Are Surge protectors needed for Air Conditioning units? - Page 1
Forum section: electronics / general

author: Johnny10
author_rank: Frequent Contributor
timestamp: May 19, 2019, 02:27:14 pm
content: My neighbor needed a service call on her 4 year old air conditioner.The technician sold her over $600 dollars for a service, new capacitor and surge protection.Is surge protection necessary for AC motors?Or great salesman?I think the manufacturers would have considered transients in design of units.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 19, 2019, 02:41:47 pm
content: If there is actual need for one, a whole house surge protector is a better idea.

author: coppercone2
author_rank: Super Contributor
timestamp: May 19, 2019, 03:53:21 pm
content: well I have a portable AC on wheels in this room, it tends to trip one of the GFIC (but not the one its connected to).You can.. measure it

author: Ampera
author_rank: Super Contributor
timestamp: May 19, 2019, 04:08:42 pm
content: Surge protectors are (intended) for surges coming from the mains to the AC. No I do not believe you need a surge protector, and I'd actually check if he threw in some bolt on GFCI instead, as ACs are most definitely wet electronics and a fault to ground might not be a great position to be in.Not that I know all too much about what I'm talking about, but I seem to recall the common surge protector you'd just throw into an installation like that doesn't protect from a whole lot, really only what power falls in the strange position of being stopped by the MOV (either through resistance increasing, or it exploding), but not tripping some other form of current protection, or not doing so quick enough (some places don't like fuses). I imagine there's other types of surge protection too that aren't just a plastic stick with a MOV in it.Now I am wondering a few things though. What sort of AC is it to where an 800 dollar service after 4 years wouldn't warrant just throwing the damn thing to scrap? I imagine this isn't some window unit, and the only thing I can really think that would drive that sort of bargain is a proper HVAC split component with an external heat exchanger, or something like a heat pump. Maybe the guy has it in his mind that a bolt of lightning is going to strike it, not that a surge protector is going to do shit when you have a black smear where your aircon used to be.The aircon in my room costs 99 bucks from Aldi, and has been working reliably for years, just saying.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 19, 2019, 04:12:03 pm
content: Motors, not really no. A surge will probably saturate the core momentarily, drawing a large slug of current for the remainder of the line cycle, but then return to normal soon after.Capacitors, entirely possible. They're usually rated for 330 or 660VAC or something like that, so they have some excess rating to begin with, but maybe not enough for full 1.5kV (or more) surges. All it takes is one weak spot in the dielectric.AC with internal electronic control -- maybe. If they use a transformer to develop the control voltage, it'll behave similarly to the motor -- takes a hit, then not much really happens. If it's an SMPS, it may blow up, and then the low level stuff is probably fine (if you could run the fan and compressor independently, it would work), but to get it back to original operation you'd need a new control board.Or if this is a fixed installation, there probably isn't much electronics inside the unit. If it's driven by relay/contactor from the 24V thermostat, that should be fine. I'm not sure exactly where the surge protection would be placed, but if it's at the inlet to the box, that would be fine, or it would still be fine if it were exactly across the capacitor and nothing else.Tim

author: Johnny10
author_rank: Frequent Contributor
timestamp: May 19, 2019, 04:13:26 pm
content: OK, I have been reading up on Lightning and Surge suppression as a layered approach for AC motors.So it can be necessary but I also see that lightning will jump most surge suppressors.I don't know why I obsess about feeling people are being taken advantage of by salesman, $600 dollar service call for $38. dollar bad capacitor just seems a bit much.We live in an area that has over a 10 year period had 4 major hurricanes and lots of intense lightning storms . Yet only one time was small amount of damage done by lightning.

author: rstofer
author_rank: Super Contributor
timestamp: May 19, 2019, 04:22:41 pm
content: The capacitors only have a finite life and you can expect to have to replace them from time to time. Component quality will be a factor, of course, but just expect them to go out-of-tolerance. It's a common component to test and replace.The total service bill seems over the top. I wonder if the salesman enrolled her in a pre-paid customer service plan. This plan may include semi-annual inspections and routine maintenance (replace filters, check refrigerant level, check flame igniter system, etc). Still the price is too much.Why don't you get the statement and see what was charged?If it really is a rip-off, there are sometimes Contractor's Licensing Boards that deal with over-charging. Of course, some states don't even license service contractors so there won't always be an organization to help.Blank the names and post it as an attachment.

