I plan to shut off the main water supply to my 2 story house before leaving for a week on vacation.  I have an AO Smith gas 'powervent' water heater in the garage that I would like to  set to 70*F rather than turning it off.  Since there are no issues with freezing pipes here in  the SF Bay Area, I wasn't planning to drain the water lines within the house. Would the cold water feed on top of the water heater need to be turned off also?
123570
I have a brand new AO Smith 50gal gas water heater. Today there was a burst pipe from the cold spell we're having currently, so I had to turn off the water main to the house until the plumbers get here tomorrow.  With that, nobody had used any hot water all day so it should be full, but do I need to turn the water heater off until the water can be turned back on tomorrow to avoid any damage etc?
102578
When adjusting my water heater, what temperature should I set it to? Is the answer different if you have:   Concerns about diseases A dishwasher Young children or elderly that can be easily burned Electric vs Gas heat Type of plumbing (e.g. PEX or Copper)   Also, is there a preferred technique to check the temperature of the water after adjusting it?
74150
Last night, my neighborhood had a blackout, but for some reason, only half of the electrical circuits in my house went out. I was under the impression that there was only one main electrical feed going into a house. Can someone please explain how this works?
26497
When I studied how AC mains power works, I learned that one of the wires is connected to the ground or a body of water so that it can get back to the power station. The concept baffles me. Every source of information I've come across fails to explain how it works or quickly glosses over it as if it is self explanatory.   If power can travel through the water or the earth back to the power station, then why aren't we getting vaporized when we walk on the ground near power lines?  Also, how does an isolation transformer prevent you or your equipment from getting fried? If I touch both terminals of the secondary, am I going to get fried?
106216
I've noticed mains voltage tends to be 120V +/- 10% for 108-132VAC.  How would you go about building a regulated AC-to-AC power supply which works off of mains and outputs 120VAC with a much lower (less than 1%) variation?  The output must be a sine wave at 120Vrms.  Edit: For those asking, the output would be fairly low, 1.5A - 2A, 2.25A max.  Circuit to be powered:  Expected input: 0V-5.5KVrms sine wave at 60Hz  Simulated output: +/- 0-100KV DC.  The objective here would be to connect components in the order:  mains --> power conditioner --> variac --> 1:46 center-tapped transformer insulated for high voltage --> Cockcroft Walton Multiplier outlined above.  To achieve a variable 0-100KV DC (effectively 0-200KV DC with both channels factored in) power supply.  I am not certain the power conditioning stage is the way to go but assumed it would be since it is much easier to stabilize low voltage (120Vrms) than it is to stabilize high voltage (5.52KVrms.)  Relatively minor ripple of 5% will grow into +/- 10% by the end of the CW stage at full power, yielding around 20KV off of the expected value - not an insignificant amount.
104783
I have an electric dryer with a 30 amp circuit running to it. If I had a male-male plug to run from a portable generator to this outlet, would it be safe to run essential appliances (water pump, refridgerator, sump pump, etc) during a power outage as long as I tuned off the main breaker and the total draw was less than 30 amps?
32962
We're going to move our washer/dryer to the garage (the front loader needs to sit on  concrete to keep it from shaking our house to the ground).   I'll need to add a washer drain to the garage for the washer. Because this will need a p-trap, my understanding is that it also needs to be vented.   I could go straight up into the attic then through the roof, but my question is: do I need to actually go through the roof? Could I instead have it go into the attic then 90 degree it out to the back, second floor wall? I can't find any particular code rules on if it has to penetrate the roof or not. This is a septic system, if that matters.   The reason for trying to avoid the roof is that I'd prefer to not climb up onto the roof...it's about 45 degrees and in the PNW so perpetually wet and mossy.
74705
I am staying at a place booked via Airbnb. Something happened and there is no electricity from Friday! The house-owner has provided a super noisy generator, which is inconsistent, meaning that it "randomly" supplies power to some parts of the house, so you cannot rely on it.  Is there any rule/law in SF, CA, USA to describe the compensation one should get from such kind a situation?    The owner owns the whole building. On the ground floor there is a restaurant. On the 1st floor there are the apartments. Something happened in the restaurant, which made the electricity go off, but she didn't give more details, she said "there was an emergency and the power went off".
52659
I am considering a home solar photovoltaic installation, probably 5 kW or so.   The usual configuration around here is with a  and .  But when the grid goes down, the inverter shuts off (to avoid back-feeding into the power grid and electrocuting linemen). We are interested in being able to use the solar when the power goes down (not infrequent in this rural area).   According to the solar installer, the only way it is possible to do this is to also install a battery system like .   The idea is that when the inverter loses the 60 Hz sinewave from the grid it shuts off; the inverter in the PowerWall supplies this sinewave, so the inverter doesn't shut off, and there's also a mechanism to disconnect from the grid. That sounds reasonable.   But the cost is not.  Two PowerWalls would roughy double the cost of the installation.  During outages, we would be satisfied to only have power when the sun shines; this would keep food safe, allow us to draw water, etc.  Electrically, there is no reason this can't be done without the expensive battery system.  All that is necessary is to generate the 60Hz reference for the solar system's inverter, and to disconnect from the grid. Has anyone been able to manage such an installation? Would it be strictly DIY (perhaps feasible as I'm a electrical engineer)?
79946
This has always been a mystery to me and with all the snow we're getting I'd like to work from home but the boss man wants us to turn our computers off a night to save energy.  Figured I'd like to try Wake-On LAN, but not sure where to start.
