Static Pressure: Bathroom Ventilation

Properly sized ventilation in airtight homes and apartments helps to assure healthy indoor air quality. Both intermittent (spot) ventilation and continuous (whole house) ventilation should be considered. Intermittent ventilation is used to exhaust sources of moisture and odors, while continuous ventilation is used to remove accumulated indoor air pollutants. Ventilating fans should be located near the source of moisture and indoor air pollutants in bathrooms, laundry rooms, kitchens, hobby rooms and smoking rooms.

The first step when sizing for a ventilating fan is to determine the application. Decide whether you are sizing for intermittent or continuous ventilation. If intermittent, determine which application i.e. bathroom, kitchen or other. Use the following industry recommendations to determine Air Changes per Hour (ACH) for your specific application.

Intermittent (spot) ventilation:
The Home Ventilating Institute (HVI) recommends the following Air Changes per Hour (ACH).
I. Bathrooms - 8 ACH
II. Kitchens - 15 ACH
III. Other Rooms - 6 ACH

Continuous (whole house) ventilation:
Many building codes have adopted the American Society of Heating Refrigerating and Air Conditioning Engineers (ASHRAE) Standard 62, as shown below.

• I. House or apartment - 0.35 ACH

The second step is to calculate the area being ventilated. Calculate square feet or cubic feet depending on which sizing method you choose. The third step is to measure the Equivalent Duct Length of the planned duct run. This requires a basic understanding of static pressure caused by a duct run design and its components.

Static Pressure and Duct Run:
A ventilating fan must overcome resistance when pushing air from the inlet, through the duct, to the outside of the building. This resistance is known as static pressure. The amount of static pressure depends on the duct length, type of duct, elbows and the roof jack or wall cap.

Equivalent Duct Length (EDL):

Static pressure in a typical duct run is caused by the type of duct material, elbows, exterior wall cap, etc. The table shown illustrates the standard values for duct components. The EDL chart allows you to calculate the equivalent straight duct length in order to overcome static pressure caused by each component in a duct run. The EDL helps assure the fan performs as expected under the airflow resistance caused by the components listed in this chart.

A ventilating fan's performance is plotted on a graph called a performance curve. The performance curve shows airflow in cubic feet per minute (CFM) along the horizontal axis and static pressure (resistance) along the vertical axis. The fan with a "Closed duct" has high static pressure and no airflow; and the fan with "No duct" has low static pressure and high airflow. In reality, an installed fan will be somewhere in between these two points.

Typical sizing: (Rule of Thumb)Range of square foot: 1 sq. ft per cfm up to 1.2 sq. ft per cfm max.

The following method can be used for sizing fans. The Sizing Chart Method follows industry standards and will give you similar outcomes. The Sizing Chart Method is easier.

Note: You should check with your local building inspector to confirm that these methods are accepted in your area.

Sizing Chart Method: Example: Sizing for an 8 ft x 12 ft x 8 ft ceiling bathroom using 12-foot long, 4 inch diameter aluminum flex duct, one elbow, one wall cap.

Step 1. Determine the ACH required for the given application using the HVI and ASHRAE standards above. • Bathroom – 8 ACH
Step 2. Calculate the Area to be ventilated in Square Feet.
2a. Assuming 8 foot ceiling: room length x width. • 8 ft x 12 ft = 96 sq ft.
2b. Guideline for cathedral ceilings:
i. 10 – 12 ft cathedral = length x width x 1.25
ii. 12 – 16 ft cathedral = length x width x 1.5
Step 3. Use the Equivalent Duct Length chart above to calculate the duct run.
3a. 12 ft flex aluminum duct x 1.25 = 15 feet EDL
3b. One elbow equals 15 feet EDL
3c. One roof jack equals 30 feet EDL
• (12 ft length x 1.25 alum. flex) + 15 ft elbow + 30 ft wall cap = 60 ft EDL
This is the equivalent duct length (or resistance) the fan must overcome to move air through the duct to the outside.

Neutra-Safe Condensate Neutralizers

When it comes to a condensate neutralizer...
SIZE DOES MATTER!

