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Rinnai cycles hot cold

There's a lot of history leading up to this post. For now I'll stick with the pertinent facts. Rinnai model V2532FFUC 180,000 btu unit started cycling hot /cold after 2 years of working fine as the domestic and hydronic heat source through a Taco XPB heat exchanger. For a while, while troubleshooting, we were able to shower by turning on the heat. Then the heat exchanger started leaking,The unit now has a new heat exchanger, burner assembly and flow control but still cycles while under a strictly domestic load.



I understand that this is not an ideal application due to short cycling and condensation and will address that issue once I know the unit is functioning properly.



My challenge is that since Rinnai chose to void the warranty I can't justify the expense of a licensed technician at $75 hr and parts any further. I'd rather run off the electric tank I installed than spend more grief and money on this unit. Input would be wonderful.



I'm beginning to suspect something simple like a sensor. Wouldn't that be something.

Comments

  • JimX
    JimX Member Posts: 12
    edited November 2011
    Rinnai cycles Hot-Cold

    I had a similar problem using a shower. I talked to Kohler because it was only happening taking a shower. They said with tankless heaters like the Rinnai, low gallonage heads will not switch quickly from cold back to Hot as you ajust the shower temperature. They sent me a larger gallonage head (Free) and the problem was solved.

    By the way Rinnai’s warranties are garbage. I had my heat exchanger start leaking just before the five year deadline. I called Rinnai, they said I had to pick from a list of their suppliers to look at it. They did steer me to one. The price was outrages, to just look at it, and that does not come off any repair bills.

    His main function was to try and void the warranty; they talked to Rinnai on the phone while I was there. The installation was good, so they could not do that. Then they shipped the heat exchanger to them. When it came, they called and asked me do I want it installed. After they told me the price I told them to forget it, I could buy a new unit for the combined price of the inspection and the installation. I asked them to give me the exchanger. They did and I installed it myself.
  • Jack
    Jack Member Posts: 1,045
    That Unit

    Has a minimum flow requirement of .6gpm. Using this as a "boiler", depending upon what temp you are running your system at you will frequently see a situation where the amount of flow at the faucet requires so little hot water to arrive at your use temp that you fall below the minimum to continue operation. You can read the flow thru the unit to see if this is the case. What is your output temp setting? I've seen a lot of these systems thru the years set at 180 output and then you try to make 100 for hand washing. It simply does not work. What model controller do you have on it ( the small print, lower left)? The other side of this is the flow. Let's say you are getting a 20f temp drop across your system. With the circ on, read the flow and run the numbers on GPM X Delta T X 500= BTU. The minimum fire on that unit is 15kbtu. You can and I think have, killed that unit due to short cycling. I'm betting that this perfectly describes your situation. It is exactly the reason Rinnai does not allow their water heaters in a closed loop heating application.



    You have re-built the unit. It is now a very good water heater. I understand your issue with "lack of funds", but if you continue to operate in the same way, or try to modify the system to make it work, you will soon be back in the same situation. Try to separate the system. Conserve the Rinnai as a water heater and it will do a good job for you. If you don't do this, you are going to have to replace your water heater and get a boiler too.
  • Jack
    Jack Member Posts: 1,045
    Rinnai supported your warranty

    Within the term of that warranty. You were sent to a list of trained service providers. That makes sense as it is a gas appliance and the company needs trained eyes and ears on site. They are the interpreters for the manuf. The hx was provided, you managed to install it yourself. I guess what I would suggest is that you go to one of Rinnai's training classes and you too can become a service provider. What did your water analysis show? What was the cause of the failure? What did you see when you cut the old hx in half?
  • JimX
    JimX Member Posts: 12
    Rinnai

    What I am complaining  about is the outrages price of that inspection which renders the warranty worthless. I will give you that we have hard water here. I do not want a water softener. Other hot water heaters do not rot out here. When you have the heat exchanger of a Rennai in your hand you see how thin and light it is.

