Avoiding Downstream Problems with Upfront Data

Avoiding Downstream Problems with Upfront Data

Anybody involved with remodeling of existing buildings knows that they are full of surprises. Some issues are worse than others and some can completely derail a project (asbestos, anyone?). Less innocuous issues can still cause a brand-new remodel project to turn out less than desired.

One of the most common issues mechanical engineers run into is being told the existing systems are supplying the air and/or water services as expected. Whether it be a water or air system, the remodel engineer must rely on as-builts, information from the building engineer and what information can be gathered from the facility assessment to base their design off of; but what happens when that information is wrong?

Common Problems

Often the existing systems, for a whole variety of reasons, are not performing as they should. Chilled water may be leaving the chiller at 44°F but arriving at the remodel space at 54°F or it may appear that 200 gallons per minute is available but in fact only 30 gallons per minute is available. Possibly the chiller is simply not performing as it once did and now it only has 75% of its design capacity.

On the air side, it is common to find air handlers that should be producing 2,000 CFM but are only producing 1,600 CFM. As you can imagine, if the remodel mechanical design is based off the assumed capacity the problems will only become apparent towards the end of construction, or worse yet, once the remodeled space has been occupied.

Avoiding Problems

To avoid this, we recommend, encourage and occasionally require that a pre-design air and/or water balance be conducted.

The data from this effort does not need to necessarily be certified but using a skilled testing and balancing contractor will not only help identify any capacity limitations with the existing system but also may identify other HVAC or electrical issues with the system. This can benefit the project in a variety of ways but most importantly it can reduce change orders during construction and eliminate occupant complaints by ensuring the design documents identify all requirements necessary to deliver a completely functional mechanical system.

Design West can often complete the air side balancing ourselves; simply request it during the proposal phase of the project. Water side balancing takes special (read that as expensive) equipment so we can set you up with a TAB contractor we trust.

Redundancy in Chilled Water Systems

Redundancy in Chilled Water Systems

Hospitals, data centers and the like can NEVER go down but many other facilities can't afford to go down either. K-12 schools, universities, office buildings with leases that guarantee HVAC, and many other building types require the space have adequate heating and cooling. Often these projects see their chiller redundancy value engineered out. This can cause havoc for future maintenance and unplanned outages.

While we believe a redundant chiller and redundant pumps are critical for many building types, we understand that some projects simply don't have it in the budget to cover the additional cost. So what can be done?

Temporary chiller coming your way!

Temporary chiller coming your way!

First, by doing a little thinking and planning early on, we can avoid major costs and operational issues for the owner in the future. Here are some things to think about during the programming phase of your project:

  • Can the project afford the space for a future chiller pad so that a redundant chiller can be installed in the future? It becomes very challenging to find space once the building is occupied and commonly means the owner is making major concessions to add capacity. Even an air cooled chiller, remotely mounted away from the chiller room is better than nothing.
  • Can we provide the electrical capacity to the switchboard to allow for easily adding a chiller in the future? This is far easier than increasing the size of panel boards, transformers, cabling and buried conduit in the future.
  • If it's a water cooled system, can we oversize the cooling towers? The chiller that is installed may be more efficient with a larger tower anyway. This may provide energy savings in the near term, and if and when we need to add chiller capacity, we already have the cooling tower capacity installed.
  • What if we at least leave room for hooking up a temporary chiller and install the necessary piping to make these connections easy. That way, turning on a temporary chiller is as simple as connecting flex hoses and turning valves.
  • Can we add the electrical capacity and connections for a temporary chiller? Or at least consciously decide that rented chillers will be generator driven. At least then the owner can plan accordingly with local rental companies to provide the exact equipment they need, if and when it is needed.

All of these are worth looking at during programming. By reviewing low cost options now, like those discussed above, we can avoid them being major issues in the future.

The point is, if budget doesn't allow true redundancy then there are other steps a project can take to ensure that a chiller issue doesn't cause a full shutdown and/or incur major future costs.

If you have questions about chiller redundancy or the various paths we can use to ensure the future success of your building operations, please get in touch. We are happy to help!

HVAC Economizers and Title 24 Compliance

HVAC Economizers and Title 24 Compliance

We've covered HVAC economizers at a high level, so let's dive deeper into what is required in a Title 24 compliant economizer.

