RINKMO Tankless Water Heater Electric 18KW 240V Instant Residential Electric on Demand Water Heater for Bathroom Bathtub rv Whole House and Point-of-Use Shower Sink Small

The 18kW Rinkmo heater I purchased for my southern Florida home appears to be well made and well designed. These are some issues I have with the product and the documentation. The printed and web documentation has zero mention about external valves that may be required or appropriate for the installation. For my installation I incorporated a 3/4” tankless isolation valve kit w/ a 3/4” over pressure / over temperature valve, per the local requirements. The copper plumbing for the 3/4” safety valve slopes downhill to the exterior of the structure, w/o any valves, w/o any reduction in size, w/o any trap, ending at the specified height above ground, all per the local code. The tankless heater parts included four sheetrock wall anchors w/ screws for mounting. There was no way I was going to attach using wall anchors. My installation in the closet next to the unfinished bathroom permitted me to add horizontal 2x4 boards between the vertical studs. Those horizontal boards accepted the right side mounting screws and the vertical stud accepted both left side mounting screws. This is a very solid mounting method. This placement permits the plumbing to enter the walls w/o jogs. The wiring design was a big disappointment. The 18kW heater has a single 3/4” wiring knock out w/ double flats and includes an appropriate cable clamp. My installation within an interior closet led me to not want to place jacketed NM-B cable so it exists within the living space. My solution was to instead use a 3/4” Schedule 40 conduit and 90° elbow. The problem is that 3/4” conduit is too small for four 8 AWG stranded conductors (with two ground wires). The only wiring option is 8/2 NM-B, unless using individual conductors in conduit, like THHN, because there is no 8/4 NB-B wire available. A much better wiring solution would be to have a rear entry, through the wall. That was not possible for me to implement, if I were inclined to modify this UL-approved enclosure, because the only space available for placement of this hole is obstructed by a horizontal mounting stud. If the wire were permitted to enter from the rear, then there would be no wiring exposure to the living space and no issue w/ the 3/4" conduit being too small. My two 8/2 NM-B wires are routed to the main exterior panel, run through 1” Schedule 40 electrical conduit, attached to the exterior wall on the side of the house, then into that exterior panel. The 1” conduit size is great for two of the 8/2 NM-B wires. A pair of 240VAC / 40A THQP240 breakers is used to supply power to the wiring. These are the smaller 240 VAC breakers, using only one panel space, straddling the barrier between phases, instead of the full size THQL breakers where the 240V breaker uses two panel spaces. Note that 1/2 size knock out filler cover panels are required when transitioning to and from THQP and THQL breakers. At least two fillers are required to properly close the dead front panel when using any of the smaller THQP240 breakers. For safety never leave any openings in the dead front panel. The tankless water heater has a small internal “paddle wheel” to detect water flow. The device includes a screen to filter crud from clogging that flow sensor. My solution was instead to place a cartridge filter in the cold water plumbing supplying the tankless heater. If that wheel ever clogs, then no hot water. The valve kit I used permits periodic usage of a tankless water heater cleaning kit, to run vinegar through the tankless heater, to remove scale. There is zero mention of cleaning in the tankless manual or the web page. My “old school” installation uses 3/4” Type L copper pipe. I run the pipe to within the wall as soon as possible for proper routing / spacing. The hot pipe is insulated w/ snap on foam pipe insulation. The safety valve output points directly into the wall making that part very clean.

Customer service was awesome and resolved this issue within days expediting shipment. Liked hot endless water while it lasted. Disliked unit broke after 11 months. Displayed error HH which means output temp is too high. The Manual’s troubleshooting solution is unit do not work. Turns out the output temp sensor went bad. I know a bit about electronics so those of you that do here's some more info. I checked the electrical resistance of the good output and input sensors and they read about 4.6K Ohms the bad one read under 1K if I remember right.

You can't control the temperature. As soon as you try to adjust the water temp it goes straight cold. Then when you try to take a scalding shower it will turn ice cold without doing anything. I have been trying to get some satisfaction from the manufacturer or customer service without any luck. Its been nine months and nothing. Once you buy it, its yours because no one will help you at all. Amazon won't get involved because its beyond 30 days. I have about thirty emails where you can see that they are stalling because they know they can't fix it and they won't give you a service denial form so Amazon would help. Do yourself a favor and steer clear of RinKmo products.

I did my due diligence when my 15 year-old 40 gallon water heater started to leak. After searching for hours, I decided that Rinkmo's 18KW model was the best candidate, compact, efficient, and very reasonably priced. Although it cost a small fortune to have it installed, I'm very happy with the quality and performance! Even more so since it's currently running on only one of the two heating units!! Have to hold off a bit longer to have the 2nd 240V line run from my breaker panel to the tankless water heater. Rinkmo wasn't sure about using the heater in this configuration, but it seems to work fine for now. I have the water output temp set at 113 (like they recommend), and within a minute or so I have a steady, constant temperature, and consistent supply of hot water.

Works fine on my river cabin water gets very hot! one shower and 2 sinks