McLARNEY RESOURCE LIBRARY
HVAC SYSTEMS
Frequently Asked Questions for Mechanical Systems
1.
Do
I need to have a separate A/C unit for my data server room?
If the data stored on your server is critical to your company’s success then it makes sense to add a separate A/C unit that is run off of emergency power.
2.
What
are the mechanical requirements for my new class clean room?
The requirements for clean rooms depend on the
classification and use. Clean rooms in
the microelectronic business are somewhat different than those in the
pharmaceutical business. The following
table identifies the basic requirements for a typical microelectronic facility.
Criteria Class 10 Class 100 Class 1000 Class 10K Class 100K
Air Changes
per hr./min 600/10 480/8 to 300/5 180/3 60/1 36/0.6
HEPA Filter
Coverage (%) 100 70 to 40 20 to 30 7 to 15 4
to 5
CFM per Sq.
Ft. 90 65 to 36 32 to 18 16 to 9 8
to 5
Typ. Filter
Efficiency 99.9997 99.997 99.997 99.997 99.97
Typ. Ceiling Type Gel Seal 2”Tbar/Gskt. 1”
Tbar/Gskt. 1”Tbar/Gskt. 1”Tbar/Gskt.
Typ. Return
Air System Raised Floor Low Wall Low
Wall Low Wall Low Wall
Or
Ceiling Or Ceiling
Very Generic Cost Range
Class 10 $600sf to $750/sf
Class 100 $450/sf to $650/sf
Class 1000 $160/sf to $260/sf
Class 10K $60/sf to $70/sf
Class 100K $40/sf to $50/sf
3.
What
can I do to minimize sound problems caused by the mechanical equipment, if
possible?
·
Install mechanical
equipment over un-occupied areas such as restrooms and storage areas
·
Make sure mechanical
isolation and flex connectors are provided for all mechanical equipment
·
Use spiral ducting to
eliminate “rumble” low frequency noise
·
For larger A/C units
use horizontal airflow discharge
·
Locate shafts on
adjoining walls to restrooms and storage areas when possible
4.
What
type of floor to floor clear heights should I plan to design into my new
building to accommodate mechanical systems for various types of buildings?
2.
Typical office
buildings.............................................................................................. 12’
to 14’
3.
Typical electronic R
& D facility................................................................................ 14’
to 16’
4.
Typical
microelectronic clean room facility without raised floor......................................... 20’
5.
Typical
microelectronic clean room facility with raised floor.............................................. 22’
6.
Typical biotech
R&D facility...................................................................................... 16’
to 17’
7.
Typical
biotech/pharmaceutical manufacturing facility without large vessels.......... 20’ to 22’
5.
What
is the difference between Plan and Spec vs. Design Build construction
strategies? What are the advantages and
disadvantages?
Description: Plan and specification Approach Design Build Approach
Definition A
design consultant programs, designs A
contractor with in-house design capabilities is
specifies, and draws all
aspects of the MEP selected to
program, design, specify, and draw all
scope. These “plans and specs” are then bid aspects of the MEP scope. Price is usually
out to multiple MEP
contractors to establish the negotiated
during the pre-construction process.
Lowest initial price.
Descriptions Plan and Specification Approach Design Build Approach
Typical The architect
works for the owner/developer. The
architect works for the owner/developer.
Project All design
consultants work for the architect. The
general contractor works for the owner/developer
Organization The general
contractor works for the and all
design build subcontractors work for the
owner/developer and all
subcontractors work general
contractor. This creates a TEAM
for the general contractor. atmosphere
conducive to a quality project.
Descriptions Plan and Specification Approach Design Build Approach
Advantages 1. Longer
design time allows for more 1. Speed of project delivery. Design build
thorough
programming and more complete projects
reach completion 20% to 50% faster.
plans and
specifications. Than
conventional plan and spec strategies.
2. Better
initial cost control due to bidding 2. Single source responsibility for
system
process. performance. Design engineer is directly
3.Engineering
firms are not involved with responsible
for final product.
