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Thread: Stiebel Eltron Tempra 29 Plus, issue with shower

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    DIY Junior Member Atticweb's Avatar
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    Question Stiebel Eltron Tempra 29 Plus, issue with shower

    Hope I have the right place, I'm new here.
    Just had installed the electric tankless model in title of this post, and upgraded my electrical supply to 200 amp to handle it. Costly but various reasons for doing so (venting issues, etc.).
    All work was well done. Everything works fairly well, minus wait times for hot water and occasional cold shots when someone else turns on a faucet.
    Main issue follows with the pertinent facts; I've seen other similar issues here with showers, but I believe mine may be different.
    Facts are this: one shower and one sink in one bathroom, upstairs, both off the same hot water supply line.
    Sink is within couple degrees of set temp on unit (set to 108° for example, get at least 106°).
    Shower, the supply for which breaks off same pipe as sink, is 20° colder! Luke warm at best.
    The SE unit adjusts pressure to the temp requested; that is, to keep desired temp, it reduces gpm.
    I have an old Moen shower faucet/mixer type, over 30 years. I'm pretty sure it must be mixing cold with the hot and basically not "talking to" my new tankless. I don't think the cartridge has anti-scald it's so old, but it might. Seems to me if you can set your heat at the unit, you don't need the anti-scald. Also the "posi-temp" feature seems like it might interfere with what the tankless is attempting to regulate.
    I've found no help online or anywhere else so far.
    I was all set to order a two-valve non-mixing Kohler unit to replace the mixer, as I'd like to be able to control just hot, etc., myself without the mixer deciding what's best for me and fighting with the heater.
    To keep already high expenses down, a plumber just convinced me to just replace the cartridge and thinks that might do it.
    Any thoughts or suggestions would be helpful, and also any discussion of these mixer features vs. tankless flow control and temp setting may be helpful for others.
    Thanks for your time.
    Will James

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    DIY Junior Member Atticweb's Avatar
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    Something I forgot to mention. I left the old tank for now, just put shutoffs on both the cold and hot lines to it. Swapped out the tankless for the tank this morning to get a hot shower. No problem. So, don't see how it could be the mixer (shower faucet) if not affected when going back to the tank. This is one for Sherlock seems to me. Help?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Does your shower have an old showerhead or one of the newer, flow-restricted ones. An old one may just try to flow way too much volume, and the tankless can't keep up. Also, if it is a single-handle valve, it may have a limit cam/screw/lock and that is preventing it from going to all hot. Buffalo can have some very cold inlet cold water temperatures...what does yours measure? For most people, an electric tankless, except as a single point of use item, is usually inadequate, as their flow rate is way too small for some uses.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Atticweb's Avatar
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    Thanks for the reply jadnashua. Removed limit cam, no better. Yes the inlet water is cold, I live in Buffalo, but I researched this thoroughly before buying and it works great including unrestricted high flow in basement tub. Does slow up a bit sometimes to keep temp requested. I realize I can't raise temp to 120° and get great flow, just not a 20° drop from same hot water supply at reasonable level. Went with the 29+ instead of 24+ which was ok for this region to get the three heating modules. I'm not expecting perfection, but it's made to handle this temp increase (50° to 110° e.g., 60° rise). Can't keep my hand under the sink hot only a few feet away. Think if I could swap out the old Moen standard single with same (may be letting cold in, very old), might do it; but posi-temp and balanced control is going to mess with the unit which modulates and sets high temp itself. Hope that made sense. Thanks again, see what I can do!

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    Retired Defense Industry Engineer jadnashua's Avatar
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    FWIW, I've measured incoming water temp here in southern NH at 33-degrees, so if it's capable of 60-degree rise at full flow, that's not even body temp. Most single handle shower valves don't have a means to adjust the flow rate, so it's trying max all the time. Once you direct it to the shower, that has some flow restriction (if it is a recent head, otherwise, who knows). A vanity faucet is typically restricted to about the same as a showerhead (if not lower). Could be an issue with that valve...just don't know enough about the inner workings.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Atticweb's Avatar
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    Incoming is 50° now. I just don't see a 20°drop from the sink same supply a few feet away. Was thinking about putting in Kohler two single valves (just turn cold off) but plumbers don't seem to want to install it.
    Also if shower is restricted (I'm getting same results tub/shower), wouldn't it bring it down to about the sink and I should get same temp?
    Might be of interest: http://www.tanklesswaterheatersdirec...ltronspecs.htm
    Last edited by Atticweb; 12-09-2013 at 07:13 AM.

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    In the trades Dana's Avatar
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    The pressure drop at full flow across a tankless is substantial even when it ISN'T restricting to maintain temp, and which can interact with shower mixers.

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    DIY Junior Member Atticweb's Avatar
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    Which is why I'm thinking about swapping out the mixer with something like this that I can control.
    Name:  KohlerJob.jpg
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    Also... doesn't take me long - finally went downstairs and shut off the cold water supply. Bingo, immediate hot water from tub (tankless). It's the mixer.
    Last edited by Atticweb; 12-09-2013 at 11:27 AM. Reason: more info

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    DIY Senior Member lifespeed's Avatar
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    I have not encountered any issues using a thermostatic shower valve and a tankless (natural gas) water heater. The mixer adjusts the balance between hot and cold. Yes, the tankless sees flow variations but they can deal with this.

