Winter (cold December)

72 deg. Fahrenheit (22 deg. Celcius) dry bulb

up to 30% maximum relative humidity if

humidification is provided

The relative humidity (RH) should not fall below 20%.

One of these reasons is that humidity has a strong effect on the wood of furniture, paneling and other interior equipment and finishes. The shrinkage of wood lateral direction of the grain often results in unsightly cracks and the loosening of furniture joints. Another reason is that skin becomes rough and dry in low humidities.

Modern houses are increasingly air tight and the moisture produced by domestic operations is usually retained in the building to afford a reasonable humidity. This is emphasized by the fact that exhaust fans are often used in bathrooms while showering, their purpose being to reduce concentrations of moisture that cause copious condensation or mirrors and other glass surfaces.

OPERATIONPOUNDS OF MOISTURE

Floor mopping (7.2 sq.m kitchen, 0.03 psf) 2.40

Clothes drying indoors 26.40

Clothes washing 4.33

cooking

From food From gas

Breakfast 0.34+ 0.56 0.90

Lunch 0.51+ 0.66 1.17

Dinner 1.17 1.52 2.69

dishwashing

Breakfast 0.20

Lunch 0.15

Dinner 0.65

bathing

Shower 0.50

Tub 0.12

Human contribution, family of four/hr. 0.46

Gas refrigeration per hour 0.12

House plants, each per hour 0.04

Humidifier, when used per hour 2.00

(Source: from research in home humidity control, by S.C Hite and J.L Bray)

3 WAYS WHEREIN HEAT IS TRANSFERRED:

Conduction – the inside of a concrete wall which has one side exposed to outside winter temperature feels cold to touch. Heat is being conducted from the side of higher temp. to that of lower temp. to prevent heat loss by conduction, we must use materials that are poor conductors.

Radiation –from this point it is transferred to the outside air by radiation. To prevent loss by radiation, materials must be used which will reflect rather that radiate heat

Convection – when air is heated, it expands and begins to circulate. During the circulation, it comes in contact with cooler surfaces, some of its heat is given up to them. It is therefore important to try to prevent air currents (convection currents) from being set up in the walls and ceilings of our buildings.

To prevent heat from the inside to escape to the cold climate outside, THERMAL INSULATION MATERIAL are used.

a. Natural materials – wood, peat, and natural oils (such as

whale oil and seal oil )

a. Fossil fuels – gas, oil, and coal

b. Hydroelectric power

c. Nuclear plants

d. Heat pump

e. Solar energy

f. Geothermal energy

g. Trash – type of trash from incinerators has a heating value of 8500 Btu/lb. This value is 58% of the comparative value of anthracite coal.

SOME SYSTEMS COMPONENTS:

Furnace – a typical furnace embraces within its housing the fan (blower), motor, filters, oil burner and heat-transfer surfaces.

Ducts – constructed of sheet metal or glass fiber—either round or rectangular.

Dampers – these will be necessary to balance the system and adjust it to the desires of the occupants. Splitter dampers are used where branch ducts leave the larger trunk ducts. Each riser can have its flow controlled by an adjustable damper in the basement at the foot of the riser.

AIR CONTROLS IN DUCTS:a. Air adjustment by Opposed-blade Dampers

b. Air adjustment by Splitter Damper

c. Conventional turns in ducts

d. Right-angle turns with turning vanes (more compact method)

Registers – supply registers should be equipped with dampers and should have their vanes arranged to disperse the air and to reduce its velocity as soon as possible after entering the room. A common method is to provide vanes that divert the air in half to the right and half to the left. When a supply register is in the corner of a room, it is best practice for the vanes to deflect all the air in one direction, away from the corner. Return grills are of the slotted type in walls and of the grid type in floors. All registers and grills should be made tight at the duct connection.

o A 2- 1 4 in. x 12 in. floor register (diffuser). One of many sizes and shapes. It has diverting vanes for “spread” and an adjustable damper.

o Concept of spread and throw. By aspiration (suction), cooler air is induced to join the stream of warm air, resulting in a bland and pleasant air stream that crosses the room.

