Hello all -
What's the proper and SAFE way to test a 3-prong 240 volt
socket for a dryer?
I have an old analog (with the needle) Radio Shack
multimeter and I'd like to check both sides of the dryer
electrical circuit to make sure that each side is live.
The receptacle has two "straight" slots, each angled at
about 45 degrees.
Above that is an L-shaped slot.
I think the "L" is the neutral, is that correct?
With either side at 120 volts?
There should be 120 from each side to the neutral; hence 240 between.
Just have long enough probe to reach conveniently.
The simple acid test would be to plug the dryer in and turn it on... :)
"The simple acid test would be to plug the dryer in and turn
it on... :)"
The problem is that the dryer _does_ turn on (i.e., spin),
but there's no heat.
It's a 15-year-old Kenmore (Sears) that was made by
Whirlpool (I think).
I've been working on it a couple of days and am about ready
to throw in the towel.
I've replaced the heating element _and_ the thermal sensor
and thermostat on the side of the heater housing.
On top of that, cleaned it all out - 15 years' worth of lint
and dust, looks like new now.
It spins as it normall would, but, no heat.
I also replaced the old 3-prong outlet with a new one. The
old was was cracked and loose. It actually fell apart in my
hand as I went to take the old wires out. The new receptacle
seems much better, but I'm wondering if both "sides" of the
circuit are live at 120v.
I'm about at my limit for investment into the old machine.
If I can confirm that the problem isn't with the incoming
voltage itself, I figure that the next trip I make will be
to buy a replacement.
Agreed, the safety stuff is usually what goes. You've got a meter,
use it. The heating element will be pretty low resistance, well less
that 100 ohms. Any safety devices in the circuit should read 0 ohms.
Check the controls since that is also part of the circuit. Was there
a schematic inside? There usually is. Can you read a schematic?
Take the time to diagnose and test with your meter. Then buy parts.
"By "thermal sensor" do you mean the thermal fuse? If not,
or you're not sure, I'd concentrate my efforts there as it
sounds like a classic case."
Yes, I believe it was the thermal fuse.
Looks like the item shown on the page you posted.
Hello all -
I'm the original poster of this thread, which deals with
dryer problems (dryer runs but no heat).
After fooling with the dryer, and on the recommendations
form this forum, I got out an old Radio Shack multimeter and
figured out how to check the 3-prong 240 volt outlet.
Well, here's one part of the problem (may be a LARGE part of
- one side of the circuit tests ok, but
- on the other side, no voltage.
Upon further checking, I did a closer examination of the
fuse block (NOTE: my house was built in 1911, still has a
60-amp service with old "knob and tube" wiring). There are 2
large pull-out fuse blocks at the top of the electrical
panel, one marked "main" and the other marked "range". The
range panel is for the dryer (house has a gas range in the
The fuse block has 2 30amp fuses, type FRN-R-30. They are of
Because of the smaller diameter, they require "adapters" or
"collars" (I don't know the correct term to describe it),
that slip over the ends of the fuses. With the collars in
place, the fuses snap into the fuse block.
One of these collars shows marks that indicate corrosion,
resistance, not sure what. All the others are fine.
I started checking continuity with the multimeter.
Both fuse cartridges (by themselves, without touching the
collars) are fine.
One side (good collars, good fuse) checks ok when I touch
the probes of the multimeter to the large prongs on the fuse
The OTHER side does NOT give good continuity, due to the
corroded collar. It's like it has almost a "coating" on it
that is preventing the flow of current. The collar needs to
Well, thought that it would be easy to find these little things.
But it isn't.
Stopped by Sears, Home Depot, Lowe's. Yes, they have 30 amp
FRN-R-30 fuses, but NO collars. The guy in the department
said you can't even get those anymore.
They have larger-diameter fuses, but nothing in the 30 amp
capacity. The proper diameter to fit into the fuse block
without adding the collar looks to be about 3/4". The only
larger fuses they had were 35 amp.
That would fit, but of course I'd be "over the limit" as far
as protection goes.
Anybody know a source for the 9/16"-to-3/4" fuse "collars"
that I'm looking for?
Anyone know of a source for FRN-R-30 fuses that come in a
larger, 3/4" form factor so that I don't have to use the
collars any more?
If I can't get those collars, would putting ONE 35 amp fuse
on ONE side of the fuse block be a workable temporary
solution (at least until I can get my service upgraded to
100amps with circuit breakers)? It goes without saying that
I want to protect the house.
Answer to both questions: forget hardware stores (most of them, anyway)
and department stores. Get yourself to a "real" electrical supply house.
You know, the place where electricians buy stuff. Contrary to popular
myth, all of these places I've ever been in will sell to anybody. Tell
them what you need (or, better yet, bring in the old one); there's a
good chance they'll have it.
Found--the gene that causes belief in genetic determinism
Make sure the power is off. Remove your adapters. Lightly sand
the contact surfaces, both male and female. Test the continuity
through the adapter with your multitester. Sand and/or lightly
bend the contacts that the adapter goes into to insure good
contact. I'm guessing these will all be brass or copper and you
should be able to see the bright shiny new metal.
Keep the whole world singing . . . .
I am sure you will amazed that these are called "main and range" panels.
Using an adapter-to-30A, as you have, is common.
It is inconceivable they are not available. Look for Bussmann (or Buss)
#263 fuse reducers. Electrical wholesale houses would have them but may
not want make that small a sale. Buy it from an electrical contractor?
Nope. The fuse sizes are regulated. 30A is the max electrical size in
that physical size. Larger size starts 35A.