Construction costs;
therefore no cost 3. Design build contractors understand the
oversight
is typically required. actual
cost of designing and building a variety of facilities.
4. No change orders for items that the engineer
accidentally
left out of the plans and
specifications.
5. Value
Engineering occurs during the pre-
construction
process to make sure that the
project
maintains budget goals.
Descriptions Plan and Specification Approach Design Build Approach
Disadvantages 1.Process
takes longer than design build due 1. Some DB contractors do not have adequate
to RFI
process, bidding process, series engineering
depth to fully design the job.
approach to project
schedule. 2. Contractors must be focused on balancing
2. Typically
more expensive than design owner
budget with functional requirements.
build in overall project
costs. performance. Design engineer is directly
3. No
functional ownership for final product. DB
contractor team.
6. What should I plan for my mechanical roof
loads (lbs./ sq. ft.) based on building type?
1.
For a typical office
building: 3 pounds per square foot.
2.
Typical electronic
R&D facility: Actual weight of equipment.
3.
Typical
microelectronic clean room facility: With interstitial level design load @ 150
pounds per square foot, and 20 pounds per square foot for roof design load.
4.
Typical
microelectronic clean room facility: With interstitial level design load @ 150
pounds per square foot, and 20 pounds per square foot for roof design load.
5.
Typical biotech
R&D facility: 20 pounds per square foot live load, 10 pounds per square foot for
mechanical equipment, plus other mechanical load, and any dead load structural
framing.
6.
Typical
biotech/pharmaceutical manufacturing facility:
20 pounds per square foot live
load, 10 pounds per square foot for mechanical equipment, plus other mechanical
load, and any dead load structural framing.
7.
What is the suggested minimum preventative maintenance
schedule for various mechanical systems based on building usage? Preventive maintenance service frequencies
are generally dictated by the type of
system and how critical it is to the company’s operation.
·
Typical office
buildings (VAV Sytems):.............................................................. Bimonthly
VAV systems
(office buildings – non-critical operations) should be serviced bimonthly.
Quarterly
service is acceptable if the buildings exposure to open areas, construction in
progress, high
traffic areas etc. is minimal and equipment if fairly new. Older equipment
and high
contamination areas (for filters) needs the 60 day frequency.
·
Typical office
buildings (Small Package Systems)............................................ Quarterly
Simple small
package unit systems, serving non-critical operations, (2.0 to 20.0 Ton)
·
Typical electronic
R&D facility: ......................................................................... Bimonthly
·
Typical
microelectronic clean room facility:....................................................... Monthly
Cooling towers/ water treatment, scrubbers, DI/RO, chillers, steam boilers, CDA
systems, and vacuum pumps, gas monitoring and all life safety systems always require
monthly service.
·
Typical biotech
R&D facility:.............................................................................. Bimonthly
·
Typical
biotech/pharmaceutical manufacturing facility (GMP).......................... Monthly
·
GMP facilities
require monthly service (as well as a schedule of lesser frequencies on some
equipment as specified by the manufacture’s manual).
·
Typical
biotech/pharmaceutical manufacturing facility (GMP).......................... Bimonthly
Non GMP biotech facilities require bimonthly service for simple systems...... monthly if
towers,
chillers, etc. are in use.
·
If your mechanical
systems include cooling towers, chillers, CDA................... Monthly
·
Air handler systems are service bimonthly unless they use
100% outside air. Then they are service
monthly (for filter changing).
8.
What are some of the things that I need to be concerned with
when planning to build
out an
existing facility or considering a new building which can affect my mechanical
and plumbing
systems?
·
Identify existing vs.
new utility requirements, i.e., water, sewer, and gas main sizes. This
Information should be evaluated as early as possible in a project due to the extreme cost and possible delays that can be caused when upgrading them.
·
Determine if you have
to get a permit from Bay Area Air Quality Management District (BAAQMD) for any
process exhaust systems. This process
can range from 2 weeks to 6 months in duration based on the application.
