy what you will need to run the hvac. 55 amps looks like you’d need another 7000is for paralleling.

 

[solar8484]

Cost is an issue in principle since a second unit in parallel (or for boost) wouldn't be used much unless the weather required it. I suppose you could look at it as extra "insurance" cost...or having a backup generator in case the primary unit failed. I could buy a second Honda and not use it unless it was needed, but that is another $5k just sitting around in the garage. At least they have good resale value though.

The Victron Multiplus looks like it would be just as (if not more) expensive since I'd require 2 units for split phase, plus a large battery to provide the boost current.

I suppose I could also consider paralleling a smaller Honda like this guy did but I don't think Honda advises it and it could potentially be bad for the inverter module:

Yep, "insurance" is not cheap. That's why I mentioned portable A/C. You can get a couple for < $1K for the few times that you need some A/C.

 

[Browse]

Yep, "insurance" is not cheap. That's why I mentioned portable A/C. You can get a couple for < $1K for the few times that you need some A/C.

This is probably the most sensible and least expensive approach.

One thing I hadn't considered about the Ecoflow units is that even though they claim a short term surge capability higher than their continuous rating, it isn't clear if they retain this capability when also being charged. Would 100% of the power from an external generator go into battery charging or is it passed through to the load? I'll have to ask Ecoflow how this is handled, but either way it's not looking like Ecoflow would be an economical solution.

 

[solar8484]

This is probably the most sensible and least expensive approach.

One thing I hadn't considered about the Ecoflow units is that even though they claim a short term surge capability higher than their continuous rating, it isn't clear if they retain this capability when also being charged. Would 100% of the power from an external generator go into battery charging or is it passed through to the load? I'll have to ask Ecoflow how this is handled, but either way it's not looking like Ecoflow would be an economical solution.

All power stations have some surge capability but I don't think they have the generator power assist function. They have no chance of starting a 4-ton A/C by themselves.

 

[zephyranthes]

I have a 3 ton and 4 ton and have frequent power outages. I installed solar and will add batteries later but I never considered having use of either AC unit during an outage, even with soft start.

I installed a mini split in our bedroom to assist with cooling or heating that one room and then having the ability to power crucial loads. Power went out for 3.5 days in sub freezing temps. Froze my well, water softener system. Then in September, transformer fell off the pole down the block, lost power for 8 hours, ran mini, lights, wifi and a TV off a generator for 7 hours on 20 pound propane tank, no problem.

It might be cheaper to replace a casement window with a double hung and a window unit.

How long do you expect the power to be out? In the navy, we had rigging for reduced electric to conserve the batteries, and that was my mindset to run only the essential loads for freeze protection, water, food, light, heating/cooling one main room, and charging electronics and wifi.

 

[AstroBob]

I have a portable A/C I use to cool a 250sqFt room at my cabin when it's really hot. It was like ~$260. All of my windows are casement in that room. It works quite well to cool things off.

 

[redleg]

I have a Honda 240V inverter generator (EU7000IS) that I use to power my load center via interlock, 30A breaker and input box during power outages. The generator powers the whole house with the exception of my main HVAC unit. What would be the easiest and least expensive way to add a battery backup inverter solution which could pass through the power from the generator and also add power from the batteries during a power surge like when the HVAC compressor starts up? I was looking at the Victron Multiplus units, but they don't seem to have something for 240V that would handle a 60A 1 second surge. Also, what battery would you recommend for a setup like this? Thanks!

Have you thought about a soft start....

 

[jberger]

Redleg has it right in the response above, add an easy start and take the load off of the inverter when starting.

EasyStart™ Soft Starters

Buy an EasyStart™ today. Our product line offers the best-in-class soft starter for single-phase motors operating at 115-240VAC/50-60Hz, only available at Micro-Air. The unmatched performance and compressor-protection features allow you to start your air conditioner on a limited power source...

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[Paul_in _Berkeley]

You could upgrade the unit to inverter A/C one then you would have no high start current and a very efficient A/C.

If you're truly a hacker, you could add a $300 inverter to your existing compressor...you'd need to work the controls to do a very soft start... but you can get the inrush down to almost nothing. When the thermostat calls for cool, take 30 seconds to ramp that baby up to 60 Hz. If you want to get fancy, you can run it as two stage... most compressors can handle 80 Hz OK... or 40 Hz if you want turn down. Depends on whether recip or "centrifugal" (there's a different term of art). Online discussion about such mods for capacity control.

Paul