The Publish 360

The World Best Stories
Sizing Domestic hot-water heater Systems

Sizing a domestic hot-water heater system constitutes an kind quite a particular science. for love or money aside from alittle residential system, you can’t simply attend a table or chart and make your selection. Codes provide only generalizations like “Hot and cold water shall be supplied to all or any sinks, lavatories, showers, etc.” they are doing not indicate what proportion predicament is required. Codes do, however, give information about pipe materials and minimum and maximum flow rates to fixtures (combined cold and hot water), and that they address safety concerns like maximum temperatures and required safety devices.

A number of things must be considered when sizing a system, and knowledge plays an enormous part. Every system is different, therefore the path that results in final selection is additionally different. Two buildings are often physically an equivalent (i.e., have an equivalent number of fixtures), but the number of water required could also be different if the buildings are going to be occupied by different groups of individuals . as an example , an apartment house for older people would have a special use profile than one that primarily houses families.

Information Gathering

So how does one size and choose a domestic predicament system? the primary step is to gather the knowledge needed to define the system parameters and narrow the choices . a number of the knowledge are going to be readily available, but some may require a touch digging. the subsequent may be a fairly long list of questions, but not all of them apply to each situation.

  • Where is that the building located?
  • What code or codes should be followed?
  • Do any local amendments apply?
  • Does the building’s owner or operator have any unusual requirements?
  • Are there the other predicament systems within the building?
  • what’s the world used for?
  • what percentage plumbing fixtures will there be?
  • What quite fixtures will there be?
  • Who are going to be using them?
  • Are there any high-usage fixtures, like hot tubs or laundry machines?
  • Are there plans to expand the power within the future?
  • Will there be a laundry or health spa area?
  • If so, what percentage areas are going to be used simultaneously?
  • what proportion space is out there for the system?
  • What energy sources are available? (Natural gas? Propane? Steam? Hot water? Fuel oil? Heat reclamation?)
  • Which energy source is most economical for the location?
  • Where within the building will the equipment be placed?
  • Will flues or combustion air be a drag , thanks to the location?
  • what’s the cold water source?
  • what’s the water hardness?
  • Will the system be inactive for long periods of time?


With the knowledge you’ve got gathered, you’ll calculate the load (i.e., recovery rate and storage volume) required for the power . once more , this is often not an easy process. There are several methods for calculating the load of a building. One method isn’t always better than another, although one could also be better fitted to the actual application. Several methods are available; most of them are from the American Society of Plumbing Engineers ( ).

Heater System Selection

With the demand and storage volume established, subsequent step is to pick the sort of kit to be used. this is often another point at which experience plays a key part. Several factors need to be weighed-the most practical or economical fuel source, expandability, available space, location with reference to roof and wall locations, heater efficiency, budget constraints, and owner preference are just a couple of of them. Add the varied sorts of equipment available, and you’ll find that equipment selection are often a somewhat intimidating venture. the simplest approach is to deal with each of the parameters, and narrow the chances to at least one or two that fit the appliance . Make the ultimate selection supported your experience.

Safety Devices

All domestic hot-water heater systems are required to possess safety devices. Water heaters and storage tanks are required to possess temperature and pressure (T&P) relief devices, which are intended to stop catastrophic failure of the vessels. If the system fails, T&P devices relieve pressure thanks to expanding water inside the tank and predicament system. When the building service features a backflow prevention device thereon , often the code requires a thermal expansion tank on the cold water inlet to the heaters; this compensates for the expanding water within the system. It doesn’t affect the operation of the T&P safety valve .

Many codes also require that the utmost temperature allowed at a rest room or shower to not exceed 115°F. To properly maintain the temperature, a thermostatic mixing valve is required. The thermostat on the heater most frequently isn’t considered a suitable temperature regulatory device. the blending valves are often located at a central point or at the individual fixtures.

Experience is significant to properly sizing a domestic hot-water heater system. there’s just one thanks to get that experience-by trying new things. once you size a system during a building that’s a touch different from your norm, try a few of various methods to calculate the dimensions . ask a number of your coworkers or perhaps a sales representative. check out the ways different approaches to an equivalent problem yield different results. you’ll be surprised to find out that a tried-and-true method is simply not the simplest fit the system.

Julian Arhire may be a Manager with – may be a leading provider of online HVAC eTextbooks and course materials. Our online catalog is straightforward to navigate and search, and every one products have an image and an outline . If a customer has any questions on a product, they will call and speak with one among our product experts. Our mission is to supply the simplest prices anywhere to our customers.

Leave comment

Your email address will not be published. Required fields are marked with *.