by Rich Grimes
Water Solutions Marketing

I have had many projects where lack of combustion/ventilation air has been the issue. It reminds me of how many installations I have seen like this. Surely more than I can remember… Lack of air on a water heater is similar to lack of air on a car or small engine. Poor combustion results in lost efficiency and more hazardous emissions. Symptoms such as sooting and constant flame failures can be indicators of air issues. Imagine a candle snuffer that does not touch the wick of the candle, but it captures all of the heat from the flame. The flame uses up all of the air inside the small candle snuffer and the flame cannot maintain combustion. Soot is produced as the fresh air is used up by the flame. Gradually, the flame is extinguished due to lack of combustion air.

 

In this article we shall discuss combustion and ventilation air requirements for gas-fired appliances. Combustion and Ventilation Air requirements are set forth in the National Fuel Gas Code and typically apply to Atmospheric or Fan-Assisted Combustion. As we discussed in previous articles regarding venting, Category IV appliances typically have a direct air intake from outdoor, negating the need for separate combustion/ventilation air louvers in the wall or door. Separate Air Intake systems for gas-fired appliances are specified by the manufacturer and must be part of the vent system approval.

 

PRINCIPLE

Gas-fired appliances require adequate Intake Air for Combustion and Ventilation. There are two methods for sizing Intake Air. The Standard method is used almost exclusively, requiring a minimum volume of 50 cubic feet per 1,000 BTU/hr. The second is the Known Air Infiltration Rate Method. This method is rarely used and requires calculations based on atmospheric or fan-assisted combustion and air change per hour.

The movement of air between two louvers allows fresh air to enter the mechanical room and be circulated. A larger, single louver can be utilized to allow enough air to enter and circulate. Each particular air intake arrangement has its own sizing based on the total BTU input of all appliances in the room and where the air is communicated from. The sizing of combustion and ventilation air is specified in the National Fuel Gas Code / NFPA54 / ANSI Z223.1 Section 9.3.

 

REQUIREMENTS

The intake air sizing is based on the total BTU input of all appliances and is determined by the following installation parameters:

 

AIR FROM OUTDOORS (TWO PERMANENT OPENINGS)

This method requires two (2) permanent openings. One opening is located within 12 inches of the top of the enclosure and the other is located within 12 inches of the bottom of the enclosure. These openings must communicate directly, or by ducts, with the outdoors or spaces that freely communicate with the outdoors:

1) Where communicating directly with the outdoors (LOUVERS) or through VERTICAL DUCTS, EACH opening shall have 1 Square Inch per 4,000 BTU/hr, the total of all appliances.

Example: 200,000 BTU Heater = 200,000 ÷ 4,000 = 50 Square Inches Free Area per opening.

2) When communicating directly with the outdoors through HORIZONTAL DUCTS, EACH opening shall have 1 Square Inch per 2,000 BTU/hr, the total of all appliances.

Example: 200,000 BTU Heater = 200,000 ÷ 2,000 = 100 Square Inches Free Area per opening.

 

 

AIR FROM OUTDOORS (ONE PERMANENT OPENING)

This method requires one (1) permanent opening. This opening is located within 12 inches of the top of the enclosure. This opening must communicate directly, or by Vertical or Horizontal ducts, with the outdoors or spaces that freely communicate with the outdoors:

1) Where communicating directly with the outdoors (Louvers) or through Vertical or Horizontal Ducts, EACH opening shall have 1 Square Inch per 3,000 BTU/hr, the total of all appliances.

Example: 200,000 BTU Heater = 200,000 ÷ 3,000 = 66.67 Square Inches Free Area opening.

2) The minimum free area must be not less than the sum of the areas of all vent connectors in the space.

 

AIR FROM INDOORS (TWO PERMANENT OPENINGS ONLY)

This method requires two (2) permanent openings. One opening is located within 12 inches of the top of the enclosure and the other is located within 12 inches of the bottom of the enclosure. These openings must communicate directly via Louvers, with an indoor space that is adequately ventilated:

1) Where communicating directly with another interior space, ON THE SAME STORY, VIA LOUVERS, EACH opening shall have 1 Square Inch per 1,000 BTU/hr, the total of all appliances.

