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Erronius

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I will never understand why when 3 phase is an outlet with 3 hot wires that are out of phase and a 240 outlet is 2 hot wires that are out of phase, they call the 240 outlet single phase. That seems like it should be considered 2-phase.
So...phase is really a wave relationship. And each phase is shifted 60 degrees from each other (3 phases and 6 poles, so 6*60 = 360 degrees), and this corresponds to your standard generator and how each phase is derived as it rotates

lIACOng.gif


If you take any single phase, when one pole is 'peaking', it is 'pushing' current 100% towards the other pole. And vice versa. This will oscillate to the point that you derive frequency (hertz), with one cycle being one full rotation. In the gif above, look at the graph of A phase (blue): you start at 0, go up to +1, back down past 0 and all the way to -1, and then you finish the A phase cycle when you hit 0 again. In the US, that's 60hz (60 cycles per second) versus 50hz in Euro and many other places. Also, if you ever spend time in transformer rooms, you'll start to notice that the sound of the 'hum' is different, due to that frequency difference that results from the difference in source generator speed. This is also how you can control the speed of AC motors using VFDs...using solid state switching to pulse at certain frequencies...before this, you had to use DC motors and various speed control strategies.

But I digress...point is, any single phase is pushing current either direction, plus or minus, at any given time (or at 0 for a literal split second). The two poles that current passes between...they aren't out of phase with each other...because they're both directly opposing each other, and aligned across the generator axis. It's like...have you ever seen two men using a buck saw? that's what single-phase power is like

CookedExcitableFowl-size_restricted.gif


Now, I was out drinking tonight, so this is probably a bad idea, but I'm gonna keep going.

Functionally, there's really only 2 differences between 120vac and 240vac in the US. One...is that we ground one leg of the 120vac as the neutral (the center tap of the transformer). It's just a reference point. Both points are still tied to the transformer, and both points are 'hot'. But...with the way we ground things, the neutral is a 'grounded' conductor. But it still carries current, and current still goes back and forth constantly at 60hz. If you ungrounded the neutral, you could totally run the system as a 120/240 isolated system (don't do this) and it would function.

240vac is just the same as as 120vac, except it uses twice the number of turns/windings on the transformer, hence double the voltage. You could, technically, ground one of those legs, but in practice it's a 120/240 center-grounded single phase system

HdUzm.gif


But it's still single phase. It's derived across a single set of poles, and transmitted through a single transformer. And you could have any number of taps on the secondary side...and the current will still oscillate between any two points.

Now, 3 phase...I had a lot typed up...but it's overkill, and having to explain why they cheat on three and four wire 3 phase systems. Suffice to say, 3 phase is pulling 3 different sources from the same generator. Usually we cheat and run them sharing conductors, which really muddies the waters.

In the first gif, that's a 4-wire system. 3 phase conductors, and the other 3 tied into a single neutral. Meaning it's a Star, or Wye, config. The other is Delta, or looks like a pyramid, and can use as few as 3 wires. But regardless of the relationship they're setting up by interconnecting 3 phases, you still have 3 separate phases, because they're truly out of phase with each other.
 
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Erronius

Macho Ma'am
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I think it's because they're on the same phase. Eg each one is 120v and alternates from -120 to 120 opposite but in unison. In 3 phase theyre shifted and that's why you end up with 208 instead of 240.

Maybe.

Electricity is magic.

I still have a hard time remembering Delta and Wye calcs. Fucking vectors/phasors or whatever the fuck. [(sqrt3)/2]*240v is all the further I go anymore, and I needed to Google that as a refresher. I still get sqrt3 confused with sqrt2, and then I'm like 'oh yeah, that's RMS, 1.414 or 0.707 depending on which way you're going.
 

Fogel

Mr. Poopybutthole
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Thing I was always curious about is whats the practical purposes of going 3 phase over single phase
 

Hateyou

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Thing I was always curious about is whats the practical purposes of going 3 phase over single phase

There’s several reasons in industrial. Instant power, its more efficient use of the conductors. Its always generating heat/mechanical energy, whereas single phase doesn’t as it alternates you have power dips. Think fans and motors that are running for years on end like in conveyor belts.
 
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Erronius

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What Hateyou Hateyou said. A large part of it is that with single phase, you aren't actually transmitting power 100% of the time.