author: rdl
author_rank: Super Contributor
timestamp: May 19, 2019, 04:38:11 pm
content: My apartment AC has blown a few capacitors over the years. One of the maintenance guys told me they keep a few boxes in stock. It takes about 15 minutes for them to replace one.

author: soldar
author_rank: Super Contributor
timestamp: May 19, 2019, 05:49:16 pm
content: Quote from: T3sl4co1l on May 19, 2019, 04:12:03 pmThese days anything you buy is going to have electronics even if completely unnecessary and detrimental.I used to have a washing machine with electro-mechanical timer and I could advance, add clothes, and generally control the whole cycle. No longer. Now I have a washing machine that does whatever it wants and will not let me control anything.Same thing with the refrigerator. Electronic control, totally unnecessary IMHO, but there it is.Air conditioners are more justified in having electronic control but still... you connect power and it takes the darn thing five minutes before it starts working because it is doing the self check and making sure everything is OK before it starts.Any of those things gets an overdose of volts and you're truly phuckd because they repairman will inform you it costs about the same to replace the control board than it does to repace the whole darn thing.

author: james_s
author_rank: Super Contributor
timestamp: May 19, 2019, 05:52:08 pm
content: I'm of the general opinion that surge protectors are mostly snake oil, certainly you do not need one for an AC unit.The motor run capacitor is a very common failure item, I've had to replace it in my own unit as well as the one at my mom's place. I keep a spare on hand, they're only about 10 bucks and can be replaced in a few minutes with nothing more than basic hand tools. Anyone who can use a screwdriver and follow instructions can do it, no need to wait for a repairman to show up. Be sure to pull the power disconnect before removing the access panel.

author: james_s
author_rank: Super Contributor
timestamp: May 19, 2019, 05:54:58 pm
content: Quote from: soldar on May 19, 2019, 05:49:16 pmWhat it's doing is allowing time for the pressure to equalize so that in the event of a momentary power interruption the compressor doesn't stall and overheat trying to start against the high head pressure. It doesn't know if it has been without power for 3 seconds or 3 years so it waits a few minutes before trying to start up.

author: coppercone2
author_rank: Super Contributor
timestamp: May 19, 2019, 06:41:02 pm
content: Keep in mind lighting is not digital, you can have a close hit that can be absorbed by surge protectors. Just not too close. You are increasing your protection radiusHowever lighting is not going to hit most likely in a perfectly uniform fashion, I think it has strike radiuses around buildings that are non linear (it's not exactly like throwing darts). There are IEC standards I linked some where in my posts about lighting protection, I believe some of them have data about lighting strikes near structure but I am not sure.And keep in mind it might go from a hard failure with fire to a soft failure or just a melt vs flames shooting out of something.

author: soldar
author_rank: Super Contributor
timestamp: May 19, 2019, 06:44:27 pm
content: Quote from: james_s on May 19, 2019, 05:54:58 pmMine does a lot more than that. If it was just the pressure thing it would be simpler to put a battery and clock like computers have or check refrigerant pressure. But once you put a microcontroller in a device they will write a flowchart for it a mile long.You can tell mine is doing a lot of things. It probably checks for inside and outside temperatures and other parameters. Then the compressor starts first but not the fan. Then one fan. And, finally, when everything is ready, the inside fan starts and the thing starts doing some useful work.I see much less need in a refrigerator or clothes washer but, still, everything now has a microcontroller and soon everything will be connected to the internet. Pretty soon when your dish washer stops working you will search for the error code and find that Google shut it off because you are using an ad-blocker on your refrigerator.

