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?
Thanks,
- John
...
...
Yes...
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... :)
--
Just plug the dryer in. If it runs AND heats it's good.
what did you see when you tried?
If you can't figure out how to use two probes to test every combination of a 3 or 4 prong socket, you should probably put the meter away and simpy see if the dryer works.
Hint: there aren't that many combinations.
1 to 2, 1 to 3, 1 to 4 2 to 3, 2 to 4 3 to 4If none of them read 240, you have a problem.
Those are the two hot legs.
Yes.
120V each hot to neutral, and 240V hot to hot.If you see 120 and 0, respectively, the circuit is wired incorrectly at the panel.
Think about it.
Why is the OP asking this question? The most likely reason is that he
*already* has a dryer plugged in which *doesn't* both run and heat -- and he wants to verify that the circuit is good first, before he tears the dryer apart looking for a problem.It's not a very good test in any event. If the appliance functions properly, both the circuit and the appliance are good -- but if the appliance does not function properly, there is no indication of whether the problem is with the appliance or with the circuit. Or both.
The heating element runs off the 240 Volts, the dryer motor normally operates off of one of the 120V legs.
RE: "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.
- John
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.
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.
There is an interesting device made for 110 that looks like a plug with small LEDs on it. You plug it in, and by the light combination, it tells you if all the wires are wired correctly. Any safety inspector carries one in his pocket, as in buildings, it is extremely rare to test circuits and have them come up straight. Sometimes more than half are wired wrong.
Do not know if they make it in 220 or not.
Steve
I'd suggest to talk with your friends and neighbors. See if anyone else has experience repairing electric dryers. Might be something simple that you're missing. I'm thinking thermal cutout.
RE: "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.
- John
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 the problem):
- 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 kitchen).The fuse block has 2 30amp fuses, type FRN-R-30. They are of
9/16" diameter.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 block.
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 be replaced.
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.
Question 1: Anybody know a source for the 9/16"-to-3/4" fuse "collars" that I'm looking for?
Question 2: 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?
Question 3: 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.Thanks,
- John
On 8/29/2009 10:20 AM John Albert spake thus:
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.
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.
Retest.
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? Internet?
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.
QUESTION: 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.
Thanks,
- John
From your posts and what you described you have:
Knob/Tube wiring An old panel that has corroded and/or loose contacts A fuse holder on a dryer circuit in the panel that is cracked and falling apart.
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.
Junk the old fuse box.
Get a "new" kind of fuse holder - and the fuses that go with it.
In the alternative, a circuit breaker box like is used for A/C equipment.
RE: "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?
- John
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.