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Author:
rppgen (MA)
Dear Folks
Please advise on my situation.
I have a 5gpm tankless rinnai water heater (2004) with water pressure drop when HWH is ON.
Situation 1:
Level 1: Faucet = ON
Level 2: Faucet = OFF
Outcome: Water pressure = OK
Situation 2:
Level 1: Faucet = ON
Level 2: Faucet = ON
Outcome:
Level 1 Pressure = Major drop
Level 2 Pressure = Minor drop
Hot water temp = OK
Situation 3:
Level 1: Faucet = ON
Level 2: Shower = ON
Outcome:
Level 1 Pressure = Major drop
Level 2 Pressure = Minor drop
Hot water temp = OK
Situation 4:
Level 2: Faucet = ON
Level 2: Shower = ON
Outcome:
Level 2 Faucet Pressure = Minor drop
Level 2 Shower Pressure = Minor drop
Hot water temp = OK
Situation 5:
Level 2: Tub = ON
Level 2: Shower = ON
Outcome:
Water Pressure = MAJOR DROP
Hot water temp = OK
Situation 6:
Level 1: Washer Dryer = ON
Level 2: Shower = ON
Outcome:
Level 2 Shower Pressure = MAJOR drop
Hot water temp = DROP
Situation 7:
Level 1: Faucet = ON
Level 2: Shower = ON
Outcome:
Level 1 Pressure = NO CHANGE
Level 2 Pressure = NO CHANGE
HWH = OFF
Situation 8:
HWH = ON, Water supply to house = DISCONNECTED
HWH output is toggled every 30 seconds.at HWH
Outcome:
Hot water temp had 20 second gap in regenerating hot water temp.
Folks
Please advise...
Qs 1) Should i perform any other additional tests
Qs 2) What is the cause? Does HWH need more capacity?
RPP
Edited 1 times.
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Author:
hj (AZ)
By HWH "off" I assume you mean you The power is turned off. If so, the results of #4 and #7 are ambiguous because the power only controls the gas burner, NOT the water flow, and therefore the pressures should be the same. The rest of the results are also strange, because the pressure in "level 2" should always be less than level 1 because of the difference in elevations.
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Author:
m & m (MD)
"5 gallon" is rather ambiguous in terms of tankless water heater output because that is relative to temperature rise. What is the maximum BTU input of the unit?
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Author:
m & m (MD)
Your winter-time incoming cold water temperatures are probably 40* or thereabouts. A comfortable shower or tub will need about 100-103* water temp., requiring ~60* rise in temperature. Your unit will supply those winter-time hot water temperatures but at a reduced gpm production.
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Author:
packy (MA)
yeah, and if you want to hand wash dishes at the max temperature allowed by law (125), now you are looking at 85 deg tenperature rise.
this is why i don't recommend tankless water heaters for anyone around northern new england.
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Author:
rppgen (MA)
thanks folks.
but how does this explain water pressure drop?
Edited 1 times.
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Author:
KCRoto (MO)
Rinnai doesn't sacrifice temperature for water volume. If the incoming water temperature is lower than normal, your output volume will be reduced as it takes more heat and time to get the same water to the final temperature.
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