Recirculating pump on a Rinnai tankless

ronaldsz123 · April 3

Hello everyone,

Came here looking for help since Rinnai customer support said they could not talk to me…

I had a Noritz tankless that went bad on me.

Bought the Rinnai RX199i on Amazon and had it install with a local plumber .

Now, i have a dedicated plumbing line with a dedicated recirculation pump that was working with an Aquastat placed on the pipe but when i read that the Rinnai could control it i thought it was better idea.

Bought the External Pump Harness: Rinnai Part #:105000250 (It came with 2 cables , pump cables and controller connector)

Eliminated the aquastat and connected the cables from the pump to the new harness that i connected to the motherboard in the rinnai . The second set of harness cable that say control i am not using and it does not show on the manual what those are for.

Turned the rinnai on and all seems to work as before but the recirculating pump does not seem to be coming on.

By the way i did change all parameter neccesary for a dedicated pump on the system.

Any ideas what i ma doing wrong?

Thanks

Jamie Hall · April 3

I doubt that they included that other harness cable for control for fun. But I don't have the manual to tell you what it does… I have found in the past, though, that the Rinnai manuals are pretty thorough.

ronaldsz123 · April 3

So i am attaching some pics for context.

My thought are the aquastat is a simple device that detects temp and gives continuity to the cables that come out of it to turn on or off the pump.

So the cables that i installed with the new harness should do the same, but i testes the cables with a multimeter and did no see any continuity even though the flame ligth was slowly blinking wich means that its signaling the pump to be on.

Jammie regarding your comment i agree but on the subject of the exterbal recirculating there is not a lot of info.

anyway this is the link to the manual

https://images.salsify.com/image/upload/s--pdKkmXZb--/ycbfmbyhllwrlmre5ouw.pdf

Thanks

Jamie Hall · April 3

I presume the cable with the heavier black and white wires which is plugged into the socket at the lower left corner of the motherboard is the pump cable? I don't know what the socket it's plugged into is for — but according to the manual, that's not the correct socket…

ronaldsz123 · April 3

Hi Jamie,

The picture i sent is the way the motherboard comes. The new harnesses are not plugged in.

ronaldsz123 · April 3

The heavier cable black and white only fits in the red square plug, the other one only fits on the blue square, i tried connecting the pump cable to the harness on the red square but the pump would not come on. after that is when i plugged both and tried testing continuity with a multimeter there was none in either.

Kaos · April 4

I think the pump power is the only connection you need. What did you configure the unit for in the menu? Some options will need a day of usage monitoring before it will run the recirc pump.

If you want the recirc pump to run on a programmable timer, you have to get one of the Rinnai modules to set it.

P.S. make sure to include the inline fuse they show. A blown board is a very expensive repair if the pump fails.

EBEBRATT-Ed · April 4

Page 62 in the manual I think is what you need for the connections. Then it must be configured properly. Looks like the controller to run the pump is included in the standard package.

ronaldsz123 · April 4

Hi Kaos and Ebebratt-Ed,

The more i research the more i think this only works with the External Rinnai GTK15 pump.

I don't think i can do it with my already installed pump.

My pump has the cables for power and one for ground and i keep trying to figure out how to connect it to the rinnai….

The rinnai pump has the same plus two extra cables, one blue and one red with a fuse….Look at the pic.

What do you guys think?

hilltown · April 4

controller cable is if you need to attach an additional controller such as a mc601, mc195 T if you want to program your recirc and the RWM200 Wi-Fi module. Save it.

Did your turn in #17 in parameters to B. That should run the pump for the first 24 hours randomally. Other than that the pc board is going to learn your habits of when you use water and run the recirc at those times. You can research Rinnai Smartcirc for more info.

If you unplug the unit from power wait 30 seconds and plug it back in does it do a recirc event?

hilltown · April 4

the gtk15 is a pump with timer so there is power for the timer and power for the pump.

As you may be aware and I understand you were probably trying to save some many you could have purchased a RXP unit that has a pump installed inside already, not to late you can get the internal recirc pump conversion kit. Not sure of the part # rx2rxpkit?

hilltown · April 4

the pump controller molex/whip is only going to fit in one place, It looks like where you put the red box in one of your pics

Kaos · April 5

Look at P62 of the manual. The external recirc pump is only connected to the larger wire set. The smaller one is not needed.

hot_rod · April 5

Was this recirc pump on the previous boiler? When was it installed?

ronaldsz123 · April 5

Hello Hilltown and Kaos,

So according to what you guys are saying the harness with the white/black cable should be connected directly to the pump rigth? To test this I plugged it in (Red square is the only place it fits and its just where the manual says) and connected a multimeter to both leads. It should read the 120v needed to run the pump, but i got no power at no point after turning the heater back on. Keep in mind according to the manual the pump should run when the flame on the panel is blinking and it was yet no power.

Tested for like 10 min and nothing.

I also tested both fuses on the board just in case, both were good.

Finally i am attaching a page of where all the settings are.

Any other ideas?

ronaldsz123 · April 5

ronaldsz123 · April 5

https://forum.heatinghelp.com/discussion/comment/1851198#Comment_1851198

The original setup was a noritz gas tankless with a dedicated plumbing recirc line from when we remodel the house about 15yrs ago, but the pump was controlled with an Aquastat

hot_rod · April 5

https://forum.heatinghelp.com/discussion/comment/1851229#Comment_1851229

Aside from not getting power, I wonder if that is the correct pump for that heater? I imagine the internal Rinnai pump is a variable speed. The Rinnai models with a "P" include the pump.

I don't think that is a LF, lead free brass pump, it looks to be a 1990 version? It will have a LF in the model number if it is lead free. If that matters to you?

Recirc pumps tend to be stainless or composite now.

Kaos · April 5

Settings looks ok, try commercial for operation and disable smart circ.

If it still doesn't run the pump, put the pump on a programmable timer and call it a day. I used before a programmable timer with a 110F temp switch on the return, works very well.

hot_rod · April 5

If ever you need to or want to replace the circ, take a look at this new Alpha. It does many of the functions that boiler control does. Built in temperature control, variable speed, etc

Screenshot 2025-04-05 at 12.00.29 PM.png

hilltown · April 6

if the fuse has continuity, and we are 100% sure we are not getting power when the flashing flame indicator is happening or after plugging it back into power, I would say a new board is needed, settings look correct, If you plug the pump into an outlet is it working?

Won’t say it never happens but Rinnai quality is pretty good, hard to fathom a bad board out of the box, it can happen though

Slimpickins · April 7

Rinnai isn't going just to give you a PC board without doing any troubleshooting. Have your plumber that installed it to be onsite and call 1-800-621-9419. If your plumber isn't capable or doesn't want to, go to Rinnai's website and go to, Find a Pro. They won't pay for the service call but if the PCB is bad, they will pay to have it replaced.

ronaldsz123 · April 9

Hey guys,

So i called Rinnai today and said i was an installer and was finally able to talk to someone and after 5 min of troubleshooting the tech said i have a faulty board. Not proud of it but it just doesn't make sense that they cant troubleshoot with a homeowner that has basic electrical experience .

He is sending me a new board and from what i see should be very simple to change.

Can anybody give me an idea what Amp fuse should i use for the recirculating pump? (Pump pic above)

Thanks again to all that have taken the time to write and help out.

hilltown · April 11

I would say 4 amps, I believe they don’t want a pump that is over 2 amps. Just a guess on the fuse size

Slimpickins · April 11

Hilltop is right, 4 amp would be correct. That's what comes with the Rinnai GTK 15 pump kit.

Recirculating pump on a Rinnai tankless

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