I had a service guy tell me that sometimes electr. boards fail inside
the dryer due to electrical spikes. I wondered if this was BS
because this is a 220 appliance and I didn't think they are as
sensitive to such things. If it is true, can you buy a surge
protector just for the clothes dryer? Thoughts on this...
Did the board in your dryer fail, or is this a hypothetical question? If
it did fail, I'd be more suspect of lead-free soldering than a voltage
spike. Circuit boards are not directly line-powered. I think the dangers
of spikes, in general, have been overstated by 3-4 orders of magnitude.
But I don't think a 220 volt unit is any less vulnerable than a 120 volt
Spikes come in on the power lines and don't care about the voltage, so it's
certainly possible that one can damage a 220 volt appliance just like a 120
volt model. Yes, you can buy 220 volt surge protectors -- do a Google
search. Another choice is to wire a surge protector in at the main breaker
and protect the whole house.
* I believe this to be true. It seems as though microprocessor controlled
appliances fail earlier than their mechanically controlled predecessors.
Steps you can take to help reduce the risk of this is making sure that your
grounding electrode system is in good condition. Check your ground clamps
at the water pipe and ground rods (If visible) for corrosion and tightness.
Here's a photo example from my site of a clean connection:
Make sure your water pipes are bonded to each other:
Have a bonding jumper across the water meter:
You should also install a surge suppressor in the main electrical panel.
The grounding and bonding will help protect against lightning strikes and
the surge suppressor will help protect against spikes as a result of other
equipment, particularly those that are motor driven.
That's the best and most cost effective solution.
And of course voltage spikes can damage a 240V
dryer with electronics just like a 120V microwave.
Lightning hitting the utilities could sends a 3000V
spike down the lines. 3000V going into something
designed for 240V is just about as bad as it going
into a 120V appliance.
On 10/5/2012 7:02 AM, firstname.lastname@example.org wrote:
I agree a service panel protector is a real good idea.
If you have a strong surge from lightning on the power service it likely
lifts both hot wires above ground. Since the neutral is bonded to ground
and the earthing system at the service I would guess that surges
line-to-line are smaller than line-to-neutral or ground, but they easily
could damage 240V equipment.
If you have no service panel protector and you have a strong surge, at
about 6,000V there is arc-over from the service panel busbars to the
enclosure. After the arc is established the voltage is hundreds of
volts. Since the enclosure is connected the the earthing system that
dumps most of the surge energy to earth. Surge protection at the
equipment is likely to have more problem with a 3000V surge than one
that is much stronger.
Any decent protector will shunt spikes line to neutral and line to
line. (3 or more MOVs)
In the dryer, they usually connect the motor and the controller board
line to neutral.
I bet this happened when the dryer was off and the only thing
connected was the circuit board.
On Fri, 05 Oct 2012 12:11:25 -0400, email@example.com wrote:
Repair guy said that most newer dryers were hot wired to timer not
control knob like this older one was. He did say that when it was
off, the power was still going to the control knob so if I understand
you correctly, you sound correct.
Diligent bonding and connections to water pipes is good, but it's not a
substitute for a proper ground, e.g., one or more copper rods driven six
feet or more into the earth. A water-pipe bond is just to prevent the piping
systems in the house from remaining live with voltage if they come in
contact with a live wire.
That is not really true if you are talking about the all metal water
systems in days of old. The whole city is a grounding grid with miles
of electrode in the dirt.
These days it is hard to find a new metal water pipe.
A metal municipal water system will be a far lower resistance to earth
than any other earthing electrode you will have a house.
It certainly is a good earthing electrode, which is why the NEC has
required its use since time began.
Perhaps this will explain:
"You've probably seen project requirements that call for the grounding of
piping systems and exposed structural steel. Those requirements, although
well intended, miss the mark. The stated intention of such requirements is
nearly always the removal of dangerous voltage on specific types of metal
parts in the event of a ground fault. These metal parts include exposed
structural steel members, electrically conductive metal water piping
systems, metal sprinkler piping, metal gas piping, and other metal piping
systems. But these requirements fail to make that intention a reality.
That's because you remove dangerous voltage on metal parts through bonding,
not through grounding."
"The NEC (section 250-81 through 250-83) requires that the electrical system
connected to all of the following, if available for grounding purposes:
* metal frame of building
* concrete encased electrode (rod, pipe, plate, braided wire)
* ground ring and
* metallic water pipe with 10 lineal feet in contact with earth
The NEC has noted that metal piping will corrode over time and possibly lose
its continuity with the soil (i.e. ground) or be replaced by plastic pipe.
Accordingly, should this occur, the NEC has mandated the 3 other paths to
ground be utilized."
In other words, attaching a metal water pipe to an earth ground is used to
protect the user from the plumbing, not to provide a ground for the
electrical system. Using metal water pipe as an electrical ground is
I am not fond of the term "grounding" because you may be talking about
"bonding" or "earthing".
Your quote has that problem. (The NEC has started to clarify which use
The NEC has 3 electrodes that are *required* to be used as earthing
electrodes (where present).
One is metal water service pipe (10 ft...).
Another, in general, is structural steel (because of its connection into
the rebar systems in the concrete foundation).
Your source is incorrect - water pipe and structural steel *must* (in
general) be used as earthing electrodes.
If they are connected as earthing electrodes they are also "bonded".
The correct list has electodes that may already be present in a building
and does not include ground rings and everything after "concrete encased
Cite for corrode.
Cite where water pipe has worse corrosion problems that ground rods.
The NEC has NOT mandated that "3 other paths" to earth be utilized.
The requirement to use water pipes as an earthing electrode is in a
section on the earthing system and the electrodes to be used.
It is in your list of required earthing electrodes, above.
You have bullsiht information and are using a bullsiht source.
(What a surprise.)
Sorry. I thought the material was righteous on its face. Evidently not. See:
"Grounding vs. Bonding - Part 10 of 12"
"Your source is incorrect..."
Does not exactly satisfy your request, but of interest:
"The NEC has noted that metal piping will corrode over time and possibly
lose its continuity with the soil (i.e. ground) or be replaced by plastic
pipe. Accordingly, should this occur, the NEC has mandated the 3 other paths
to ground be utilized."
Yes it has. (See above)
I assume your "non-bullshit" source is your own dim remembrance of things
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