WHAT IS CONDENSATE?

Condensate is produced after the transition of a gas into a liquid due to a drop in temperature or pressure. In the case of burning natural gas in a high efficiency boiler, furnace or water heater, this condition occurs when the temperature of the flue gases starts to drop below 130°F.

This condensate is made up of several ingredients and will generally have a pH of between 2.9 and 4. As such it is considered to be acidic and can cause serious damage to piping systems, sewerage systems, treatment facilities, septic systems and other items it may come in contact with. Many communities now insist that this condensate be rendered benign before it enters the common drainage system. The easiest way to accomplish this is with the addition of a condensate neutralizer.

HOW DOES A CONDENSATE NEUTRALIZER WORK?

The acid neutralization takes place when the acidic solution comes in contact with the media. The calcium carbonate in the media changes the solution into water, CO2 and various salts which tend to collect in the bottom of the tank or tube. All lime and limestone (marble) contains different percentages of calcium carbonate so making totally accurate capacity statements is not realistic. The pelletized lime is more consistent but turns to mud and eventually solidifies.

ABOUT OUR PRODUCT SOLUTION...

• Our Condensate Neutralizer Is BIGGER Which Offers Greater Performance & Longevity
• Our Condensate Neutralizer Offers Higher Capacity On Our Smallest Unit ~ One Size Fits Most Residential Applications
• Our Clear Cartridge Allows You To See The Consistent Quality Of Our Media
• Our Condensate Neutralizer Has Superior Media Quality Which Is Tumbled, Washed & Dried To Prevent Dust & Clogging

We offer three sizes:

• CN2STR: 220,000 BTU
• CN3STR: 400,000 BTU
• CN4STR: 1,200,000 BTU (shown above)

Click here for literature

Click here for product photos

The Buffer Zone

The Facts of the Matter

When sizing and selecting modulating-condensing boilers we, as heating professionals, size the equipment based on the Btu load of the home. Most homes in the New England area have a heat loss of around 25-35 Btu/h per square foot.  Most mod-cons have a reset controller built in to vary the supply temperature based on what is happening outdoors.  The colder it is outdoors the warmer the water in the boiler; the warmer it is outdoors the cooler the water in the boiler.  Boilers also have thermistors on the supply and return which adapt the firing rate of the boiler based on the load i.e. the boiler control will increase or decrease the firing rate based on the difference between the supply and return temperatures. Today, most mod-con boilers have a turndown ratio of at least 5:1.

The DHW Conundrum

When sizing the boiler for say, a 2,500 sq  ft home with a heat loss of 75,000 Btu/h, we find that the DHW load (as much as 150MBH) is significantly higher than the heating load. Unlike tankless type water heaters, this shortfall in Btus can be overcome with the addition of an indirect water heater.  But the boiler is still oversized for the heating requirements.

To further complicate matters, many of today’s larger homes will have a combination of heat emitters which require different temperatures. It is not uncommon for a 2,500 sq  ft house to have as many as 6 zones with varying temperature requirements: high temp for the DHW; moderately high for the baseboard and/or air handlers; moderately low for the staple or dry fit radiant and low for in slab radiant.

To better understand the challenge, let’s take a look at one of these zones. 

500 sq ft zone heated with 25 feet of baseboard with a rated output of 610 Btuh @ 180°F per linear foot.

Assuming that the heat loss for this zone requires 30 Btuh per sq ft on the coldest day, the calculation is simple: 500 sq ft x 30 Btus = 15,000Btuh.

This represents the total required Btu/h for this zone. So what effect will outdoor reset have on these numbers?

Short Cycling

When the temperature of the water drops to 150°F at an outside temperature of 35°F, the baseboard will now deliver just 400 Btu/h per foot instead of 610 Btu/h per the manufacturer’s ratings. The mod-con, which was sized for the DHW load, has a 150 MBH capacity with a 5 : 1 turn down ratio, is now firing at 30MBH to satisfy a load of just 10MBH. Can you say short-cycle?

