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anti scalding mixing valve

maybemark
maybemark Member Posts: 1,131
1st i want to thank everone on here, most all of you have been a great help, i've acutually learned. Far from a professional.
My question today, most of you know i will be putting in a whn85 with a 40 gal dhw. In all of the piping shown in the manual, it shows a mixing valve at the tank as optional. I would like to hear from you guys, showld i put one in, or not? Is it true you loose some pressure with these valves? My old time plumber friend says don't do it, and just lower the boiler water temp to the tank.
I am also putting in a faster hot water system. It takes almost 2 minutes to get hot water to my shower.
I would very interested on what your thoughts are, and why you think this way.
thanks again
mark
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Comments

  • Gordy
    Gordy Member Posts: 9,514
    edited December 2014
    Raising tank temp, and mixing down extends usage. Keep tank min 135 to kill legionella bacteria. So mix down.

    By faster hot water system I assume you mean a recirculating line?
    Mark_72
  • maybemark
    maybemark Member Posts: 1,131
    So if I keep the tank at 135, are you saying to get a mixer?
    does these anti scalding valves reduce pressure?
    it uses the cold water line as a recirculating line, and has a pump at the tank, with a motion swich connected to it. Fred put one in for my friend, it works great
  • j a_2
    j a_2 Member Posts: 1,796
    I agree with Gordy…..If you do a recerc system be careful of cross connections
  • maybemark
    maybemark Member Posts: 1,131
    JA
    I'm sorry, but I don't understand about being careful,
    are you saying put a mixer valve in?
  • maybemark
    maybemark Member Posts: 1,131
    Gordy
    Am i getting myself into hot water with this faster hot water?
  • hot_rod
    hot_rod Member Posts: 15,040
    Yes, use a mix valve, for all the above reasons. Code requires 120F temperature to fixtures.

    Also read this journal regarding mix valves and recirc systems. It needs to pipe correctly to prevent temperature creep.

    http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_11.pdf

    As for pressure drop, If you use a valve with a 3 Cv, you get 1 psi drop at a 3 gpm flow rate. At 6 gpm expect about a 4 psi pressure drop. the more you flow thru a device the higher the pressure drop. Here is a chart for a 3 Cv mix valve.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • maybemark
    maybemark Member Posts: 1,131
    hot rod
    thank you
  • wogpa67
    wogpa67 Member Posts: 238
    mixing valves should be installed as a secondary safety on every water heater imo.
  • j a_2
    j a_2 Member Posts: 1,796
    Yes put a mixer in….My saying being careful is on a recirc. system,be careful of cross connections….You got a lot of sound advise here
  • Eric_32
    Eric_32 Member Posts: 267
    We always put mixing valves on indirect water heaters, as a safeguard.

    Say your check valve gets stuck open, and the tank heats every time a zone runs. May not be an issue most of the year with outdoor reset, but when it gets cold outside, the indirect could get pretty hot in there.

    I actually heard thru the grapevine, in MA we may be required soon to put a mixing valve on all tank type water heaters.
  • Tom_133
    Tom_133 Member Posts: 773
    I don't know about MA, but Vt has required them for a while now. It is a bit of a pain to install for some water heaters, and yes it drives up the cost of the install but it does help with the killing of Legionella and any possible scalding scenarios. I still think that on owner occupied that the customer should have the choice but all commercial and rentals should be required to have them, but thats my frugality driven opinion.

    To the OP, you may want to know what your local code dictates and not to sound snobby, just do a bit more research and make an informed decision. We've all been where you are and had to do the research to know more.
    Tom
    Montpelier Vt
  • jonny88
    jonny88 Member Posts: 1,139
    Always use them,my preferred brand is Caleffi I forget model number but it has a temp gauge.Again it just helps us to store water in tank at a higher temp.
  • maybemark
    maybemark Member Posts: 1,131
    I thank you all for your advice and thoughts. When i saw optional on the manual for a mixer, my thought goes, why spend the money, it's 2 adults living in the house, we can be careful. I have been doing alot of reserch before i purchased the boiler, and in the reserch, seen many youtubes, and most of the pictures i've seen, do not have mixers. This is why i brought this question to this site.
    Thanks all
    Mark
  • maybemark
    maybemark Member Posts: 1,131
    ja
    when you say cross connections, are you referring to the pipes being of 2 different metals? or refering to hot and cold. i am sorry if this sounds like a stupid question, but i am just verifying
    your right, i am getting alot of sound advice, and i appreciate all of it. This is a big part of my reserch, by asking questions
    thanks
    mark
  • j a_2
    j a_2 Member Posts: 1,796
    Yes between, hot and cold
  • j a_2
    j a_2 Member Posts: 1,796
    I read it as you were thinking of a recirculation system as well, that is where you need to be careful of cross connections...
  • maybemark
    maybemark Member Posts: 1,131
    ja
    please help me understand when you say, be careful. Am I creating something that is going to give me trouble? Are you suggesting that this faster hot water is a bad idea?
    Please help me understand
    thanks
    mark
  • j a_2
    j a_2 Member Posts: 1,796
    How you planing on making the hot water faster, not a normal term out here
  • maybemark
    maybemark Member Posts: 1,131
    well, it's a plumbing thing, not heating, so i can understand that it's not normal.
    I came across a very cool system, to bring your hot water up to your fixture quickly, without having a 3rd line, for a hot water loop.
    I had Fred my plumber install it at my friends house, and she loves it.
    I wait a long time, before I can take a shower, for the water to be hot enough, this just gets it to any fixture faster, without adding a loop (circulating return)
  • j a_2
    j a_2 Member Posts: 1,796
    Just curious, can u send spec. sheet….I am a Master plumber,
  • maybemark
    maybemark Member Posts: 1,131
    fasterhotwater.com
  • maybemark
    maybemark Member Posts: 1,131
    I am curious to have your thoughts about it. My plumber is old school, and he didn't think it would work, when the job was complete, even he was impressed
  • SWEI
    SWEI Member Posts: 7,356
    maybemark said:

