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Can you run two Rinnai i120cn's in paralell?

noobbathroom
noobbathroom Member Posts: 6
edited April 24 in Domestic Hot Water
I know you can run some of the stuff in paralell, but not sure if. you can run that series in paralell? One would have been fine, but we're going for a nice steam shower with a number of different spray heads which could easily use more water than the max gpm of a single 120cn.

Also, I would greatly appreciate if someone could tell me what extra's/accessories I need for the whole setup. I'm purchasing everything on wayfair.com (get a discount), and i'm trying to have everything prepared before we start renovating the new house.

https://www.wayfair.com/brand/bnd/rinnai-b31688.html

Comments

  • mattmia2
    mattmia2 Member Posts: 3,980
    Are you also using this for domestic heating? Do you have an adequate gas supply for this? 400,000 btu/hr is most of a typical residential service.

    There are probably better options. If you are using it for domestic heating as well, a heating only boiler and a large, well insulated indirect are probably a better option than a tankless with enough input capacity to cover your worst case instantaneously.

    If you are using it for dhw only, HTP makes high efficiency gas tank type water heaters. Electric heat pump water heaters are another option.

    Make sure you do your math very carefully with how much dhw your new shower will need, what your worst case incoming water temp is, and how much hot water your proposed system will make under those conditions, not the conditions used in the chart in the manual.
  • noobbathroom
    noobbathroom Member Posts: 6
    mattmia2 said:

    Are you also using this for domestic heating? Do you have an adequate gas supply for this? 400,000 btu/hr is most of a typical residential service.

    There are probably better options. If you are using it for domestic heating as well, a heating only boiler and a large, well insulated indirect are probably a better option than a tankless with enough input capacity to cover your worst case instantaneously.

    If you are using it for dhw only, HTP makes high efficiency gas tank type water heaters. Electric heat pump water heaters are another option.

    Make sure you do your math very carefully with how much dhw your new shower will need, what your worst case incoming water temp is, and how much hot water your proposed system will make under those conditions, not the conditions used in the chart in the manual.

    Yep I'm also using this for heating. Thing is I'm getting a super good deal on the i120cn. That's why i'm intrigued by the prospect of running two in parallel. Do you know if you can run two of those in parallel?
  • Jamie Hall
    Jamie Hall Member Posts: 17,103
    The short answer is yes, sort of. That is to say, you can hook two of those things up in parallel and, if you do it very very carefully indeed with regard to getting exactly balanced flows between the two units, which is not as simple as it sounds, you can get approximately twice the flow through the combination. Will that get you the hot water you want? Seems doubtful. That rated flow (9.8 gpm) is at a 40 degree temperature rise, so if your incoming water is below 70 you're going to have a nice cool steam shower.

    Plus, as noted, do you have adequate natural gas service? Also seems doubtful.

    Are there better ways to do this luxury shower? There are indeed. I would suggest a big natural gas fired hot water heater. In fact, possibly two -- one big one for that shower, and another for all the rest of your DHW needs.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • noobbathroom
    noobbathroom Member Posts: 6

    The short answer is yes, sort of. That is to say, you can hook two of those things up in parallel and, if you do it very very carefully indeed with regard to getting exactly balanced flows between the two units, which is not as simple as it sounds, you can get approximately twice the flow through the combination. Will that get you the hot water you want? Seems doubtful. That rated flow (9.8 gpm) is at a 40 degree temperature rise, so if your incoming water is below 70 you're going to have a nice cool steam shower.

    Plus, as noted, do you have adequate natural gas service? Also seems doubtful.

    Are there better ways to do this luxury shower? There are indeed. I would suggest a big natural gas fired hot water heater. In fact, possibly two -- one big one for that shower, and another for all the rest of your DHW needs.

    The existing water heater is only six years old, so what about leaving that in place and hooking that up with the Rinnai i120cn? Could that work?