Main Beam of a Residential House

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Main Beam in Residential

Main Beam in Residential

I check with the builder, there is specks that come with factory beams. The last one we did is said center third and upper third. Semper Fi.
 
Again thanks a lot to all of you. All of you are very helpful.

Here's what I come up with for load calculation. This is just APPROXIMATE because I still don't know the kW of the appliances that will be installed. But mainly I would like to know if my load calculation procedure is correct. I will adjust the calculated numbers later.

4200 sq ft Single Dwelling
Computed load
General lighting load

4200sq ft at 3va /sq ft = 4200 x 3 = 12,600
Small Appliances load:
Dishwasher 1500
Garb disp 1500 3000
Laundry 1500 1500
________
Total general light & appliances load 17,100
3000 v-a at 100% load 3,000
17100-3000 = 14,100 v-a at 35% 4,935
_________
Net General Lighting and small appliances load 7,935
Range Load 8,000
Dryer load 5,500
Hot tub load 8,000
Water heater 2,500
Wall Mounted oven/microwave 3,000
Air conditioning 10,080
__________
Total Load 45015

For 120/240-volt 3 -wire single phase service feeder
45015 /240 volts = 187.6 A
 
Brady:
Thanks a lot for that important specs. But what I was thinking is to drill the (one)hole for the feed wire of the subpanel on top of the cross beam to minimize the load stress but I will do as you said "center third and upper third" . And I will still ask the achitect who drew the plan to be sure.
 
bencelest said:
Brady:
Thanks a lot for that important specs. But what I was thinking is to drill the (one)hole for the feed wire of the subpanel on top of the cross beam to minimize the load stress but I will do as you said "center third and upper third" . And I will still ask the achitect who drew the plan to be sure.
Click to expand...

That's the only way you're going to find out.

Typically all the load for a beam that's subject to bending forces (meaning, the load isn't being transferred straight down through the beam) is in the "extreme fiber", meaning the further you get towards the edges the greater the load. This is why, for example, you never, ever notch the top or bottom of a beam. Drilling in the center is generally safe (but again, check with the architect or engineer -- I used to know American Bureau of Shipping rules, but this ain't a ship ...), but the further from the center you get the less safe it is.

You could take, if you wanted, a pair of 2x4's, hold them 4 1/2" apart by some rigid means, and it would be just about as strong as a 2x12 (90% as strong, approximately -- section modulus of 99 versus 89 assuming the neutral axis is 5 3/4" from the extreme fiber, if my memory serves correctly). That's how those annoying engineered beams work -- the compression and tension are in the top and bottom boards and the cross-bracing in the middle just make sure the two boards stay where they belong.

But, yeah, ask the engineer who put the beam there in the first place.
 
bencelest said:
Here's what I come up with for load calculation. This is just APPROXIMATE because I still don't know the kW of the appliances that will be installed. But mainly I would like to know if my load calculation procedure is correct. I will adjust the calculated numbers later.

4200 sq ft Single Dwelling
Computed load
General lighting load

4200sq ft at 3va /sq ft = 4200 x 3 = 12,600
Small Appliances load:
Dishwasher 1500
Garb disp 1500 3000
Laundry 1500 1500
________
Total general light & appliances load 17,100
3000 v-a at 100% load 3,000
17100-3000 = 14,100 v-a at 35% 4,935
_________
Net General Lighting and small appliances load 7,935
Range Load 8,000
Dryer load 5,500
Hot tub load 8,000
Water heater 2,500
Wall Mounted oven/microwave 3,000
Air conditioning 10,080
__________
Total Load 45015

For 120/240-volt 3 -wire single phase service feeder
45015 /240 volts = 187.6 A
Click to expand...

I think you're off on some things with your calcualtion. The small appliance circuits are for receptacles (like kitchen counter and laundry receptacles). The dishwasher and garbage disposal can not be on those small appliance circuits, they are in addition to them. The laundry washing machine, however, can be on the laundry small appliacne circuit. So you should have 4500 VA for a normal house plus the dishwasher and disposal.

Next, the water heater looks too small. Most are 3500 to 5500 watts.