Example: 200,000 BTU Heater = 200,000 ÷ 1,000 = 200 Square Inches Free Area per opening.

2) Where communicating directly with another interior space, ON A DIFFERENT STORY, VIA LOUVERS, EACH opening shall have 2 Square Inch per 1,000 BTU/hr, the total of all appliances.

Example: 200,000 BTU Heater = 200,000 ÷ 500 = 400 Square Inches Free Area per opening.

 

ALTERNATIVES

There are a few options available such as engineered installations and mechanical air intake fans. Mechanical air intake systems can provide a controlled air intake. These systems employ a Power Air Fan that will force fresh air in at a given CFM. These must be interlocked with ALL appliances to insure that combustion air is being provided and proved prior to burner ignition. There are also many products that can utilize Direct Air Intake through a fan-assisted/power burner combustion process and separate air intake pipe. These heaters and boilers have become very popular because of their multiple vent and air capabilities. High Efficient appliances that utilize PVC and other plastic vent materials are great options when combustion air is limited.

 

CONSIDERATIONS

Many restaurants operate in a negative pressure within the building. This is mainly due to exhaust hoods that extract smoke and fumes from cooking. These exhaust fans are extremely strong and can cause burner operational problems. They will draw up and consume the combustion air needed for proper operation. If you open a door to the outside, air rushes into the building.

Equipment such as atmospheric stoves operate properly because they are located directly beneath the exhaust hood and all available air is drawn by them. A water heater or boiler that is located in another part of the restaurant can experience sooting, leakage of combustion products and flame failures due to this lack of air. The big problem is that leakage of combustion products equals spillage of carbon monoxide in the restaurant. The vent stack for the heater becomes an air intake pipe and air is drawn down from the rooftop. When the heater fires, the combustion exhaust spills out at the draft hood as it cannot be drawn up the vent pipe. It is very common to see atmospheric gas heaters choking in this type of installation. A smoke test at the draft hood of the heater will help indicate if flue products are exhausting properly. The test should be performed with the burner on and off and with the door open and closed. A burner that is starving for air will burn very yellow or orange in color. When the air pressure is relieved by opening a nearby door, the burner flame should be blue in color with slight yellow/orange tips.

These situations can be resolved with heaters that allow for direct air intake. Just because there was an atmospheric heater originally installed, replacement may be better suited to a higher efficient heater that allows or requires direct air intake. Restaurants are not the only buildings that can have negative pressures. The same problem can occur in a small mechanical room where an exhaust fan has been installed. This has the same effect, just in a smaller application. Unventilated closets can produce the same problems.

Louvers should also be checked for free area of square inches. Many louvers can restrict the free area and sometimes a larger size louver is required. Mesh screens should not be placed over louver openings as they will clog up and eventually create an air issue. Double-faced louvers can cut free area by one half, requiring twice as large of a surface area compared to an unrestricted, full flow louver.

 

SUMMARY

All of these are extremely hazardous installations because they put the inhabitants in direct contact with combustion exhaust containing carbon monoxide. Combustion and Ventilation Air is often overlooked and should be investigated and accounted for when installing any gas fired appliance. Combustion and Ventilation Air are crucial to a good, safe installation.

I hope that these articles are helpful to you and we look forward to seeing you in the next issue!

Thanks,

Rich Grimes

by Rob Spence (Mechanical Engineer) and Abigail Cantor (Chemical Engineer)

Introduction

This article is part of a series discussing the growth of microorganisms in plumbing systems.  As previously noted, microorganisms can grow and thrive in a plumbing system when water that enters a system is not used for a long time.   This article looks at sizing pipes and tanks in order to minimize the volume of water stored on-site and the residence time of water in the plumbing system.

Current plumbing and home designers are at odds with this desire to reduce system volume.  New homes and bathroom remodels are incorporating multiple head showers, body sprays, and large whirlpool tubs.  This drives up the plumbing system requirement with larger pipes, water heaters, water softeners, expansion tanks, and filtration units.  Many times the added capacity is only utilized a fraction of the time, which results in very long residence times.

