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4 way mixing vs injection

that injection mixing woks well if properly piped and the control is set properly and the contractor spends the time to be sure it works well We teach the guys who buy these to pipe them properly but without fail it seems 80% screw up something.. Four way valves are easy to understand and pipe but more expensive in most applications..Just be sure you have a pump to deliver proper gpm to the valve...Proportional injection valves also seem to work well..


prisco

Comments



  • Wallies, I have always used 4 way mixing for my low temp installs, just looking for reasons to switch, pros and cons to either that you guys see. Thanks in advance
  • hr
    hr Member Posts: 6,106
    personal preference

    I started years ago with 4 ways. We had problems with vanes breaking and motors snaping their shafts. In retrospect it probably had more to do with not flushing and treating our systems fluids. Later versions had "exercisers" to rotate the motors ocassionally.

    Seems the tappings were never square to one another often. Hard to make nice piping layouts.

    I switched to injection and have been very happy with the results and performance. Pros and cons to both, however I think you would be hard pressed to see a performance difference in the actual heat delivered to the space. In my opinion.

    hot rod

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  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    VSI...

    is like having a clutch, an accelerator and an automatic transmission between your boiler loop and the main distribution loop.

    A four way valve is like having a manual transmission with no clutch between your boiler loop and your distribution loop. It "hunts" a lot.

    VSI coupled with a good PID control logic is the ultimate in temperature control.

    The only thing that would make the system as a whole better would be variable speed distribution pumps based on delta P or delta T, and we're told they're just over the horizon.

    A word of caution on VSI. On most residential applications (under 10K square feet), the smallest pump you can find will probably be too big 90% of the time. In this case, bigger is NOT better...

    Do it, you won't regret it.

    ME

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  • Tim_4
    Tim_4 Member Posts: 3


    I agree with Mark's word of caution on VSI on resisdential jobs. I have always used the samllest circ I could find and reverse injected and still have to throttle way down. I am on the west coast though where the climate is pretty mild. I think one of the new DC circs would be great for injection, anyone played around with these?
  • Dave Yates (PAH)
    Dave Yates (PAH) Member Posts: 2,162
    in a word

    injection

    That's all we've done since getting turned on to its precision. Like ME said, it gives you cruise control and with proper reset controls, the chauffeur comes along to take over the driving!


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  • heatboy
    heatboy Member Posts: 1,468
    I don't know what it's like here on earth...........

    but on my planet, we use properly sized 3 & 4-way mixing valves. While I have seen mixing valve systems that "hunt", the ratio of bad injection systems is alarming. I do both, and if done correctly, there is no difference in performance. Mixing valves will consume less watts over their life span than VSI, especially when boiler reset comes into play. Also, VSI is the absolute wrong selection when it comes to condensing technology. A modulating three way is the ticket here. That way, return water temperatures to the boiler are kept at the same temperature as coming out of the slab, raising efficiencies.

    Warm Regards,

    hb

    "Expert in Silent Warmth"™

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    heatboy



    The Radiant Whisperer





    "The laws of physics will outweigh the laws of ecomomics every time."
  • hr
    hr Member Posts: 6,106
    I'm not clear hb

    seems with modulating condensing mixing would not be needed? Unless you need a bunch of different temperatures.

    As far as injection pumps look at DHW recirc pumps. I have used 15-18 and the new 15-10 for low flow pump applications.

    A great looking pump is that 10-16 Grundfos DHW pump 1.5 gpm at 2 ft. (25 watt) How about it Grundfos a 10-16 Mixi Miser?!!!

    hot rod



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  • heatboy
    heatboy Member Posts: 1,468
    I may be wrong..........

    but most boiler controls don't give a tight enough differential to really run a floor without the fine tuning a mixing device would give, especially, in a residential application. Could I? Probably, but I wouldn't. Commercially, it's a different situation. No wood floors, no bare feet(for the most part!) and indoor temps may not need to be as tightly controlled.

    Warm Regards,

    hb

    "Expert in Silent Warmth"™

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    heatboy



    The Radiant Whisperer





    "The laws of physics will outweigh the laws of ecomomics every time."
  • hr
    hr Member Posts: 6,106
    Tight differentals

    The Polaris condensers come with a 2 degree diff. Some tekmar controls will let you adjust the boiler diff also.

    I'll bet if Viessmann were to offer VSI and tekmar interface, you may change your tune :) I know for a fact you are willing to look at different options if they are presented to you right.

    I remember a time not long ago when you stated high mass cast was your only option. Seems the Vitoden has recently caught your eye.

    Yes, you can teach a middle aged dog new tricks :)

    hot rod

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  • heatboy
    heatboy Member Posts: 1,468
    Middle Age!!

    Yes, I have to admit it. If I had known I would live this long...................

    hb



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    heatboy



    The Radiant Whisperer





    "The laws of physics will outweigh the laws of ecomomics every time."
  • plumberhoo
    plumberhoo Member Posts: 8
    VSI piping

    I am in the middle of my first variable speed injection system. I've got a peerless boiler, indirect water heater, 3 zones of radiant floor heat. I have a boiler loop w/the IDW coming off of it. Also my VSI comes off with 2 1.25"x1/2" T's close together. I have the 1'drop to create a heat trap. My question is can I bring the drop back up without causing any problems?

    I'm also controling this system with a Raumix 99 with outdoor reset.

    Thanks for any input.

    plumberhoo
  • molly
    molly Member Posts: 43
    pump size

    just started my first injection install today. it's a 140,000btu munkin lp, piped up with 11/4" primary/secondary. the pump on the injection loop is a taco 007. the load is 3 zones of radiant in a 2500 sq ft residental house and a 40 gal indirect for dhw. do you think the 007 will be too big? what happens when it's too big? over heat? hard to throttle down? also, the injection loop is 3/4" should it be 1/2"? does it matter? the tees for the injection loop are separated by a close 11/4" nipple. any and all comments, worlds of wisdom, warnings etc. are welcomed by this newby to injecition pumps.
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