author: james_s
author_rank: Super Contributor
timestamp: May 19, 2019, 07:10:35 pm
content: Quote from: soldar on May 19, 2019, 06:44:27 pmDoing that would require a RTC and battery, or a pressure transducer, these all add cost while adding a 5 minute delay to the startup routine costs nothing in production. Whatever else it's doing and what possible benefits that might bring I don't know, but there's no reason that having a microcontroller has to result in it starting up slowly.I do agree in general though that there is far too much technology for the sake of technology. There is definitely something to be said for the simplicity of electromechanical controls, but these days it's a lot cheaper to use a microcontroller. It's easy to forget the development and production costs of something like a mechanical timer for a washing machine. All those individual gears and cams need to be designed, tested, injection molded and assembled. While simple in concept, it's complex and labor intensive in practice. This sort of mechanical engineering skill is being lost, it's just not the way things are done anymore. We can complain about it and be irritated or we can just accept that the world has changed and try to stick with the most sensible stuff where we can and where that isn't possible, adapt as needed.Personally I rather like my 1st gen Maytag Neptune washer and dryer with the mechanical timers, these machines were notoriously unreliable when they came out but once I fixed the 2 or 3 problems they almost all had the set that I have and the similar set my mom has have been working now for over a decade since I got them all for free after they broke down. Lots of old stuff out there still and you can keep it going almost indefinitely with a little effort.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 20, 2019, 01:38:44 am
content: What is really needed is a UPS and that would be expensive. Appliances such as AC units really don't like power flickers. My neighbour was gone on vacation and for some reason his AC was running, and we got a power bump and it sent the unit into what I can only guess was a stall. Very loud 60hz buzz, and the air coming out was cool, and not hot, indicating the compressor was probably not actually cooling. I shut it off by the disconnect on their house to save it from burning out.Come to think of it, they should make whole house cut off switches where it constantly watches for any unclean AC or a power outage, and it cuts off cleanly and just stays off for a few minutes, then turns back on. That would eliminate a lot of issues that power flickers or dirty power outages by ensuring a clean cut. Even standby UPSes will often let stuff through if the power cut is not instant.

author: amyk
author_rank: Super Contributor
timestamp: May 20, 2019, 02:24:53 am
content: Quote from: james_s on May 19, 2019, 05:54:58 pmIn other words the manufacturer cheaped out on having an unloader on the compressor or just making the motor big enough that it can "hot start" (see 2:50 in this video):https://www.youtube.com/watch?v=jzKnHBOm9BI#t=2m50s

author: james_s
author_rank: Super Contributor
timestamp: May 20, 2019, 03:30:00 am
content: I have never encountered a refrigeration system that has an unloader, I suspect it would cause as many problems as it solves due to having an additional failure point. Likewise with a bigger motor. If the motor is big enough to hot start against high head pressure then it is too big the rest of the time and results in not only higher cost but wasted energy throughout the life of the equipment.It's far easier to just incorporate a delay when power is lost, which is not a situation that should happen often. Most don't even have that, at least not the older ones, they rely on the overload cutout, if the compressor stalls it will trip that and by the time the cutout cycles the pressure will have equalized.This really is a non-issue, momentary power outages are not something that should be encountered frequently and if it does happen a lot, an electronic delay seems like the most sensible solution to me.

author: james_s
author_rank: Super Contributor
timestamp: May 20, 2019, 03:34:04 am
content: Quote from: Red Squirrel on May 20, 2019, 01:38:44 amI would find that incredibly annoying. Lights and most appliances will ride out a momentary glitch without any issues at all. I don't want the lights to go out completely for a few minutes every time there's a blip during a wind storm. If poorly designed equipment cannot tolerate power glitches then protective devices belong on that equipment, not the whole house.

author: amyk
author_rank: Super Contributor
timestamp: May 20, 2019, 05:05:40 am
content: Quote from: james_s on May 20, 2019, 03:30:00 amThey certainly used to have unloaders:https://patentimages.storage.googleapis.com/70/59/b1/50b14f9f2b0830/US2751143.pdfAs far as I know, big refrigeration compressors still have them.

author: james_s
author_rank: Super Contributor
timestamp: May 20, 2019, 05:47:03 am
content: I'm not surprised it's been done, but I've never encountered it. For the average consumer refrigeration equipment I doubt it would be worth the cost of added complexity.

author: soldar
author_rank: Super Contributor
timestamp: May 20, 2019, 10:16:33 am
content: I have never seen it in home refrigeration and I can't see the need. It's just one more thing to give trouble.

author: soldar
author_rank: Super Contributor
timestamp: May 20, 2019, 10:18:42 am
content: Quote from: Red Squirrel on May 20, 2019, 01:38:44 amThat's a terrible idea. It is worse than the problem it is trying to solve. No thanks.

author: Yansi
author_rank: Super Contributor
timestamp: May 20, 2019, 10:23:07 am
content: Quote from: soldar on May 19, 2019, 05:49:16 pmSelfcheck, maybe, but in fact that is to prevent trying to start a compressor against backpressure. Even those "mechanically" controlled aircons had delayed start relay for exactly this purpose.Most of them are single-phase, that would not simply start the compressor with a pressure on it.

author: soldar
author_rank: Super Contributor
timestamp: May 20, 2019, 10:38:03 am
content: Quote from: Yansi on May 20, 2019, 10:23:07 amReally? I've never heard of this before.

