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Heat-Pump Basics

Posted by on 20/ 11/ 15

Heat-Pump Basics

A

ir-to-air heat pumps use pressurized Freon® gas to absorb heat from the air outside and transfer it to your home. When the thermostat calls for heating, Freon is pressurized, it condenses, and then it turns
is distributed through registers in the floors, walls, and ceiling. At the same time, a fan in the condenser sends cold air outside. You can reverse the cycle for cooling in the summer. (Ground-source heat pumps

to hot liquid. A blower forces air across warm Freon-
use a water/glycol mixture to exchange heat energy

filled coils and through a system of ducts; warm air

 

with the earth

 

Branch duct

 

Fan

 

Disconnect box

 

INDOOR UNIT

 

Trunk duct

 

Damper

 
Heat-Pump Basics

Coils

 

DAMPERS ADJ...

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Wind Can be a Serious Problem

Posted by on 20/ 11/ 15
Подпись: Fig. 4.16: Fiere, graphically, are the basic ways that wind can affect a structure. Illustration courtesy of Simpson Strong-Tie Co., Inc.
image52

Подпись: 8"x8"Подпись:image53In certain areas of the country like the southern U. S. Gulf Coast, Hawaii, “Tornado Alley,” coastal Alaska, and other areas, code demands a more positive tie-down mechanism than the positioning pin and gravity technique that I employ in northern New York. Fortunately, several manufacturers make a variety of anchoring fasteners whose purpose is to tie the base of the posts to foundations. Three companies are listed in Appendix C. One of the leaders in the field is Simpson Strong-Tie Co., Inc. In their High-Wind-Resistant Construction Product Selection Guide (catalog C-HW02, November 1, 2002), on page 4, they say: “Newer building codes such as the International Building Code (IBC), the International Residential Code (IRC), and the Florida Building Code (FBC),

Подпись: different post bases, courtesy of Simpson Strong-Tie Co., Inc.Подпись: Fig. 4.17: Four Illustration Подпись: 2” minimum sidecover image56"have had a pr...

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Is Your Heating System an Energy Beast?

Posted by on 20/ 11/ 15

Is Your Heating System an Energy Beast?

■ BY DAVE YATES

The economy is down, fuel costs are up, and chances are that your heating budget is already busted. You need to do something—but what? Only a few of us are ready to invest in geothermal or solar. The rest of us need to find the answer in the heating system we already have.

For 70% of U. S. households, that sys­tem consists of a furnace that forces hot air through ducts; for 17%, it’s a heat pump; and for 11%, it’s a boiler that heats with water or steam radiators. The remaining 2% of homes use wood, coal, geothermal, solar, or other heating methods. When it comes to fuel, 58% of us use gas (either nat­ural or propane), about 35% use electricity, and almost 7% use fuel oil.

Your home might not have the most ef­ficient heating system available, but there’s good news: Yo...

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Working with DWV Materials

Posted by on 20/ 11/ 15

As mentioned earlier, DWVstands for drainage, waste, and venting. ABS and PVC plastic pipe are by far the most common DWV materials, although cast-iron is still specified where sound suppression is important. Plastic pipe is strong, the most corrosion resistant of any DWV pipe; is easy to cut and assemble, using special solvent – based cements; is light enough for one person to handle; is reasonably priced; and is extremely slick inside, which ensures a good flow of wastes. It’s by far the favorite DWV material of amateur plumbers—and many pros. But there are few disadvantages. Many codes prohibit using plastic pipe on exteriors because of durability and UV degradation issues, and if you don’t spread the cement evenly or allow it to cure before stressing the joints, plastic can leak.

Cas...

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Gritting Materials

Posted by on 20/ 11/ 15

Grits usually consist of different types of aggregates, such as the following:

• Aggregate 2/5 (or 2/4) mm, cleaned and hot, applied at a rate of 1.0-2.0 kg/ m2, for SMA with a gradation of at least 0/11 mm (Figure 10.14)

• Aggregate 1/3 mm, washed and hot, applied at a rate of 0.5-1.5 kg/m2, for SMA with any gradation

• Aggregate 0.25/2 mm, washed and hot, coated with about 1% binder (m/m), applied at a rate of 0.5-1.5 kg/m2, for SMA with any gradation but preferred for SMA 0/5 and 0/8

Generally, the use of finer grains for gritting means a lower quantity per square meter. Additionally the smaller the maximum aggregate size of the SMA, the smaller the grit grains that should be used.

