Hello all,
I'm looking at metering a new construction building with a single controller. The specific controller that I'm looking at has the capability to monitor each individual end use (Lighting, Plug Loads, HVAC, water, gas, etc.). However, I'm also trying to minimize the cost of the overall installation price. After much thought I've come to the conclusion that I need to minimize the amount of CT's (current transducers) that I'll be using when metering the loads coming off the distribution panel boards.
My question is can I meter everything on a distribution board except one specific end-use, say HVAC for example, and have the controller programmed to calculate the difference in the main power usage and all the metering loads to back out the remaining loads (HVAC loads) and still obtain the advanced energy metering credit? This will still provide the energy usage of multiple air conditioning units and will reduce the cost of CT's as each unit will require 3 each.
This is my first post and I am new to LEED to I apologize in advanced if my question is not clear.
Thanks!
Erik G.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
January 12, 2015 - 10:25 am
Deriving energy use by subtraction is a viable method for metering by end use.
The potential issue I see with your example is that "HVAC" is not an energy end use. HVAC can include space heating, space cooling, fans, pumps, etc. which are end uses. You are required to have metering in place that will enable you to determine the energy use by end use for each end use that uses more than 10% of the total energy consumption.
The key to cost effective metering starts with organizing the panel boards by energy end uses. Trying to create the necessary meters within mixed boards can be very difficult and expensive.
Erik Gutierrez
Mechanical DesignerC&J Technical Solutions and Services, Inc.
January 12, 2015 - 2:35 pm
Hi Marcus,
Thank you for your response. I have another question. Initially, I proposed metering all the power, water and gas usage that represents 10% or more of the total energy consumption. When metering the air conditioning, is it enough to measure the power consumption of the packaged gas/electric units? or will I actually need to measure the total BTU/hr (space heating/cooling) of the ac units?
Thanks again!
Erik G.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
January 12, 2015 - 3:19 pm
If they are more than 10% you will need to be able to separate heating, cooling and fan energy assuming the the RTUs impact all three end uses. It is not enough to meter the RTUs alone in most cases. There are often methods you can employ to meter energy use indirectly in this situation. If you meter the overall RTU energy use and the building control system can trend fan run time (and a % if they are variable speed) you could derive fan energy use and subtract that to get the cooling value.