Fridge score! Wow it’s big.

[Yeti Tom]

I measured my TF130 power usage this past July(90 degree days in Colorado) on two consecutive days. 40ah one day, 44ah next day

 

[Paddy]

Your fridge is burning propane to cool and ~.7a for controls. The amp draw is higher when the reigniter is firing but that's brief. A DC compressor fridge typically averages about 1.5a/hr. If you had enough solar and battery capacity you could run a DC fridge indefinitely and never need propane. How much is enough? 1.5 x 24 = 36ah. Let's say you need to run 3 days straight without the sun (bad weather, shady parking spot, etc) and want an inexpensive battery, lead-acid (not AGM or Lithium, etc). So 36 x 3 = 108ah and 108ah x 2 = 216ah. That's pretty much 2 basic golf cart batteries (actually 215ah) and about $180 (90 each) at Sam's Club. To recharge them in a single sunny day you would to replace 108ah you'd already used, plus the 36ah you'd need that day, so 144ah in about 6 hours of sun (most places in the USA for most of the year). 144ah/6h= 24a. The Renogy Eclipse 100w panel has been reported to produce 5a by several users. 5 of those panels = 25a per hour x 6 hours = 150ah. That's about $1,500 in solar panels, charge controller, cabling, batteries, etc plus the fridge at $300-1,500. That's a lot of money BUT it'll run forever (barring mechanical breakdowns) without buying any gasoline, propane, or ice. If you connect the batteries to your alternator and drive regularly you can save a lot on solar. Likewise if you didn't go 3 days without charging, you could recharge with less solar.

I think you’re downsizing my fridge with those numbers, and you’re also dismissing the noise issue, and you’re also taking into account a sunny parking place, which is usually something we try to avoid at all cost in the summer. So, I’m not disagreeing with you at all, just saying that in my experience, the compressor fridge has drawbacks that are being understated by your calculations. Do you know of a 6 cu/ft compressor fridge that draws 1.5a? I don’t think I’ve seen one that large. Also, are you taking into account that you can’t only use 50% of a lead battery capacity for appliances? That’s the safe DOD for lead acid. They are also heavy.
If the only drawbacks to propane are “leveling” (something I do anyway) and fuel cost (very very minimal, and also must be compared to degradation of panels, and batteries) then don’t see it making sense to put up with the noise. I’ve had Engle, and whynter brand which both use danfoss swing compressors, so I’m not shooting in the dark here.
Also, many people seem eager to cover their roof with solar, and then park in the sun. However, we have gear like kayaks that take up a lot of sun space on the roof, so there’s also that compromise. We have dogs.

 

[Paddy]

I think they rate these fridge power consumption based on a fridge that’s not opened. And as we all know a vertical fridge when opened flushes all it’s cold air out. So, unless you don’t open you fridge, it will be hard to tell the real life consumption. Ive slept with 3 of them at this point and I don’t like the racket they make. Just my opinion. If we need propane anyway, then why not a gas absorption fridge? Zero moving parts!

Here’s another wacky idea i had. You know how mosquitos are attracted to CO2? Well is it possible that a gas absorption fridge would confuse them, possibly drawing them away from people, or, maybe even giving an opportunity to zap them with some sort of device? (Tread lightly philosophy aside of course)

 

[luthj]

Yeah, not going to knock the absorption units, they are a good fit for many. I will say that all my danfoss fridges have been very quiet. The secret is to replace the garbage fans they ship with. Lots of great low noise PC case fans that will bolt right up. The second key to low noise is to loosen the rubber compressor isolators. At the factory they are over-tightened. Mcmaster Carr also has some good isolators that you can replace them with for even lower vibration transfer. My current fridge is inaudible over the maxxfan on low. I would say its about as loud as your average mouth breather.

Now the swing compressors (like engel) are very vibration prone. Not much to be done there. I have sat next to an engel mounted left right in vehicle. It was actually making the vehicle rock back/forth ever so slightly!

The newest danfoss/secop compressor controllers have a built-in soft start feature, which eliminates the thunk-thunk-whir-whir of the compressor spinning up.

 

[Paddy]

I thought the danfoss compressors were all swing type, and the quietest available. In any case maybe I’m picky but when I camp I like the quiet at night and I’d silence the sound of your typical mouth breather too if I could, but chances are she wouldn’t speak to me for days if I tried (again). So, some noises are “acceptable losses” lol.

