## First Hour Rating For Storage-type Water Heaters * Purpose / Goal * Definition * Brief History * Opinions on First Hour Rating », 

### Maintain present structure ,, Alternative sizing descriptors * Address specific issues about proposed methods

## First Hour Rating For Storage=typeWater Heaters e 

### Purpose/ Goal fa 

### Definition 

## e Brief History fit 

### Opinions on First Hour Rating » 

### Maintain present structure »

### Alternative sizing descriptors 

### e

### Address specific issues about proposed methods

## Purpose/ Goal * Sizing information; a means for comparing different units * FTC Labeling: alternative to storage capacity * Single descriptor that embodies: ,, storage capacity ,, recovery capability

- heating input rate

- location of heat input 

# Purpose/ Goal e Sizing information; a means for comparing different units 

### e FTC Labeling: alternative to storage capacity 

### e Single descriptorthat embodies: » storage capacity » recovery capability

- heating input rate -location of heat input

## Definition An estimate ofthe maximum volume of "hot"water that can be supplied within an hour that begins with the water heater fully heated (i.e.., all thermostats satisfied) 

# Definition An estimate ofthe maximum volume of "hot" waterthat can be supplied within an hourthat begins with the water heaterfully heated (i.e.., all thermostats satisfied)

## Brief History * Repeated Test Procedure Revisions * Reasons Behind Revisions », 

### minimize impact of mixing and lab tolerances (thermostat and water inlet) via normalizing », 

### avoid overstated ratings », 

### avoid repeatability problem », 

### avoid understated ratings (test method not consistent with definition) 

## Brief History e Repeated Test Procedure Revisions 

### e Reasons Behind Revisions » minimize impactof mixing and lab tolerances (thermostatandwater inlet) via normalizing » avoid overstated ratings » avoid repeatability problem » avoid understated ratings (test method not consistentwith definition)

## Brief History Fist Hour Rating Is referenced by:

,, FTC: for size ranges intheir labeling program ,, HUD: FHA minimum water heater capacity requirement ,, Offered asaguideline inbuilding codes ,, Discussed inthe ASHRAE Applications Handbook ,, GAMA Directory shows howto use it ? IsFirst Hour Rating usedwithin manufacturer residential sizing guidelines? 

## Brief History e Fist Hour Rating Is referenced by: » FTC: for size ranges in their labeling program » HUD: FHA minimum water heatercapacity requirement » Offered as a guideline in building codes » Discussed in the ASHRAE Applications Handbook » GAMA Directory shows howto use it ? Is First Hour Rating used within manufacturer residential sizing guidelines?

### Despite the noted references, First Hour Rating's popularity asa sizing descriptor isquestionable * New Construction ,, purchasing decision: usually builder ,, uses rules ofthumb that do notfactor in First Hour Rating 

### * Replacement market ,, purchasing decision: plumber and/or homeowner ,, again, First Hour Rating probably is not considered ,, selection is often driven bythe needto restore hotwater service quickly; likelyoutcome:

- same size/type of unit as presently installed

- closest match from available stock

- one size higher if presently having excessive runouts 

### Despitethe noted references, First Hour Rating's

popularityas asizing descriptor is questionable • New Construction » purchasing decision: usually builder » uses rules ofthumbthat do notfactor in First Hour Rating • Replacement market » purchasing decision: plumberand/or homeowner » again, First Hour Rating probably is not considered » selection is often driven bythe need to restore hotwater service quickly; likely outcome:

- same size/type of unit as presently installed

- closest match from available stock

- one size higher if presently having excessive runouts