this presentation is posted for public use. aceee does not endorse
TRANSCRIPT
This presentation is posted for public use.
ACEEE does not endorse any product or service.
ACEEE accepts no responsibility for any facts or claims this presentation may contain.
Section 4: Domestic Hot Water Systems
Domestic Hot Water Assessments in Multifamily
Buildings
Section 4: Domestic Hot Water Systems
What We Will Cover
DHW in Multifamily Buildings
• How is it produced?
• How is it distributed?
• How is it controlled?
• What are the common problems?
• What improvements can be made?
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Section 4: Domestic Hot Water Systems
• Tankless Coil or other Combined System– Single unit produces hot water or steam for heat and hot water for potable use
• Separate Unit– There are two separate units – one for heating and one for DHW production
Methods of Production
Options
Section 4: Domestic Hot Water Systems
• Indirect Water Heater (Indirect Fired Unit)– There is a separate unit but no fire, water from heating boiler is circulated through coil located in an additional storage tank, or through an external heat exchanger.
• Instantaneous or On Demand Water Heater– A separately fired unit that does not have any storage capacity. The unit is turned ON when there is a demand
• Seasonal Switchover– Combi system during heating season, dedicated unit in non‐heating season
Methods of Production
Section 4: Domestic Hot Water Systems
Separate Gas Fired/Electric DHW Maker with Built‐in Storage Tank
Section 4: Domestic Hot Water Systems
Cracked liner
Section 4: Domestic Hot Water Systems
Galvonic Corrosion
Section 4: Domestic Hot Water Systems
Gas/Oil Fired Unit with Separate Storage Tank
Section 4: Domestic Hot Water Systems
Tankless Coil in Scotch Marine Steel Boiler
Seasonal efficiency loss of as much as 35%!
Section 4: Domestic Hot Water Systems
Scale on Water Side of Heat Exchanger• Acts as an insulator• More heat lost through chimney
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Heating System Efficiency
Section 4: Domestic Hot Water Systems
Consider Adding Storage
Section 4: Domestic Hot Water Systems
Multiple tankless coils in boiler
Whenever you have multiples of anything,pay attention to the fact that flow seeks the path of least resistance
Piping Practice
1st Out
1st In
Section 4: Domestic Hot Water Systems
First in First Out ‐WRONG
Boiler
Section 4: Domestic Hot Water Systems
First in Last Out ‐ RIGHT
Boiler
Section 4: Domestic Hot Water Systems
What the…
Section 4: Domestic Hot Water Systems
Indirect‐Fired Water Heater
Dual Coil for Solar
Thermal Preheat
Section 4: Domestic Hot Water Systems
Indirect‐Fired Water Heater
This pump circulates boiler water in the unit
Section 4: Domestic Hot Water Systems
Indirect Water Heater (piping with priority control)
Section 4: Domestic Hot Water Systems
Tankless Water Heater (Instantaneous)
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Section 4: Domestic Hot Water Systems
Flat Plate Heat Exchangers
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Brazed Flat Plate
Section 4: Domestic Hot Water Systems
Benefits of Flat Plate Heat Exchanger
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Section 4: Domestic Hot Water Systems
Pump Operation
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Section 4: Domestic Hot Water Systems
Electronic Mixing Valves
Section 4: Domestic Hot Water Systems
Is this joke?
Section 4: Domestic Hot Water Systems
Boiler Replacement??
Section 4: Domestic Hot Water Systems
DHW Distribution Types
Trunk & Branch System
• Standard type of system in smaller buildings (4‐15 units)
Recirculation System
• Standard type of system in larger buildings (>15 units)
Section 4: Domestic Hot Water Systems
Trunk & Branch Distribution
Section 4: Domestic Hot Water Systems
Recirculation System
Section 4: Domestic Hot Water Systems
DHW Circulators & Controls
Section 4: Domestic Hot Water Systems
Domestic Hot Water Recirculation– According to NYSERDA, 6 ‐11% of DHW energy
consumption can be saved by controlling the DHW circulation pump
– However, some mixing valves require constant circulation for proper operation
Domestic Hot Water
Section 4: Domestic Hot Water Systems
DHW Controls
Timers
Demand DHW Boiler Controls
Aquastats
Packaged Pump Controls
Demand Pumping
Boiler Control Expansion Module
Section 4: Domestic Hot Water Systems
Need recirc loop?