TYPES OF STEEL AND CAST IRON BOILERS:

Oil-fired steel boiler – a refractory chamber receives the hot flame of the oil fire. Combustion continues within the chamber and the fire tubes. Smoke leaves through the breeching at the rear. Water, outside the chamber, receives the heat generated in the combustion chamber. If the domestic hot water coil is connected for the use, a larger capacity boiler is selected. An aquastat (water thermostat) turns on the burner whenever the boiler water cools off. Thereby maintaining a reservoir of hot water ready for heating the house.

Gas fired cast iron hot water boiler Cast iron sections contain water that is heated by gas from below the unit. Output is related to the number of sections. It may be considered a “package” unit because the connected circulating pump stands ready to move water through convectors or baseboards.

Oil-fired cast iron hot water boiler primary and secondary air for combustion may be regulated at the burner unit. Flame enters the refractory chamber and continues around the outside of the water-filled cast iron sections.

High-output, package-type sell boiler. For large buildings using steam as a primary heating medium, one or several such boilers may be used. The relative lightness of this boiler type makes this package type suitable for use on upper floors of tall buildings.

Convector, steam to hot water – when, in a building rising primary steam boilers, secondary circuits using hot water for heating are required, a convertor is used. It is considered a heat exchanger. A convector may also be used to transfer heat from steam to domestic water.

Electric boilers - for hot water heating are of high capacity output. Electric steam boilers are also commonly used in large buildings.

Coal-fired steam boiler –as less polluting use of coal is achieved, a return of this variation of equipment is seen.

CIRCUIT TYPES

Series perimeter loop

This series loop system usually run at the perimeter of the house. The water flows to and through each baseboard or in tube in return. Valves at each heating element are not possible since any valve would shut off the entire loop. Adjustments is by a damper at each baseboard, which reduces the natural convection of air over the fans.

The One Pipe Series Loop uses less pipe than any other hydronic piping arrangement therefore it is less expensive to install the piping but you need bigger radiators or longer baseboards at the end of the loop because this part of the loop will have less heat. The radiators or baseboards at the beginning of the loop use most of the heat thus the reason for the larger radiators and baseboards at the end of the loop. There is also a larger temperature drop in this type of loop between the supply and the return versus other types of hydronic piping arrangements. The near boiler piping may need to be modified to prevent large delta T between supply and return.

Two-pipe reverse-return

Water nearly at boiler temperature is supplied to each baseboard without being cooled by passing through a previous baseboard or accepting the cooler return water equal friction, resulting in equal flow, is achieved through all baseboards, by reversing the return instead of running it directly back to the boiler.

This equality is affected by equal lengths of water flow through any baseboards together with its lengths of supply and return main.

The Two Pipe Direct Return Loop utilizes more pipe than the one pipe series loop but all radiators and baseboards receive the same temperature of water therefore it is more even heat than in all the radiators and/or baseboards than the one pipe series loop. Another advantage of two pipe direct return loop over the one pipe series loop is that it can be zoned. Zoning gives you more control over where and when you want heat and this can save you money on the cost of heating. As with many hydronic loop systems the two pipe direct return needs balancing valves.

SPECIAL FITTINGS

Special fitting for one-pipe systems. Venturi-type jet tee used here. In the return branch connection to the main it induces flow through the convector by retarding the flow to force water into the supply branch and producing a jet to reduce the pressure in the main following the return branch.

AIR VENTS AND WATER DRAINS

Air must not be allowed to accumulate at high points in the piping or at the convector branches. These air vents relieve these possible air pockets, which would otherwise make the system air-bound and inoperative.

If a system is to be drained and left idle in a cold house, water trapped in low points could freeze and burst the tubing or pipings. Operable valves must be provided at such locations and, of course, at the bottom of the boiler.

CIRCULATING PUMP

a centrifugal pump is selected to overcome the friction-of-low in the piping and fittings and to deliver water at a rate sufficient to offset the hourly heat loss of the house or buildings.