The Tank › recovery numbers
- July 24, 2006 at 9:13 pm #5084johnr60ParticipantI’m trying to intelligently replace a lowboy electric water heater (limit 35 in high, 28 dia). Reliance 606 30 gal shows a 20 gph recovery with 9000 watts. Their mobile home lowboy shows 44 gph with 3800 watts ??? I like thew AO Smith ELJC20 but it shows a recovery of 11 using 6000 watts! Can anyone decipher or suggest a heater. Marathon wont fit.July 25, 2006 at 1:24 am #5085Larry WeingartenParticipant
Hello: I’m guessing you do not really have an apples to apples comparison. Looking in my Rheem book it states that a 4500 W element will heat 21 gallons per hour through a 90 degree temperature rise. It really doesn’t matter which manufacturer you use, that amount of heating is what you get with that power consumption (at 240 volts).
Unless you’re talking about a commercial heater, you don’t see wattage over 6000, so something doesn’t line up with the 9000 W heater. Look for “recovery in gallons per hour @ 90 degree rise” when comparing heaters. If you were comparing different size heaters, the “first hour rating” would be useful.
Hope that is less rather than more confusing :D.
Yours, LarryJuly 25, 2006 at 9:19 am #5086johnr60Participant
Thanks for the quick response.
Silly as it seems those Reliance numbers are as I quoted. Rheem shows a recovery formula of wattage/2.42 x 90 which makes sense to me. Recovery then is simply a function of wattage. If the tank then will supply sufficient water for your longest job–say a long hot shower and the outlet always draws the hottest water, then the answer to watts seems to be How many minutes do you want between showers?
Do you have a comment on side inlet and sediment?
Relaince has a 2 gal tank with a 4400watt element. Got any idea what the constant output temperature of that water would be?July 27, 2006 at 5:16 pm #5098energyexpertParticipant
4500 watts will heat about 30 gallons of water 60 F increase per hour. If inlet is 50 F, outlet will be 110 F which is about the minimum for shower temperature. So once you empty the heater of hot water, a five minute shower of 3 gallons per minute means you will need to wait 25 minutes to start the next shower.
A lot of WH nameplates will list for example “upper- 4500; lower-4500; total- 4500.” This means the lower thermostat is “slaved” to the upper thermostat. The upper thermostat supplies power to the upper element until the upper thermostat is satisfied. Then the upper thermostat takes power away from the upper element and sends it to the lower thermostat. So only one thermostat can supply power to its element at a time.
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