Heating and air-conditioning layout

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Figure 4-12 (a foldout at the end of this chapter) shows a heating and air-conditioning layout for a hospital. You can see that the air- conditioning plant consists of four separate self- contained units, three of which are located in the mechanical equipment room, and one on the porch of the ward. Note the cooling towers, that have not as yet been mentioned. In a water-cooled air-conditioning system, cold water is run over the coils of the condenser (rather than air being blown over the coils). The purpose of the cooling tower is to cool the water. Water is sprayed at the top of the tower, and as it falls through the redwood louvers, it is cooled by the air. Sometimes, large blowers force air through the water, making the cooling tower more efficient. You can read more about cold-water air-conditioning systems in the UT2 TRAMAN. In figure 4-12, you can see the line of air-conditioning ducts running from each of the air-conditioning units. Note that the section dimensions of each length of specified size are noted on the drawing. Notice, too, that these dimensions decrease as distance away from the unit increases.

You should notice, also, that some spaces are heated by radiators, rather than the air-conditioning system. These spaces (all the toilets, for example) may contain odors or gases that would make it inadvisable to connect them with the air-conditioning duct system. On each of the radiators, the heating capacity, in British thermal units (BTUs), is inscribed. In each space not connected to the air-conditioning system, you can see an exhaust fan (for ventilation) shown. On each fan, the air capacity, in cubic feet per minute (CFM), is noted.

In each air-conditioned room, you see a circle (or more than one circle) on the duct. This indicates an outlet for the conditioned air. In this case, the outlets are diffusers, and the capacity of each diffuser, in CFM, is inscribed. Note that this capacity varies directly with the size of the space serviced by the outlet.

Steam lines from the boiler in the mechanical equipment room to the air-conditioning units and radiators appear as solid lines. Small diagonal lines on these indicate that they are low-pressure steam lines. Returns appear as dashed lines.

In the upper left corner, a detail shows the valve arrangement on the steam and condensate return lines to each of the air conditioners. Referring to the mechanical symbols specified in MIL-STD-17B, the detail indicates that in the steam line, the steam headed for the unit passes agate valve, then a strainer, and then an electrically operated modulating valve. This last reduces the pressure to that for which the unit coils are designed.

The steam condensate leaving the unit first passes a gate valve, then a strainer, then a union, and then a steam trap. This trap is a device that performs two functions:  (1) it provides a receptacle in which steam condenses into water and (2) it contains an automatic valve system that periodically releases this water into the rest of the return lines.

Beyond the steam trap, there is another union, next comes a check valve, and finally a gate valve. A check valve, as you know from the EA3 TRAMAN, is a one-way valve. It permits passage in one direction and prevents backup in the opposite direction.


Every drawing prepared in the drafting room must be checked and edited. As a capable EA2, you maybe delegated the job of doing so. When checking a drawing, you are inspecting it to make sure that it accurately conveys the information contained in the data source. That source may be survey field notes, sketches, written data, another drawing, or any combination of these. Any error or omission of information in these sources will result in inaccuracies in the drawing; therefore, the first check is to make sure that the source accurately provides everything needed to make the drawing. "Editing" means that you are inspecting the drawing to make sure that the procedures and conventions prescribed in relevant NAVFAC publications and military standards are followed. It might be said that editing begins as soon as drawings begin-meaning that you must constantly edit drawings to ensure that proper procedures and conventions are followed at the time the drawings are made.

When checking and editing a detail drawing, the checker ALWAYS uses a print of the drawing, rather than the original. That way, any corrections that need to be made can be marked with a colored pencil or pen on the print without disturbing or destroying the original. The detail drafter then uses the marked-up print to make corrections to the original drawing. After all of the corrections have been made, the checker compares a print of the corrected drawing with the originally marked-up print.