What does short cycling do to these low mass condensing units? You will burn more gas; you will create wear and tear on all components; you will shorten the life expectancy of the heat exchanger and yes, your customer will not be happy as you recommended the more expensive super efficient boiler that was supposed to save them money!  So what can be done?

The Buffer Zone

A simple way to overcome the short cycling is to add a buffer tank; a 4 port, well insulated vessel designed to act as a Btu reservoir. The buffer tank is installed between the boiler and the system, much like a hydraulic separator (see illustration below). This also has the added benefit of eliminating the need for primary/secondary piping.

Sizing is important and easy as the manufacturer provides a calculator on their website. Or you can use a simple formula: Lowest Firing Rate - Lowest Load x Run Time ÷ 10,000 (ΔT x 500). Or in our case: 30,000 Btus – 10,000 Btus x 10 minutes ÷ 10,000  = 20 gallons. So, by installing a 20 gallon (or next nearest size) buffer tank, you get the following benefits:

• Elimination of short cycling
• Easy piping for mixed temperatures as primary secondary is no longer needed
• Prevention of wear and tear of your boiler components
• Hydraulic separator for better mixing
• ½ °F loss per hour of your heated water
• Increased water content for heating loads
• Ability to micro zone

See What's On The Tube...

Did you know Emerson Swan is on You Tube? Our channel features educational videos that highlight the products we sell and the applications they're used for. Sometimes just reading about something isn't good enough. Learning from seeing can put things in a better perspective. Putting together short, informative videos is a priority for us going forward and we invite you all to stop by our You Tube page at www.youtube.com/emersonswan and tell us what you think. Here's one of our more recent videos from our trainer, Bruce Marshall. He goes over the negative effects of air in a hydronic heating system.

If you like what you just saw, be sure to check out our You Tube page, www.youtube.com/emersonswan, for even more videos. And this is just the beginning. We will be updating our page with content throughout the year. We hope you find it beneficial.

Heating Edge: Maximizing Return Through Diligent Design

Condensing

A condensing boiler is only slightly more efficient than a non-condensing boiler - unless the flue gas temperature has reached its dew point. The magic of flue gas condensation really starts to happen when the return water temperatures reach 130°F. It is at this point that the products of combustion, carbon dioxide and water vapor, turn to liquid condensate and release the energy that would otherwise have gone out the flue as waste. This latent heat is added to that already captured by the heat exchanger, resulting in an overall increase in efficiency. The lower the return temperature - the more latent heat that is recovered – the higher the efficiency.      

Conventional baseboard was designed to operate at 180°F water supply temperature with a 20°F ΔT. So, a 10’ length of baseboard would provide approximately 5,500 to 6,000 Btu. However, with a supply temperature of 150°F (for a return temperature of 130°F), this same baseboard would provide just 3,800 Btu – a 40% reduction in delivered heat. One of two things must now occur – add more baseboards or increase the supply water temperature. The former is seldom done while the latter, being the most commonly implemented solution, results in a non-condensing boiler.

It is quite clear therefore that conventional baseboard is not a way to maximize efficiency when it comes to condensing boilers. So what are the alternatives?

1. In-Floor Radiant: Operates most effectively with low water supply temps. May not be feasible in all applications.
2. Flat Panel Radiators: Designed for high temperature but can work effectively with lower temperatures if sized accordingly. Also require significant system re-piping to accommodate monoflo tees. Account must also be taken of the amount of wall space required to accommodate the panels.
3. Heating Edge HE2 High Capacity Hybrid Element: Designed to be installed in place of traditional baseboard. Provides significantly higher outputs at lower temperatures (see performance data here). Keep in mind that these ratings reflect average water temperatures with a 20° ΔT so an average temperature of 130°F should result in significant condensing of flue gas. By installing Heating Edge HE2 High Capacity Hybrid Element in place of the same footage of baseboard we can achieve the same BTHU outputs with Average Water Temperature of 140 degrees, which with a 20 degree delta T, will bring water back the boiler at 130 degrees ensuring that your condensing boiler is operating within the desired range and maximizing its potential.