Gear Driven Dampers

One of the most common fail points of economizers from years past were the linkage arms. They would fail early and often leaving the maintenance team to either continue fixing them, or, the more common solution, simply close them. Now this meant no further maintenance issues but it also led to no outside air being provided to the building. Occasionally complaints of stuffiness would result. In one case, we've seen a maintenance person use a 2x4 piece of wood to prop open the damper to let a little bit of fresh air in. Ingenuity? To resolve these band-aids, Title 24 requires gear driven dampers. They are exceptionally more reliable with life cycles of 10 or more years but they are heavier, more difficult to fabricate and of course more costly.

Fault Detection and Diagnostics

Fault detection and diagnostic technology identifies problems by continuously testing the sensors and dampers in the system. This lets maintenance personnel know when a problem exists.

This technology is great for resolving economizer problems. In fact, Title 24 requires the controller have, as a baseline, the ability to detect outside air sensor failure, dampers not modulating, excessive outside air, among others. This definitely helps maintain the efficiency of the unit, but it also takes a smarter controller to do this. But smarter controllers = higher cost.

JADE Economizer controller

JADE Economizer controller

Additional Requirements

Powered Exhaust Fan VFD

Powered Exhaust Fan VFD

There are other requirements Title 24 puts on economizers and, in our opinion, are good requirements but they do increase the cost.

For most rooftop package units it still makes sense to install them because the only way to get rid of them prescriptively is to provide a higher efficiency unit. In non-coastal climate zones this means a unit that is 30% better than the baseline or the equivalent or 17-18 SEER depending on the unit. It is important to note that the cost to increase the efficiency is typically much greater than that of the Title 24 economizer.

When we start to review the economizer requirements for units like fan coils and VRF the story changes substantially. To install economizer capabilities (i.e. 100% outside air) on a 5-ton fan coil becomes challenging. This is mostly due to the fact that we need to install a full size duct to the unit and provide an actuated damper for the return and outside air paths. All sorts of concerns crop up, such as; do we have enough room, where can we penetrate the roof/wall, the list goes on and very quickly we start considering other options.

One good aspect of fan coils and VRF is that the higher efficiency units are very easy to come by and are relatively close to the same price point. The additional cost of the high efficiency unit is often a fraction of trying to install the duct work, dampers and controls for an economizer.

Avoiding HVAC Economizers

If the energy modeler builds a performance model, the HVAC economizers might be able to be removed from the project entirely. This is contingent on other improvements in the building making up for the penalty of not installing them. This can be a difficult item to model out due to the penalty the CEC calculator attributes to not installing an economizer but it may be an option.

To summarize, in general RTU’s and large custom air handlers should probably go with economizers as their compliance path. Fan coils and VRF are typically better off increasing their efficiency. And if neither of them seems like viable options we can review building a performance model to further review the project’s options.

If you have any questions on any aspect of economizers feel free to get in touch. We’re happy to help!

Understanding HVAC Economizers

Understanding HVAC Economizers

At Design West, we strive to bring energy efficient designs at competitive construction costs. One the most useful equipment options we can specify in meeting this goal is called an airside economizer.

Title 24 Compliant Economizer

Title 24 Compliant Economizer

An airside economizer basically looks at the outside air temperature (OAT) to determine if it is cooler than the return air temperature of the space. If it is, it makes sense to bring in outside air, instead of return air, because it takes less energy to cool down the colder air stream.

Generally HVAC systems function to produce ~55°F supply air. Return air temperature generally range from 72°F to 78°F. When the outside air is less than 72°F we bring in as much outside air as possible and supplement the cooling with refrigerant based compressors to maintain the 55°F supply temperature. This lowers the time the compressors are on. The compressors are the largest consumer of energy for a HVAC system, so keeping them off inherently saves energy.

At lower outside air temperatures, we can completely shut off the compressors, saving vast amounts of energy. The equipment then just modulates the outside air and return air dampers to maintain the supply air temperature.

HVAC Economizers & Title 24

The 2013 Title 24 code cycle included a prescriptive requirement for adding economizers to all units with 5 tons of cooling and above. This will continue into the 2016 code update effective January 1, 2017. This is not just any old economizer, the Title 24 economizer requires gear driven dampers, automated fault detection, and specific setpoints that can only be accomplished by a relatively advanced controller among other requirements. All of this drives up the cost of the overall unit and subsequently sometimes it may be advantageous to pursue other paths of compliance.

New Title 24 economizer designs have eliminated the maintenance issues of yesteryear. While they are more expensive, in most applications they pay for themselves quickly.

If you have any questions about HVAC economizers feel free to get in touch, we’re happy to help!

Power Metering: When, Why, How?

Power Metering: When, Why, How?

