HVAC Systems Design Handbook part 14

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HVAC Systems Design Handbook part 14

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While drawings and specifications in a sense are the designer’s end product, this is not really the case. From the owner’s point of view, the built and operating facility is the only real product. All other activity is only a prelude to the real thing. To truly succeed, the designer must follow the design through bidding and construction to start-up and eventual operation.

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  1. Source: HVAC Systems Design Handbook Chapter After Design: Through 14 Construction to Operation 14.1 Introduction While drawings and specifications in a sense are the designer’s end product, this is not really the case. From the owner’s point of view, the built and operating facility is the only real product. All other activity is only a prelude to the real thing. To truly succeed, the designer must follow the design through bidding and construction to start-up and eventual operation.1 Some parts of the in-construction work and project closeout work, with transition of the project to the owner, are assigned by specifica- tion to the contractor. Such work should include, as a minimum: first- run inspections; preparation of operating and maintenance manuals; testing, adjusting, and balancing; and instruction of owner’s operating personnel. But getting the project off on the right foot with the con- tractor, being available during construction, and helping the owner take over and get the project running well are also of serious concern to the project designer. 14.2 Participation during Construction Designer participation during construction and beyond varies greatly with design office practice and with the owner’s desires. Some design offices have one or more individuals dedicated to construction review in service to the owner. Some owners have their own people watch the job during construction, relieving the design office of any possible in- volvement, except to clarify a conflict in documents or a design error. 429 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  2. After Design: Through Construction to Operation 430 Chapter Fourteen 14.2.1 Bidding period When the project design is completed, drawings and specifications are given to contractors with a request to prepare a proposal, to submit a bid. During the bidding period, the bidders may identify missing in- formation and discrepancies or errors in the documents. The owner may identify additional services or installations which are wanted as part of the contract. In each case, the designer will prepare clarifying information which is added to the documentation by an addendum. Addendum information should have the same character and quality as the original documents. When the contractors submit their bids, the bids may be opened publicly and read aloud, as in the case of most government institu- tions, or they may be opened privately, as is more common in industry and private enterprise. Public bid openings are often quite exciting if there are several bidders and if the bidding is quite close. Thousands, sometimes millions, of dollars of work for a contractor may hang on just a few dollars’ difference in the bid offering. Bidding is the marketing effort for the typical contractor and is an established mechanism for finding the right price for a scope of work. Preparation of a bid for a project is typically time-consuming and may involve considerable expense for a bidding contractor. Where several contractors with many subcontractors are involved in a takeoff, yet only one team can succeed, it is clear that all bidders should be treated with respect for their effort. 14.2.2 Submittal (shop drawing) review As a part of quality control for a project, the contractor is usually required to show her or his intentions for materials, equipment, and construction technique to the owner prior to ordering, delivery, and installation. The owner’s representative, who may be the designer of the work or an associate or another appointed agent, then reviews the contractor’s submittals for conformance to the specifications. The con- tractor is usually required to verify that he or she, too, has checked the submittal for quality and conformance. Even though contractually the submittal is checked only against the drawings and specifications, there are the background questions such as the correct size, coordi- nation between trades (adequate structure, adequate access, correct electrical support). This joint review creates one more opportunity for checking the design in the sense of ‘‘measure twice, cut once.’’ Submittal information is usually stamped with a note of acceptance or rejection, with written clarification of observed deviations or omissions. See Fig. 14.1. