Tips for restaurant hot water systems

Today restaurant designers or engineers must use innovative strategies that will deliver the service of hot water as efficiently as possible, while meeting the increasingly challenging regulatory codes and user expectations. This is fundamentally a four-step process: (1) reducing hot water use of equipment and faucets while maintaining performance; (2) increasing the efficiency of water heaters and distribution systems; (3) improving hot water delivery performance to hand washing sinks; and (4) incorporating “free-heating” technologies like waste heat recovery and solar pre-heating. Through high-efficiency system design and equipment specifications, the potential exists to cut the energy use for water heating restaurants in half.

Hot water is the life-blood of restaurants. Therefore, it is essential to design the water heating system to meet the needs of hot water using equipment under peak operation.

Restaurant operators expect: unlimited access to hot water; immediate hot water delivery to faucets and equipment; a system that is reliable; and minimal investment and operating costs. Unfortunately, owners’ expectations are rarely met.

Designing in a reverse direction, starting with the hot water using equipment and moving back to the water heater, is an effective thought process to achieve high system efficiency and performance in restaurant applications. Reducing hot water consumption not only results in lower water and sewer costs; it is the most effective way to reduce water heating energy. This simple tactic is overlooked as operators do not receive a dedicated bill for hot water use.

Step 1: Designers should start by specifying high-performance equipment and accessories that use less hot water. The best location in the kitchen to achieve savings is the dish room. Reducing the water use per rack of the dishwasher and flow rate of the pre-rinse spray valve is the foundation of an optimized hot water system.

Step 2: The distribution system is the second target. Delivering hot water more efficiently yields permanent energy savings and improved system performance. Once the fixtures and the sanitation equipment are specified, the placement of sinks and equipment in relation to the water heater is a key factor to the efficiency and performance of the distribution system.

Step 3: The heart of the system is the water heater. If natural gas is the energy choice, specifying high-efficiency condensing units, either storage or tankless, is imperative.

Step 4: Before the hot water system design is finalized, consider integrating pre-heating technologies.

Step 5: Proper installation and simple monitoring equipment can play an important role in commissioning and maintaining the system. Verify that the blueprints enable the contractor to build to the specifications. Requiring that digital photographs be taken of the entire hot water distribution system (before it is concealed by drywall) is one way to secure pipe layout and insulation specifications.

Look for Part II, which will deal with distribution systems, in HPAC March. <>

Design Path for Savings

Specify efficient hot water using
equipment and fixtures.

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Specify branch and twig sizing and pipe insulation to meet plumbing codes and satisfy water flow requirements including: time to tap, volume, temperature, and water velocity.

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Optimize position of hot water using sinks and equipment in kitchen, restroom, bar, etc.

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Size and optimize the layout of distribution (trunk) line(s) based on the type of
distribution system chosen.

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Specify and centrally locate high-efficiency water heater(s) and, if applicable,
point-of-use tankless heaters.

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Consider pre-heating (free heating)
technologies like solar and waste heat recovery.

Track hot water use by placing a water meter on the supply line to the
water heater.

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Commission hot water system and
set thermostat to meet restaurant requirements.