I wouldn't. The adapters should be readily available.
Dan's idea of cleaning the adapter might be all you need. If the adapter
has overheated it may have annealed and lost its "spring". In that case
it should definitely be replaced. If the cleaned adapter has a tight
connection to the fuse and pullout it is probably good for another 50 years.
Changing to a 100A panel is a separate issue. If you are not blowing
fuses the existing fuse box may be adequate. Circuit breakers are
certainly more convenient. I have more faith that a 50 year old fuse
will blow at its rating that a circuit breaker.
Hello all -
I'm the original poster of this topic. Sorry, been busy the
last few days.
My last post asked about [what I now know are properly
called] "fuse reducers".
Got a more serious problem now.
My house has the old 60-amp service with 2 "fuse blocks"
(again, I'm not sure of the proper name for the part)
located above a row of fuses.
The one on the left is marked "main" and the one on the
right is marked "range". The "range" circuit is being used
by my dryer.
After investigating with a multimeter for continuity, I
found that the root cause of my dryer not getting power was
not either fuse in the block, and not specifically the fuse
reducers (although one was worn and pitted).
Of the four contacts in the fuse block, one was marginal,
i.e., not "gripping" the fuse tightly. I believe that when
the block was pressed into the electrical box, this marginal
contact was made worse. The end result is one contact point
between the fuse reducer and the fuse lugs is weak, perhaps
arcing, and sometimes losing contact altogether. No good.
Well, I tried bending the contact lug and the thing broke.
Not the lug, but the fuse block itself!
I've gone to a couple of electrical supply houses in town
(the places where I assume electricians go when they need
parts), and they guys just say, "nope". Not made any more,
they can't get them.
I tried a search on ebay. No go.
I've tried googling, not getting anywhere.
Clearly, I need help or advice from others who know a lot
more than me.
Can anyone provide a source for these old 60-amp parts,
used, salvage, whatever? A name, phone number, URL would be
a BIG help.
Ever tried to super-glue one of these back together? I
assume it's made from Bakelite, it's not plastic. The break
is clean, with some surface area for a grip, but I'm
wondering if it won't just break off in place once I press
it back into the circuit box.
If I can't find another one, or can't repair the one I've
got, guess the only option is to start looking for someone
to upgrade my service to 100amps with circuit breakers. Will
electrical contractors do this, but still leave in place the
old knob-and-tube wiring for the time being? I can't afford
to have the entire house wiring replaced.
From your posts and what you described you have:
An old panel that has corroded and/or loose contacts
A fuse holder on a dryer circuit in the panel that is cracked and
All that taken together to me sounds like a prescription for possible
disaster. For example, the corroded connection points will generate
heat. At some point, that heat could become enough to ignite
something on fire. If it were my house, I would not be comfortable
using super glue to repair a crumbling, failing fuse holder.
I would recommend getting a pro in to assess the situation. He can
give you options that will work and be safe.
"If it were my house, I would not be comfortable
using super glue to repair a crumbling, failing fuse holder."
That's why I'm looking for a source of a replacement part,
either new or salvaged.
The rest of the box seems ok.
I need a fix for _now_ - I fully understand what I need in
the longer term.
Does anyone know where to find parts for the old 60-amp systems?
You have a problem. The parts have not been made for almost 50 years.
Finding used replacements will not be easy - most are scrapped when
pulled - and the vast majority were pulled years ago. Might try an OLD
Putting in a new panel is pretty much your only solution, and most
electricians won't touch the K&T.
Only solution is to put the K&T to junction boxes and wire from there
to the new panel with romex. It will have to be "temporary"
You will also be replacing the wires in the stack, and possibly the
overhead as well because it will HAVE to be at least 100 amp
Another possibility is an electrical contractor that works on older houses.
There are weatherproof fused disconnects that use a cartridge fuse
pullout. They are used with A/C compressor/condenser units. I doubt they
are the same size. All the ones I have seen are 30A rated.
I would describe what you are looking for as a "fuse pullout for a main
and range panel".
Don't know why it is "temporary". It should be code compliant. The
jurisdiction may have requirements beyond the NEC for what to do with
K&T, and for what is required with a new service.
"K&T is not code compliant, and "officially" cannot be
connected to a new panel. Totally different "architecture""
Does that mean that anyone who happens to own a house with a
60-amp knob-and-tube system must replace the ENTIRE wiring
of the house along with the fuse panel? With lathe & plaster
walls, what would that entail? We could be talking 15-20,000
Sorry, cant - and WON'T - do that.
Haven't got the money, plain and simple. Or to put it more
succinctly, considering the deteriorating neighborhood this
house is in, it would be foolish to throw much money into it
with any hope of getting it back, dollar for dollar.
My house was built in 1911. I'm _guessing_ that the K&T is
original from that time, but that the original fuse panel
was replaced at some point with a more "modern" (at least
for the time) 60-amp service panel. I notice that "between"
the 60-amp fuse panel and the runs of K&T, there is an
"intermediate" junction box. It has [what I think is called]
"BX" armored cable between it and the fuse panel. I'm going
to guess that the current panel was installed not long after
the advent of BX. Would that be, say, late 40's or early 50's?
The intermediate box is what I was saying would be required to
connect K&T to a "current" fuse box.
Up here in Ontario Canada, NO insurance company will write new
business on a house with K&T wiring. Depending where you are you MAY
be able to get an electrician to install a new panel and connect it to
the existing wiring - but it would not be code compliant. Depends on
your level of inspection requirement etc.
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