SPECIFYING ARI STANDARD 400-2001

SPECIFYING ARI STANDARD 400-2001
For Plate And Frame Heat Exchangers

Why should you specify and install Bell & Gossett GPX plate and frame heat exchangers?

Bell & Gossett GPX plate and frame heat exchangers offer maximum efficiency, a small footprint, and exceptional application flexibility. The modern plate design allows the Bell & Gossett GPX plate & frame heat exchanger to perform with less than one-third the surface area required by conventional U-tube heat exchangers designed for the same application. Finally, and most importantly, the Bell & Gossett GPX line of plate heat exchangers are ARI-400-2001 certified, guaranteeing you the performance you expected and designed for.

What is ARI Standard 400-2001?

ARI Standard 400-2001 is a certification program established to define test requirements, rating requirements, and conformance and marking conditions for liquid to liquid heat exchangers. The certification requires annual testing by an independent ARI approved testing lab. These test results are then compared to the manufacturer’s published performance ratings.

ARI Certification is only granted to units that meet or exceed the following manufacturers’ published thermal performance ratings.

• Total Heat Transfer Rate: >95% of published

• Tested pressure drop: <110%>

Failure to meet the test requirements requires re-rating or ceasing of labeling of the failed product as ARI certified.

ARI Standard 400-2001 provides a common method for evaluating the thermal performance of liquid to liquid heat exchangers. Specifying ARI Standard 400 certification allows buyers and end users to make equal comparisons between manufacturers.

Why do you need an ARI Standard 400-2001 Certified Heat Exchanger?

• To ensure "alternate" products do not take "liberties" with their published performance data (defined in more detail later)

• It ensures all three main components in commercial HVAC systems are independently certified. The three main components of a commercial HVAC system are the cooling tower (CTI Certified), the heat exchanger (ARI Certified), and the chiller (ARI Certified). These components work together as a complete system. Their relationship has a large effect on energy savings since a chiller’s efficiency improves with colder water. Since energy prices are increasing continuously, it is very important to look at every component in a system to ensure that each component performs as originally specified and assured by the manufacturer and that each one is as energy efficient as possible. If your cooling tower is CTI certified and your chiller is ARI certified, shouldn’t your heat exchanger be ARI certified as well?

• ARI certified components, including the heat exchanger, may assist in obtaining LEED Certification. One category that HVAC systems can impact LEED certification in is Energy & Atmosphere. This category requires a reduction in building energy consumption and has the greatest number of potential points towards LEED certification. It is estimated that a chiller’s energy efficiency increases 2% for every degree cooler the supply water is to the chiller. An ARI certified plate heat exchanger ensures that the chiller receives water at the temperature specified. Therefore the engineer can then specify closer temperature approaches and be confident that what is specified and expected is actually what the plate heat exchanger will provide.

• An ARI certified plate heat exchanger will result in cost savings for the end-user. Undersized (non-ARI certified) plate and frame heat exchangers will increase operating costs by requiring the chillers to start sooner and operate for a longer period of time.

What do we mean by "liberties"?

Due to the ability of plate type heat exchangers to achieve close temperature approaches with high heat transfer rates, altering the design temperatures by even tenths of a degree or understating the actual pressure drops can significantly reduce the amount of surface area required and therefore, cost of the heat exchanger. Many times these "liberties" are taken by our competitors but are not disclosed to the buyer or end-user. To counteract this practice, members of ARI’s Liquid to Liquid Heat Exchanger committee developed Standard 400.

Though members included delegates from ITT, Alfa Laval, Tranter and FlatePlate, only ITT and one other manufacturer obtained their certification. Please help even out the playing field by specifying ARI Standard 400. This will help ensure an "apples to apples" comparison at bid time and procurement time.

How to specify ARI-400-2001:

By adding the following wording to your specifications, you can be assured that what you specify is what will be provided. Thereby guaranteeing the performance you demand

• The manufacturer shall provide written guarantee to the accuracy of the heat exchanger thermal design.

