Wiring dedicated inverter for new AC only fridge

[kthoennes]

You electricity guys are always such killjoys.

 

[luna]

Jeff.

I don't get it either.

If someone wants to run the refer. only on a dedicated small inverter and experience the losses from battery charging, and inverting whenever the refer. is on, versus running it off of the grid likely 80 percent of the time and off a 3kW inverter the remaining 20 percent of the time, then have at it.

Remember, 20 percent of the time is 1752 hours or 73 days per year.

I would sure like to see the calculations that justify the system design.

 

[O C Diver]

O C Diver.

Just so I understand your point, is the "Energy Guide Label" the same label as "refrigerator electric label" that you referenced?
What does the info. on the Energy Guide label (typically Annual Energy Consumption in kWh and Annual Cost, based on $0.12 per kWh) have to do with sizing an inverter to power the refer?

Regardless of your responses, if the refer. has a defrost element (H to T says his Magic one does not) and that element draws 5 Amps at 120 V AC (mine does) would you power it with an inverter that is not capable of producing the 600W of power required to run the defrost element? If so why?

What I don't get is the "No" part.

Sorry if I came across as abrupt.

The Energy Guide label is different from the manufacturers label (usually inside the refrigerator). The Energy Guide test is done by an independent testing agency that in addition to the consumption test also verifies the product information label. The amperage draw on the manufacturer's label is for the maximum possible amperage draw.

My 10 CUFT. Summit refrigerator is frost free and draws under 2 amps in the defrost mode.

The No was in response to the blanket statement that frost free refrigerator draw 5 amps in the defrost mode.

Ted

 

[O C Diver]

While I won't speak for HeadedToTexas, the smaller inverter has a much lower standby consumption and probably a greater efficiency at the lower wattage. Most inverters have an efficiency range and advertise their peak efficiency. If you're using a 3,000 watt inverter to generate 250 watts, it may not be as efficient. The point being, if you spend the night at anchor, the smaller inverter might consume significantly less energy that the large one between standby consumption and inefficiency.

Ted

 

[luna]

Rather than stating an approximate value for the current draw of the defrost element, I likely should have said to size the inverter for the largest draw, which in most instances is the defrost element, if so equipped.

Different manufacturers fit different sized elements and run them at different intervals and durations. It's all about the Btu's required to melt the ice on the evaporator.

 

[BruceK]

Jeff.

I don't get it either.

If someone wants to run the refer. only on a dedicated small inverter and experience the losses from battery charging, and inverting whenever the refer. is on, versus running it off of the grid likely 80 percent of the time and off a 3kW inverter the remaining 20 percent of the time, then have at it.

Remember, 20 percent of the time is 1752 hours or 73 days per year.

I would sure like to see the calculations that justify the system design.

My DE/EV 0041 happily switches between 12v and 240v. Using 240 whenever it`s there.
I also don`t get the wisdom of constantly passing amps in and amps out to power the inverter, especially when perfectly good 120/240 is there. Do batteries like being kept that busy?

 

[mvweebles]

..... If you're using a 3,000 watt inverter to generate 250 watts, it may not be as efficient. The point being, if you spend the night at anchor, the smaller inverter might consume significantly less energy that the large one between standby consumption and inefficiency.

Again, standby power draw of the 3000w inverter is 15w. 1.25ah. Overnight, draw is 12ah-15ah draw down. The OP hasn't described the size of his house bank, but 400ah is common, 200ah (two x 12v) is minimum I've seen.

So maybe a 400w inverter is 2x more efficient (....maybe), but does it really may a difference? Rather than add another inverter with cabling, circuit protection, and a selector switch, maybe just add another battery?

Peter

 

[O C Diver]

Again, standby power draw of the 3000w inverter is 15w. 1.25ah. Overnight, draw is 12ah-15ah draw down. The OP hasn't described the size of his house bank, but 400ah is common, 200ah (two x 12v) is minimum I've seen.

So maybe a 400w inverter is 2x more efficient (....maybe), but does it really may a difference? Rather than add another inverter with cabling, circuit protection, and a selector switch, maybe just add another battery?

Peter

If you plan to stay a day or so at anchor, inefficiency and standby waste add up.

Second point is that you also gain redundancy. For under $300 (if you can do it yourself) you have a second power source that doesn't require running the generator 24/7 when away from shore power.

Ted

 

[O C Diver]

It's all about the Btu's required to melt the ice on the evaporator.

Actually it's about doing it often enough to melt the frost before it forms ice. Manufacturers learned that waiting for ice to form required far more energy to melt and then returning the unit to the desired temperature. My Summit has approximately a 30 minute defrost time in 24 hours of compressor time.

Ted

 

[HeadedToTexas]

...the smaller inverter has a much lower standby consumption and probably a greater efficiency at the lower wattage.

