Roger W. Griffith, P.E.

Sleeper Sofas and Gas Appliances

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Gas appliances could pose a threat to people when they are sleeping, unaware of any impending danger. The threats include oxygen depletion and elevated levels of nitrous oxide or carbon monoxide. For this reason, the fuel gas codes restrict the use of gas appliances in sleeping rooms.
 
The 2018 International Fuel Gas Code (IFGC), Section 303 – Appliance Location contains the following criteria.
 
303.3 Prohibited Locations. Appliances shall not be located in sleeping rooms, bathrooms, toilet rooms, storage closets or surgical rooms, or in a space that opens only into such rooms or spaces, except where the installation complies with one of the following:
 

There are six exceptions listed for paragraph 303.3. These six exceptions allow gas appliances in these prohibited locations when specific conditions are met. [Read more…]

Careful! The Wrong Showerhead May Scald You

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If not specified and installed correctly, showerheads can cause scalding!

Currently, standard shower valves and showerheads have a minimum flow rate of 2.5 GPM. There are water-saving shower valves and showerheads available with lower flow rates. WaterSense showerheads are rated at 2.0 GPM. There are also showerheads available that have 1.5, 1.0, and even 0.5 GPM flow rates. These various options for minimum flow rates in shower valves and showerheads create an opportunity for misapplication and dangerous results.

When the flow rate of a showerhead is less than the minimum flow rate of the corresponding shower valve, the potential for scalding increases for the following reasons: [Read more…]

Roger W. Griffith appointed to ICC Plumbing/Mechanical/Fuel Gas Code Action Committee

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Roger W. Griffith has been appointed to the Plumbing/Mechanical/Fuel Gas Code Action Committee (PMGCAC) of the International Code Council (ICC). The role of this code committee is to review and propose revisions to the International Plumbing, Mechanical, Fuel Gas, Private Sewage Disposal, and Swimming Pool and Spa Codes and the International Residential Code, chapters 12 through 33, which covers the mechanical, plumbing, and fuel gas systems in residential occupancies. I am honored to be appointed as a member of this committee for the upcoming 2018 – 2019 code development cycle.

These important codes define how mechanical, plumbing, and fuel gas systems must be designed and installed to protect the health, safety, and welfare of the public.

Tools and Resources for Mechanical Insulation

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NIA-logo

When designing mechanical systems, engineers and designers often need help specifying the type and thickness of insulation for ducts and piping. Good resources are always valuable and welcome when time constraints leave little time for items like insulation and other accessories.

The National Insulation Association’s (NIA) new redesigned website is a helpful resource for all things insulation, from training, design helps, and specifications. Check out their new website and bookmark it for return trips. Enjoy!

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Thermal Expansion Tanks: Part 3

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Selection and Installation of Thermal Expansion Tanks

thermal expansion tank support

See Part 2 for calculating the expansion tank volumes. Now, using the calculated acceptance volume and total volume for the tank, select an expansion tank from the manufacturer’s data that meets these requirements.

Be aware that in most states, unfired pressure vessels larger than a certain volume must have an ASME stamp. Check your state’s requirement for this limit. If the expansion tank you need is larger than this limitation, it must be constructed in accordance with ASME Section VIII requirements. ASME rated vessels are much higher in cost than non-ASME vessels. Installing multiple smaller tanks, which are below the volume limitation for ASME tanks, is also an option. Most tank manufacturers offer both ASME and non-ASME thermal expansion tanks.

[Read more…]

Thermal Expansion Tanks: Part 2 – Sizing

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How To Size Thermal Expansion Tanks For Hot Water Systems

thermal expansion tank

In Part 1 of this series, we looked at where thermal expansion tanks are needed. When it is determined that a tank should be included in the plumbing system, the next task is to determine the correct size for the tank. Referring to sizing tables in an expansion tank manufacturer’s catalog is the easiest method, although not the best method, for sizing thermal expansion tanks. Sizing tables provided by the manufacturers, give the tank model number and size based on the water heater’s volume and the system supply pressure. These tables, however, are based on three important assumptions that designers need to be aware of.