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  3. After Design: Through Construction to Operation After Design: Through Construction to Operation 431 NO EXCEPTIONS TAKEN AMEND-RESUBMIT MAKE CORRECTIONS NOTED REJECTED-RESUBMIT REVIEWED BY: DATE: RECOMMENDED BY: DATE: CORRECTIONS OR COMMENTS MADE ON CONTRACTOR’S SHOP DRAWINGS DURING THIS REVIEW DO NOT RELIEVE THE CON- TRACTOR FROM COMPLIANCE WITH CONTPACT DRAWINGS AND SPECIFICATIONS. THIS SHOP DRAWING HAS BEEN REVIEWED FOR CONFORMANCE WITH THE DESIGN CONCEPT AND GENERAL COMPLIANCE WITH THE CONTRACT DOCUMENTS ONLY. CON- TRACTOR IS RESPONSIBLE FOR: CONFIRMING AND CORRELAT- ING ALL QUANTITIES AND DIMENSIONS; FABRICATION PRO- CESSES AND TECHNIQUES; COORDINATING WORK WITH OTHER TRADES; AND SATISFACTORY AND SAFE PERFORMANCE OF THE WORK. Figure 14.1 Typical shop drawing review stamp. Because construction is based on a contract between the owner and the contractor, the designer or submittal reviewer needs to be careful not to assume contractor responsibility in her or his review. In these days of increasing litigation, the language of review has evolved from approved to no exceptions taken, or some similar noncommittal ex- pression, meaning that the reviewer finds no apparent fault, but still leaves the responsibility for conformance to the contractor. Such fancy footwork notwithstanding, material will occasionally show up on the job which is not really what was wanted or needed. Rejection at such a late date is awkward and sometimes embarrassing, but it is better handled sooner than later. The designer or reviewer needs to be ac- quainted with the design intent in this phase of the work. 14.2.3 Work oversight and field review The designer can only expect what the designer inspects! Periodically during construction the project designer or an assigned representative should visit the project to review the work accom- plished and to answer questions that may arise. Sometimes a clari- fying sketch or an explanation of design intent is all that is needed. Sometimes the designer will want to check material and equipment at the job site for conformance to documents and to submittal infor- mation. This is done to confirm to the owner that the project is being installed in a correct manner. Given the adversarial nature of fixed- cost construction (the owner wants the maximum for his or her dollars, Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  4. After Design: Through Construction to Operation 432 Chapter Fourteen the contractor wants to maximize the dollars left over), there is an element of fairness and integrity required of the designer in evaluat- ing adequate contractor response to the document or contract re- quirements. Construction review is shaky ground for a neophyte. Ex- perience at the hands of a good mentor is invaluable. 14.2.4 Change orders In the process of construction, nearly always a condition will arise that is inadequately or incorrectly defined by the contract documents. Of- ten this will be the result of conflicts with other trades, due to lack of coordination among designers. A classic case of this occurred when the HVAC inspector caught a deep concrete beam, ready to pour, without the slot required to allow a large duct to pass through. (Fortunately the forms were adjusted to provide the slot.) Hopefully, the condition will be encountered before the constraints are cast in concrete or fab- ricated in steel. Upon identifying the problem, the construction team—designers and constructors—will seek a solution. Often an ad- justment can be made which incurs no additional cost to the contrac- tor, and the work proceeds. Sometimes correction of the problem cre- ates additional cost and effort for the contractor, who then seeks added compensation. Such is granted by change order to the contract. A change order involves a documented scope of work, a price, and a time, and it becomes part of the contract when it has been agreed to by all parties. The pricing mechanism is sometimes awkward since the ele- ment of competitive bidding is gone. Even as some owners will try to obtain more service than the documents truly define, some contractors will seek compensation beyond the value or cost of the added work. In a field review, the designer must work hard to see that equity is main- tained. When a design error is involved, the contractor is not inter- ested in covering the cost, and some owners become an immediate designer’s adversary. Design fees are typically inadequate to provide contingency funds, even for small items. Errors-and-omissions insur- ance protects against major lawsuits, but there is a cost range where designers must fend for themselves. Fortunate is the designer who works with an owner who realizes that no set of construction docu- ments is perfect, that 2 to 3 percent of basic cost for added clarification is reasonable, and that openly working through problems is better than trying to hide or barter them away. Construction budgets should contain a percentage, typically 10 percent, to allow for changes. 