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Why 30A tandems with every load center kit?

AntonLargiader

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The cheapest option for my new 100A subpanel is a kit that comes with a tandem 30A breaker and a few single 15s or 20s. Pretty much every other kit also includes a 2x30.

I don't need it. Not a big deal; I'll take it to work and maybe someone can use it there but what is so ubiquitous about a double 30 that it gets included in every kit instead of something else?

An AHU and a compressor are on 240V 30s but they are not moving to this panel. Water heater and well pump are on smaller tandems. Maybe 100A panels are very commonly used for serving HVAC? Would love it to be a tandem 15 or 20 instead.

It's just curiosity.

EDIT: I meant DOUBLES not tandems!!
 
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Milton Shaw

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Electric dryer and electric water heater would be most likely reason for those breakers. Electric stove would be double 50, and Heat pump/Ac would depend on the size of units in the design. But around here probably 8 out of 10 have electric water heat and dryer.
 

zmaxmotorsports

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I guess I think of 100A panels just as subs, but are they still used as mains? I can see bundling a water heater or dryer breaker with a main.

A 100 service is more than enough power for the majority of houses and small shops.
Put a,clamp on amp meter on your service feeding your house some day and see what it actually uses for power some time,you might be really suprised.
30a 2poles are commonly used for dryers and a/c condensin units and normal stoves and welders......
 

wyliesdiesels

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dryer, AC compressor, well pump, wall oven, electric cooktop and water heater are typically protected by 30a DP breakers.
 
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AntonLargiader

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100 amps may be more than enough, but the real question is whether or not 100A panels are being installed as mains out in the real world. Agree that actual loads are relatively small. I'd love to see a graph of our usage. We have a decent amount of LED and are not extravagant with HVAc.

30A for a well pump? Our well is 125' and runs on a 15A tandem. We have NG so a lot of those heaters don't apply to us.
 

wyliesdiesels

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100 amps may be more than enough, but the real question is whether or not 100A panels are being installed as mains out in the real world. Agree that actual loads are relatively small. I'd love to see a graph of our usage. We have a decent amount of LED and are not extravagant with HVAc.

30A for a well pump? Our well is 125' and runs on a 15A tandem. We have NG so a lot of those heaters don't apply to us.

yes to both.
 

mike93lx

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100 amps may be more than enough, but the real question is whether or not 100A panels are being installed as mains out in the real world. Agree that actual loads are relatively small. I'd love to see a graph of our usage. We have a decent amount of LED and are not extravagant with HVAc.

30A for a well pump? Our well is 125' and runs on a 15A tandem. We have NG so a lot of those heaters don't apply to us.

I stuck with 100a for my panel replacement a couple years ago, but i bet they are rarely used in new construction. No meaningful extra cost to go 200a from the beginning and i would bet a lot of people think of it as better.

NG heat here too, so only big load is the dryer at 30a. My well pump is a little deeper and is 20a
 
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AntonLargiader

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Our house is only about 2000 SF but it got 200A service before we bought it. I did a load calc and it comes out to about 111A although I think our real world usage is less; we have a decent amount of LED and 2-stage compressor on the main HVAC that pretty much stays on first stage.

The strip heaters on the 2nd floor AHU are over a quarter of the load calc. I suspect they are overrepresented. They're on a 30A breaker so I sized them at that full load; they may draw far less which would put us under 100 (until the EVSE is added). I don't know what the heater configuration actually is and it's not really important. Thinking about it I guess they should be listed at 80% since that's how the circuit should have been sized.
 

wyliesdiesels

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Our house is only about 2000 SF but it got 200A service before we bought it. I did a load calc and it comes out to about 111A although I think our real world usage is less; we have a decent amount of LED and 2-stage compressor on the main HVAC that pretty much stays on first stage.

The strip heaters on the 2nd floor AHU are over a quarter of the load calc. I suspect they are overrepresented. They're on a 30A breaker so I sized them at that full load; they may draw far less which would put us under 100 (until the EVSE is added). I don't know what the heater configuration actually is and it's not really important. Thinking about it I guess they should be listed at 80% since that's how the circuit should have been sized.

For load calcs, u dont use the breaker size you use the nameplate VA. And continuous loads are factored @ 125% of nameplate not 80%. A heater can be expected to run for more than 3hrs, so its considered a continuous load.
 
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AntonLargiader

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I don't know the nameplate on that one. The AHU can be configured with all kinds of heaters and it's not shown what it is. Same with the well pump; I'm not about to pull it out to see what model it is. All I can see is what breaker they are on and the load is clearly less than that.

Most everything else I found the nameplates for.

By 'not important' I mean it's not actionable; I'm way under 200A. It is interesting to me in an academic sense so I'm happy to learn more about doing it properly, but there's no reason to call in a pro to get a real number.
 