That is my understanding as well. While I would not tackle upgrading or installing a new big inverter, the small Phoenix line is very straightforward and well within my ability.

I also don`t get the wisdom of constantly passing amps in and amps out to power the inverter, especially when perfectly good 120/240 is there. Do batteries like being kept that busy?

That is a great question, Bruce. On the surface, my suspicion is that they do not and that is why my original diagram shows a pass through 120 VAC supply with a switch to select the power source. That said, the charger "side" of the SW 3012 is always running in float when on shore power whether there is load or not. There are parasitic loads that are always causing amps to leave the batteries and be put back in.

The OP hasn't described the size of his house bank...

Our house bank is three 198 amp hour AGMs. They have had a couple episodes of being discharged to 0% on our Balmar Smartgauge. While I have not done any real load testing to document their state or condition, my observation is that the state of charge on the Smartgauge drops far faster than it should.

Before we do any real depending on the batteries, they will be replaced with the best option of the day. Separate issue, of course, but our objective is to spend days at a time on the hook and away from shore power. We keep our fingers crossed that our 9000 watt Kohler remains dependable, but it will almost certainly be supplemented by 1000 watts of solar when the time comes.

 

[Gdavid]

I doubt the parasitic losses from the xantrex are substantial enough to go through this exercise. As long as you don't have loads running though it, which it cannot handle inverter mode (like the Aircon and water heater), I would let it run the refrigerator and if anything, spend the funds to expand your house bank to offset any losses.

I have the Xantrex freedom 2k unit, it only supports a single circuit which includes the outlet for the fridge. 99% of the time (at the dock) it is in pass through mode on the AC side while also floating the house bank. When I unplug from shore power it keeps the fridge running and we can charge electronics on a couple other plugs or make coffee, etc. If it were to fail while I was out cruising, I would just bypass it, throw some blocks of ice in the fridge and run the generator more often and order a new one. I could get by with plug in battery charger in the short term.

Edit: 99% was high, I am away from the dock more than 3.65 days/year but not by enough.

 

[luna]

Ok, frost or ice they are both forms of solid water just with a different origin and formation process as frost is formed by the water vapour in the air turning to the solid state (ice) without ever seeing the liquid state. It's called deposition.

I am pleased to see that we tend to agree on the approximate duration of the defrost cycle (I said in post 24 "around 5 Min. every 6 Hrs. or so", while you state "Approx. 30 Min. in 24 Hrs. of compressor time") but I question if your Summit Refer. actually tracks compressor run time or is it just time?

 

[MacPhid]

Our house bank is three 198 amp hour AGMs. They have had a couple episodes of being discharged to 0% on our Balmar Smartgauge. While I have not done any real load testing to document their state or condition, my observation is that the state of charge on the Smartgauge drops far faster than it should.

If the Balmer Smartguage is set up like our LinkPro, when it reads 0% it is at the banks 50% discharge. Check the actual amp hours consumed. If only 300 then you did no harm at all to your bank. If the Balmer is set up differently or not programmed for actual bank size then perhaps.

James

 

[O C Diver]

I am pleased to see that we tend to agree on the approximate duration of the defrost cycle (I said in post 24 "around 5 Min. every 6 Hrs. or so", while you state "Approx. 30 Min. in 24 Hrs. of compressor time") but I question if your Summit Refer. actually tracks compressor run time or is it just time?

The Summit has a mechanical 24 hour timer with the defrost cycle built in. It's accessible from inside the refrigerator to bypass the defrost cycle when I was diagnosing the faulty thermostat.

Ted

 

[HeadedToTexas]

That Summit FF83PL is a slick unit, but it's just too tall to fit the cabinet on the Mariner 37.

 

[jgwinks]

A 250 watt inverter produces 2.1 amps continuous at 120 VAC. Thought your refrigerator amperage was going to be higher than that. I was thinking the 500 watt unit was probably the minimum.

Ted

My ac only fridge is labeled 1 amp at 120 volts, so 120 watts. That would be 10 amps on the inverter, plus whatever the inverter losses are. That probably doesn't include start up surge, so double it. I run the whole boat except the AC's and water heater on my 3000 watt inverter/charger which also has 30 amp pass through when shore or gen are available. Works fine for us.

 

[O C Diver]

My ac only fridge is labeled 1 amp at 120 volts, so 120 watts. That would be 10 amps on the inverter, plus whatever the inverter losses are. That probably doesn't include start up surge, so double it. I run the whole boat except the AC's and water heater on my 3000 watt inverter/charger which also has 30 amp pass through when shore or gen are available. Works fine for us.

If the manufacturer's label says 1 amp, that should include the startup surge.

Ted

 

[luna]

If the manufacturer's label says 1 amp, that should include the startup surge.