Your air conditioning seems huge unelss this is multiple air conditioners. Use the MCA value on the nameplate and not the max breaker amp rating because the breaker will be substantially larger than the load to account for startup surges. A typical new 4 ton AC would have an MCA of around 28 amps plus about 3 more for the inside air handler fan.

Does this house have a range and a wall mounted oven? I can't seem to find the nameplates on a lot of new ovens and ranges, so it is difficult to estimate. Using 8KW for the range is good, as that will cover a range up to 12 KW with the allowed demand factor.

Your disposal, dishwasher, water heater, and hot tub provide 4 or more fastened-in-place appliances. This allows a factor of .75 to be applied to each. You may want to add a few more for good measure -- garage door openers, bath and kitchen vent fans, ....keep looking at the plans.
 
Thank you Tallgirl and Mark.
Both of you are very helpful to me also.
I'll adjust my calculation as per your advice. I still have to see the HO as to what kind of appliances and add ons he has in mind. Thanks for reminding me of the bathroom fans and garage door opener(s) .
HO is paying me by the hour so I don't have to rack my mind up about bidding. And yes, he even pays if I go to the suppliers to get the parts or for consultation/meeting.
 
bencelest said:
And yes, he even pays if I go to the suppliers to get the parts or for consultation/meeting.
Click to expand...

They do that anyway..whether they know they are paying for that "service" or not :)
 
wag said:
If you did an analysis of the beam loading you would find the top of the beam was in compression, the bottom is in tension, and the center is neutral.
Click to expand...
Also, as you move away from the midpoint and towards the endpoints of the beam, even the web (or center) will be under increasing vertical shear. It's rarely the limiting factor in residential construction, but it's one of the things that must be checked when sizing a beam.
 
The general rule is that the center third of a beam, both vertically and horizontally, may be penetrated more liberally. For anything outside this zone, you must follow manufacturer's instructions.

Hole diameters, spacing, and locations are all much more critical as you leave this area.
 
Thanks Barry and Larry for the good pointers.
I think I am good to go.
I only need one hole for an SE cable to feed a 100 amp subpanel on the otherside of the main beam.
 
Mark, I don't think 10KW is huge for a 4200 sq ft house in Calif. It could take up to 10 tons to cool a home this size especially if it is in the desert. Even well insulated and designed, at least six tons, which puts the condenser loads alone at 10KW.
 
monkey said:
Mark, I don't think 10KW is huge for a 4200 sq ft house in Calif. It could take up to 10 tons to cool a home this size especially if it is in the desert. Even well insulated and designed, at least six tons, which puts the condenser loads alone at 10KW.
Click to expand...

I didn't notice he was from California, but there is still a huge disparity in cooling loads across that state. He could easily have more than 10KW if this is in Mojave or well less if this is in the northern mountains. My point was it was too high for a single compressor. Best find out now how many air handlers and compressors are going to be installed and at least their tonnage (and preferably the nameplate data).
 
Right on that. I am just used to large cooling loads being in the southwest desert myself. We never have to consider heating load since our cooling load is always way bigger. In the hotter months AC can become a continuous load here!
 
Even here in MA, our cooling loads is always higher than our heating load.
 
The owner is not installing any A/C unit but only the ductwork. He said he prefers the buyer to install it if he wants to.
The temperature here is moderate throughout the year 50 to 70's being close to the ocean. I can't recall I turn on my aircon for the last 10 years except when there was a unbeleavable heat wave a couple of years ago. And Monterey area is unique place to live. It is always cool all the time but 40 miles away they may be hovering at 100 * temperature, Monterey stays on the 80's or high 70's.
But I am waiting for a call from who will install the ductwork for the specs of the A/C and Heating of the house.
 
stickboy1375 said:
Unless your installing electric heat... :)
Click to expand...

I was thinking the same thing but full electric heat is pretty rare for single family homes in this area.

My brother in law has full electric heat, its in the ceilings, glad I don't pay his bills.

When we do some hotels the electric heat far exceeds the AC.

The meter spins nice with a 4000 amp 208Y/120 service. :D
 
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