25728
TL;DR: Can you terminate more than one common on the furnace C terminal?   Background:  I've linked a diagram of how my non-programmable thermostat is currently hooked up. I want to replace it with a Trane Z-Wave thermostat that requires constant power. There's already a blue wire in the 18/5 bundle, but it's disconnected on both ends. The C terminal on the furnace control board is already in use by the rooftop condenser. If possible, I'd like to connect the blue wire to the stat and terminate it on the same C terminal on the furnace that is already in use by the A/C.    Some model numbers:   Furnace: Goodman GKS9 Gas Furnace with A/C (CAPF) -  Old stat: Honeywell TH3210D1004 non-programmable New stat: Trane TZEMT400BB3 Z-Wave
104335
I have read that National Code requires you to use copper for 18 inches from your water heater.  How can I do this when everything existing is PEX?   I need to replace my existing low boy water heater next to my kitchen sink.  It was installed by the builder ten years ago. All the pipe in the house is PEX.  The existing water heater is connected using PEX as well.    The supply line comes directly thru the wall to the HW Heater. There is no space to run 18 inches of copper! The heater is under the kitchen counter, and the countertop is directly over it. Only about an inch clearance.
63016
I currently have an HVAC system that is connected to a Nest thermostat (2nd generation) and I'm planning to use the same Nest thermostat to control a 110 swamp cooler that is currently not connected.  Before dealing with the trouble to connect both systems to the same thermostat (maybe using switches/relays to shut down one system while the other is on) I want to know if it possible to control the swamp cooler using the Nest thermostat. I don't have too much electrical knowledge, but I've been doing some research and I think it is possible if I buy some additional things.  The swamp cooler has a 2-speed motor, therefore I would like the Nest thermostat to control both speeds using Y1 and Y2 terminals. As far as I know 2 stage thermostats will apply power from the R terminal to the Y2 if more cooling power is required at the same time power is applied from R terminal to Y1. I also want the water pump to work everytime the thermostat calls for cooling (for both speeds), but I want the water pump to run alone for some minutes before the motor is started.  I have found that the Honeywell RC840T-120 might allow me to use the 24v Nest thermostat with the 110v swamp cooler and using a SPDT relay I could connect Y1 and Y2 to the 2 terminals of the 2-speed motor. Honeywell RC840T-120 was created to connect line-voltage controlled heaters to 24v thermostats but I think it will also work with the swamp cooler. This device will be the first relay that will decide if the pump and motor are going to receive power. This first relay will be connected to a PTD102 Delay that will delay the power to the SPDT relay, this last realy is the one that will control the power to the motor based on Y2 terminal from Nest thermostat. The thermostat will send power to Y1 only for 1st speed and in case it needs more cooling power it will start  sending power to Y1 and Y2 at the same time causing the SPDT relay to switch power to High through terminal 3 as the following diagram shows:    Please let me know if you think this way to connect the thermostat will allow me to control the swamp cooler and if it will also control both speeds
96763
Thanks to the help of a few of the other guys I have my AC to DC rectifier working, and the rest of the power supply working.  Now while testing the power supply, my 18V AC transformer gets rectified and put into my circuit below   And I end up with 1.3-26V DC output selectable via the pot R2.  Now while running this @12V with a LED strip light, running about 600mA my heat sink got quite hot. Not hot enough to cause the thermal protection in the LM317 to cut in but hot enough to get me thinking.  Power dissipated = (Vin - Vout)*Il = (26 - 12)*0.6 = 8.4W  My heat sink is rated at 11 C/W and I pasted the LM317(TO-220) on.  Max C/W is = (MaxRunningTemp - ambientTemp) / power = (60-25)/8.4 = 4.2 C/W  Does that sound right, never done any heat sink calculations before. So I would need a heat sink rated at &lt;4.2 C/W  I would not see my self running this over 500mA again but running this circuit at 5V would change a lot? The power dissipated would be 42W if 5V @ 500mA. What can I do to prevent needing a HUGE heatsink? and are my calculations above correct?
69357
I'm a little OCD when it comes to traveling. I have learned from experience that when I am away, I constantly have visions that a pipe in the wall had burst and that the water is slowly filling the house. Having been through this enough times, I am tempted to put my worries to rest by simply turning off the main water line (in the garage) before we leave. My new fear with doing this, of course, is that I will cause something else bad to happen.  So I am curious, is it bad to turn off the water and drain the pipes prior to leaving for a week? In addition, what other precautions should I take aside from turning down the water heater? A few details - our house is two story, copper pipes, and we would be traveling in the spring time so temperatures in the house would stay at around 70 F.
27586
Turned on our 2 year old stove (Whirlpool Gold) and heard fizzing noises, then smelled electrical burning. Went downstairs and shut off the breaker (40 amp). That was the only way to get it to stop "fizzing". (6 gauge wire by the way). The range is 240 volt electric 3 wire hooked up to a 40 amp breaker (6 gauge wire). When I took the back panel off the stove I saw exactly where the problem occurred. The black wire was burned, the terminal block was melted, and the inside of the back metal panel that I removed was pitch black in the spot that was facing that area before removal. I removed the stove top and inspected all wires and other electronic components. No problems at all.   So my questions are:    Why did the black wire only, at the terminator block, start burning?  Why did the breaker not pop off?  Is it safe to just replace the terminator block or is this an indicator of a much larger problem?  Is 6 gauge the correct gauge for a 40 amp breaker?
108640
I recently purchased a early 1970's home that has this interesting outlet installed in the master bedroom. It is the only outlet in the entire house like this and I'm not real sure what it is for and if it should be removed. I haven't checked it for voltage or current yet as I don't have a multi-meter handy.    Just by looking, can anyone identify this for me? Is it safe, should it be removed? I haven't been able to see what it's wired to in the attic yet either as the wall is hard to get to in the attic.