    fasterhotwater.com

    Lots of similar options out there -- some with more efficient ECM circulators. Check out the B&G Autocirc line.

    Caution: Some jurisdictions (MA comes to mind) consider the pushing of cold water from the hot line into the cold line to be contamination.
  • maybemark
    maybemark Member Posts: 1,131
    SWEI
    I did check out several types, and this one seemed to be the most easiest, with only 1 pump, and able to turn the pump on, by just priming (turning on) the hot water for a sec. The whole house gets circulated then.
    I did not think of code, to be honest, and you might be right, that is something i shuld have considered
  • maybemark
    maybemark Member Posts: 1,131
    would the caleffi 521 series be a good mixing valve for me? I already purchased a temp gauge for the hot water.
    If you have others that you think might be better for me, please let me know
  • maybemark
    maybemark Member Posts: 1,131
    but the one i showed, gives fast hot water to everywhere in the house, not just that one sink, plus, how often do yu find electricity in a vanity cabinet?
  • j a_2
    j a_2 Member Posts: 1,796
    Hi I am a Mass. plumber and thats why I urged caution….We don’t as of my last reading allow that type…of system…We have a product approval section online availabe to the public…If its not listed we can’t use it…Hope I did not cause you any unnecessary worries…We do, require a recirc. or heat taped line on a hot water line over 100 liner feet….
  • Gordy
    Gordy Member Posts: 9,514
    edited December 2014
    It needs to be plumbed right with a return line3/8 from farthest point of use first of all . All I have is a little Laing with a built in tstat at the water heater actually it will gravity and work also. Water heater never kicks on from recircing.
  • maybemark
    maybemark Member Posts: 1,131
    hatterasguy
    my plumber hought the same thing, that no way could it work. He was very impressed when the install was complete.
    and my friend tells me, she used to wait forever to get hot water, she is so happy with it.
    I'm getting way off track. I am not trying to help his sales, I was just mentioning what I was putting in, for the purpose of the water mixer.
    I still would like to know peoples thoughts on what mixer i should use. Again, I already have a temp gauge, so, I won't need a combination mixer with gauge
    thanks
    Mark
  • j a_2
    j a_2 Member Posts: 1,796
    Pretty much all the same when it comes to mixers, for domestic hot water….I really like the idea of water being stored at 140, and mixed from there….Mass tells us hot water is not hot until its 120 and its to hot over 130….there are other conditions where the high temp. is variable….We have codes/laws for everything and its all available online, when I advise, its in a general way
  • Gordy
    Gordy Member Posts: 9,514
    The temp gauge is for domestic output
  • Gordy
    Gordy Member Posts: 9,514
    The big concern is elderly, and small children, disabled .
  • maybemark
    maybemark Member Posts: 1,131
    I am sorry i brought this up about that product. It was not my intent to talk about it
    I would just like to know what mixing valve would be good for me to purchase.
  • j a_2
    j a_2 Member Posts: 1,796
    Is your goal, comfort or conservation related? I am guessing both….The best way I know is with a third line installed..
  • j a_2
    j a_2 Member Posts: 1,796
    I looks like it does and I have always been a fan of B/G…I would say if the local code allows it then go for it
  • maybemark
    maybemark Member Posts: 1,131
    Again, i am sorry i brought it up, I'm not getting the answer I was hoping to get.
    If you have thoughts, or doubts, call the guy up, he's a real down to earth guy.
    I would like to know from you proffesionals, which mixer should i purchase?
  • Gordy
    Gordy Member Posts: 9,514

    j a said:

    Is your goal, comfort or conservation related? I am guessing both….The best way I know is with a third line installed..

    This unit appears to accomplish all of the goals without the third line and without any 120V requirement at the fixture:

    http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2013/10/A-439B.pdf

    Interesting device.
    Tempers cold water wondering why happens when some is getting a glass of water at another fixture when it's circulating

  • maybemark
    maybemark Member Posts: 1,131
    Gordy
    what mixing valve would you put in if you were doing the job?
  • maybemark
    maybemark Member Posts: 1,131
    the system i am getting, does exactly what Hat says, it's pumping the hot water out of the tank, and putting it into the old side lines, until it reaches a certain temp, then it stops.
    what water is circulating out of the hot side, goes back to the cold side in the hot water tank. It works
    my plumber put it in
    my friend is so happy.
    I don't even know why i turn on the hot water to wash my hands after, well, whatever i am doing. it comes out cold anyways. It's a habit to turn the hot on