looking at this fridge

dolcesails

Hi guys,
looking at this fridges, I'm wanting to put it on a 38 ft. catamaran where I need to be conscious of space the first is a Model #: Avanti RA7306WT 7.4 cubic ft. has auto defrost, which I may be able to unplug that feature, the second model #HVDR450SE Vissani 4.5 cu. ft. Mini Refrigerator no defrost, both are rated to be energy efficient. I plan on running it thru and inverter (what size) you'll need to tell me, I have a lot of 120 watt panels, thinking about 5 for this project with an MPPT controller (what size and make) you'll need to tell me, plenty room for batteries, I have a watt meter but don't have the fridge so what am I expecting, what do you think........ I really don't want to buy a 12v model..........
Thanks, Nick

jcheil

Re: looking at this fridge

dolcesails wrote: »

Hi guys,
looking at this fridges, I'm wanting to put it on a 38 ft. catamaran where I need to be conscious of space the first is a Model #: Avanti RA7306WT 7.4 cubic ft. has auto defrost, which I may be able to unplug that feature, the second model #HVDR450SE Vissani 4.5 cu. ft. Mini Refrigerator no defrost, both are rated to be energy efficient. I plan on running it thru and inverter (what size) you'll need to tell me, I have a lot of 120 watt panels, thinking about 5 for this project with an MPPT controller (what size and make) you'll need to tell me, plenty room for batteries, I have a watt meter but don't have the fridge so what am I expecting, what do you think........ I really don't want to buy a 12v model..........
Thanks, Nick

Energy Star Rating on the first unit shows 251kwh per year. So that would be about .69kwh per day. The second is 235 per year (so might as well go with the first and get the extra space for only a few kwh/year more). The experts here can do the math for you exactly, but that "might" be cutting it close with the panels you have. You also need to let everyone know what OTHER loads you expect to be running from this system. And usually you can't disable the auto-defrost features without causing other problems. We talked about this on a thread a few days ago.

dolcesails

Re: looking at this fridge

Ok other loads will be backed up with a Honda EU 2000 generator such as coffee maker, microwave, when needed, so other 12v loads would be led lites, stereo, fans I have room for 3 more panels if needed.

Cariboocoot

Re: looking at this fridge

dolcesails wrote: »

Ok other loads will be backed up with a Honda EU 2000 generator such as coffee maker, microwave, when needed, so other 12v loads would be led lites, stereo, fans I have room for 3 more panels if needed.

Uh, that would be always.
The Honda is 1600 Watts and the coffee maker or microwave would pretty much pull maximum power (over 1kW each for those two I should think).

This is not the kind of power you want to pull from a 12 Volt system.

Trouble with refrigerators is that they do not have consistent energy use; it varies with ambient temperature and how often you open the door. Whole great long thread on refrigerators: http://forum.solar-electric.com/showthread.php?12272-Just-how-bad-a-small-frige-is

Panels are not what power the system: batteries do. You need to size up a battery bank to supply the power need and then determine what you have to have to charge it. With space limitations you may have to work backwards and learn to do without or run the gen more.

For example five 120 Watt panels is 600 Watts, about enough for 220 Amp hours @ 24 Volts with an 8.7% peak charge rate. It would work in good sun conditions and low DOD. You could see around 1200 Watt hours AC from this, maybe more with some careful load management. I know because I squeeze another kW hour out of my slightly larger array on good, sunny days (which we're having none of now).

I know you said 12 Volt system, but if you go 24 the heavy usage items can run off the inverter and the gen will only have to be used to recharge when the sun doesn't cooperate (which has been the past week here). Any 12 Volt equipment may be run with a DC to DC converter, or switched to 120 VAC since the inverter will be running all the time anyway to power the refrigerator.

Desert Rat

Re: looking at this fridge

I keep close tabs on several refrigerators, and have found that actual usage in extreme hot ambient temperatures is consistently 1.5 times the Energy Guide specification. So for the Avanti: 251/365 X 1.5 = 1.03 kW/day. This is what you should expect for a maximum draw in hot weather.

jcheil

Re: looking at this fridge

Desert Rat wrote: »

I keep close tabs on several refrigerators, and have found that actual usage in extreme hot ambient temperatures is consistently 1.5 times the Energy Guide specification. So for the Avanti: 251/365 X 1.5 = 1.03 kW/day. This is what you should expect for a maximum draw in hot weather.

I agree, mine which is listed at 360kwh per year consumes about 1.4-1.5kwh per day in the 90+ degree summer.
But still WAY better than the 12-year old one I had in my on-grid house that I swear NEVER turned off

jonr

Re: looking at this fridge

There are some important specs that are hard to find answers to. For example:

1) start-up current draw and whether it can easily be reduced.
2) can it be turned off for many short periods without excessively changing the defrost cycle. This can be useful to avoid inverter idle losses.
3) can it be turned off for longer periods and have enough excess capacity to catch up. For example, always off from 3am to 9am would save on battery wear.

cupcake

Re: looking at this fridge

I use the infamous Kenmore "30-watt" refrigerator/freezer combo. It is 3.1 cf.

It's small, but big enough - has a freezer. It averages 30 watts. When its on it will use 60 watts, but its 'on' 50% of the time, so that's where the 30 watt-hours comes from...


It takes a bit of a surge to start, so I had to get a higher capacity inverter.

Other than that it's nice making ice-cubes from the sun...


Start-up surge WILL be an issue, FYI - keep that in mind when shopping...