Applications 

Now that we have identified a practical and affordable way to deliver heat at lower temperatures, let’s consider other potential applications.

1. Geothermal (GSHP): One of the challenges faced by geothermal installers is the relatively low supply water temperatures. Typically delivering temperatures of between 110°F and 120°F, hydronic applications are often hampered by the emitters. Traditional baseboard or in the case of commercial installations, convectors, would have to be tripled in size in order to satisfactorily heat the space. Radiant would require extensive and expensive integration. Heating Edge, with its higher capacity, could easily be installed in place of the existing baseboard with little or no additional labor costs.
2. Solar Thermal: Ideally, solar thermal heating should be designed around a low temperature delivery system, typically in the 120 degree range. As with geothermal systems, the challenge is how to match the low temperature BTU output to the load. Heating Edge’s high output design makes it an ideal fit for this application.

Heating Edge is a high capacity, perimeter heating convector constructed of 20 gauge steel and aluminum designed for use in both residential and commercial applications. It is available in a variety of lengths from 2’ up to 8’.

ROI

Products such as condensing boilers, ground source heat pumps and solar thermal heating systems generally have higher upfront costs than their less efficient counterparts. While each technology has inherent features and benefits, each is also judged on its ability to provide a return on investment – whatever that might be. For this reason it is imperative that careful attention be paid to the application of the equipment and the distribution system being utilized by these technologies.

Payback calculations are based on performance criteria commensurate with the operating characteristics of the technology. These assumptions are generally based on “ideal” operating scenarios – a holistic approach that is often dependent on extraneous factors, not least of which is the distribution system.

Heating Edge can be characterized as an enabling resource inasmuch as it allows these technologies to perform to their optimum efficiencies and provide their respective returns on the initial investment. In other words, Heating Edge helps to make that ROI possible.

Learn more about Heating Edge here.

TempTAP™ Thermostatic Faucet Series

State-of-the art technology meets simplicity in TempTAP™, the faucet with a built-in paraffin actuator to ensure water temperature control that’s precise, reliable and repeatable.

Each year thousands of people, from children to seniors, are scalded, and most of those burns occur in the bathroom. That’s why it’s critically important to specify a thermostatic solution. TempTAP™ meets or exceeds plumbing codes and standards nationwide, including ASSE 1070 for protection of users from scalding.

The TempTAP™ faucet's time-tested temperature-sensing valve technology has been a proven performer in shower valves for years, so you can install it with the confidence that TempTAP™ offers the easiest way to be code compliant and reduce potential injury liability.

With TempTAP™ water tempering is simple and certain.

Layout, installation and maintenance are simplified with TempTAP™ because all key components are above sink level for easy access. Installers no longer have to bother with installing a separate tempering valve below the sink. Because TempTAP™ faucets don't require a separate thermostatic valve, there are fewer parts and fewer leak points. That translates to less time spent on installation, less inventory and fewer callbacks for maintenance.

View the brochure here.

Radiant Heating

 

Radiant heat is the most comfortable and efficient form of home heating. Radiant floor heating systems conduct heat through the floor which then broadcasts heat to every cold object in the room, especially to you. It's an unparalleled sense of comfort, and the fuel efficiencies can be tremendous. Moreover, there are no vents in the way of your furniture plan, and no forced air to stir up dust or make noise. Watts Radiant hydronic heating systems are clean, quiet, and decorators love them. With no vents or baseboards present furniture can be placed anywhere. Any type of floor covering can be installed over these systems. There simply is no match for radiant floor heating.

Our radiant heat systems warm homes, businesses, warehouses, garages, and even airplane hangars. Our hydronic tubing is easily installed in new construction and retrofitted into existing structures. Premium Onix™ tube or RadiantPEX+™ Cross-linked Polyethylene tubing can be installed above or below subfloors in Staple-ups™, slabs, thin slabs, or sandwiched between subfloors. For ease of installation our innovative SubRay™ radiant heat system provides your installer with even more options and flexibility.

Enjoy the comforts of a Watts Radiant floor heating system - you'll thank yourself again and again!

Learn more here.