Why does my Central A/C Keeps Blowing its Fuse? For years, my A/C condensing unit has blown a fuse once, maybe twice a year.  It's 27 years old now and blew a few fuses last spring.  Now it blows a fuse every few days.  So, I replaced a bad running capacitor on the compressor and replaced a leaking capacitor on the condenser fan motor, still blows fuses every few days.  Dangdest thing is that it has a very respectable amperage reading - 20 amps on each leg (it's 220v) even when it's very hot (105 degrees outside) and the fuse only blows in the evening when the temperature has gone down for the day! I thought that maybe it blew a fuse when cycling off and on, so, I tried just operating the A/C manually (turning it off when the inside temp was comfortable and on when I wanted some cooling) - still blows a fuse.

I now wonder if the problem is with the fuse box or power supply.  It is typical that after a day or two of replacing a fuse, the new fuse darkens - it still works, but can get quite dark.  A blown fuse will be really dark and the nice clean copper is pretty scorched.  I cleaned off the contacting surfaces of the fusebox and tightened the wires down.

I'm now suspicious of a possible occasional voltage drop in our power supply.  Wouldn't that spike the amps to my A/C unit and burn a fuse?  A few weeks ago the power company installed a box to monitor power quality right outside my house.  When I asked them what they were doing they informed me about monitoring the power and then asked me if I noticed lights flickering and so on.

I thought I might monitor voltage last night to see if I might catch a drop (wishful thinking I guess).  But anyway, just using a 120v receptacle, the volts were 120.0 volts to begin with, 118.8 volts when the A/C came on, went down to 117.4 volts, then ranged between those last two numbers 'till I turned the A/C off an hour later.  Then the reading was 120.9.  First thing in the morning, the voltage was 123.0 volts  So, there's quite a swing in voltage - I imagine that's normal, but I don't know.  I'm up a hill, at the end of the power line in a city area.

Here's the particulars of my A/C condenser - it's a 1985 Sears 3.5 ton (NCABA42AB01) - full load on condenser= 21.5 amps time delay fuse called for is 30 amps and that's the fuse I keep replacing.

Anybody have any ideas - poltergeist, maybe?

Update:  It just blew a fuse again - mid day this time.  I noticed that the fuse box was really hot - I measured it with an infrared thermometer - 220 degrees F!  The condenser unit was buzzing, only one fuse blew - the other looks fine.  I'm thinking I need to replace the fused disconnect.

Long-term darkening of a fuse on a high-draw circuit like an AC is not unusual. However, darkening as quickly as you have described means the fuse is operating right at its limit for too long.

The first thing I would do is call an electrician and have the fuse replaced with a breaker. At least that way you don't have to touch a hot fuse to replace it. They may also find a problem with the wiring (corrosion or a break) that could explain your problem.

Next is I would buy/borrow a multimeter that has an amp clamp on it. Measure the current used by various parts of your system (blower motor, compressor, condenser fan) as well as the main power feed to find out how much current you are pulling. This may help you identify which component is causing the problem.

defective electrical disconnect / just replace it


Why does the main circuit breaker trip but not the smaller branch circuit breakers? We have one circuit breaker (40 A) where our electrical service enters our house, then it is divided into a 32A line for level one and a 25A for level two.The main circuit breaker (40A) trips every several hours, but the other two circuit breakers (the 32A and the 25A) don't trip.  I am thinking the problem is that the 32A breaker and the 25A breaker makes 57A, which is bigger than the 40A main breaker.

Am I right?  Should the total rating of the different circuit breakers in one system be less than the rating of the main circuit breaker?

The two branch circuit breakers will trip if the load on their protected circuit is greater than 32 amperes, and 25 amperes respectively. However, since the main breaker trips at 40 amperes. If both branch circuits are pulling a full load the branch circuit breakers will not trip, but the combination of the loads will trip the main breaker (32 + 25 = 57 > 40 as you have said).

It's a very common situation to have the branch circuit breakers total more than the main breaker, but this is almost never a problem since the circuits usually don't pull a full load. Remember, circuit breakers are there to protect the wires. They shut off the power if you are drawing enough power to damage the wire, so installing a larger main breaker is likely not an option (unless you contact your power company and have the service upgraded, which will include upgrading the feeder cable).

Contact your local power company, and speak to them about a service upgrade.  Other than plugging less stuff in, or cycling loads, there is not much you can do yourself in this situation.

Heres is the easy answer. Breakers and fuses are used to protect wiring from overheating and starting fires. They have nothing to do with protecting the load. Match your breakers to what your wire is rated for and you will never go wrong. If your circuits still trip then you need to increase wire capacity and put bigger breakers on it or decrease the load on the circuit. Do not use breakers that will allow more current to run the wire than the wire is rated for, a fire will result or at the very least your wires will melt.