• The manufacturer shall be listed with the ARI Liquid Heat Exchanger Certification Standard 400 for the model being supplied.

• Should the heat exchanger not perform to the specified conditions as defined in ARI 400, the manufacturer is responsible to replace or repair the heat exchanger in order to achieve the stated performance.

• If the manufacturer is not ARI 400 certified, a witnessed factory performance test must be completed and documented per the testing specifications of ARI 400.

Please feel free to contact your local Dawson Company representative for a complete ARI-400 formatted Bell & Gossett GPX specification, or to assist you with sizing of your plate and frame heat exchangers. For more information on ARI-400 please visit www.ari.org.

Copper Finned Tube Boilers and Primary/Secondary, Why?

"Hey Jim, I need to bring something to your attention. This copper finned tube boiler isn’t piped primary/secondary. Unfortunately we won’t be able to complete our start-up until the boiler piping is corrected".

"Dave, what do you mean you can’t complete start-up, we have to be on line tomorrow for the grand opening!"

"I’m sorry Jim; this boiler should be piped primary/secondary to insure trouble free long lasting operation. If it’s not piped primary/secondary, you may get a low flow condition or condensation may form. Both will cause tube bundle failure and it will not be covered by warranty"

"But Dave, this is the way it’s shown on the plans…"


This is one of the most uncomfortable situations I’ve been faced with as a manufacture’s representative and, unfortunately, one that occurs all too often. The use of copper finned tube boilers has grown tremendously in the last ten years through plan/spec, design build and replacement projects. The recent improvements of copper finned tube products, their low cost and ease of use have increased their use. In the past, the consulting engineer or contractor has designed/installed copper finned tube boilers on the job as they always have using a steel tube boiler with primary pumping. What they don’t realize is that copper finned tube boilers differ from other boiler types and special consideration must be taken when piping them, especially in comfort heating applications.

The biggest difference between the two technologies is the amount of water they hold. Steel tube boilers are high mass units, typically holding many gallons of water. They also take longer to reach set point and are slower to respond to system demands. Due to the amount of mass they hold, they can handle variations in flow well as variable speed drives and 2-way control valves respond to system demands.

Conversely, copper finned tube boilers are low mass units and hold a small amount of water. The water they hold is based on the amount of water the heat exchanger tubes can hold, which depending on the size of the boiler may only be a few gallons. They basically heat the water via convection and gas radiation by passing the products of combustion through a series of baffled finned copper tubes, thus heat transfer is very effective and warm up time is fast, almost too fast. In fact, copper finned tube boilers are often referred to as "quick-start" boilers because they are able to heat the water inside the tubes up to 9 times faster than cast iron or steel tube boilers.

Copper finned tube boilers are designed to handle high "heat flux" or heat transfer, and rely upon higher tube bundle velocities to keep the tubes free from scale build-up and to "unload" all of the heat they can transfer. Therefore, a basic element of design for all copper finned tube boilers is the flow rate that the heat exchangers require. Piping these boilers using direct primary pumping can pose a myriad of problems and in most installations will shorten the life of the boiler drastically. Problems that may occur include:

• Over pumping: if the pump isn’t matched to the boiler properly, excessive velocities may occur in the tube bundle leading to tube erosion and premature failure. When higher flow rates are required, such as in domestic water heating applications with high hardness levels, cupro-nickel finned tubes that have greater resistance to erosion may be ordered instead of the standard copper finned tubing. I must stress that even cupro-nickel finned tubes have limits on internal velocities and direct primary pumping may still pose a problem.

• Low/no flow over heating: in a 2-way valve variable volume and/or variable speed system, the flow constantly varies to match the system’s load. As the valves begin to modulate closed or the pump speed is reduced, the flow through the boiler may not be enough to take away all of heat the boiler is producing, causing excessive heat flux, liming inside the tubes, and ultimately, tube bundle failure. Even if the boiler turns off, there still may be enough residual heat in the combustion chamber to cause damage. Thus the pump must continue operating until the heat is dissipated.