 

[luthj]

Lol, my wife pops her jaw when she sleeps...

The common bd 35/50 are rotary compressors.

 

[Mwilliamshs]

...Also, are you taking into account that you can’t only use 50% of a lead battery capacity for appliances? That’s the safe DOD for lead acid...

Yes, I did take that into account.

...an inexpensive battery, lead-acid (not AGM or Lithium, etc). So 36 x 3 = 108ah and 108ah x 2 = 216ah. That's pretty much 2 basic golf cart batteries (actually 215ah) and about $180 (90 each) at Sam's Club...

Why else would I multiply 108 by 2?

 

[Paddy]

Yes, I did take that into account.



Why else would I multiply 108 by 2?

Okay, but the compromise there is a smaller fridge, not bad, but it’s 33% smaller. More importantly I seriously doubt you can get 5a from those panels for 6h and if you could it means your van is in Death Valley. But for a device as important as a fridge, I’m forced to design it to work well in the worst scenario situation. So considering no solar gain on the system (a best case scenario on the hottest, highest fridge load days), you’re saying it would take about 150lbs of “fuel” to run the fridge for 3 days (plus the weight of the solar panels), where a propane model would use about 3lbs. Now, I’m not out of weight capacity yet, but this could be a consideration on many builds. Not to mention the cost of that (battery) fuel, which degrades over time. I have propane tanks from decades ago that still work perfectly lol.

It’s a layered design consideration for sure, and I’m curious if the propane solution will be right for me.

 

[luthj]

My last absorption fridge used something like 1 gallon a week of LPG (it was pretty small). Your unit probably will use about 1 gallon every 2 days in hot weather? You can look up the BTU/hr rate for the burner, and estimate the duty cycle.

 

[Mwilliamshs]

...Not to mention the cost of that (battery) fuel, which degrades over time. I have propane tanks from decades ago that still work perfectly lol...

OPD valves have been around a while longer but since about 2007 they've been a requirement for LPG cylinders being refilled. So your "tanks from decades ago that still work perfectly" will need some fairly pricy work to be refilled. You're comparing batteries to propane tanks which doesn't quite make sense. Yes, batteries have a limited service life shorter than a steel tank but the tank is useless without fuel inside it.

I didn't intend to start a debate about fridges. I was just answering your questions and offering something to consider.

 

[Paddy]

Pretty sure I have old tanks that are 20 yrs at this point but you apparently missed my point about them both being fuel storage for the fridge. See, I can’t even say anything without sounding snotty, lol. I’m not really, just thinking out loud. So batteries can get charged up by driving, or parking in plug-ins, and propane can be filled at stations. They both have a certain weight and take a certain space. I see them as being very comparable in this scope of use. I need to have some amount of both for other uses on board. There are many considerations with this design choice really.
For me I just don’t like relying on solar, and I want the quietest fridge possible.

 

[dwh]

Horizontal tanks manufactured prior to Oct. 1, 1998 are exempt from OPD requirements.

 

[Arctic Travelller]

I ran a similar sized unit on my boat for 14 years, and it was never level while underway. They want tobe level so the flame impinges between the coils, not on them. Eventually the coil will burn through when not level, as mine did. The escaping ammonia almost suffocated my wife one night while she was asleep. Still, it took about 10 years to happen. You should be fine, but a gas detector would be a good idea, might even save your life.

 

[Paddy]

I ran a similar sized unit on my boat for 14 years, and it was never level while underway. They want tobe level so the flame impinges between the coils, not on them. Eventually the coil will burn through when not level, as mine did. The escaping ammonia almost suffocated my wife one night while she was asleep. Still, it took about 10 years to happen. You should be fine, but a gas detector would be a good idea, might even save your life.

Wow scary. But in a van vs boat could that happen? The ammonia wouldn’t vent out with propane fumes. I’m still putting in a CO detector as well as smoke. I guess gas or ammonia won’t be detected but I’m not sure that’s a concern.

 

[Mwilliamshs]

Wow scary. But in a van vs boat could that happen?

Yes, the cooling packages do rupture in campers, not just boats. My grandparents have had 1 spray ammonia rather violently. Just like other pressurized gas systems (air conditioning, pneumatic tools, tires) leaks can and do happen.

The ammonia wouldn’t vent out with propane fumes.

Do what now?