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Author Topic: Surge protection for a washing machine  (Read 8457 times)
KE2KB
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Posts: 633




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« on: August 05, 2017, 12:01:26 PM »

Hi;
I just bought a new washer, and it has sensitive electronics (computer) so I want to protect it from surges, just as I do my computer, TV, and yes, my ham radio gear.

First, I need to tell you that I already have a whole-house surge protector connected directly to the service panel. It uses a 2-pole 30A breaker.

The washer is on its own 20A breaker and plugged into a GFCI receptacle.

Researching single-outlet surge protectors, I found one in particular (Defiant model YLCT-29 sold by Home Depot) where one reviewer states that it came with a notice saying that the device would not protect the appliance if there are less than 30ft of cable between the receptacle where the device is connected and the service panel.

I suppose that its capacity (joules) is too low to protect against the instantaneous current that could flow through the device when a large spike is present. The more wire there is between source and load, the higher the resistance, and the lower the max surge current can be.
This particular device has a claimed surge capacity of 1,000 joules.

Besides that, I have another possible issue: Since this surge protector will be plugged into a GFCI receptacle, could a spike (even one that is not large enough to damage the device) cause the GFCI to trip?
In effect, passing the spike to ground will cause an imbalance of current between line and neutral, thus tripping the FGCI.

My thinking is that most of the surge protection devices available to the consumer are simple devices that clamp voltage at some designated level; sending over-voltage (spike) current to ground via the ground conductor.
I have opened up some surge protection devices and found little more than a MOV or two. The better ones have small toroidal chokes on both line and neutral at the input.

If that is indeed the case, then perhaps a better surgr protection device would be one that does not send surge current to ground, but instead stops it from passing in the first place. I'm thinking of toroidal chokes.
But how large does a toroidal choke need to be, and what ferrite mix should I use to build such a choke?
The washer draws heavy starting currents, which is not usually an issue for ham stations.

Any thoughts?

Thanks

Frank <KE2KB>



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SWMAN
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Posts: 1066




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« Reply #1 on: August 06, 2017, 11:57:13 AM »

I have a 2 year old nice GE washer that got hit several months ago. We had an almost direct lightning hit at the house. It vaporized my 10 meter vertical and a few CFL light bulbs in the house and killed the board in the washer. Believe it or not my warranty would not cover the new board because it was a lightning struck. Luckley  my local parts supplier had one fo 90 bucks and I fixed it myself.
 Now I use a good Triplite Isobar and just keep it switched off when not in use and switch it on when I want to wash. Worked out good so far. The isobars are rather expensive but had some extras at work.. Good luck,  73. Jim. W5JJG
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K1HMS
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« Reply #2 on: August 08, 2017, 08:21:51 PM »

Frank,

The key to mitigation is bonding, that is tying everything together so the potential difference stays small. It is not hard but it is tricky.
A couple of assumptions:
A typical strike is 20kA, nano seconds rise time, 1 msec duration.
A good 3 ohm to ground "ground rod" will be at 60kV given V=I*R = 3x20kA
Wire is 18nH/foot or .12 ohms per foot at 1 MHz or about 2200 V/ft
Earth ground doesn't stay at zero volts but follows V=I*R and I is large and R is significant.
Fusing current of 12 AWG copper 32ms 5.3 kA !! It is well over 10kA at 1ms. ( google fusing onderdonk)


Disclaimer to minimize nit pickers, ground rod resistance varies, Wire Xl/ft varies with wire gauge, bends, and insulation, freq spectrum varies, side strikes might only be a few kAs, all the current will not be on one conductor, etc etc. The intent is to show the magnitude of the problem. It is rise time in ns, high current in kA, resistance, and inductance in ohms. Volts of lightning is not important.

A field strengh of +/- 2kV/m or more at your location for a strike 1/4 mile away is not uncommon. You have exprienced it and not known it because everything went up and down together. It is  potental differences that does damage due to current and heat.