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zmaxmotorsports

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100 amps may be more than enough, but the real question is whether or not 100A panels are being installed as mains out in the real world. Agree that actual loads are relatively small. I'd love to see a graph of our usage. We have a decent amount of LED and are not extravagant with HVAc.

30A for a well pump? Our well is 125' and runs on a 15A tandem. We have NG so a lot of those heaters don't apply to us.
100A service panels are commonly place around here.
Builders are normally too cheap to spend the extra money
On a full blown 200a service if they don't have to.
I come across plenty of 20-30 year old houses with 125-150a service panels full of split /tandem breakers just to save $150.00 over what a 200a service would have cost when the house was built.
If a 100A service is big enough on a service upgrade I generally go straight to 200a.
 

Norcal

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100A service panels are commonly place around here.
Builders are normally too cheap to spend the extra money
On a full blown 200a service if they don't have to.
I come across plenty of 20-30 year old houses with 125-150a service panels full of split /tandem breakers just to save $150.00 over what a 200a service would have cost when the house was built.
If a 100A service is big enough on a service upgrade I generally go straight to 200a.

Tract, or spec, homes are built as cheap as the builder can get away with.


A tandem is another name to refer to twin, dual,or piggyback, breakers, took me a bit to realize that the OP was referring to 2-pole breakers.
 

wyliesdiesels

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Tract, or spec, homes are built as cheap as the builder can get away with.


A tandem is another name to refer to twin, dual,or piggyback, breakers, took me a bit to realize that the OP was referring to 2-pole breakers.

could catch.

funny i didnt notice he used tandem to describe double pole. My mind went straight for the double pole when he said double in the second paragraph and talked about heaters and compressors on "240v 30s"

funny how the mind works.... :lol_hitti
 

Wirepuller

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Sberry do you have paypal? I'd like to make a deposit to your account you kept you're replies short an meaningful. A step in the right direction.


Sent from my iPhone using Tapatalk
 

dbphelps

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When I was shopping for a home about 5 years ago we saw a lot of places with 100a service. A few had 150a and a few had 200a.

There was this one place that had dual industrial power running to it. I am talking a dedicated transformer, huge dual industrial service panels (over 2k amps per, and I am thinking they were over 3k amps per if I remember correctly), and they had enough heat/AC to take care of a decent sized apartment building. Like dual 25 ton AC units, all point of use water heaters (at least 6 I could find) but with a gas manifold that had 8 3/4" take offs and a custom regulator with a high pressure feed. Furnace units were dual with over 500k BTU each if memory serves. This was all for a uniquely designed home with 4000 sq/ft. A lot of it did not make sense.

Come to find out, the place had an underground facility below it. The new owners found out about 6 months after buying the place. We are talking cargo elevators and multiple levels below the house. Last I heard someone bought it from them within a year of them buying it.

The place I eventually bought was built by an electrical contractor. It has dual 200a services. One panel is the "lighting panel" with all 120v circuits in a 40-breaker panel. The other is the "power panel" with all 240v circuits on dual breakers in a 40-breaker panel. The place has both NG furnace/central air and electrical baseboards in every room, so the baseboard heaters take up at least 9 of the dual-breakers. The rest are the garage sub-panel, water heaters, kitchen stove, lower kitchen stove, dryer, AC unit, central vacuum, hot tub and pool pump.

Since I added the garage sub-panel (a 100a 12/24 circuit box), I moved the two original garage circuits to it, added in another 6 more 120v circuits (most are 20amp with one 15amp for lighting), a welder outlet, plasma cutter outlet, circuit for the air compressor and even one for a 6000w electric heater. So that sub-panel is packed as well.

When I redo the rooms downstairs I am planning on redoing more of the lighting panel than I did before and consolidating some circuits to be more efficient. I am filling out the lower kitchen with more "regular" appliances such as a garbage disposer and dishwasher (originally they only planned for a refrigerator/freezer and electric stove), as well as putting in "to code" outlets (dual 20amp 120v circuits). I also am reconfiguring lighting and such to make better use of the breakers that are there. I already did one round a few years after moving in of cleaning up the circuits/wiring and configuring for how we use things to better "load balance" the phases.

As it stands I have 6 dual-outlet GFCIs in the upstairs kitchen all on their own 20-amp circuits, along with dedicated circuits for the refrigerator, dishwasher, garbage disposer and trash compactor. They did use a shared circuit for the microwave (with dining room and dinette outlets) as well as the lights and fan for the kitchen being on a shared circuit as well.

This place has plenty of electrical outlets though, with 184 duplex outlets and 48 duplex GFCIs. That was why I was kinda shocked that they "only" had 2 circuits for everything in the garage originally.

So, regardless, this place was way overbuilt electrically, but I find I prefer to have it that way.