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FIGURE 10.14 Gritting particles among SMA coarse aggregates...

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Selection of Crash Cushions

Posted by on 20/ 11/ 15

Selection of the most appropriate crash cushion depends on site characteristics, perfor­mance of the systems, maintenance characteristics, and life-cycle cost. Both the geometrical conditions encountered and the space requirements for the different systems vary widely. Obstacles greater than 16 ft (5 m) wide can be shielded by systems such as arrays of sand-filled barrels, or the bullnose attenuator. Where space is limited, narrow systems are appropriate. The structural and safety characteristics of alternative systems must be carefully reviewed and matched with needs. Items to consider include impact deceleration, redirection capability, impact debris, and anchorage and backup require­ments. Table 6.10 has been prepared to compare the maintenance requirements of the different systems...

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Fiber-Cement Siding

Posted by on 20/ 11/ 15

FIBER-CEMENT SIDING has been around a long time. The first house I worked on in the late 40s was cov­ered with fiber-cement siding. It was a bit brittle and not too attractive but just about indestructible. It fell out of favor because it was hard to work with and full of asbestos, while high – quality wood siding was inexpensive and becoming widely available.

Times have changed. Today, wood siding is expensive and often lacking in quality. Modern fiber-cement sid­ing, on the other hand, contains no asbestos and offers all of its old advantages and a few new ones, too. Like vinyl, it’s fairly easy to work with, thanks to the new cutting and nailing equipment available today. Unlike wood, it doesn’t cup, curl, rot, or attract termites...

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STEP4 Complete Ventilation and Electrical Work

Posted by on 20/ 11/ 15

Before you install the siding, soffits, and exte­rior trim, its important to resolve some venti­lation and electrical details. For example, this house has a rectangular attic vent centered beneath the ridge in each gable-end wall. If you chose to sheathe the gable-end truss on the ground, this is the logical place to cut the hole for the vent. If the hole hasn’t been cut yet, do so now, then install the vent (see the photo on the facing page).

Referring to your house plans, an electri­cian will be able to locate any outlet boxes that need to be installed in the exterior walls. Outdoor receptacles are placed at convenient locations; the same is true for outdoor lights.

This is also the time to cut the hole for the dryer vent. A standard dryer vent requires a 4-in...

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Characteristics of Crash Cushions

Posted by on 20/ 11/ 15

Crash cushions are impact attenuators developed to prevent errant vehicles from impacting fixed obstacles. The crash cushion should either decelerate the vehicle to a safe stop, such as in a head-on hit, or redirect it safely away from the obstacle, in the case of a side hit. Crash cushions are typically used where fixed objects cannot be removed, relocated, converted to a breakaway design, or shielded by a longitudinal barrier. Examples of application sites include exit ramp gores where a bridge rail end or bridge pier presents a hazard, and the ends of longitudinal barriers. Most crash cushions are patented systems developed and tested by the manufacturer, who can also provide design charts for selection of appropriate designs.

Most crash cushions perform their function by the principle ...

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BARRIER END TREATMENTS AND CRASH CUSHIONS

Posted by on 20/ 11/ 15

Barrier terminals and crash cushions are developed to gradually decelerate an impact­ing vehicle to a stop or to suitably redirect it. Otherwise, untreated ends of barriers and fixed objects can cause severe accidents. A crashworthy end treatment is essential if a barrier terminates within the clear zone or other area where it is likely to be hit by an errant vehicle. Requirements for testing and performance are contained in NCHRP 350. Suitable devices must be able to perform under both head-on and side impacts, with no objects penetrating the passenger compartment or encroaching on other traffic. The vehicle should remain upright and not be redirected into adjacent traffic lanes. Occupant deceleration levels must be within target values...

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