First, for most manufacturers, the tables are based on a maximum allowable line pressure of 150 psi. This is the maximum allowable working pressure of most water heaters and thermal expansion tanks. It is also the setting of the water heater relief valve. In other words, the thermal expansion tank, if selected by the tables, could accommodate the thermal expansion up to a system pressure of 150 psi, which is the relieving point for the water heater relief valve. Remember that the purpose of the thermal expansion tank is to avoid the relief valve from relieving. Sizing the thermal expansion tank for a maximum allowable pressure of 135 psi, which is 10% below the relief valve set point, is a better alternative.

[Read more…]

Thermal Expansion Tanks: Part 1 – The Need

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thermal expansion tank 2

When are thermal expansion tanks needed and/or required in plumbing systems?

When heated, water expands. We know that. When water is heated in a water heater, the water expands, if possible. But what happens when water is heated in a water heater and there is no hot water usage?

This can occur after a period of showering/bathing during peak times followed by a period of no hot water usage. For example, evenings are a time when there is hot water usage for showering followed by a period of no usage while people are sleeping during the night.

During peak usage times, hot water stored in the water heater is distributed to the end-users, and cold water fills the water heater. The cold water in the tank is then heated, but when there is no subsequent hot water usage, the heated water has no room for expansion. If there is no place for the expanded water to go, the pressure in the system increases significantly. This leads to one of two possible scenarios:

[Read more…]

Duct Smoke Detectors – Locate In Supply or Return Ducts?

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duct smoke detector

Duct smoke detectors, when installed in HVAC systems, automatically stop the system fans upon the detection of smoke. For HVAC systems with airflows exceeding 2,000 cfm, duct smoke detectors are required. This includes where multiple air handling systems utilize common ducts with a combined design capacity greater than 2,000 cfm.

But when duct smoke detectors are required, where should they be located? Let’s look at the requirements in two of the prominent codes and standards.

[Read more…]

What’s Wrong With This Picture?

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Water Heater T&P .001

If you stay in this business long enough, you see a bit of everything. Notice the water heater’s T&P valve in the above photograph. The T&P valve discharges vertically up. What’s wrong with that?

There are many specific code requirements (13 to be exact) for the discharge piping from water heater T&P valves (Ref: 2012 International Plumbing Code 504.6). This installation violates requirements 8 and 9, which are:

8.  Not be trapped.

9. Be installed so as to flow by gravity.

Obviously, with this incorrect installation, the discharge cannot flow by gravity. Also, water can fill and remain in the discharge pipe. Over time, stagnant water that remains in the discharge pipe can corrode the pipe and cause it to fail.

This is just a reminder. During field inspections, check the discharge pipe to verify code compliance.

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NFPA 13R Sprinkler Systems – Are You Double-Dipping?

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sprinkler riser

For residential occupancies, a 13R sprinkler system is permitted by the building codes for many applications, and a 13R system offers numerous economic advantages for the building owner. Most notably, with a 13R system, attics and concealed spaces do not have to be protected with sprinklers.

But, be careful! Although the building codes permit a 13R system for residential occupancies, a 13R system is not permitted when a 13 system is used by the Architect for tradeoffs to other code requirements.

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Floor Registers in Commercial Buildings

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2014-06-05 14.42.20

Commercial buildings typically have ceiling diffusers or sidewall grilles, but occasionally there is a need to locate air supplies or returns on the floor of a facility. Floor registers are common in residential applications. Before locating them on the floor a commercial building, a careful review of the applicable codes is imperative.

Building codes typically do not prohibit floor registers in commercial buildings, however, the fire codes can restrict their usage. For example, NFPA 101: Life Safety Code, paragraph 9.2.1 states that “Air-conditioning, heating, ventilating ductwork, and related equipment shall be in accordance with NFPA 90A.” NFPA 90A: Standard for the Installation of Air-Conditioning and Ventilating Systems, paragraphs 4.3.7.3.1 and 4.3.8.3.1 state that “Air inlets/outlets shall be located at least 3 inches above the floor, unless provisions have been made to prevent dirt and dust accumulations from entering the system.”

[Read more…]

Roger W. Griffith, P.E.
P.O. Box 702
Jefferson City, TN 37760
(865) 471-8142

Email: rgriffith@griffithengineering.net

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