Fixture Units

Residence time can be addressed first in design by considering “fixture units”.  The Plumbing Code assigns a fixture unit to each type of device in the plumbing system so that pipes can be properly sized with adequate flow and pressure to each fixture.  The plumbing designer must tally up all the fixture units serviced by each segment of the piping system (hot, cold, combined, branch, and mains) and size the pipes accordingly.  Therefore, as we add bathrooms, whirlpool tubs and extra shower heads, the pipe sizes must get larger.

Let’s contrast a typical home with 2 ½ baths utilizing single shower heads to a luxury home with 3 full baths and two ½ baths.  One of the luxury baths will have a rain head shower and a hand-held spray plus six body sprays, as well as a 75 gallon soaking tub.

In our example, the luxury house fixture count would require 1¼” supply line and 1” hot and cold mains with a 1” branch just to the master bath.  The shower alone could have a fixture count as high as 15.  In contrast, our standard home would only require a ¾” main.  Note that the 1¼” supply pipe in the luxury house has over six times the volume of water per linear foot than the standard ¾” supply pipe.  The Code doesn’t allow us to reduce the pipe size in these cases, but there are things we can do to reduce the load on the pipe so that the number of fixture units are lowered and the pipe sizes are calculated to be smaller.

Consider using diverting valves in shower systems rather than volume controls or separate valves on each device.  This lets the user choose only one of the multiple heads at once rather than the ability to have all functions at the same time.  Some of the pre-assembled shower towers utilize this functionality as well as low flow body sprays, so they only require ½” supply lines.  Contrast that with a luxury shower with individually mounted body sprays, which would require a 1” equalization loop going to all six locations. As you can see by utilizing a shower tower or diverting valve you only have to count one of the devices in the shower, which reduces the pipe sizes in the shower, branch circuit, and even the mains.  This choice reduces piping system volumes as well as labor for installation!

One other plumbing option to consider for reducing pipe volume is a “home run system”.  This is a design where manifold pipelines host connections to groups of fixtures instead of each fixture connection branching off from the main piping all through the building.  This type of system utilizes individual ½” or ¾” lines to each fixture or bath group.  The design will typically increase the overall linear feet of piping, but because it is smaller diameter pipe, the system volume is less.

Hot Water Tank Volume

As with considering fixture units, the Plumbing Designer must also adequately size a hot water heating system to handle all the potential flow. The Code states that the design “must provide adequate hot water for peak load”.  With traditional tank-type systems, our luxury home might need to be designed with several hundred gallons of storage.  We’ve all heard it:  “This is a high end customer and they don’t want to run out of hot water”.  So, the system is designed with multiple large tank-type heaters or a boiler system with several indirect tanks.  All of this hot water is sitting and waiting for one or two days per year when it is really required.  It makes sense to consider tankless water heaters that do not store any hot water.  It is true that in some cases, it will require two or three tankless water heaters.  But, the risk for damaging biofilm growth is greatly reduced.

Educate the home owner of the risks of over-sizing the domestic hot water package.  By utilizing the diverter valves in the shower system, we can get by in our luxury home with only two tankless water heaters.  In addition, the Plumbing Code now gives an alternate method for sizing tankless heaters.  It allows the designer to base the heater size on 65% of the peak fixture load.  Using this method, our typical home only requires one tankless heater.

One other method of reducing water heater tank volume is the use of an indirect water heater mated to a boiler system.  Typically, these systems have higher recovery rates (rates of heating and re-heating water), so many times a smaller hot water storage tank can be used than in direct heating.  For example, a standard 75 gallon gas water heater has a first hour delivery of 120 gallons per hour (GPH) compared to a 30 gallon indirect water heater that is rated at 183 GPH. In this comparison, there is an increased first hour delivery rate for indirect water heaters with a tank volume reduced by 45 gallons.

For water systems with private water sources, utilizing a constant pressure well pump will also decrease system volume.  A typical expansion tank for a standard well pump is 50 to 75 gallons.  However, that drops to 5 or 10 gallons on a constant pressure pump system.