Copper Water Pipes used as Electrical Ground I am replacing a section of copper water pipe that burst behind tiled shower wall. Since the pipe run is along an exterior wall subject to winter temperatures, I'm considering replacing this section with PEX given it is less prone to freezing. But in this house (built 1959) copper water pipes are used as electrical grounds in multiple above ground locations, i.e., where 2prong receptacles were replaced w/3prong receptacles w/the addition of a copper wire (green/insulated)-1 end wound under green ground screw on receptacle, other end bound by a grounding clamp to a nearby cold water pipe. Splicing in PEX will interrupt the "continuous ground". Is PEX therefore  contraindicated or is there a way around this?

You'll want to consult a licensed electrician in your area, but you can probably simply bond a 12 or 14 gauge bare copper wire to the copper pipe on either side of the section you replace with PEX to maintain the preexisting continuous ground.

Pay more attention to the first part of this answer than the second part.

It is unlikely that anything electrical is connected to the pipes above the ground level. Normally the ground connection is from the junction box in the basement to the main where it enters the house.

Nevertheless, for safety reasons all the pipes needs to be grounded so you will have to attach grounding jumping wires to keep all the plumbing grounded.

If you have any question about it, you can check your outlets using a tester to make sure they are grounded after you do the repair. The tester looks like this:

There are also ground testers you can use on the pipes to make sure they are all grounded.


How do I install an electrical outlet on a live circuit? In my dorm room closet, there is a junction box with a blank plate (no outlet). Inside there are three wirenuts (hot, neutral, ground).

I know it is generally unsafe to do any work on a live circuit, so I will see if I can set the circuit breaker. If I cannot, is there a safe(ish) way to perform this operation?

There is a reason they put a blank over that box. They do not normally put outlets in a closet, as cords plugged into them tend to get buried in junk if close to the floor or a shelf, creating a potential overheating and fire hazard.  Under no circumstances should you attempt to wire an outlet to these wires hot. It is never a good idea, even if you knew what you were doing. SO DON'T!!!!

[ Caution: community members have reported that this advice is potentially dangerious ]

put a light socket with a outlet in that box . then if you decide to plug something up, plug it in then run the plug's cord along a safe passageway, then secure it there with glue or something else that wont damage the cord but will keep it in one place . its safe ways to have power in the closet . but when dealing with live circuits, use rubber insulated gloves, insulated tools, insulated fiber glass ladder, etc. I heard its good to even use a thick rubber matt to keep you off ground.


spa weight of 4,250 lbs I have a pre-existing patio and would like to add a spa tub which weighs 4,250 lbs filled with water. Unknow is, re-enforced with re-bar? the exposed one side appears to be at least 18 inches thick. What is the minimum thickness of normal concrete to hold that much weight, with or without re-bar?
?

I have mine on a 4" thick reinforced concrete pad, no problem. If not reinforced, I'd go with 6". Basic cheap "Quickcrete" is 3,000PSI compressive force, plenty strong enough when you factor in the surface area of the tub's structure that will be contacting the slab.

Keep in mind though that concrete strength takes a long time to get to the peak strength levels. So don't place your tub and start filling it immediately.

Age  vs Strength percent

1 day    16%
3 days   40%
7 days   65%
14 days  90%
28 days  99%

Oh wait, you said it was already existing... never mind.


What could be causing my water heater inlet pipe to corrode? There is corrosion forming on the inlet and TP valve connections to my water heater; the outlet seems to be fine.  More specifically, the nipples are what is corroding.  I have read the copper pipe and galvanized steel will cause this, and I assumed this was the issue.  Upon further investigation, "Dielectric" is clearly readable on the nipple labels so they are not steel I guess.

I thought that these nipples were produced to avoid this exact problem.  Why are they still corroding?  The inlet nipple has corroded to the point that there is now a tiny drip present.

Edited for adding pics below.  I am suspecting that maybe the nipple is corroding from the outside?

Click any image for full size (8Mpixels)

I'm thinking that the installation is missing this dialectic union. Your "dialectric" nipple has an ABS plastic coating inside a galvanized steel pipe. If the dialectic union were used in conjunction with this nipple it would provide electrical isolation from the copper - galvanize connection. This document explains this in better detail.

It is electrolysis from two dissimilar metals. You have copper pipe in contact with galvanized steel pipe. A small electrical current is created (Google "thermocouple"). There is no dielectric union between these two metals.


