It’s our ability to focus on the details that make a difference. This keeps construction prices down when drawings are fully engineered rather than making the contractor guess existing conditions during the bidding process. It also allows the installers to do their best work rather than doing ad hock field design. Timing the project is one of the biggest details that can really enhance designs. Other details are unique and specific to hot water boilers, steam boilers, chillers, cooling towers, rooftop units, plumbing, exhaust, refrigeration and VRF systems. Click these links or continue reading for more information in those areas.
TIMING THE PROJECT
We work closely with facilities when it comes time to replace or modernize existing HVAC and plumbing systems. To get the best results, we recommend starting your heating system engineering in the fall to give plenty of time for observation, bidding and installation in the summer. For cooling systems, we recommend engineering in the early to mid summer with installation following in early to late spring. This allows engineers time to observe, test and evaluate an existing cooling system’s performance. When replacing rooftop systems, it is worth while to replace those in either the early fall or the late spring. We recommend avoiding doing panic rooftop replacements and compromising with “off the shelf” units. The incremental benefit of planning for a quality rooftop with a few extra features will pay for itself many times over the life of the product. For plumbing systems, they are not weather dependent. Each system will need to checked and evaluated for the best way to minimize down time or provide temporary hot water service.
HOT WATER BOILERS
Most hot water systems are using condensing boilers capable of 90 % or more efficiency. However, caution in applying these systems is needed. The high efficiencies usually only occur in the spring and the fall not in the dead of winter when you use the most gas. When retrofitting, caution also needs to be applied when designing and installing the flue liner in existing chimney’s. Flue liner failures are very common. Further caution should be applied with using condensing boilers for both heating and hot water. Some early heat exchanger failures have occurred. Contact us for expert design and advice when planning to install condensing boilers.
Steam boiler engineering is becoming a lost art. Correctly downsizing can be done when replacing old steam boilers with new but caution should be applied because the water content of the new boilers is less than the old ones. Correct selection of boiler feed tanks is critical. Water treatment is also very important. Finally correct burner control options can greatly enhance your steam boilers. Contact us for expert design and advice if you are planning to install a steam boiler.
CHILLERS AND COOLING TOWERS
Whether you have air cooled chillers, water cooled or absorption chillers, there are several things to consider. In retrofits, matching power, weight and performance are obvious considerations. However, are the chillers very over or undersized? Is the condenser and chilled water flow rates correct for the chiller? What kind of controls are running your chiller? Are you using BacNet? Hard wired? Is your chilled water system mission critical? How about your cooling towers, are they sized correctly? Should you be considering gear fan drives verses belt drives on your smaller towers? If you have these and other questions , contact us for expert design and advice when replacing your chillers and cooling towers.
Rooftop units seem like easy box replacements. It is as simple as getting a crane and lifting it off and dropping another one on …. isn’t it? Are you trying to upgrade the controls? Should you replace it with the same one because it fits on the old cub or should you consider a better unit and use an adapter curb? How are you going to seal the adapter curb? Is the curb manufactured correctly so it does not bend or warp when the unit is placed on it? Should you specify special gasket material for the unit and curb? Usually, there are small changes that can bring big benefits when replacing rooftop units if you carefully consider the options. If you have these or other questions, contact us for expert design and advice when replacing your rooftop unit.
As discussed earlier under hot water boilers, some plumbing hot water is made from the heating system. Realize that plumbing hot water is typically 140 F. As discussed above, condensing boilers save energy in the spring and the fall by lowering the building hot water temperature to as little as 110 F in the spring and fall. Unfortunately, domestic hot water at 140 F can not be made with 110 F building water. Therefore the heating boiler typically has to heat up to 180 F to make 140 F domestic hot water. The cycling of the heating boiler from 110 F to 180 F on a daily and sometimes hourly basis, can cause stress and strain in the boiler’s heat exchanger. Some boilers have been known to crack and the replacement of the heat exchanger can be very expensive. Therefore the early savings in not putting in a separate domestic water heater may not actually turn out to be that big of a savings. This is just one of many considerations when designing a domestic hot water system. If have these or other questions, contact us for expert design and advice on your plumbing systems.
Like steam systems, there are only a few engineering firms that really understand refrigeration systems. We have been designing refrigerated warehouses for the beverage industry for 20 years. We have also developed custom calculation methods that can reduce the amount of refrigeration equipment need. Usually we see systems that are very oversized in the beverage industry. Contact us if you have questions about your refrigeration system and want expert design and advice.
SUPPLY AND EXHAUST DUCT SYSTEMS
Correctly designing duct work is both an art and a science. Care needs to be taken in the installation, sealing and overall design. We have designed high velocity duct work that is whisper quiet. We have also design exhaust systems for labs and industrial applications. We use both computer models but also use good engineering judgement for both duct work design and fan selection. This is especially true in lab exhausts. Those fans are typically under high negative pressures and also variable flow. Improper design can cause early bearing failures. In critical lab operations this is not acceptable. Contact us if you have questions on your duct work and want expert design and advice.
Variable Refrigerant Flow (VRF) systems are increasingly popular among both engineers and contractors. The software to design these systems is proprietary to the equipment manufacturer. Therefore the engineer has little control over the piping sizing. Oil flow within these systems is critical. The only way to insure proper oil flow is to field verify exact piping lengths and sizes before installing. A difference of a 10 to 15 feet can change the size of the piping. Therefore, careful back and forth between the contractor and the VRF manufacturer should take place during installation. Another key point often overlooked is the OSHA eight hour exposure limits. Normally designers follow the ASHRAE 15 and 34 calculations but neglect OSHA exposure limits which for most refrigerants is 1000 PPM. When small spaces like patient rooms or offices have units in them there can be small leaks that could expose people to low level concentrations for long periods of time. We advise using inexpensive refrigeration monitors in these areas. ASHRAE has written recent articles highlighting awareness in properly ventilating and monitoring VRF installations. These articles reflect current thoughts but are not currently code or design requirements. We are probably way ahead of the curve on this but we feel it is good practice that we expect will be adopted as these systems increase in popularity. If you have more questions or want expert design or advice on VRF systems then give us a call.
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