We’ve been talking about decreasing system volume to reduce the risk biofilm growth, which is the primary goal of this article.  However, if it is determined that the system must have large hot water storage tanks, the design temperature of those tanks can be elevated to a much higher temperature (160 to 180 degrees F) to prevent biofilm growth.  This system must be fitted with an anti-scald valve to reduce the temperature to a safe level for the distribution to the house.  Indirect water heaters are a good choice for this type of system since they typically have a much lower energy loss as the water sits in the storage tank.

The Tub Dilemma

The required hot water tank volume also depends on the fill rate of bath tubs.  Large whirlpool tubs typically have tub fillers capable of 12 to15 gallons per minute (gpm).  Most designers would recommend an additional hot water storage tank at least as large as the tub volume, since no tank-type heater will keep up with 15 gpm fill rate.  Again, this requires large piping and major domestic hot water heating equipment that can lead to the growth of biofilms.

However, plumbing designers can educate homeowners about this dilemma.   If a homeowner can accept a slightly lower fill rate for the tub, one or two tankless water heaters can be used instead of a large tank-type heater with hot water storage.  In addition, the tankless heaters will maintain outlet temperature indefinitely so that there will be no drop in temperature as the tub slowly fills.  With a large tank-type water heater and additional large storage tank, a 75 gallon tub could potentially fill in 5 minutes.  With one tank-less water heater, the max fill time would be, at worst, 15 minutes.

There are a few issues that must be considered when applying a tank-less heater.  There is a phenomenon called a “Cold Water Sandwich.” That is, the first gallon or two of water is room temperature because it has been sitting in the room’s piping.  Then, the cold influent water comes in and has not had adequate time for heating, so there is about 3 to 5 seconds of cold water.  Then the properly heated water arrives.  A person can’t jump right into a shower or a bath tub and can’t turn the water on and off repeatedly.  But, a 2 to 5 gallon buffer tank can be used to solve the cold water sandwich problem.

Another issue is that there is higher pressure drop in tankless water heater units which must be considered in the plumbing design.

Water Treatment Equipment

The water softener and other water treatment equipment are also sites of large residence times.  As plumbing features of a luxury home are added, the peak flow rate increases.  This large flow rate alone given to a water treatment designer may result in very large water softening and treatment system.  However, the homeowner can describe the intent of how the luxury plumbing features will be used.  If the use of multiple luxury features is only going to occur for a short period, say 10 to 15 minutes every few weeks, consider installing a smaller softener and any other required water treatment equipment.  As long as the connections to the softener and other water treatment equipment are sized to handle that flow, the momentary surge will only result in partially softened/treated water going down stream for that short period.  Size the water treatment equipment for every day flow.

Hot Water Recirculation Lines

Hot water recirculation lines are needed in larger buildings so that hot water is immediately available throughout the building instead of having to travel from the hot water tank first.  However, hot water recirculation lines are notorious for biofilm growth because of added residence time of water and because the recirculation serves as a means to spread microbiological colonies to previously unaffected parts of the hot water system.

The “home run” plumbing system discussed in the section about “Fixture Units” can eliminate the need for a hot water recirculation line.

Summary

In summary, it is difficult to lower water residence time and water volumes in modern plumbing systems, but it can be done.

Using diverting valves, shower towers, or home run system design can decrease the number of fixture units in a plumbing design. This will result in smaller piping and decrease the size of heating and water treatment equipment.

Homeowners can be encouraged to choose tank-less water heaters and to accept lower tub fill rates to drastically reduce system volume.   Where tank-type water heaters are used, indirect heaters require less hot water storage than direct heaters.

Water softeners and other water treatment equipment can be sized for typical daily flow if peak flows are minimized by the homeowner.

Volume can be reduced further on systems with private water sources by using constant pressure well pumps.

We can’t expect plumbing designers and consumers to eliminate all the luxuries that we have grown accustom to.   But, as a plumbing community we need to be smart with our designs and educate our customers on the consequences of over-engineering.  With very small concessions, consumers can enjoy substantial energy savings as well as lower risks to health and to pipe integrity.