To get the same amount of power with a single phase circuit to the end load/device, as compared to 3 phase, it's going to take much more wire and a larger circuit. Motors would end up being gargantuan with a price tag to match.

Here's a link with a chart: For example, look at 10hp motors. a single phase, 120v 10hp motor would need a 100A circuit. There are still houses with 60A and 100A services out there, LOL. Depending on copper/aluminum, insulation type, and a number of other derating factors like # of conductors in a conduit, ambient temp, distance of the circuit, etc) you're going to be looking at 2 conductors (with probably a slightly smaller ground) that are at least #2 or #1, and potentially into the 1/0 or larger range. A 480v 3 phase 10hp motor is going to draw...14 amps. Sure, it's 3 hot conductors instead of two, but you're looking at probably 12g conductors, or maybe upsized to 10g depending on other factors. But even in some serious worst-case-scenarios, let's just say 8g, because fuck it...even if you run an 8g ground as well (too lazy to look up the ground size needed at that fault current), 4x8g is WAY less conductor, and will be cheaper, than 2(3) conductors for single phase.

1/0 is around 1Kcmil (100,000 circular mils), and that's just 1 conductor. 4x8g combined is like...just under 70k. So you could possibly be looking at a 3:1 comparison of wire. And then you get to run much larger conduit, and pulling larger conductors is usually more difficult. Larger enclosures, larger...everything. Like, a 3ph 20a fused disconnect versus 1ph 100a or 125a fused disconnect. I don't even want to bother pricing it all. I'm serious when I say that most people wouldn't even bother with a comparison, it's just largely academic.

http://www.sprecherschuh.com/download/sscdn7500F/index/hp-volts-fla_chart_v206.pdf


(I'm still waking up and pulled some of this completely out of my ass)
 
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Dandai

Lesco Brandon
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I’d like to thank AvE for familiarizing me to angry pixies enough to follow most of what you guys are talking about.
 

Dandai

Lesco Brandon
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It’s getting late in the season, even for NC, but I’m gonna reseed the numerous bare areas in the lawn tomorrow. I sent these pictures to my mentor to see if he had any advice on the best approach.

Generally what my back yard looks like. This is definitely run off from hard rain shortly after seeding so it’s not much of a mystery:
6996D273-4E6F-47AB-8930-487B39650165.jpeg


Soil has a thin sandy layer then richer clay underneath, but it’s not very compacted.
DC8A542E-900E-4948-B7EF-F20EADF85551.jpeg


530240B1-76E7-4852-B6B7-9B2D556202A0.jpeg


This is the front lawn. I already did reseed the bare spots up here and weaseled them in before I left town for a week. I found lots of ungerminated seed just below the surface so it could’ve dried out too much between the rains and when I got home.
E3B2776D-4D43-4A27-ACEA-82028040D26F.jpeg



This spot in particular wasn’t very compacted but there were several areas that were probably too compacted for good germination.
F26B6A0F-7E06-42E7-9617-488DB95184EB.jpeg


9D4B3D73-0690-4BCA-A958-2CB7E6020424.jpeg



The bare spots up front were much more sand than clay too.
BCD78103-DD64-4583-9859-A909566765CE.jpeg


But the puzzling part is that within and around the bare patches are patches like this where the grass came in really nice and thick.
CEAAA9ED-CD78-45AD-8B95-DF2C028740BD.jpeg


So all in all, I’m just gonna try to remediate each area individually and do my best to keep the seed moist so it’ll come up before daytime temps get too cold.
BA5269C6-717D-4E23-B7C8-275647B2CFCE.jpeg
 

Dandai

Lesco Brandon
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It’s getting late in the season, even for NC, but I’m gonna reseed the numerous bare areas in the lawn tomorrow. I sent these pictures to my mentor to see if he had any advice on the best approach.