Ted

My understanding is that the current draw shown on the label of electric motors typically states Full Load Amps. (FLA)

Older motors used to show the Locked Rotor Amps (LRA) which is your start up surge, but this seems to be replaced with a Code now that you need the key (a list) in order to calculate the suitable value.

As this LRA occurs for only about 150 milliseconds at each start and is 3 to 6 times the FLA, I doubt if it is included in the current draw shown on the motor label.

 

[O C Diver]

My understanding is that the current draw shown on the label of electric motors typically states Full Load Amps. (FLA)

Older motors used to show the Locked Rotor Amps (LRA) which is your start up surge, but this seems to be replaced with a Code now that you need the key (a list) in order to calculate the suitable value.

As this LRA occurs for only about 150 milliseconds at each start and is 3 to 6 times the FLA, I doubt if it is included in the current draw shown on the motor label.

I don't think they're are referring to locked rotor amps, but surge that would pop a fuse or trip a breaker.

Ted

 

[Jeff F]

Before we do any real depending on the batteries, they will be replaced with the best option of the day. Separate issue, of course, but our objective is to spend days at a time on the hook and away from shore power. We keep our fingers crossed that our 9000 watt Kohler remains dependable, but it will almost certainly be supplemented by 1000 watts of solar when the time comes.

Skip the dedicated inverter and put the funds and efforts into batteries/solar. Easy choice IMO.

 

[ranger58sb]

I was just reviewing the MultiPlus manual for a different reason... and it looks like some of the optional settings can reduce parasitic loss quite a bit.

Can't say I've noticed inverter overhead as much of an issue, at least in our case, with the 3000W unit. Not enough of a blip to get my attention.

The biggest load we've had on there seems to be the bridge fridge, which is an AC/DC model living in a greenhouse. The AC source for that would be our inverter bank. The DC source for is one of the other 255-Ah banks, so I simply switched off the AC breaker for it... and I think reduced the overnight inverter load by quite a bit.

-Chris

 

[Mike H]

Just remember that the inverter has to handle not only the running amps/watts of the fridge but also the in-rush current at the start of the cycle. Good inverters can (which includes Victron). Off-brands, who knows?

 

[jgwinks]

Just remember that the inverter has to handle not only the running amps/watts of the fridge but also the in-rush current at the start of the cycle. Good inverters can (which includes Victron). Off-brands, who knows?

That's an issue for sure. A few years back I rewired my home furnace to be able to run off my portable inverter generator. Furnace label said it should be able. But sure enough on the next power failure (we get a lot of them here) the inducer fan on the furnace would not start. I suspect the inrush was too high. It's a pure sine inverter so I don't think it was the control board.
I posted earlier here that the household fridge in my boat was labeled at 1 amp at 120 volts. Someone responded that included the inrush, but I just can't believe the compressor would start using only 1 amp. Probably more like 5 or 6, but only for a fraction of a second. An average of 1 amp over a period of time I would believe.

 

[Jeff F]

I think the concerns over inrush are based on outdated technology. Modern fridges have variable output compressors that run the majority of the time. The compressors don't run on line voltage.

See https://www.energystar.gov/products...eakthrough-for-energy-efficient-refrigerators

 

[ronobrien]

I thought he was going with a small inverter for just the refer. Maybe I misunderstood???

You read it correctly. The intention is for a dedicated inverter. Assuming I read it correctly.

 

[Nepidae]

Dedicated inverter

I can tell you that a switch is a bad choice.

We initially had a switch installed and it was a PITA to have to deal with. On a refit the owner asked about that and said that we shouldn't have to do that. He said it should work automatically.

Now, we don't throw any switches. When we hook to shore power the inverter drops out and vice versa when we disconnect shore power.

It's so automatic that we have lost shore power when attached and it went out that we never knew it. That got to be problematic.

We have an ELCI on board and the last electrician connected a small LED light to it so that now we see a small light when connected to shore power and if shore power goes out the light goes out and we know.

You don't mention your battery bank or your desire to anchor out but even if you don't now you might want to in the future, therefore I'd put in a charger/inverter that would handle a night on the hook.

We have a Victron MultiPlus 3000/12. A lot of nice features that the 10yo Xantrex SW3012 didn't have when a marina sent a surge to it and needed replacing.

Good luck with your plan.

 

[HeadedToTexas]

If the Balmer Smartguage is set up like our LinkPro, when it reads 0% it is at the banks 50% discharge. Check the actual amp hours consumed. If only 300 then you did no harm at all to your bank. If the Balmer is set up differently or not programmed for actual bank size then perhaps.

James

Hmmm, I had to go back to the Smartgauge manual for that one. I don't see where 0% could represent 50% discharge unless you trick the Smartgauge by calibrating it manually.

Does your Smartgauge read negative SoC when the actual is less than 50%?