What type of lightbulb is this? I need to replace a faulty lightbulb but it's not one I've come across before. It's being used in a light fixture in my washroom above the vanity. Can anyone here identify it? I'm hoping I can order one from Amazon or my local Home Depot.
(Loonie for scale)

This is a G9 halogen bulb:

Note G9 is the name of the socket and form factor, but it says nothing about wattage. Voltage should be mains.
Yours is a G9 COB LED:

Since the original bulb uses LEDs, the fixture may not be designed to handle the heat of halogen, so it's better to replace it with a G9 LED bulb. As for wattage, check the fixture, but really you should be able to use a bit more watts like 5W instead of 2W if you want more light, it shouldn't melt... If you put a 20W halogen lamp in a 2W all-plastic LED-only fixture it will probably melt.
Get a flicker-free bulb if you can, they're easier on the eyes. If you use a dimmer, make sure it says "dimmable". Note the LED bulbs don't all have the standard length, so you might want to measure the space inside the fixture to make sure it fits. For example this one is bigger, so you'd have to check.

It's a "quartz halogen" lamp. You will need the voltage and wattage off of it or the fixture, and that is what's called a "G9 base", which is important to pay attention to because there are several different bases in this style of lamp and that has to match.


Adjusting Craftsman Garage Door Motor Height Travel Just bought a new garage door opener and it opens about 6 inches short than what I want it to.  I read about adjusting the travel screws, but this model has no travel screws on it. The model number is 139.54930. What is the proper way to increase the height of the door?

Here's the manual. On page 29 it shows the following:

On page 30 it describes how to check and adjust the reversal mechanism. I suggest that you do so.

The instructions for this garage door opener are readily available online if you don't have a copy.  The adjustments are done electronically using the control panel on the opener.  See the instructions for detailed directions on how to do this.


Should roofing nails be visible in the attic? I have a colonial built in 1913 and I live in NYS. My roof was just completed today and I have exposed nails across the entire roof!

It was not like this before. When I asked the contractor about it, he said this is normal, but I'm having a difficult time accepting this answer. I have included a picture to show what the entire roof looks like from the inside of the attic.

That's perfectly normal. I would have preferred to see the vertical joints in the sheathing line up with the rafters, but that's about it. Roofing nails actually should come through about a quarter inch - I'd be more concerned if they didn't.

Nails should never go through the plywood, water does go under the shingles and rust the nail thus making it thinner, more water to go through, the correct nail length should be the sum of the shingle thickness plus the underlying materials minus 1/4 inch...it is strange that protruding nails are thought to be normal! it is a common error in American building construction methods...you will not find this elsewhere in the world!


What size sub panel do I need I need to install a 30 amp 120v RV outlet 140 feet from main box.  I thought I would use a sub panel to allow for a few lights and two 110 outlets.  Can I use a double pole 30 amp breaker with number 4 wire? My thoughts were since I was useing a double pole breaker I could use one hot to feed the rv plug and the other the rest. Thanks DC

To answer your question, the smallest sub panel you can find. You would need to use conduit and correct fittings for running wire. However, I wouldn't buy a sub panel for just one double poll breaker. Instead, since this is a sub panel we're talking about here, I would set up a two or three breaker sub panel. 1 or 2 for the lights and other outlets, and 1 for the RV outlet. For the RV outlet, if it is a 120V outlet, which I think it is, they make up to 50 amp single poll Square-D breakers. Although, you would need a 40 or 30 amp single poll. For the other breaker(s), I would use a 20 amp. Just a suggestion...


Armstrong S-25 Pump Motor Lubrication? Recently replaced a leaking bearing assembly on my Armstrong S-25 pump. The previous one required oiling, the new one is the permanently lubricated MF/BF model. I look forward to not having to lubricate the bearing assembly, but what about the motor? The original manual that came with the pump indicates that the motor has oil cups that must be lubricated at the start of each season. However I don't see the cups, nor any inlets to add oil to. How would I go about lubricating the motor?

That black plastic circle is where the oil/lubricant should go. Twist to loosen it, then pull it out.


How to prevent wall-mounted TV above fireplace from getting hot? The place I just moved in to has a wall-mounted TV above the fireplace. However, I'm not sure how the previous residents dealt with the fact that the bottom of the TV gets very hot. Maybe the TV (which they left) is capable of handling the heat? I'm considering adding a shelf to block the heat, but I'm not sure if this is a good idea. Here's one from IKEA that I considered: http://www.ikea.com/us/en/catalog/products/70221461/ but it's made of glass, so it might be dangerous. Another possibility is one made of wood. Any suggestions?

I see this has been asked before but the answers do not seem satisfactory:

Here is a picture of my wall-mounted TV:

A shelf or mantle is what I've read is usually done for the purpose of protecting the TV.

Comment: TV above a fireplace is absolutely the worst place to put one. Not just for heat reasons but, ergonomically, it should be placed at eye level for most comfortable viewing.

It looks like a zero clearance insert, so it might not be an issue. Check the UL label on the unit. It would be best not to have a fire while watching TV, or be sure to turn on the blower for extending the TV's life.


