NEBB®

Delivering High Performance Buildings and Systems: Solutions for Sustainable Spaces

Certelligence Portal

Questions and Answers from NEBBinar on Low Delta T Syndrome

Question: What is the average cost for the valve? Payback data?
Answer: List Prices are available in the current Product Guide and Price list. Payback is dependent on the size of the facility along with the condition of the coils and the operating sequence of the plant and AHU control.
 
Question: Does Webview/Web Server require a Windows 7 / 64 bit platform? Is there an IPhone App?
Answer: The Webview/ Web server does not require Windows 7 it can be used with XP, and Windows 2000 platforms. Currently there is an optimized interface for mobile phones in web view but not an actual App.
 
Question: You could lower energy more if you measured the secondary fluid temp (like air in a AHU), but AHU controller is doing that, so much of the time, the algorithm isn’t stepping to keep the system out of waste zone, until BAS or AHU commands for maximum performance. Is my assessment incorrect?
Answer: If DT Manager is disabled, the Energy Valve will control to the flow setpoint determined by the DDC control signal (either via BACnet or wired analog signal) very similar to a Pressure Independent VAV terminal unit. If Delta T Manager is enabled and a DT setpoint is entered the Energy Valve will still control to the DDC flow setpoint as long as delta T is greater than 2 degrees below the entered DT setpoint. When DT drops at least 2 degrees below DT setpoint for 5 minutes, then DT Manager will become active. It will override the DDC and reduce the flow setpoint until the DT setpoint is reached. When the DT setpoint is reached, control will be released back to the DDC. DT Manager low limit flow setpoint is adjustable but can be set no less than 30% of the design flow of the coil. So, theoretically the DDC does not have to be at design flow for DT Manager to turn on to prevent operation in the waste zone.
 
Question: In a large system, where are the best places to locate these valves?
Answer: On large water coils, water to water heat exchangers and some tertiary loop applications.
 
Question: To install energy valve, should the chilled water pumps be of variable flow type?
Answer: Yes, ideally. But as long as differential pressures across the Energy Valve are maintained from a minimum of 5 to a maximum of 50 psid they will operate properly, even if “riding the pump curve” on non-VFD pumping systems.
 
Question: Is there still manual balancing with a system under this level of control, and if so implications of the controls valves in that process.
Answer: There can be manual balancing valves to balance coil flow where multiple coils are in parallel with one Energy Valve controlling them. And manual balancing valves may be used in very large systems to ensure that each lateral (riser) gets sufficient pressure from the pumps. But, manual balancing valves should not be used to try to literally balance the flow in a system. It is unnecessary and counter-productive with all PI valves.
 
Question: You talked about chilled water application and indicated the RTDs are for a finer temperature span. Would this work for two pipe systems using hot and chilled water?
Answer: Yes, the action of the DDC control loop would need to reverse depending on mode but the Energy Valve does not care. It will measure and report delta T and heating or cooling BTUs appropriately. This is because when you configure the EV, you tell it where the EV is located (supply or return of the coil). It knows from that information if supply temperature is less than return it is chilled water. If supply temperature is greater than return it is heating water. And as a result, it will calculate BTUs heating or cooling appropriately.
 
Question: Could you go over valve operation modes more in depth?
Answer: (1) Pressure Independent w/DT Manager enabled – provides PI operation (flow control based on DDC signal as flow setpoint) and DT Manager ensuring minimum DT is maintained. (2) Pressure Independent w/DT Manager disabled – provides PI operation (flow control based on DDC signal as flow setpoint) with no DT Management. (3) Position Control w/DT Manager – DDC signal is the valve position setpoint. No PI flow control. DT Manager maintains delta T setpoint by reducing the valve position if necessary (minimum valve position for DT manager is adjustable but cannot be set less than 30% open). (4) Position control only. Operates exactly like a regular pressure dependent control valve. In all 4 modes of operation, BACnet communication and all flow/temperature/Btu readings and calculations are still reported and stored.
 
Question: How much space is required to install this valve (i.e. is there a straight pipe requirement at the inlet to the flow body)?
Answer: Yes, 5 pipe diameters to the inlet but 0 pipe diameters to the valve outlet.
 
Question: Does this equipment need to be connected via communications all the time or is there a way to get analog data I/O at the unit?
Answer: Yes, by connecting directly to the valve with a PC to read real time data and also to download stored data from the Energy Valve (up to 13 months). Also there is a Data Analysis Tool (available free of charge) than can help analyze this data with Microsoft Excel.
 
Question: What is the current lead time when ordering?
Answer: Most all orders can be fulfilled within five business days.
 
Question: Is the 2% accuracy related to an actual flow reading, or 2% of the full-scale range of the flow transmitter?
Answer: The accuracy of the flow sensor is +/- 2% over the range.
 
Question: What is the sample rate for trending over an hour?
Answer: 30 seconds. This is the sample rate for the week’s data as well and 2 hours is the sample rate for the monthly data.
 
Question: What if the DDC system wants more flow to control SAT? Will the algorithm reduce the flow anyway?
Answer: If DT Manager is enabled AND a DT setpoint is entered AND DT tries to drop 2 degrees below the DT setpoint, then yes, DT Manager will turn on and begin to reduce the flow to re-achieve the DT setpoint. You can also enable and disable DT Manager from the DDC should this be a problem if you have a BACnet interface.
 
Question: What is the benefit of flow valve downstream verses upstream?
Answer: The Energy Valve will work on the supply to the coil or the return from the coil. However, in general, we recommend the control valve be installed on the return from the coil. That way, when the valve is closed, the coil remains pressurized to the same value as the supply pressure. If installed on the supply when the valve closes, the coil pressure will be the same as the return pressure. In some cases, this can be at or near atmospheric pressure. This may cause air to be injected into the system from the air vents on the coils.
 
Question: What is the accuracy of the flow sensor rated as (% of reading or range)
Answer: The accuracy of the flow sensor is +/- 2% over the range
 
 
 
© 2019 NEBB. All Rights Reserved
Website Design & Website Development by Americaneagle.com
NEBB ®
8575 Grovemont Circle
Gaithersburg, MD 20877
P: 301.977.3698 | F: 301.977.9589