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  1. #1
    Join Date
    Jan 2008
    Posts
    1

    Default Inconsistent water temp with tankless heater

    I have a new tankless water heater which provides plenty of hot water as long as the flow is high enough. However, if only a small flow of hot water is needed, the heater will either not kick on or cycle on & off giving inconsistent temperature. Isn't there a solution for this involving a circulating pump and controls?

  2. #2
    Join Date
    Aug 2007
    Posts
    443

    Default Re: Inconsistent water temp with tankless heater

    It's my understanding that these units require at least 1/2 gallon per minute water flow for the heater to kick in & produce hot water; just a trickle from the faucet will give you cold water.

    I don't know what the remedy is; perhaps you can contact the mfg to see if they have a fix, or the unit can be adjusted to kick in more quickly.

  3. #3
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Inconsistent water temp with tankless heater

    I agree with JacktheShack .... there has to be a higher flow than a trickle at first use.

    The other thing is a circulating pump would have the unit on all the time .... defeating the purpose of only being on when needed.

  4. #4
    Join Date
    Feb 2008
    Posts
    1

    Default Re: Inconsistent water temp with tankless heater

    We have a similar issue with our tankless water heater. We've had it installed for about 2 years when we first moved into our house. We do enjoy it but it has it's quirks. The tankless water replaced about a 25 year old tank water heater and it's located less than 3 feet from the bathroom and kitchen (they share a wall). Our house is about 58 years old and has galvanized pipe but the new water heater is connected via PEX to the system.

    Our problem is that when you first turn the water on in the shower it's nice and hot, but after about a minute the temperature lowers enough so that it's not that nice hot shower that you want on a cold morning. When someone else uses the sink in the bathroom for example and runs cold water, the shower water will get hot again. Then will get back to not being that nice and hot temperature when the sink is turned off.

    We have a low flow shower valve because I don't think you could buy anything different here in CA. One more thing is that we never have to turn on any cold water when heating the shower water. It's almost like the hot water is being diverted somewhere else in the hot water pipes.

    Any suggestions?
    Last edited by thxcolm; 02-15-2008 at 06:46 PM. Reason: added info about how tankless water heater is connected to the system

  5. #5
    Join Date
    Feb 2008
    Location
    Memphis, not Egypt
    Posts
    183

    Default Re: Inconsistent water temp with tankless heater

    Sounds like a problem with the volume control? Have you run a code check on the unit. Has this always been like this or is it new? Is there a change in your thermal rise necessary to bring ground temperature water to the desired hotness? Is this a seasonal problem? What brand is this animal? or it could be blah blah blah or maybe ists just dfkjkldfjklsa;adsf;lkjasdf;lkj,

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