14.2.5 First-run inspection There is an assumption that the basic work of each trade is complete, that power is available to run equipment, and that devices can be Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  5. After Design: Through Construction to Operation After Design: Through Construction to Operation 433 placed in operation without fear of damage. All equipment is verified as ready to run with shipping stops and protective wrap removed, protective covers in place, surfaces cleaned of construction spatter, ro- tating parts able to move freely, etc. Valves and dampers are placed in a normal position; fluid-handling systems have been flushed clean and pressure-tested. Insulation may or may not be finished, but work is at least in progress. Control installations are complete and may have a first-time setup. With all components essentially there, the commissioning team goes from one device to the next, verifying basic function. Motors are jogged to verify rotation; fans and pumps are run for enough time to see that things are all right, that power is available where needed, and that automatic valves and dampers will stroke. The first run does not require calibration or test of capacity or ad- justment. It merely confirms that the systems are intact, ready for tuneup and test by the specialist. 14.2.6 Testing, adjusting, and balancing (TAB) With all systems in place and all devices capable of operation, the TAB team takes over to prepare the work for final delivery to the owner. This team is best managed by the general contractor, who has ultimate responsibility for the quality of the project and who can assign the work of all subcontracts. The work of the team then usually proceeds under the direction of an individual, or firm, independent of but work- ing with the mechanical, sheet-metal, control, and electrical contrac- tors, who can operate and adjust the systems without vested interest and with broader experience than any one of the specialized contrac- tors might have. Such a team leader is often referred to as a TAB contractor but the need is broader than just TAB. What is needed is an operator who can place a system in operation and tune it up to optimal operating condition. The system designer can be a help as well as a referee in the TAB work. The designer knows the intent of the design and the anticipated interrelationship between components. Some humility is required, however, for many designers have little actual operating experience and may not know how to manipulate and operate systems as well as do some of the old hands. It is essential to have a member of the owner’s eventual operating staff on hand for the start-up and TAB work. Early familiarity with and knowledge of the system minimizes questions later on. Some con- tractors, even designers, are reluctant to expose unfinished work to the owner’s staff because the loose ends of a major work are sometimes Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  6. After Design: Through Construction to Operation 434 Chapter Fourteen embarrassing, but the owner’s people are often a great help with cor- rective ideas. The work of the TAB team proceeds from one system to the next, covering air handling, fluid handling, central plant, and controls. There are established procedures for TAB work for nearly every type of system. ASHRAE, the Associated Air Balance Council (AABC), the National Environmental Balancing Bureau (NEBB), and other agen- cies all have documentation for test and balance procedures. Note that the objective is not just to make the systems perform as the drawings say, but now to actually do the job. Design calculations are at best a prophetic estimate of what will be needed based on an owner’s ex- pressed intended use and an architect’s designed structure. Real life may vary somewhat from the anticipated. The TAB team should be instructed and be willing to adjust to final needs. This does not mean willing to rebuild, unless defects are encountered, but to adjust within the capacity range of the systems. One of the final products of the TAB work is a report which docu- ments the work accomplished. The report usually includes reduced- scale drawings that show the nomenclature and location of all points of test and adjustment and shows in tabular form the quantities sought (design performance), the initial condition encountered, and the final condition attained, with analysis of any discrepancy and a report of corrective action. Part of the report may reflect work with the control contractor in verifying the calibration and proper function of each control device within the system context. At the conclusion of the TAB work, the designer and owner might ask the TAB team to reread selected measurements to verify the in- tegrity of the work. See Ref. 2 for further discusison of this topic. 14.3 Commissioning Commissioning is an old idea, but, as a formal concept, is of fairly recent origin. In the ASHRAE Handbook the term first appears in the Applications, 1995 volume. The activities it includes are those that have been found necessary—beyond the actual construction process— for achieving a complete and working HVAC system, which satisfies the requirements of the design and the needs of the owner. The term ‘‘quality assurance’’ is sometimes used. The ideal, from owner’s viewpoint, is that the commissioning team, selected by and working for the owner, will assist in the design phase as well as the construction phase, ensuring that the owner’s needs are met by the design. This is rarely the case except for those owners who have staff personnel with these capabilities. And many owners do not Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  7. After Design: Through Construction to Operation After Design: Through Construction to Operation 435 desire the extra expense, although this expense is compensated