Inverter for fridge... April 12, 2017, 01:13:24 pm Have made one short trip so far with fully automatic en-route inverter power for our fridge, with no problems. The delayed fridge switching even gives just enough time to get up and turn it off after entering gas stations before it switches back to propane. This whole system I self installed, but not that difficult once I figured out routing for our rig. The inverter is only used for this function.I know giving a review at this point is a little like posting a product review a week after purchasing, as the on-line retailers would have you do, so take with a grain of salt. If I have issues down the line, I will repost.Steve 1 Likes
Re: Inverter for fridge... Reply #1 – April 12, 2017, 02:44:07 pm Can I ask what inverter you installed? Or perhaps it was in another thread I missed...
Re: Inverter for fridge... Reply #2 – April 12, 2017, 03:45:24 pm Inverter is Harbor Freight # 69660, 750 Watts. The 12V relay is a Stinger SGP38, 80 Amp, powered thru a 50 Amp fuse from the chassis battery terminal of the battery isolator. The relay coil is switched on by the alternator terminal of the battery isolator. The wiring is 4 gauge for positive, 6 gauge for the short negative run to chassis ground. The inverter is mounted behind the cab seat on the same side as the fridge, with lots of air circulation. It does not get warm to touch.The fridge heater draws about 350 to 360 Watts when cycled 'on', and my transfer relay is home-brew, and switches power to the socket the fridge plugs into.Steve
Re: Inverter for fridge... Reply #3 – April 12, 2017, 04:04:04 pm Steve scribed: "The delayed fridge switching even gives just enough time to get up and turn it off after entering gas stations before it switches back to propane."(This paragraph is focused on fill-ups at gas stations...)So, is there a time delay built into your home-brew transfer relay, or is it handled within the fridge... something like "wait 30 seconds, then switch to propane" so you have a window of opportunity? Or functionally, do you just turn off propane (while traveling) so even if it tries to go to gas, there's nothing there. And does AC power have priority, so it reverts to AC when you start the engine again. (I have a new-to-me 2000 FL, and haven't been out in it as yet, other than just trips around the state to gauge its reliability.)I have a much larger, non-sinewave inverter that I can press into service for this very use. And from other wise advice, the resistor heater doesn't care about waveform fidelity. But at 3000W, it's way overkill for just this purpose. Maybe I go small on this...Chip
Re: Inverter for fridge... Reply #4 – April 12, 2017, 04:57:24 pm The transfer delay is the normal delay of the fridge switching modes. We do not turn off propane while driving, as the fridge is AC priority in auto mode. The only manual part is to turn the propane off, then back on, during fuel stops.A larger inverter may require bigger gauge wiring, shorter wiring runs than I used, if used for more than just the fridge. Some have wired their inverter to power an entire 120V circuit from the converter, including the fridge, but then you have to be careful about what else may be plugged in when you start the engine.Although the 120V fridge heater works fine with modified sine wave, the same is not necessarily true of relay coils, such as the one I used in my transfer switch - it buzzes, which might be ok, and is not audible in operation (engine running). I don't know if a commercial transfer switch would also have this issue.Steve
Re: Inverter for fridge... Reply #5 – April 13, 2017, 01:08:40 pm As this is the only thread I have mentioned our fridge inverter, I will post a few pics. These show the inverter mounting, using scrap parts I found, and not modifying the unit in any way that would prevent returning it should it fail. The relay and fuse mounting on the left inner fender is shown, below the coolant tank. The next photo is of the diode isolator - the heavy red wire comes from the inverter relay contact, and the small red wire is from the relay coil. Finally, the last photo shows the AC socket in the fridge compartmant, with two additional runs of romex added, entering the right side of the box (hidden here). Copious sealant replaced the original below the socket. The pass-thru below the socket was large enough for the additional wiring without enlarging. The AC transfer switch is located remotely. 1 Likes
Re: Inverter for fridge... Reply #7 – May 21, 2017, 08:27:21 pm Update on my installation - the inverter failed. However, I believe I know why: I had resolved never to start the engine - which would activate the inverter - while connected to shorepower. I violated that rule. The reason for the rule is I had noticed a bright flash during testing from my transfer relay doing exactly that. I surmise that the relay contact separation caused a small spark, inducing a plasma, and then a resulting short between the out-of-phase power sources - if anyone cares. Anyway, the replacement inverter now works, and I will find another solution for the transfer relay before using the inverter again.Steve