·
Do you have any
hazardous materials that will be used in the new site? Put together a Hazardous Material Inventory
Statement (HMIS) early in the project programming to give to your consultants
early visibility to possible code and occupancy issues.
·
Do you share any
utilities with an adjoining tenant? Do
they need to be split to meet code or be billed correctly?
9. What is the best control system to use for comfort control
in my building?
Most of the major control system manufacturers have similar
features and are priced competitively.
Pneumatic systems are finally being replaced by DDC systems for the same
price. Like any other service, it’s the
people doing the work rather than the product.
Look for a system that has been around for awhile and well supported by
more than one contractor. Avoid using
products that are “sole sourced” or you may be stuck with a product or company
that is too high priced or just won’t service you well with no other
alternatives. Get references, review
work scope, and review submittals on everything from points lists to graphic
layouts before issuing a contract.
10
What sound level from the HVAC equipment should I expect in
my building spaces?
·
Low end open office
space: ........................................................................ -40
·
High end private office
space:................................................................... 30-40
·
High end open office
space: .................................................................... 35-40
·
High end conference
space: .................................................................... 25-30
·
Class 100,000 clean
room space:............................................................ 45-50
·
Class 10,000 clean
room space:.............................................................. 55-60
·
Class 1,000/100/10
clean room space:.................................................... 60-65
·
Biology Lab space: ................................................................................... 55-60
·
Chemistry Lab space:............................................................................... 55-60
·
Engineering Lab
space:............................................................................ 45-55
·
ISO 9000+
manufacturing space:............................................................. 55-60
11.
What procedures for installation, start up, commissioning
and validation does your company employ to insure the highest quality of
mechanical installation?
Qualified contractors will have available for your review
SOP’s (Standard Operating Procedures).
These documents will establish a minimum standard for
planning, organizing, and auditing the quality assurance program. They will define and limit the work to be
performed under the heading of start up, commissioning and validation. These standards will become the basis of the
organization structure for the ongoing maintenance of your facility.
12.
Will there be a maintenance program established by the
building contractor to assure warranty and consistent operational standards?
The constructing contractor is the best qualified to
maintain your mechanical system after start up and during the one year
warranty. This contractor knows the
project intimately and can most effectively resolve problems which may arise
from mechanical system failures or just nuisance.
13.
What considerations should be made during the design and
construction process to enhance
Serviceability
and longevity of the systems?
·
Provide sufficient
service access, both for routine maintenance service, and for repair
service. Pay particular attention to
space requirements for replacing large components or long parts,
such as shafts.
·
Position equipment
and access so as to avoid or minimize interruption to normal access.
·
Never position
equipment above owner’s equipment which makes access difficult or
impossible. Strictly avoid equipment
overhead which might result in damage to products or equipment below.
·
Provide for isolation
capability which will facilitate normal repairs or service without interrupting
normal operation.
14.
What kind of payback can I expect from utilizing gas
humidifiers in lieu of electric humidifiers?
The payback time frame is depending on operating hours, size
of the humidifier and design conditions.
However, with 24 hour operation and 45+/- 55 design requirement you can
expect a 1-2 year payback.
15.
Does it make sense to evaluate the impact of energy
consumption and energy cost on my mechanical system?
Yes. The cost of
energy can be a significant percentage of your operating expenses. Energy efficient mechanical systems will
have a higher up front cost but the payback in energy savings can make them
very attractive. A qualified contractor
can assist you in making your decision.
16.
Are there any alternative ways to finance energy efficient
systems?
Many electrical energy suppliers will offer rebates based on
energy savings. These cost rebates will
reduce up-front costs and reduce payback time.
In addition, there are many companies that will finance your system. They will supply the energy and finance the
equipment. You will make a monthly
payment over a number of years. These
types of arrangements can be very cost effective.
The foregoing information is to be used only as a general
reference guide.
Please refer to the appropriate trade contractor for
completeness, accuracy and workload.
UPDATE 6/99