for in the long run by better system performance and more user satisfaction. The objectives of commissioning are: To ensure that the system design satisfies the owner’s needs. To ensure that the system performs in accordance with the design intent. To require complete and detailed documentation of operation and maintenance requirements, including reference and training man- uals. To provide basic training for operators and maintenance personnel. To observe, coordinate, and document all system performance tests (TAB). This is especially desirable in connection with DDC control technology, to prove the proper operation of the DDC software. To assist in the resolution of disputes, subject to the terms of the contract documents. To ensure compliance with all code requirements. To advise the owner when each part of the work has been satisfac- torily completed and can be accepted. For these purposes the commissioning team should be selected and paid by the owner and operate separately from the design and con- struction teams. Commissioning can also be applied to existing systems with some- times amazing results in improved performance and better use of energy. This usually happens as a study with recommendations for redesign and upgrade, followed by implementation of the recommen- dations. 14.3.1 Substantial completion All the preceding work should bring the project to a point of substan- tial completion. This is usually defined as the time when the owner takes beneficial occupancy of the project with a ‘‘punch list’’ of items which the contractor has yet to complete. Substantial completion usu- ally initiates the warranty period. Owners are recognizably reticent to award substantial completion; contractors are overly anxious to come to this point. If a project has a deadline with damages for late delivery or a bonus for early delivery, the potential consequences can be very important. The designer needs to be fair and helpful to both the owner and the contractor at this stage of work. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  8. After Design: Through Construction to Operation 436 Chapter Fourteen Many owners make a big mistake in failing to recognize that they should proactively take over the project, on the first day of beneficial use, for operation, maintenance, and improvement purposes. No pro- ject is perfect on inauguration day. Wear and tear begin the first time a device is turned on. For a system to still be well maintained and functional in 10 years’ time it must be well maintained in the first year. Warranty ensures the quality of construction. It has nothing to do with operation and maintenance. 14.3.2 Operating and maintenance manuals and training The preparation of these manuals and the training of operating and maintenance (O&M) personnel are usually, and rightly, the responsi- bility of the contractor. As part of the commissioning process, the de- signer and the owner’s representative, with the operating personnel, should go through all the operating procedures described in the man- ual. Emergencies should be simulated to check emergency response procedures. The manuals should become a lifetime resource for the operators of the building and its systems. 14.3.3 Observation of operation Many specifications require the HVAC contractor to certify in writing that the HVAC systems and controls are operating as designed and specified. This should not be sufficient to satisfy a competent, profes- sional designer. There is no substitute for personal observation of sys- tem operation, not for just a few hours but for several times under varying load and climatic conditions. Among other things, this will expose any need to adjust controller gains and set points as system gains change with the load (see Chap. 8). 14.4 Summary If the ‘‘proof of the pudding is in the eating,’’ then the proof of a suc- cessful HVAC design is in the eventual operation and performance of the system in the hands of the owner. The designer, or someone he or she assigns, needs to follow the project from bidding and contract, through construction, through startup, to final takeover and operation by the owner. As elements of quality control, the designer needs to verify adherence to documents through submittal review and by in- construction review. And the designer needs to support the transition of the project from contractor to owner during start-up, test and bal- ance, and instruction of the owner’s personnel. With some inexperi- Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  9. After Design: Through Construction to Operation After Design: Through Construction to Operation 437 enced operating personnel, the designer may need to continue this effort into the operating period for a time. The bonus reward of all this effort is a functional project which serves as a credential in the search for the next design assignment. References 1. ASHRAE Handbook, 1999 HVAC Applications, Chaps. 34–41, regarding building op- eration and maintenance. 2. Ibid., Chap. 36, ‘‘Testing, Adjusting, and Balancing.’’ Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
  10. After Design: Through Construction to Operation Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.
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