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Domestic Gas Water Heater

This is a Savegas control install completed in May 2023 on a multi-family property with four separate buildings each having their own centralized gas water heater system. This case study below is on one of the fours buildings with 66 dwelling units and a three AO Smith 199,990 BTU Water Heaters all plumbed in parallel and a Grunfos return pump. We begin our process be gathering base-line data following the first 7 days of install. If the system is found to functioning well with no issues detected, a Savegas custom set-back energy schedule is created and based on actual demand and implemented.

Test A - The boiler system was functioning well when we installed the Savegas service and an initial 7-day base-week was collected. We found the water heaters were being staged, WH3 was set highest, then WH1 would kick in and WH5 was set the lowest which had the least runtime recorded. (The recorded therms being burned during base-week = WH1 19.10 therms/daily, WH3 26.52 therms/daily and WH5 10.88 therms/daily.)

Test B - Next steps were for our Support Team to work with the property and their service contractor to adjust the water heater to equal set points allowing the Savegas control to help even out the runtimes on the system. Once this adjustment was made, our commissioning team created and implemented a Savegas Control custom set-back energy schedule for the system based on actual hot water demand found within the base-week data recorded. The pink line in the data below depicts the Savegas energy control schedule. Raising temps between 118-119º for high demand periods and throughout the day since this building houses many tenants who work from home offices daily. Then lowering to 110-111º between 3am-5:30am when hot water demand is the lowest. After evening out the system runtime, and average overall energy savings reported on this water heater system is 11.38% when in a Savegas controlled environment. (The recorded therms being burned during Savegas control-week = WH1 18.24 therms/daily, WH3 18.02 therms/daily and WH5 13.81 therms/daily.)

Test Results: This property burns an average of 56.51 therms/daily of gas under standard operation. Under Savegas control, this property burns an average of 50.08 therms/daily which is 11.38% less gas. This calculates to a total of 195.56 therms saved per month and over 8400 therms saved a year.

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