Tankless WH issue

DustinB

New User
Location
Dallas Tx
I am a plumber and we do 2 to 300 new houses a month. We primarily intall 2 brands of tankless water heaters, Rheem and Rinnai. Often these heaters are installed either on outside wall or up in attic and we then run a low voltage unshielded thermostat wire to a controller usually located in master closet. With the Rheems the terminals to connect controller are located at bottom of heater and incased in a plastic piece. From there plug directly into pcb board. When running 2 heaters we will also connect units with a communication link making one unit the master. With the Rheems each end of communication link connects directly to pcb board. The Rinnais are the same with 2 subtle differences. The controller terminals are located at the pcb board and only one end of the communicatiin link connects to pcb board, the other end plugs into a wired plug connector, which this unit is the master. We have no issues with the Rinnais. However the Rheems we are constantly dealing with a code 76 and occasionally a code 82. Code 76 means the unit and controller are having issues communicating. 82 means the chip on pcb board has malfunctioned. To remedy both problems usually means moving controller next to the heaters. I know unshielded electrical lines in house create a magnetic field that can cause interference issues on low voltage line. My question is why do we not have this issue with the Rinnais? Rheem has been no help, but is it possible that the terminals and the wired plug connection inside the Rinnais are grounded? Would grounding terminals on Rheems solve code 76. Code 82 not sure how to ground since both ends of link connect directly to pcb board.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
DustinB said:
I know unshielded electrical lines in house create a magnetic field that can cause interference issues on low voltage line. My question is why do we not have this issue with the Rinnais? Rheem has been no help, but is it possible that the terminals and the wired plug connection inside the Rinnais are grounded? Would grounding terminals on Rheems solve code 76. Code 82 not sure how to ground since both ends of link connect directly to pcb board.
To answer your first question, Rinnais are obviously not manufactured by Rheem so there can be a world of differences.

As to grounding the wiring on the Rheems, all I can say is don't. That could cause major damage or at least cause it not to work.

You say that the controller works when connected close to the heater but not when installed in the closet. So some questions:

1) Is thermostat wire the recommended wiring for this?
2) Is the length within the allowed limits?
3) Are all installations of Rheems having this problem or is it not every one.
4) If not every one can you see anything that is done the same with those that have the problem but not with the ones that do work?
5) You are sure that there are no staples or other damage to the wire?
6) What happens if you just unroll a comparable length of wire across the floor and connect it up? Will the controller work then?

As for interference, anything is possible. You might want to try using a twisted pair cable like CAT5. You haven't said how may wires you need in that thermostat wire. If you do go the CAT5 route I would have to see what the connections are to be able to tell you how to divy up the pairs. I may even be able to recommend a different cable. Could you link the installation manual?

-Hal
 
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hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
200 to 300 homes a month should warrant a personal visit from Rheem at their expense.

Even 2 to 3 should get a good phone number for help.
I agree. At 200-300/mo you have to be one of their biggest customers. If they won't play ball tell them that you are going to go exclusively with Rinnai.

-Hal
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
I certainly agree you should be getting the support your need from Rheem. It sounds like you're getting Rheem'ed. ;)

In addition to what Hal posted, I would route the wiring to the controller away from the main power feed to the water heaters as much as you can. Switching of the high current loads in the water heaters could be causing significant interference.
 

ramsy

Owner/Operator
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
..I may even be able to recommend a different cable. Could you link the installation manual?

..If they won't play ball tell them that you are going to go exclusively with Rinnai.
To be properly compensated, rather than share any solution with Rheem, continue leveraging price against Rinnai for the extra labor effort, and register your company with Rheem Technical Support division as the specific-solution provider for Rheem tankless control issues.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
... I would route the wiring to the controller away from the main power feed to the water heaters as much as you can. Switching of the high current loads in the water heaters could be causing significant interference.
The OP never indicated. I assumed that these were either nat gas or LP. If these are all electric, that's something to keep in mind.

-Hal
 

kwired

Electron manager
Location
NE Nebraska
I'm having trouble even seeing the need for a controller that is remotely located from the water heater:?

Timer on a tank heater maybe makes some sense, why does one need anything remote on an on demand heater?
 

GoldDigger

Moderator
Staff member
My propane tankless has a remote control pan that allows you to select the temperature. You can.bkost the set point for running dishwasher, etc. thenower it again for safety and economy. You would not do that with a storage heater because of the thermal mass.

PS: 15 seconds to post. :(
 

kwired

Electron manager
Location
NE Nebraska
My propane tankless has a remote control pan that allows you to select the temperature. You can.bkost the set point for running dishwasher, etc. thenower it again for safety and economy. You would not do that with a storage heater because of the thermal mass.

PS: 15 seconds to post. :(
My guess most will turn setting up but never turn it back down.
 

kwired

Electron manager
Location
NE Nebraska
Not my experience, but I am sure some will do that.
I'm willing to bet that very high percentage of hot water users expect to turn on the hot water faucet and out comes hot water, maybe with a somewhat short wait for the heated water to make it's way through piping to the outlet, or turn on their dishwasher and expect it to handle such things on its own. Most dishwashers are capable of additional heating of the water - at least for a portion of the running cycle anyway.
 

GoldDigger

Moderator
Staff member
True. But if your tankless is piped natural gas, it is a lot cheaper to heat water before it gets to the dishwasher instead of using the electric element.
Turning on the faucet still always gets hot water with no other steps, it is just sometimes hotter than other times. :)
I also really like being able to turn the temp up to 180 for clearing drains and washing crud in the garage sink.
 
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