I sure would like to hear what Prepperdoc has to say about the conclusions of G.D. on the resilience of the simple freezer in the event of an EMP. It would be nice to know brand name. I have looked at Sundanzer products (24vdc) but was not encouraged by reviews and troubled by the exposure to EMP. It is preferable not to wander in the wilderness. – R.V.
Prepperdoc Responds: Great question, made me do even more study. My personal plan has included household freezers just as contributor G.D. is using. Are these susceptible to EMP / solar flares (e.g., Carrington event)?
Apologies in advance, this is somewhat tedious stuff.
Your biggest concerns are to protect against both the E1-type and E3-type components. Let’s take them separately.
The E1 component of an EMP contains huge amounts of radio frequency power from very low frequency radio waves on up to and well beyond 100 MHz. (The solar flare doesn’t have an E1.) Over in only a few nanoseconds, this can destroy any transistorized components that have the misfortune to be connected to any wires long enough to act as suitable antennas. The old-fashioned refrigeration compressor/mechanical thermostat system might well be fairly immune to E1. The main risk I foresee is that induced higher RF voltages in the compressor windings might puncture enamel insulation if you are unlucky, causing undesired shorts, and burnout due to resulting later current. I can’t really be certain whether the Soviet generators that failed during EMP tests were damaged more by E1 or E3. In any event I believe you could reasonably protect old-fashioned refrigerators/freezers from E1 by a reasonable quality three-varistor surge protector at their plug into the wall outlet, and if you added a commercial low-pass filter in their power cord, I think your protection against E1 would be phenomenal. By contrast, it is possible (but not guaranteed) that a modern microprocessor-based unit even with these power-line protections would have its control circuitry destroyed in a flash…including the brushless DC motor control circuitry of the otherwise innovative Sundanzer DC refrigeration unit.[2, 3] It all hinges on how much wiring is there to pick up the vast radio frequency energy of the E1 EMP component. A surge protector/low-pass filter and a very short amount of wiring, effectively shielded by a metal cabinet, with a well-designed control circuit might survive. I’m not willing to bet on that, however… The good news: an AC compressor could be freed from a destroyed microprocessor controller and rewired with a simple thermostat and would likely be up and running again. So either use plain systems or have thermostats that you can wire in… But I’m concerned that should the Sundanzer individual-winding synchronized DC feeds be damaged, it might never work again unless you have an appropriate replacement control system.…and then what do you do for the 2nd, 3rd and 4th strikes?
E3: Both EMP and solar flares do have an E3 geomagnetic type risk where the shoving aside of the earth’s magnetic field creates relative movement between varying magnetic field and stationary copper wiring, causing vast currents to be induced in any really long (read: power line) wires. Literally THOUSANDS of amperes of current were induced in long wires in the Soviet tests over quite some seconds. The risk that I understand is that these very low frequency currents will unbalance voltage/currents in grid-interconnection and long-distance electrical transmission lines, resulting in very dangerous magnetic saturation of the cores of high voltage interconnection transformers, leading to very high losses and heating, resulting in their destruction (and years of power loss to the affected nation). The worrisome part of that for people who have backup power generation is that during this destructive grid process, both higher AND lower voltages may suddenly appear on either side of house wiring. In my nation, we are accustomed to exquisitely controlled and balanced house wiring voltages. Few households have any protection circuitry. Damage to the neutral wiring (or cores) of transformers anywhere along the power distribution system may cause completely anomalous voltages to appear on your house feed-in. Low voltages may damage compressors by causing excessive currents [though typical protection devices may disconnect the compressor in time] and excessive voltages might permanently damage the compressors, or the Ham radio, battery charging, and other equipment the homeowner might be counting on for later use.
The E3 solution here is first to employ surge protectors (which might pop circuit breakers and get your delicate equipment off line in a few seconds), but even more, to have fast circuitry that will disconnect critical equipment (including refrigeration) in the event of potentially damaging low OR high voltages. My solar-system’s Outback GVFX3648 grid-tie battery-backed-up inverters will disconnect from unusual grid voltages within 2-120 cycles, depending on how egregious the voltage violations. For homes without that (expensive) protection, my first thought was uninterruptible power supplies [e.g., the APC Back-UPS 750], which may adequately protect more-rugged vacuum tube equipment, older refrigerators, and possibly solid state equipment and newer refrigerators. However, a little experimentation at my house showed that that modestly powered UPS’s in the absence of line voltage are completely incapable of handling the huge starting (“locked rotor amp” LRA) current of either my refrigerator or my small freezer; so you might actually prefer a lower-powered UPS so that it simply can’t even begin to damage a freezer compressor; I’m not sure of this. What I think might be an even better solution is to use a device such as a $50 ICM492 single phase line protection module, which is able to disconnect up to 1200 watts (resistive) from both higher and lower dangerous line voltages and could easily control an inexpensive 120-volt-coil relay to disconnect just about anything you needed to protect. I’ll be ordering at least one of these little jewels after doing this research! There are other systems available, particularly some by British company Sollatek, that may provide similar protection.
For my money, you are better off with:
- an older (thermostat) technology (but recent vintage) AC-based freezer;
- a spare mechanical freezer thermostat, if you have a fancier computer-controlled newer freezer;
- a spare startup-relay (or hot-start kit) for your precious compressors;
- backup power generation, either a generator or more than one capable DC inverter in a Faraday box;
- the ICM 492 or a UPS-type device that will disconnect precious equipment quickly; and
- three-wire surge protection (and low pass filtering if possible) on anything delicate as well.