Natural Gas Facts
by Sheryl Long 

You probably know that natural gas is good for your business, but it is also good for the United States economy. Check out these statistics from the American Gas Association.

Jobs, Jobs, Jobs

Homes and business served by American Gas Association (AGA) members are the largest consumers of natural gas in the country and the industry as a whole employees nearly 3 million people.

• 622,000 jobs are directly involved in exploring for, producing and distributing natural gas (direct employment). Natural gas distribution employment provided between 116,000 and 122,000 (nearly 20%) of these direct jobs.
• 723,000 additional jobs are created in industries such as agriculture and manufacturing that support and supply goods and services to the natural gas industry (indirect employment).
• 1.5 million jobs are supported when direct and indirect natural gas employees introduce the income back into the economy and create demand for further goods and services (induced employment).

 

For more information, visit http://www.aga.org/our-issues/playbook/Pages/default.aspx

 

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Employment Impact

The number of direct jobs created by the natural gas industry increased 20% between 2006 and 2008.

The natural gas industry employs people in all 50 states.

The natural gas industry’s value-added economic impact totaled $385 billion in 2008, or 2.7% of U.S. output. In addition, the gas industry provided $70 billion of direct income for workers in 2008.

The industry projects that the Marcellus shale gas play alone will result in approximately 160,000 additional jobs by 2015.

Forecasters say 2012 Likely to Be a Better Year

 

A steady increase in Florida’s population, an uptick in housing starts and a gradually improving economy should make 2012 a better year for the state’s plumbing professionals. That’s the consensus of several economists who track Florida’s housing market.

“New job creation, rising rents and the inflow of international buyers are positive factors for the state’s housing market,” said Lawrence Yun, chief economist, National Association of Realtors, at the recent 2011 International Real Estate Congress in Coral Gables.  “Today, the smart money is chasing real estate.”

Florida’s population is likely to increase by about 130,000 people in 2012, according to John Silvia, chief economist, Wells Fargo. In a recent forecast, Silvia added that tourism and healthcare are leading the recovery, but other sectors will also be adding new jobs.

New housing starts will increase in 2012, says economist Sean Snaith, director of the University of Central Florida’s Institute for Economic Competitiveness in Orlando. He predicts about 55,000 new residential starts in the coming year. About three-fourths will be single-family homes and the rest will be multi-family construction.

“Nationally, U.S. housing starts are at the lowest level since the end of the second world war,” Yun said. “America is not building any homes, even though we are adding 3 million people a year to our total population. Building activity needs to triple in order to get back to a normal level.”

However, tight credit for builders and developers, as well as home buyers, remains a negative factor for the housing market, Yun added.  “The inventory of newly build homes is very low,” he said. “That means builders are selling whatever they can complete. The problem is that they can’t get construction loans in the current environment.”

While housing prices have stabilized in most Florida markets, they are still well below the boom-year peaks of 2004-2005. That’s because foreclosure sales continue to be a large part of the state’s real estate market. However, Yun said that lenders are bringing their REO (real estate owned) properties online gradually, rather than dumping them on the market at once. In addition, many lenders are recognizing that they lose less money by approving “short sales” (where the existing mortgage is larger than the home’s market value). Some are accelerating the sales process or even offering incentives for owners to move.

For Florida residential plumbing contractors, key opportunities include repairing foreclosed homes and other distressed properties, as well as additions and remodeling projects. One trend of note: some Florida parents are investing their excess cash by buying inexpensive homes and condos for their 20-something children. That allows these Millennials to have a place of their own that they can “fix up” and decorate themselves.

On the commercial side of the business, new construction is most likely to occur in the healthcare, retail and warehouse sectors. Little new office construction is likely as vacancy rates are now at 12 to 20 percent in the state’s major markets.

Yun notes that international trade will be one of the driving forces in the state’s economy in 2012. That could create new commercial opportunities in the state’s gateway cities like Miami, Fort Lauderdale, Jacksonville and Tampa Bay.  As Yun said, “In Florida’s commercial markets, the worst is probably over.”