For a thorough job of checking and editing, you should first make an overall check with the following questions in mind:

1. Does the drawing reproduce well? Any poorly defined or weak line work and lettering must be corrected.

2. Does the size and format of the drawing conform to the MIL-HDBK-1006/1 requirements for Naval Facilities Engineering Command (NAVFACENG-COM) drawings? As specified in that publication, the project drawings should be prepared on flat C-, D-, or F-size paper. It also specifies that a vertical title block format is mandatory for D-size drawings and optional for F-size. Examples of both horizontal and vertical format title blocks can be found in MIL-HDBK-1006/1.

3. For a set of drawings, is a different drawing number assigned to each sheet and are all of the drawing numbers correct? Is the set of drawings arranged in the correct order as specified in MIL-HDBK-1006/1. That is, are they arranged as follows:

a. Title sheet and index of drawings (only for projects containing 60 or more drawings).

b. Plot and vicinity plans (including civil and utility plans). This sheet should include an index for small projects.

c. Landscape and irrigation.

d. Architectural.

e. Structural.

f. Mechanical (heating, ventilating, and air conditioning).

g. Plumbing.

h. Electrical.

i. Fire protection.

If the overall check is satisfactory, proceed with more detailed questions, such as the following:

1. Is the method of projection appropriate?

2. Are the views shown the minimum number required to show all the data?

3. Are sectional views constructed correctly and is the section lining correct?

4. Are line conventions and symbols consistent with the requirements of appropriate and current standards? Are all symbols (especially nonstandard ones) explained in a legend?

5. Are proper scales used for the drawing and are the scales shown? Appropriate scales for construction drawings are as follows:

a. Floor plans and elevations: 1/4", 3/16", 1/8", or 1/16" = 1 O".

b. Architectural details: 3/4", 1 1/2", or 3" = 1 0.

c. Molding sections and similar details: full scale or half scale.

d. Mechanical and electrical details: 3/8", 1/2", 3/4", or 1" = 1 0.

e. Structural details: 3/8", 1/2", 3/4", or 1" = 1 0.

f. Structural erection drawings (such as structural floor and roof framing plans): 1/8" or 1/16" = 1 - 0".

g. Site (plot) plans: 1" = 10, 20, 30, 40, 50, 60, 100, or 200.

h. Utility plans: 1" = 20, 30, 40, or 50.

6. Are graphic scales shown as required by NAVFACENGCOM (MIL-HDBK-1006/1)?

7. Do the dimensions agree with those shown in the data source? Does the sum of partial dimensions equal the overall dimensions?

8. Are all of the required dimensions shown? Are there superfluous dimensions that are not needed?

9. Are all necessary explanatory notes given? Are all general notes in their proper location on the drawing?

10. Are terms and abbreviations consistent with military standards? Are the abbreviations (especially unusual ones) explained in a legend?

In addition to all of the above, you also should be constantly alert to misspellings and the improper use of phases and statements. Oftentimes, phases and statements that are used in common practice are not acceptable for use in project drawings. Listed below are some of the most common errors found in project drawings. (A correction follows each incorrect phrase or grouping of phrases.)

1. Incorrect: "As instructed by the architect."

Correct: "As directed" (Note, however, that you should avoid using this type of language since it indicates un-certainty as to what the requirements are.)

2. Incorrect: "As approved by the architect."

Correct: "As approved."

3. Incorrect: "By the Navy."
                 "By others."

Correct: "By the Government."

4. Incorrect: "By the electrical contractor."

Correct: "By the plumber."

5. Incorrect: "By the plumbing contractor." (Usually no statement is necessary since the government recognizes only the prime contractor.)

Correct: "12 gauge zinc-coated steel flashing."

6. Incorrect: "copper flashing."

Correct: "Metal flashing." (Metals are referred to only as metal and not as a particular kind or gauge. Type and weight should be covered in the project specifications.)

7. Incorrect: "Formica."

Correct: "Laminated plastic." (Proprietary or brand names are not permitted.)


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