Now, since everything but the furnace is electric (well, I did add a lower laundry with a NG dryer as well), our electric bills are hell. Gas bills are REALLY low, especially since the house is super-insulated, but I can't get away with outrageous electric bills. Having 5 kids and my mother living with use means we are always doing laundry and the stove gets a real workout. That is why I put in the lower laundry, I want to know if a gas dryer is going to make a substantial difference in monthly utilities. I would love to go with a gas stove as well, but I am screwed since the way this place is constructed it is damn near impossible to get a vent out for the kitchen. I was SOOO disappointed when I removed the original range-hood microwave to find there was no vent.
 
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AntonLargiader

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I want to know if a gas dryer is going to make a substantial difference in monthly utilities. I would love to go with a gas stove as well, but I am screwed since the way this place is constructed it is damn near impossible to get a vent out for the kitchen.

For the dryer, I think you just need to look at some numbers and figure it out. Hours of running time times kW times cost per kW-hr. I'd think the heaters aren't running full-tilt for the whole time, but you can at least get an idea what the dryer adds to your electric bill.

There are energy-monitoring systems out there that can help you figure out where the costs are, too. There was a thread on them a few weeks ago.

As for the range hood, I agree that there are few things in the world less useful than a ventless range hood. My experience with that is, where there's a will there's a way. Soffits, downdraft, flue as an architectural feature, etc.
 

dbphelps

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Yeah, I would love to be able to put a flue for the range in, but the issue is the way they built this house.

The house is on a lot that faces east, the front door faces east as well as the garage doors. The house is built, for the most part, on a large rectangular foundation with the support beams every 12-15ft running east-west and the floor joists are 16" on center going north-south. The big issue is that there are almost no walls that run above one another as the layout is done so that the rooms are all offset from one another from the lower levels up to the upper levels, ie, the very few "shared spaces" that allow an open inside wall area from a lower level to an upper level that goes straight up and those that do usually has a cold air duct, heating duct or plumbing run through them.

In the case of the kitchen, directly above is a bathroom and one of the kids' bedrooms. Again the plumbing goes up one wall and then jogs over about 3-4ft under the bedroom (above the kitchen) into the bathroom.

To further complicate things, the house is built with no trusses. So I have no attic to go into, also to counter any regular "shift" they heavily insulated and used 1-1/4" drywall with 1/2" plaster over it with heavy texturing everywhere. So tearing out walls and redoing them now becomes a "matching" nightmare.

The house was way overbuilt, which is great. Just that it makes any real "changes" a huge amount of planning/work. Oh, they also used all treated lumber everywhere for everything structurally. And man, when you drill holes through that stuff does it stink.

I already added in a hot water recirculation system so that I don't have to wait 3 minutes to get hot water up in the master bath in the morning. To do that I had to snake PEX line up into not only the area behind the master suite (required me to cut out part of the OSB flooring in the storage area there) but also work through cold air ducting in the dining room to run PEX behind the sink area in the kitchen.

Don't get me started on running ethernet cables, since that took me over 3 months to complete and even then I had to concede that I wouldn't get into the upper bedrooms so I just ran ethernet-over-coax bridges and reused the cable system wiring to get 100mbit ethernet to the bedrooms. I got lucky and reused the holes they drilled to put coax cable to the upper loft area and ran 3 ethernet cables up there for server use. I also put an antenna into the small "attic" area that sits above the middle of the house (basically a 13ftx5ft "space" above the upstairs hallway) and ran a distribution system to get it to all the TVs in the house as well as to 5 digital tuners.

This place is so well insulated that the furnace is a 80% efficient 100k BTU unit from 1989 that puts out 79k BTU and it keeps the house at 70 degrees and only costs about $200/mo for gas in the dead of winter. The problem is it is also so air tight that it pulls air in through the garage. Hell, I had to put a custom circuit in place that would shut down the furnace blower motor on heating startup since if you had to set to run the fan all the time it would cause a backdraft down the chimney flue for the furnace and cause the failsafe to trip.

About the only way to get changeover air in is to go through the garage lower area from the utility area of the basement and run a duct in the back corner of the garage to a duct out the back wall of the garage. All of which would steal space from the garage, so I am hesitant to do it.

Yeah, I spend way too much time trying to figure out this puzzle of a house...
 

dbphelps

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Oh, in regards to monitoring the dryer, I know I have a 120v kill-a-watt meter... I just can't stomach the cost to pony up for a 240v unit.

The main washer/dryer setup in the mudroom are huge Kenmore Elite units, basically the largest they ever made for residential use.

The ones I put in the lower laundry are Energy-Star units that are normally used in Condos. I put them in primarily because I am setting that side of the basement up as an apartment for the kids so they can get used to "living on their own" before they move out. There was already a partial kitchen down there when we bought the place, I am just finishing off a room, hallway, the kitchen, adding the laundry and then closeting the furnace. I figure if it helps a couple of the kids become independent it is well worth it. I have a few children that are autistic so "helping them become independent" is a lot trickier than those without such needs. So I figure this way, since there is also a bathroom, theater and computer center downstairs they have anything and everything they need to be "on their own" while we are also right here to make sure they get all the support they need.
 
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