• Condensation: In today’s world, equipment manufacturer’s have been forced to design equipment to operate at the highest possible efficiency. For boilers, this may or may not pose additional design considerations. As boiler efficiency increases, the temperature of the products of combustion will decrease. If the temperature of the products of combustion falls below the dew point, condensation will form and fall back into the boiler. It turns out that this condensation is mildly acidic, about like Coca-Cola and prolonged exposure over time will cause oxidation of the copper fins, increasing the potential for soot build-up which will obstruct hot flue gasses from rising, as well as serious corrosion to all ferrous materials it comes in contact with. Premature tube bundle failure is sure to follow. (Boy, I guess I better stop drinking so much Coca-Cola!)

One way to prevent condensation from forming is to keep the return water temperature at some minimum temperature, typically 110F–130F, depending on the boiler of course. This is especially important in low temperature return systems such as water source heat pump or swimming pool applications.

Primary/secondary piping provides a good method of preventing all three scenarios I have mentioned above. I always advocate to the customer to specify/purchase a boiler with a factory mounted pump to serve as the primary pump. In some cases the factory furnished pump is not large enough, thus an external field mounted pump would be required.

Figure 1 shows typical primary/secondary piping for a single boiler comfort heating system. The boiler is piped directly to the secondary loop by placing two tees 6-12" apart. A pump dedicated to the boiler and two tees, it’s that simple.

Figure 2 shows a multiple boiler system where the primary loop is piped in reverse return fashion, assuring each boiler’s inlet temperature is the same.

Additional attention must be given to low temperature return systems because they typically operate below 100F. Figure 3 shows an additional blending loop with a balancing valve within in the primary loop to assure some of the leaving water is blended back to the boiler, raising the inlet temperature to the minimum required by the boiler.

The boiler line that Dawson represents, Laars Heating Systems, has designed a header for the Laars Pennant that includes a factory mounted 3-way mixing valve specifically designed for low temperature return system (see below). The factory mounted three way valve also comes in handy in large systems where initial system warm-up is slow, thus condensation may still be a factor.

Primary/secondary piping is not the solution to every installation, but more times than not it will keep the manufacture’s representative and contractor out of trouble and the engineer and building owner happy. Primary/secondary is a simple low cost method that works well and I strongly recommend that it be considered as the starting point of every copper finned tube installation.

Cal-Code Sight Glass is no longer required for Externally Pressurized Expansion Tanks in California

Subchapter 2. Boiler and Fired Pressure Vessel Safety Orders
Article 4. Installation
§763. Low-Pressure Boilers.

(g) All hot water heating systems shall be equipped with a suitable expansion tank that will be consistent with the volume, temperature, pressure, and capacity of the system as required by the Code. All such expansion tanks shall have an allowable working pressure at least equal to the maximum allowable working pressure of the boiler with which they are used, and the maximum allowable working pressure shall be stamped on a nameplate visible after installation.

All expansion tanks connected into systems having boilers designed for more than 30 psi working pressure shall be constructed, inspected, and stamped according to the Code, Section VIII, unless it can be proven to the satisfaction of the Division that the design and construction will provide equivalent safety. Expansion tanks connected into systems having boilers designed for 30 psi or less shall be designed, constructed, and stamped according to the Code, Section VIII, or according to good engineering practices with a factor of safety of at least 4.

All expansion tanks shall be fitted with either: (1) a water gage glass or other means for indicating visually the water level in the tank, or (2) a bladder-type expansion tank provided the tank is fitted with an airtight bladder inside the tank and it is provided with a means of determining the presence of air cushion in the tank. The hot water heating system shall be installed, inspected, and equipped with the required safety relief and shut-off devices in accordance with the Uniform Mechanical Code, Chapter 10, February 1997 Edition.

Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


The above information is provided free of charge by the Department of Industrial Relations from its web site at http://www.dir.ca.gov/.