    If your mixer does not allow you to close the cold supply nearly shut this would, of course, cool the temperature. It is not clear to me that a "dumb" mixer is required to fix your problem. Perhaps just one that isn't "broken" or a flawed design that can't close the cold side.
    Lifespeed

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    DIY Junior Member Atticweb's Avatar
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    Thanks for that info lifespeed. So you're saying that if a mixer is working properly, and you turn it all the way to hot, there is absolutely no cold mixing in? I thought I read that such valves need both hot an cold "pressure" to work. Please clarify, thanks much.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The spool valve closes when the incoming supplies are not equal, it isn't about what is actually flowing, it's the available pressure. So, if you have small lines, and someone say flushes the toilet, the cold water pressure drops, and the spool valve moves to reduce the hot going out, trying to maintain the balance. So, it's pressure, not flow (unless it gets extreme to a trickle) that those valves work on. If the plumbing was ever done with a permit and inspection, it would not pass if it did not have an anti-scald valve newly installed. The fact you can buy them does not mean it can legally be installed for a shower (maybe for a tub only).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Atticweb's Avatar
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    Quote Originally Posted by jadnashua View Post
    If the plumbing was ever done with a permit and inspection, it would not pass if it did not have an anti-scald valve newly installed. The fact you can buy them does not mean it can legally be installed for a shower (maybe for a tub only).
    Is that nationwide or local?
    I do not want the spool valve to do this: "reduce the hot going out" under any conditions. Again, I control that at the tank. Anti-scald is accomplished at the unit; I have it set to 210 right now and the cold shut off. Loses a few in cold pipes and comes out adequately hot (not extreme as the unit would reduce my flow to keep temp as requested at unit). Ergo, no possibility of "scalding" anything at any time. This code must have been written without considering this tech. It seems as though everyone is talking gas models (wherever I go inc local plumbers), not electric, and don't seem to be familiar/experienced with Stiebel Eltron whole-house units. Thanks for any more thoughts going forward. Now that I've shut off the cold completely to upstairs (which is slightly annoying), I can set the temp of my shower exactly so I've just gained a bit of time, still have to decide on the course of action.

    As far as the term "dumb" valve that I propose purchasing and installing (several are available, looking at paying more for Kohler for quality and because I'm from Milwaukee), I prefer the valve to be "dumb" and me to be "smart" instead of the valve being "smart"... think I'm already clear on that. As someone posted elsewhere, I learned early how to turn the knobs and mix the water. Thanks for all responses.
    Last edited by Atticweb; 12-10-2013 at 08:09 AM.

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    DIY Senior Member lifespeed's Avatar
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    Quote Originally Posted by Atticweb View Post
    Is that nationwide or local?
    I do not want the spool valve to do this: "reduce the hot going out" under any conditions. Again, I control that at the tank. Anti-scald is accomplished at the unit; I have it set to 210 right now and the cold shut off. Loses a few in cold pipes and comes out adequately hot (not extreme as the unit would reduce my flow to keep temp as requested at unit). Ergo, no possibility of "scalding" anything at any time. This code must have been written without considering this tech. It seems as though everyone is talking gas models (wherever I go inc local plumbers), not electric, and don't seem to be familiar/experienced with Stiebel Eltron whole-house units. Thanks for any more thoughts going forward. Now that I've shut off the cold completely to upstairs (which is slightly annoying), I can set the temp of my shower exactly so I've just gained a bit of time, still have to decide on the course of action.

    As far as the term "dumb" valve that I propose purchasing and installing (several are available, looking at paying more for Kohler for quality and because I'm from Milwaukee), I prefer the valve to be "dumb" and me to be "smart" instead of the valve being "smart"... think I'm already clear on that. As someone posted elsewhere, I learned early how to turn the knobs and mix the water. Thanks for all responses.
    So, you're having a problem with an old, broken, bad-design or scaled-up valve that won't shut down the cold. Then you predict that new pressure-balanced and/or thermostatic valves are going to have a design flaw where they can't shut down the cold water? In your application the thermostatic is likely more appropriate than the pressure balanced. Lacking evidence to the contrary I don't share your conviction that the only valve that will work is 20 year old tech.

    Perhaps this evening I'll turn the temperature down on my tankless to 105F and see if my Toto thermostatic shower valve maintains the 104F setpoint . . .
    Lifespeed

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    DIY Junior Member Atticweb's Avatar
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    I'm not predicting anything. Just going by what I read, which is often contradictory and/or irrelevant to my situation. Why do you recommend the thermostatic? This is the kind of suggestion with fact I'm looking for. Valve looks a bit pricey. I see you're in California, pretty sure you won't have an issue with temp rise at full flow.
    Last edited by Atticweb; 12-10-2013 at 09:49 AM.

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    DIY Senior Member lifespeed's Avatar
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    Quote Originally Posted by Atticweb View Post
    I'm not predicting anything. Just going by what I read, which is often contradictory and/or irrelevant to my situation. Why do you recommend the thermostatic? This is the kind of suggestion with fact I'm looking for. Valve looks a bit pricey. I see you're in California, pretty sure you won't have an issue with temp rise at full flow.
    Thermostatic because it does not reduce pressure to accomplish "pressure balanced" when one side of two inlets experiences a pressure drop. Pressure-balanced are the cheaper and original anti-scald. Thermostatic are much nicer to use with set-and-forget behavior.

    California warm water vs NY cold water, electric vs natural gas, in the end none of this really matters with regard to your valve. At the end of the day you need a valve that can put out, say, 105 degree water with only 108 coming in the hot side so it's range must include full hot.

    Yes, the Toto valve is expensive but does work really well. There are other options (Grohe for example), although I don't know if they're much cheaper. Toto replacement cartridges are inexpensive, which is NOT the case for many of the products you'll find at Home Cheapo.

    I'll try the experiment I mentioned as it is really easy, and confirm whether or not the Toto valve can operate as desired.

    Edit: I know thermostatic valves are required to be capable of completely shutting off the hot water if cold pressure is lost entirely (safety). The question is: can they do the same in the opposite direction?
    Last edited by lifespeed; 12-10-2013 at 10:41 AM.
    Lifespeed

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