Re: Inverter for fridge... Reply #8 – May 22, 2017, 04:14:21 pm Steve, if you didn't want to build another transfer relay, would one of these work? https://www.pasternack.com/medium-power-transfer-electromechanical-relay-switches-category.aspx
Re: Inverter for fridge... Reply #9 – May 22, 2017, 06:09:37 pm Quote from: JCT - May 22, 2017, 04:14:21 pmSteve, if you didn't want to build another transfer relay, would one of these work? https://www.pasternack.com/medium-power-transfer-electromechanical-relay-switches-category.aspxNo, those are all RF transfer switches, Joan. A commercial transfer relay might work better, but I think I will rewire mine from inverter-priority to shorepower-priority. I.e., the shorepower connection powers the coil and thus 'flips the switch' to shorepower mode. Several advantages:1) The relay coil is powered by sine-wave ac. Currently it buzzes with modified sine wave from the inverter, which may affect how well it holds contact and whether it heats up.2) Also, if the engine is running when I connect shorepower, I have the 2 minute plus delay of the surge protector to rectify my mistake before power switches. And, of course, if running on shorepower, the inverter cannot connect to the fridge if I start the engine. Not foolproof, but idiot-resistant.Steve
Re: Inverter for fridge... Reply #10 – May 22, 2017, 06:36:22 pm Just an opinion but I would take the fridge off of auto and put it on AC only. Power the fridge only from the inverter. When stopped at the end of the day unplug the fridge from the inverter and plug it into the coach AC.As it is, inattention, the same thing that killed the inverter, will give you a flame next to the fuel pump. Turn the propane off while you are at it. You don't need it while traveling.
Re: Inverter for fridge... Reply #11 – May 23, 2017, 01:53:20 am Our fridge has no 'AC' mode. The available positions are off, gas, or auto. And, I would not drive with the fridge off - I want it to switch to propane when we stop, such as for lunch or sightseeing. I only turn off the gas for fueling, ferries, or anywhere else mandated for safety.Steve
Re: Inverter for fridge... Reply #12 – May 23, 2017, 09:01:00 am "Our fridge has no 'AC' mode. The available positions are off, gas, or auto."And what model would that be? (My bet is there has to be a way to get it to AC only but I may be wrong.) I would want to go to propane automatically in only one place, stationary, plugged in, in the RV park. Most of the time, when you stop, the RV isn't level anyway, except in a gas station.I once thought there was no fridge that went into DC mode automatically but I was wrong on that, too. There are a select few 3 way fridges that do.
Re: Inverter for fridge... Reply #13 – May 23, 2017, 09:34:44 am Auto is usually 120 AC priority over Propane gas.
Re: Inverter for fridge... Reply #14 – May 23, 2017, 12:14:09 pm "Auto is usually 120 AC priority over Propane gas."Sure, so take it off of auto. Mine can do that. I would like to know the model that cannot.
Re: Inverter for fridge... Reply #15 – May 23, 2017, 12:17:40 pm Quote from: hbn7hj - May 23, 2017, 09:01:00 amAnd what model would that be? (My bet is there has to be a way to get it to AC only but I may be wrong.) I would want to go to propane automatically in only one place, stationary, plugged in, in the RV park. Most of the time, when you stop, the RV isn't level anyway, except in a gas station.Turning off auto goes to gas. No AC only option.Our Dometic is oem in our '04 - since yours is an '06, I'd guess yours is the same, unless it's a Norcold. No way to get AC only, though I guess you could turn off the propane so you'd get a 'check' light. My point is that the risk of food damage is greater than the risk of fire, particularly on day-long drives, if the only option is propane. My reason for adding the 12V option is to save propane, not to reduce fire risk. Camping enjoyment - w/o hookups mostly - is determined by the ability to avoid unnecessary resource replenishment during a relaxing stay in remote locations. Note that if parked off-level for a time, we WILL turn the fridge off until we hit the road again.Steve
Re: Inverter for fridge... Reply #16 – May 23, 2017, 12:28:06 pm Our control panel - for your inspection...
Re: Inverter for fridge... Reply #17 – May 23, 2017, 01:05:05 pm "Our control panel - for your inspection..."Hit the auto button till only the AC LED lights up? It must have AC when you do this. Anyhow, I won't be able to test this till I get back to my RV. When I do I will try to put it in an AC only mode and if I cannot then you are correct and I am wrong.