Generally what my back yard looks like. This is definitely run off from hard rain shortly after seeding so it’s not much of a mystery:
View attachment 179946

Soil has a thin sandy layer then richer clay underneath, but it’s not very compacted.
View attachment 179947

View attachment 179949

This is the front lawn. I already did reseed the bare spots up here and weaseled them in before I left town for a week. I found lots of ungerminated seed just below the surface so it could’ve dried out too much between the rains and when I got home.
View attachment 179951


This spot in particular wasn’t very compacted but there were several areas that were probably too compacted for good germination.
View attachment 179952

View attachment 179955


The bare spots up front were much more sand than clay too.
View attachment 179956

But the puzzling part is that within and around the bare patches are patches like this where the grass came in really nice and thick.
View attachment 179957

So all in all, I’m just gonna try to remediate each area individually and do my best to keep the seed moist so it’ll come up before daytime temps get too cold.
View attachment 179958
Here’s a “cross section” of the sandy soil grass patch that I forgot to include above:

77E3B03D-154C-4F9B-9924-3D649B7D584E.jpeg
 
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Dandai

Lesco Brandon
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Oh my god why did you dig up that beautiful patch of grass
It’s fine big P. The roots are like half an inch deep. I’ll grab a follow up picture tomorrow to show you that no grass was harmed while taking these photos!

My mentor got back to me about the issues I posted above:

26BEF1B4-3465-4D43-99DE-32B7460982FF.jpeg
 

Dandai

Lesco Brandon
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P Picasso3 see? Still going strong! Needs to be watered in the morning though. The grass is mature enough that I need to transition to watering 1/3” every other day so the roots will dig in and chase the water. I just got done blowing and raking the leaves but I’ll get some before/after shots for you guys tomorrow.

2603AEA0-E25F-4681-89E6-A93694323610.jpeg


Edit: I should also mention that it’s not uncommon to make plugs like this (in more controlled environments/pots) if you’ve only got a handful of bare spots. Think of it as mini patches of sod!
 

Lanx

Oye Ve
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P Picasso3 see? Still going strong! Needs to be watered in the morning though. The grass is mature enough that I need to transition to watering 1/3” every other day so the roots will dig in and chase the water. I just got done blowing and raking the leaves but I’ll get some before/after shots for you guys tomorrow.

View attachment 180070

Edit: I should also mention that it’s not uncommon to make plugs like this (in more controlled environments/pots) if you’ve only got a handful of bare spots. Think of it as mini patches of sod!
yea when i was making plugs, the roots never went beyond 2inchs on super mature grass.
 

Dandai

Lesco Brandon
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yea when i was making plugs, the roots never went beyond 2inchs on super mature grass.
It’s species dependent, of course, but with fescue I’m looking for 6-8” root balls by the beginning of summer. Requires some soil work and proper, deep watering, but those cultural practices are what allows those of us in the transition zone to keep green cool season lawns throughout the year.
 

GuardianX

Perpetually Pessimistic
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So I'm looking for pre-move-in input.

I wanna take down a wall fireplace in the house. The wall is an external wall, the fireplace itself is brick inside and the brick extends outside the home. What are the chances that the entire wall is brick with no wood between the inside brick and the outside?

The home is a 1978 build.

I have to do something with the fireplace regardless, it isn't safe to operate as per the inspector. They painted the indoor brick, I can't really see the fine detail on if the brick is okay, there are some issues where it looks like the brick is disintegrating but nothing that tearing it all out and doing what I want with the wall won't fix. Outside the home the brick is toast, at least on the outer later of brick. It hasn't / hadn't been serviced for a LONG time and the brick itself is disintegrating due to the elements, several spots are missing mortar to such a degree that I could fit my thumb with glove between the bricks down to the first joint on my thumb, possibly further.
 

Erronius

Macho Ma'am
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What are the chances that the entire wall is brick with no wood between the inside brick and the outside?

I'm going to say 99.999% there's no wall running between the interior and exterior brick. I've seen fake fireplaces with interior brick but I don't think they had brick outside. And if it is complete with chimney, flue, and legit masonry support of some kind (can see in the basement if there is one, or see if the foundation conforms to the outline of the fireplace layout), then it's probably all brick.
 
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Dandai

Lesco Brandon
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Took a couple flattering shots of the lawn. Gonna be seeding again Saturday as we’re supposed to get an inch of rain tomorrow and I’ve learned my lesson lol P Picasso3

May 2018:
D8AF0178-5B2F-4653-A5AA-94401F4DC48C.jpeg


October 2018
98881E92-84E2-4713-9321-98922CCA9E17.jpeg


May 2018:
55D20ADA-59C4-44B7-851D-3EC75A9FCD32.jpeg


October 2018:
3B05A269-DC7F-4354-8A21-F90B0A7FD6F0.jpeg
 
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