Can a circuit breaker become compromised by flooding? I often hear about home basements being flooded by several feet of water. Hypothetically, if the water line is high enough to submerge the outlets and the circuit breaker, can it not only short circuit the outlets, but short across the circuit breaker, turning the standing water into an elecution hazard?  If so, how can it be prevented?

Watch for flood lines.  Yes, any breaker that's been underwater should be smashed (so others don't dig it out of the trash and use it).

If you can't find an uncorrupted main breaker to cut, call the power company at the "my power is out" number and they'll send someone over ASAP because they don't want you dead. Dead customers don't buy electricity.   However if this was a large scale incident, their plate will be very, very full and your request will get triage'd and done when feasible.   Obviously, in the meantime, stay away from it.

After the flood is gone you have to size up each component.  Panels are simple affairs and it might be possible to take it apart and clean it.  Conduit should be OK but I'd pull the wires out and disassemble it enough to clean the insides by pulling a rag through them.  Every junction box would have to be cleaned out.   The wires will be ok if they say THWN or other outdoor rating.   Ratings for outdoor wire presume the wire is immersed in water 24x7.   Keeping water out of outdoor conduit isn't really possible.

Romex will be junk.  Every receptacle, switch and machine of any kind will be junk.

It is best to get it inspected and repaired by qualified Electrician.

My opinions are my own as an EE since 1975,  FYI only..

Ground Fault Interrupter (GFI or RCCD) type breakers will trip if the line and neutral current do not match within safe limits (xx uA). This implies the imbalance must be leakage to ground and does not mean current between line and neutral.  Thus is can detect leakage in wet lines.

If earth ground wire is also exposed near line neutral this serves as a good test for all wet cables for ground leakage or a safety leakage detection breaker circuit device. A DMM can be used to investigate problems.

Other info

Line voltage with wires in pure water does not conduct much between the electrodes until it gets salty or dirty, then like vaporizers will boil the water.  Generally the current only passes between the exposed wires or breaker and will trip the breaker if excessive.  Current tends to follow the path of least resistance between the wires unless you happen to be grounded and between the wires or breaker contacts. ( not likely)

Depending on degree of contamination, it may need complete replacement.
A DMM can be used to measure any stray voltage on contaminated surfaces if wet. I would expect very high impedance (1M) ( low safe current.) But an aEE or Electrician can tell the difference.

There may be rare circumstances where the contaminants are not between line and neutral and between line and the plastic surface nearby making it more of a risk.   Consult an electrician if in doubt.

With all (most) the appliances off the power meter should be turning very slowly.  If they were contaminated but now dry, conditions of 100% humidity may later change the leakage current.  Normally it may burn off contaminants but in extreme cases may reduce the integrity of the insulation. Since the breaker box is grounded , it is safe and same with basement outlets but if still wet and dirty, turn off breakers or avoid touching near proximity of outlets or breakers.  (Wear dry safety gloves if in doubt if breaker handle is wet and corroded outside.)

When I had a basement flood I had the basement breakers turned off until I was sure it was dry and fortunately it was clean water.  Exposed wet phone lines often caused erratic behavior with audible white noise on line or phantom off hook, so the line was cut.    My Power issues were no drama, but the $1500 of water that pumped into the basement from a waterline break under kitchen sink for a month with no tenants and I was living out of town was a bit of repair work. But I fixed all the drywall and paint and sold it easily in 2 weeks.

Personal experience

When you stand in electrified dirty water, one would be wise not to touch any earth ground.  But just standing in it is not a risk. Just like lightning 50 yards away into the lake where you are swimming will not electrify you but you may suffer blast effects.  Because the path of least resistance is not between you and the lake bottom its between the point of entry and the lake. I have been in metal boats near lightning strikes with no effects except for a tingle on the metal seismic wires I was touching and antenna effects picked up an ESD like event. ( I was a student doing seismic research on islands )
Did I say consult an electrician enough?  But I am EE since 1975.


Kitchen LED ceiling light blinking Hopefully someone can help with this issue. Everything I have researched seems to be related to a type of light I do not own. I have a kitchen LED light that has been working fine up until just recently when all of a sudden it will start to flash when turning it on. Sometimes it comes on and stays within a few seconds and sometimes it will take 10-15 minutes or more.

I attempted to take the cover off and check and see if any wiring was loose and could not locate anything causing it. None of the wires when touching or adjusting will cause it to start working again. It is not on any dimmer switch but has two different standard light switches that operate it.

http://imgur.com/cqOcIr8 (Image of unit without the cover)
https://youtu.be/K_YH0blbOqY (Video of the flashing)

Any help would be greatly appreciated as I am stumped on how to fix this.

Replace the fixture -- the driver's failed and isn't starting up properly.

Light switches go bad or get weak after so many "on/off's" or cycles.
This will cause flickering due to a poor connection.
Try replacing the switch.