Which brings us back to your washing machine and bonding. A MOV between the hot, neutral, and safety ground will do a lot. These 3 will stay at the same V, potentially kVs, but that is normal. But what about other paths?

The dryer a inch from the washer on a heavier gauge wire more directly wired to the panel or possibly the 1" copper water pipe in addition to a metal pipe to the well or street. All of these provde a path with the possibility of a large potential difference to the washing machine's 3 wire cord and need to be bonded. Code requires metal pipes be connected to the panel ground. Don't assume this is done, it wasn't in my 30 YO house. Plastic pipes with high mineral content water poses a special problem which is addressed in a UL or ETL marked appliances and generally not a concern.

The tricky part is to visualize what 10 or more kV will do, what paths are available to it, and bond those together. A switch rated at 600V isn't part of the solution.

I pluged my washer into a single plug surge protector. I crimped lugs onto 10 GA wire which went under rear cover screws on the washer and dryer and then to the over head copper water pipe. A dehumidifier 4 feet away was pluged into a different circuit. I moved its plug to the same duplex the washer is plugged into to ensure it was on the same circuit. Thus, appliances, circuits including safety ground, and nearby plumbing are all bonded so no delta V.




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KC4ZGP
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« Reply #3 on: August 10, 2017, 10:30:41 AM »


Now y'all got me worrying and I just finished laundry before I came back to work.

WARNING:

Ladies, never interfere with a man's housework.

Kraus
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KE2KB
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Posts: 633




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« Reply #4 on: August 10, 2017, 04:04:05 PM »

I can bond the washer to my 2m antenna ground rod, which is located (outside) very close to the laundry room. That GR is bonded to the POCO GR by a length of #4 wire. The 2m antenna mast is bonded to the GR with the same #4 wire.

I would love to have the ability to evaluate my grounding system, but I don't even know what equipment I would need. I did read something about testing the conductivity of the earth between two or more ground rods, but I don't recall exactly what it involved.

As for my ground system, the electric service is bonded to the two ground rods I mentioned above (to the POCO one first), and to the copper water line at the meter. There are bypasses around both the water meter and heater.

My dryer is gas powered, and it doesn't have much electronics. The washer and dryer are on separate 20A dedicated branches, which are wired as a multiwire branch circuit, sharing the neutral, with breakers being on opposite legs of the 110/220V service.

Should I consider the length of the 12/2 or 12/3 cable running between the service panel and the load? I currently have about 30ft of #12 BX or Romex between the breaker and the washer. It would make sense that, the longer the distance, the weaker a surge will become by the time it reaches the load. But at the same time, the length of the ground conductor is the same as that of the ungrounded conductors, so that might cancel out any benefit from the longer run.
Perhaps adding cable to the run, and also bonding the appliance cabinet directly to the ground rod using #6 or heavier conductor would be worthwhile.

It might be worth the cost to invest in a good surge protector, but if I am going to install one for the washer, I should also install one for the dishwasher, which is hard-wired to its own 15A branch.

How much protection does the whole-house protector provide? Since it is wired in parallel to all loads (except for the impedance of the service drop and entrance wiring), I wouldn't expect it to provide all that much.

In the end, I think I will get into the practice of unplugging the washer, and any other sensitive equipment whenever a strong to severe thunderstorm is likely. For the hard-wired dishwasher, I can cut off power at the breaker, which I know provides only minimal protection against high-voltage surges, but it should be better than nothing.