author: Yansi
author_rank: Super Contributor
timestamp: May 20, 2019, 11:30:22 am
content: Well, supposed you have a single-phase AC, which is more than common in US, if you try starting the single phase compressor against head pressure, you will likely end up burning the compressor.Some mobile aircons that you just plug in your wall outlet usually, after the first power up do also wait a couple of minutes for the pressure to equalize in the system, so you may not accidentaly start the compressor against head pressure. The electronics usually does not have any means of pressure measurement, so a delayed start is all what is needed.If the AC is kept plugged in for longer time and then turned on, it will usually start right away, because the electronics already knows the compressor stayed off long enough before so the pressures are equalized.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 20, 2019, 03:41:10 pm
content: Quote from: james_s on May 20, 2019, 03:34:04 amI'm thinking it could have a sensitivity adjustment. Basically it would only activate if an entire cycle is bad. Most equipment won't like that. Even mechanical equipment won't, such as motors, as they rely on the sine wave. Consumer standby UPSes will also "miss" it and the equipment takes the hit. Learned that the hard way when I turned off my main power cut off instead of the main breaker. The cut off is big and takes a lot of force to throw and I didn't do it fast enough so it arced. Half my servers locked up despite being on UPS. Of course dual conversion would have prevented that. I eventually want to upgrade to one.Of course the REAL solution is a whole house UPS or at least some kind of filter that will clean the incoming AC and buy you a couple extra cycles if there is an problem, but that would be quite costly.I guess it's probably best to just target whatever appliances are more sensitive than to do whole house though.Oh on subject of aircons, the two big 30 ton ones we have at work for the main floor really don't like dirty AC or short cut offs. When they do generator testing they usually end up locking up between the transfers. Not much can be done about that though, we just wait till they are done then we go reset them.

author: james_s
author_rank: Super Contributor
timestamp: May 20, 2019, 03:58:33 pm
content: Most things will ride out several cycles missin without any issues at all. What you are proposing would be obnoxious as well as being a safety issue. It would be shutting off all the lights leaving people in darkness due to a momentary glitch that would have only flickered the lights. Just what issues have you experienced with dirty power that this is trying to solve? I get power dips all the time in the winter and I've never had anything damaged. A whole house UPS would be ridiculous overkill although anything would be better than cutting off the power completely, that's the last thing anyone wants.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 20, 2019, 04:09:50 pm
content: Well air conditioners is a good example since we're talking about those. But yeah maybe lights could be exempt, ideally could do just the critical/expensive stuff. Computers will also hate it, but those should be on a UPS anyway, even a clean cut off is still bad for computers. Spinner disks absolutely don't like it and will take mechanical damage, but even SSDs don't like it as they may not complete a write, and it can corrupt the nand.I just know it makes me cringe whenever I get these weird brownouts at my house as I know it can't be good for anything. Though I guess what causes the biggest hit is not so much the power going out, but when the AC comes back. So if the cut off switch waited a few seconds and then turned on it would filter that part out. I can actually "feel" and hear it through the whole house when power comes back after an outage. It's like a very loud 60hz buzz all around me. It's actually odd, it does not really come from any particular direction it's just everywhere. Maybe 1 second max. Would be interesting to connect a scope (powered by a UPS or something) to non UPS backed plug and try to catch what goes on during that time. If I had to guess the equipment is seeing a couple 100 volts for a small moment as the power initially comes back. If ever there is a scheduled power outage (so I have a general idea when it comes back) I might give that a try for fun.

author: james_s
author_rank: Super Contributor
timestamp: May 20, 2019, 09:40:06 pm
content: Or just build this cutout into the individual appliances that benefit from it, as some air conditioners apparently already do. My fridge could use one, a few weeks ago the power blinked while I was at home and I heard the fridge stall and trip the overload on the compressor. It would have been preferable for it to cut out electronically but either way the overload cycled back on and it started up again a few minutes later.Most stuff just doesn't care, and stiff that does should incorporate protection because it's far easier than retrofitting millions of houses and creating a new set of problems like ensuring that lighting is on a separate circuit.

author: richard.cs
author_rank: Super Contributor
timestamp: May 21, 2019, 01:21:39 pm
content: Are you sure it's a conventional induction motor? If it's a fancy inverter-driven thing it will be a lot more vulnerable to surges.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 21, 2019, 05:06:06 pm
content: Quote from: james_s on May 20, 2019, 09:40:06 pmYou would not need to retrofit, it would just be something optional that you can buy if you want to. It could also act as an inline surge protector. But yea I guess they should just make it standard for the protection to be built in to appliances themselves.