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beginner plummer. New home with Lochinvar Noble temperature fluctuations and OUTLET MRHL error

meister19meister19 Posts: 3Member
hey guys so i recently moved to a new home and was trying to trouble shoot an issue with our tankless water heater. The mode lis Lochinvar Noble. I tried to solve this problem before I tried to hire a professional to deal with it. I would like to understand the basics at least so I don't get ripped off.

The problem I have occurs since I moved in. The shower temperatures would fluctuate hot and cold during usage. Faucet seems okay and doesn't seem to have the same issue. Recently there was errors from the unit which are OUTLET ARHL and MRHL. I resetted it and it seems to do the same thing. I did the full reset with the easy setup with factory recommended settings and it didn't seemed to help.

I was told to check a few things, which includes to purge the air inside the system, and to check if i'm losing pressure on the valve. However I would like to make sure if there are settings are correct before continuing.

I've searched everywhere on the internet and haven't found an answer at all but if I can get any help then that would be amazing.

Comments

  • nicholas bonham-carternicholas bonham-carter Posts: 7,886Member
    How old is the water heater? The settings must be right, if you have followed instructions from the manual.
    If you have a constant temperature from the faucet, but not the shower, then it would seem the problem is with the shower valve. The faucet may be passing enough water to keep the heater flame on, but the shower valve may be too restrictive.
    Try running a bit of hot water from the sink, while you are having a shower.
    If the shower stays consistently hot, then the problem is in the water heater part that reacts to the flow of water through the water heater. Some shower heads may not allow enough water to flow, for constant hot water even from a new heater.
    The shower valve itself may have an anti-scald feature, which shuts down the hot water, when the temperature exceeds a set point.—NBC
  • IronmanIronman Posts: 5,162Member
    It's a combi BOILER, not a water heater.

    The faults are Auto Rest High Limit and Manual Reset High Limit. They both indicate that there's not proper flow through the heat exchanger of the boiler.

    This could be caused by:
    1. Air in the system.
    2. A bad internal circulator.
    3. A bad internal diverter valve.
    4. The plate heat exchanger is fouled on the domestic side.

    The first three refer to the hydronic side.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rodhot_rod Posts: 11,790Member
    It is a bit tricky to purge those boilers for initial start. I've put a bucket under the relief valve and let them flow full bore for a bucket tor two.
    Assuming you have a fill valve that can keep up.

    There is a small manual purge valve on the boiler HX, did you run that clean?

    Does the boiler have a good air purger? if so running heat mode can help get the small air out.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • IronmanIronman Posts: 5,162Member
    edited August 12
    Another question would be: is the space heating side piped in with the necessary components?
    You can't run the unit without the basic components: expansion tank, relief valve, fill valve/backflow preventer, air separator (MBR).
    All of these are on the hydronic side, but are necessary for the boiler to operate in either domestic or space heating. If someone installed it thinking it was an on-demand water heater and didn't do these components, then there's your problem.
    Some pics would help.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • meister19meister19 Posts: 3Member
    Hey guys,

    Thank you so much for the help. I am going to start to get the air out of the system first and then go from there.

    I had a difficult time finding info online but i ran across the Lochinvar University videos on the unit. Hopefully that helps others when you're looking to DIY.

    https://www.youtube.com/channel/UC1eC-OSWQsZHVoqh54ahVVw/videos
  • DZoroDZoro Posts: 815Member
    Make sure the internal pump is pumping, have the combustion analysis done and set to factory specs.
    D
  • Le JohnLe John Posts: 139Member
    Hi @meister19 - Did you get a resolution for your issue? What was the problem?
  • meister19meister19 Posts: 3Member
    edited October 13
    I actually didn't have time to fix the issue. However there was one time i took the flow switch out and it was starting to work fine again for a month or so. I have a feeling it would either be the flow senor or the flow switch. I'll likely replace the sensor first and then the switch if it doesn't fixes it.
  • IronmanIronman Posts: 5,162Member
    meister19 said:

    I actually didn't have time to fix the issue. However there was one time i took the flow switch out and it was starting to work fine again for a month or so. I have a feeling it would either be the flow senor or the flow switch. I'll likely replace the sensor first and then the switch if it doesn't fixes it.

    Why do you assume a safety is bad for doing its job?

    Should a cop be fired for arresting a drunk driver?
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • DZoroDZoro Posts: 815Member
    If you have done the above, and still have a issue. There were some issues with the outlet/ high limit sensors.
    D
  • rikarorikaro Posts: 2Member
    edited October 14
    I have the same issue as well. I have contacted Lochinvar support and they say neither the flow switch or flow sensor would be at fault since the switch does not restrict water flow.


    I have attached an image of my setup. Lochinvar tech says it could be my piping.

    EDIT: I'm not sure if mine has the same issue as OP as mine runs fine on regular taps. MRHL error only shows when I'm using the shower. It would go hot and cold intermittently before i lose all hot water.
  • DZoroDZoro Posts: 815Member
    @rikaro Turn that boiler off!
    What you have there is all wrong and some very important parts are missing, and do not operate that boiler until it is installed correctly.
    Please for yours and your family safety contact a hvac guy asap.
    D
  • rikarorikaro Posts: 2Member
    @DZoro is this system supposed to be done in all hard lines? i did a quick google and have never seen a setup like this one. This was done by the previous owner where i was told he was a plumber.
  • DZoroDZoro Posts: 815Member
    @rikaro
    That system is missing and needs
    * Air separator
    * Pressure tank
    * Temperature gauge
    * Pressure gauge
    * Proper gas train
    * Proper gas line
    * Domestic mixing valve
    * Domestic pressure tank
    * And more
    I can't tell if the factory 50lb relief is installed on the top of the boiler, but I sure hope it is. If so it is missing the "hard" pipe taking it down to within 6" of the floor.
    Seriously get this all done before you turn it on....
    D
  • IronmanIronman Posts: 5,162Member
    How about posting some pics from a little farther back that show the vent piping?
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
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