The standard has a new pipe sizing chart that varies the maximum allowable flow rate through a hydronic system based on hours of operation. The Bell & Gossett system syzer® wheel has served us well for decades. (There are exceptions listed.) HVAC Hydronic Pipe Sizing and the 2015 Michigan Energy CodeĮngineers and contractors all use various methods for pipe sizing. On larger systems with a total of 75 HP or more, if DP control is used, DDC reset of the set point downward until one valve is nearly wide open. All of our sales engineers understand this and can help you with the calculation.
Deppmann has many seminars explaining how to do this properly. This means the 10 PSIG “rule of thumb” must now be calculated. The DP set point shall be measured at the controlling heat exchanger (terminal unit) and be set to no more than 110% of that needed. Most systems today are already using the DP set point for control. There are some manufacturers that only market one type of pump with sensor-less control. Remember that you can use either type of control with any pump and the choice of base mounted or inline pumps and the choice of pump control are separate decisions. (6.5.4.2 ) Bell & Gossett offers both sensor control and sensor-less control. The control of the pumps to reduce wattage to 30% at 50% flow should be controlled by differential pressure (DP) or by desired flow. Deppmann offers many variable speed pumping options to meet this portion of the code. This limitation was changed (6.5.4.2) to any system pump over 5 HP in chilled water systems with a couple of exceptions for smaller systems. It also had a requirement for pumps with heads over 100’ and horsepower of 50 or greater to be able to drop the energy used to 30% of the wattage at 50% of the flow. The 2007 version of ASHRAE 90.1 standards required hydronic systems be designed for variable flow with a few exceptions. (6.4.2.2) Most engineers do this already but this eliminates the “rules of thumb” or estimating of pump head. You must calculate the pump head including the pressure drop through the worst terminal unit and the piping losses to it.
HVAC Pumps and the 2015 Michigan Energy Code
Today most boilers scheduled are high efficiency and have great turndown but the standard (6.5.4.1) indicates the turndown must be a minimum of 3:1, 4:1 or 5:1 based on size. Obviously this can be accomplished through dedicated pumps, but in systems where the pumps are on a common header, the use of isolation valves is required. In systems where the plant has more than one boiler or chiller, section 6.5.4.2 of the standard requires that we stop the flow through the boilers and chillers that are not operating. Our experience is that most engineers have incorporated these change into today’s design. The ASHRAE 90.1-2013 Standard contains a couple of key changes affecting these systems. Deppmann Company is a leading manufacturer’s representative in boilers and water heaters. Boilers and the 2015 Michigan Energy Code We still see some schedules defaulting to the old “rule of thumb” of 10 PSIG or 23 feet. Bell & Gossett GPX plate exchangers meet this requirement.Ħ.5.1.3 Although this is not a change, I should remind you that the maximum pressure drop of water side economizers was limited to 15 feet in prior standards. This is an important change that must be incorporated into your selections and specifications.
Water Side Economizers and the 2015 Michigan Energy CodeĦ.4.1.4 Plate type heat exchangers such as those used in water side economizers or free cooling must meet the requirements of the AHRI 400 test procedures. Here is a quick summary of some of the key changes.
Deppmann seminar series have captured these changes and alerted engineers and contractors to the design changes required in hydronic systems.
There are many changes from the 2007 ASHRAE standard to the 2010 Standard, and even more from 2010 to the 2013 standard which the new code is based on. The prior Michigan Energy Code aligned around ASHRAE 90.1-2007 standards. The code follows ANSI/ASHRAE/IES Standard 90.1-2013 with some modification. The new code is available through the LARA website which links to ICC. Deppmann Monday Morning Minutes looks at a few highlights of the new code. The long expected changes to the code were filed with the Secretary of State on with an effective date 120 days after filing. The 2015 Michigan Energy Code is changing with an expected effective date of September 20, 2017.