In all the 40+ years my family has owned this house, we have had only one very minor loss caused by a lightning strike. That one exception was an A/D converter on a home-built computer system which was connected to a long run of (shielded) cable running to a back yard temperature sensor. The lightning strike was not on our property, but pretty close.
But history cannot predict the future... and several tall trees in the immediate vicinity of the house have been taken down within the past year, which reduces the number of taller targets for lightning.
I am hoping that, with my 2m vertical sitting up there above the roof, and being as well grounded as is practical, that it might sacrifice itself to save an expensive repair.
My radio equipment is always disconnected from both the antenna and power when not in use.
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N0YXB
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« Reply #5 on: August 10, 2017, 06:02:44 PM »

You might also consider a whole house surge suppressor. Many can be found at The Home Depot and Amazon.
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KE2KB
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Posts: 633




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« Reply #6 on: August 11, 2017, 10:09:47 AM »

You might also consider a whole house surge suppressor. Many can be found at The Home Depot and Amazon.
I already have a whole-house surge suppressor. I was just thinking that I might need the added protection of one at the load as well.
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KH6AQ
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« Reply #7 on: August 11, 2017, 04:23:36 PM »

Lightning 10-90% current risetime is around 1 microsecond and has a duration of less than 200us.

Given a wire with an inductance of 18nH/ft the voltage drop during the risetime for a 20kA/us strike is V=Ldi/dt = 18nH(16kA/us) = 288V/ft.

 

    http://ieeexplore.ieee.org/abstract/document/6344272/?reload=true

    http://www.atmo.arizona.edu/students/courselinks/spring08/atmo336s2/articles/Wiley_EPK_MAU.pdf
« Last Edit: August 11, 2017, 04:34:03 PM by KH6AQ » Logged
KE2KB
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Posts: 633




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« Reply #8 on: August 12, 2017, 03:37:49 PM »

What do you think about this TripLite unit?
https://www.amazon.com/Tripp-Lite-Protector-Suppressor-ULTRABLOK/dp/B00006B81D/ref=sr_1_7?ie=UTF8&qid=1502577092&sr=8-7&keywords=surge+protector&refinements=p_89%3ATripp+Lite

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KE2KB
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Posts: 633




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« Reply #9 on: August 12, 2017, 03:54:42 PM »

Or this in-wall surge protection receptacle?

http://www.legrand.us/passandseymour/surge-protection-devices/receptacles/specification-grade/audible-alarm-with-led-indicator/5362wsp.aspx

Would be nice if this one could be used in daisy-chained configuration, so it could be used to protect an appliance that isn't connected by cord and plug - such as the dishwasher, which is hard-wired. If this can protect downstream devices, then I could simply install it in-line with the dishwasher.
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KD4LLA
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« Reply #10 on: August 12, 2017, 06:38:53 PM »

I asked a local electrician about grounding in my house for electronic equipment and got more "puzzled looks" and additional questions than answers...
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KE2KB
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Posts: 633




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« Reply #11 on: August 16, 2017, 09:49:39 AM »

I asked a local electrician about grounding in my house for electronic equipment and got more "puzzled looks" and additional questions than answers...
I suppose that is because most electricians are not hams, don't understand RF, or even surges, and are mostly concerned about code for safety.

I am using an old but still functional Proxima (Newpoint) surge protector strip for my washer. It's a high quality product I had originally purchased for computer equipment, but stopped using when I bought my APC battery back-ups.
So far the Proxima surge protector is functioning well. Has not tripped out or caused the GFCI to trip out. Now I only wish I could protect the hard-wired dishwasher in the same way.
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AH7I
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« Reply #12 on: August 23, 2017, 09:14:14 AM »

It's the squirrels that will get you.

The first time they chewed through my neighbor's service drop neutral. I lost a few light bulbs, a computer, and some small electronics.

The second time, about 15 years later, they chewed through my neutral. My new refrigerator was a month out of warranty...


73, -Bob ah7i/w4
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N9AOP
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« Reply #13 on: August 25, 2017, 10:09:33 AM »

I have an ancient tub and wringer washing machine.  I don't think that a surge will bother it.
Art
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K1ZJH
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« Reply #14 on: August 26, 2017, 09:45:38 AM »

Grounding the washer to an outside ground rod just might create a ground loop, and a better path THROUGH the washer, and its electronics, for a lightning induced surge. grounding and isolation is best done before the equipment, in my opinion.

Pete
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