In existing buildings we often need to meter the current load to know how much new power we can add to the existing electrical equipment. In some cases we can use the available record drawings and/or review the installed conditions to verify if additional load can be supported, but that involves verifying the connected load of every circuit which can be very time consuming and costly. A better way to determine the existing load on a feeder, panelboard or switchboard is through the use of demand power metering.

For example, schools looking to add additional plug loads or a building with evaporative cooling looking to upgrade to DX cooling will need to know how much new load the existing electrical system can support. In order to do so, the electrical engineer must check a myriad of component capacities including fuses, disconnects, switchboards, transformers and the like and review against the current usage.

Load Studies

For all new electrical loads that are placed on an existing electrical distribution system, the NEC states that a load verification must be provided to determine if the new load will exceed the rating of the existing equipment. The NEC defines the requirements which we must operate within when using a power metering study to determine existing loads. This also depends on the authority having jurisdiction. Some AHJ’s like OSHPD only require a 3 day load study. Most, however, require a 30 day load study to be confident that the peak load is captured. It may also be important to capture the data in the warmer portions of the year if the panel has a significant HVAC load.

12,000 Volt Service Under a Load Study

12,000 Volt Service Under a Load Study

Our example shows a 12,000 Volt service being monitored by a specialty electrical contractor so we could determine if an existing 1,000 ton chiller could be increased to a 1,250 ton chiller. You can see the meter on the floor of the cabinet. The red hoop around one of the feeders is the current transducer (CT’s) which will measure the amperage draw of the line.

The meter data captures volts, amps, kVAR, kW and various other points we use to assess the status and capacity of the existing equipment. Once the data is available, the electrical engineer analyzes the amp draw at max load. The electrical engineer, per NEC requirements, must then add 25% to the average max peak over a 15 minute period to determine the remaining capacity.

Load studies can be performed for single panelboards or distribution switchboards where new circuits are added, or even on medium voltage transformers as shown above.

Alternate Methods

It is important to keep in mind that there is another method of determining existing loads through demand meter history. For electrical services with demand meters, we can take the peak demand from 12 months of utility bills to find out what the peak electrical load is.

Making a Decision

Once we have reviewed the current power usage combined with proposed additions, we can determine what, if any, electrical upgrades will be necessary to move forward with the project.

So that is when, why and how power metering is required. If you have any questions about the best approach to power metering for your projects just ask. We are happy to help!

Architectural Windows and 2013 Title 24 Standards

Architectural Windows and 2013 Title 24 Standards

Could you imagine this with vinyl windows?

Could you imagine this with vinyl windows?

As the 2013 Title 24 Standards Part 6, The Energy Code, took effect many new requirements rolled out, one of the most challenging being the prescriptive requirements for metal framed windows. It became apparent that many windows previously considered “high performing” with their dual pane, low-E glass and thermally broken frames could no longer meet the requirements.

Title 24 requires that windows obtain an NFRC label to certify that they meet the necessary U-factor, Solar Heat Gain Coefficient (SHGC) and visual transmittance (VT) required. Otherwise the energy modeler must assume a center of glass performance which most certainly does not meet the prescriptive requirements.

So what are options to architects who need to comply? Should we put vinyl windows on storefronts, airplane hangars, and classrooms? Yeah, we didn’t think so. There are really two options.

NFRC Compliant Windows

The first can be hard to achieve, but the architect can search the NFRC database. Simply enter in the window type you want, select a manufacturer you think can provide the performance you need and then you have the option of adding the performance criteria the energy modeler indicates is necessary to comply prescriptively. Get in touch and we will send that data to you. Here are a few that come close to complying:

Results from the NFRC database

Results from the NFRC database

You will notice that they are triple pane and would require some level of shading to meet the SHGC value. You also need to be careful that they meet the minimum visual transmittance criteria, which many of these don’t. If you look more, you can find a handful of double pane windows that meet the requirements as well.

The problem with this solution is even when you find a window that complies these windows are, as we’ve been told, extremely expensive. 

Performance Compliance Path

So what else might the project do? Well, the project could be modeled using the performance compliance path. While this does cost more in terms of energy modeling, often a project using LED lights can use the energy credit from the lighting to pay for lower performing windows (read that as cheaper, but still relatively high performance windows). The LED’s are going in anyway so why not pay a little more to build a better energy model in order to pay a lot less for the cost (and possible hassle sourcing) of the windows.
 
Utilizing the performance energy model approach to arrive at a lower overall project cost has other benefits. Metal framed walls, prescriptive window requirements, economizers and numerous other items can often be “modeled out” of the project.

If you want to explore these potential benefits, get in touch and let us know how we can help you bring your clients lower overall project costs through effective performance modeling.