Re: Inverter for fridge... Reply #18 – May 23, 2017, 01:37:25 pm Well, when it switches to AC, disconnect the shorepower. In a moment, you will see it switch to Gas. In auto it will select whichever is available, with a priority to AC. In 'Gas' it will stay on gas.Steve
Re: Inverter for fridge... Reply #19 – May 23, 2017, 02:00:21 pm "...when it switches to AC, disconnect the shorepower. In a moment, you will see it switch to Gas. In auto it will select whichever is available, with a priority to AC. In 'Gas' it will say on gas."----AFAIK, this is how the refrigerator power sources work in my 2003. (OEM Dometic RM2662, as I recall.) I will be interested to read the results of Harry's "AC Only" experiment!
Re: Inverter for fridge... Reply #20 – May 26, 2017, 08:05:55 am Well, as you guys already knew, I am wrong. My 3-way won't work on AC only, either, just like the manual says!I have thought of several ways to modify it to make it happen. One of them pretty easy.There is no way we should roll into a gas station with an ignitor cocked and ready to go unless we do something. I'm too senile to risk that even tho the odds of it making a difference are very slim.Not my issue because I have a 3-way with the DC element controlled by a relay. No alternator no DC element. If you are interested in an untried mod, let me know.Thanks,
Re: Inverter for fridge... Reply #21 – May 26, 2017, 11:45:42 am Is there a factual basis for the fear of driving while on propane?Can you point to an explosion at a gas station caused by the refer igniting?I have a good friend whose degree is in Nuclear Engineering. Worked his whole career at Oakridge.Will not allow a bottle of propane in his rig.We just turn off the refer when we gas up.
Re: Inverter for fridge... Reply #22 – May 26, 2017, 12:53:54 pm "Can you point to an explosion at a gas station caused by the refer igniting?"Yes. Several pictures were posted on another thread. The first one was a Roadtrek with a refer started fire at a gas station. The last one was a conflagration around a Roadtrek at a propane filling station. We don't understand that one. Why so much fuel? What was the ignition source? The thread also has video and pictures of class As going up in smoke in front of the pumps. I don't think the refer was always guilty as one was an engine fire."I have a good friend whose degree is in Nuclear Engineering. Worked his whole career at Oakridge.Will not allow a bottle of propane in his rig." Probably has a reason. I am never comfortable at a propane filling station and would be pleased if I didn't have to go there. Electric cannot replace the chemical energy in propane."We just turn off the refer when we gas up." But you probably don't do that before you get to the pumps.We have learned that people won't change behavior even after looking at actual events so it is usually a topic to avoid. I just wouldn't roll into a gas station with an ignitor that will activate if I don't do something. The fridge can be made to run AC only and not default to propane when the engine is turned off and the inverter turns off. The last time I got propane the tech said he had a tent trailer that hit something on the road and broke his propane line. He pulled over, stood back, and let it vent. No ignition. Must have been an old tank without the free flow safety valve. After that he won't travel with the tank valve open. Most of us learn the hard way.I have the first picture of the Roadtrek fire but can't figure out how to post it into a reply with an iPad. I try to choose a pump away from any other RV assuming it has an active ignition source going.Just do a search on RV fire or RV gas station fire. UTube has a few.
Re: Inverter for fridge... Reply #23 – May 26, 2017, 07:49:28 pm Quote from: hbn7hj - May 26, 2017, 08:05:55 amNot my issue because I have a 3-way with the DC element controlled by a relay. No alternator no DC element. So, when driving in 12V mode, and you switch off the engine, it doesn't auto over to propane after a delay?Steve
Re: Inverter for fridge... Reply #24 – May 26, 2017, 07:59:39 pm Nope. DC mode won't do that. The auto light is off in DC mode. The relay only interrupts the current to the DC heater. The fridge doesn't know it isn't working. The DC light stays on. If you cut DC to a fridge it is off. The computer no longer works.I have figured out several ways to make the AC by inverter mode do that, too. I don't need it but I'll post it if interested.Gas-station fire destroys Indiana couple’s RV - News - Houma Today - Houma, LAThat ought to do. A search of RV fueling fire brought it up and it is the picture I have. I found another dated 2017.Last time it was posted several said it was staged-where did the suited firemen come from so quickly.The text doesn't come up on my iPad but the picture does.Roadtreks are worst case because the gas cap and fridge are on the same side though it was moved aft from the stock van location.
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