    My Bradford White 40 gallon is still in line.  I had it valved off. I put it back on line and it started right up. After sitting there for five years. Also, there is almost no difference in gas bills between the two heaters. My brother has a superstor SSU 45 which works fine in this area without a water softener.
  • nygrosity
    nygrosity Member Posts: 7
    Let's try again

    OK, so I fried the unit.I know. I have replaced the heat exchanger, boiler assembly and flow control. It still cycles hot/ cold. It's not flow, it does this with a substantial domestic load. It worked fine for 2 years.

    As stated I realize the hydronic system design flaw and will remedy that if and after the unit works again. What else could I have "fried" to cause this malfunction?



    Since the system seems to work when the heat exchanger loop is running, hot water mixing with fresh, could it be a "fried" sensor? It only malfunctions when heating cold city water to 120 degrees for domestic use.



    Complaining about rinnai serves no purpose here, that's a different forum. I realize I'm on my own repairing or replacing the heat source.
  • Ironman
    Ironman Member Posts: 6,589
    You're Missing the Issue

    Rinnia doesn't set the rates for inspection or service; you local provider does that.



     Secondly, any brand of tankless will not last long if hard water is going through it. It's not a matter of "rotting out". It's a matter of mineral deposits forming in the passageways of the heat exchanger and metal fatigue because heat cannot be transferred into the water properly due to the deposits hindering heat transfer. A tank water heater does not have the small water ways that are necessary for rapid heat transfer.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • nygrosity
    nygrosity Member Posts: 7
    Hello?

    No response yet so one more tidbit.

    Before I replaced the rotten hx and burner assembly a rinnai tech suggested that the burner was probably to blame, running too often at minimal burn had fouled it up. Sounded good. Now that the burner assembly is new but still cycling hot/cold, what comes before that? Plugged orifices? Gas supply?
  • Jack
    Jack Member Posts: 1,045
    I am not sure I follow the piping

    can you post a pic so I can get my head wrapped around that please? When you said you replaced the boiler controller, is that the pcb in the Rinnai? If so, did you re-set the high and low gas pressures? Any time a gas valve or pcb is replaced the operation of those to components must be "co-ordinated". With either one or the other, the unit may be throwing limit codes. have you dumped the error codes since the new hx? Also, did you clean the immersion sensors at the top rt and at the hot water outlet of the unit. If they were crapped up, and not cleaned that can affect limit operation. Be careful when removing the the sensor. There is a small O-ring in the well/on the sensor. Sometimes it stays in the well, sometime comes out with the sensor and sometimes you drop it and well, just be careful. Did you send me a pm?
  • nygrosity
    nygrosity Member Posts: 7
    Rinnai

    Thanks Jack! I really appreciate your help thus far. If and when we reach the limits of my trouble shooting abilities I'll bring a tech in again. Before that I want to make sure I have a thorough understanding of this unit to avoid further unnecessary time and expense.



    I will be changing the system design to eliminate short cycling issues and will incorporate the rinnai if I get it working.



    I have installed an electric tank for domestic water. We have wood heat. My family is not suffering too badly while this stubborn Norwegian continues this process.



    Here's the trouble shooting history.

    The first symptom after 2 years of functioning just fine was hot/cold cycling under a domestic load. We were able to shower by turning on the heat system. Rinnai advised me to first flush the system with vinegar which I did, twice, even though we do not have hard water. Other Rinnai systems in my area have worked fine for many years without flushing. Didn't work.



    I then cleaned the immersion sensors. No go.



    The next step advised by rinnai was to have a tech check gas supply with a manometer. The tech who installed the system stopped by after hours, hooked up his meter, took notes and called rinnai support the next day. They needed to have him at the unit. When I questioned at who's expense this would occur I was advised that my warranty was void.



    I'm one of many going through tough economic times. The concept of paying for parts and labor solving this problem does not pencil out.



    I spoke to a local rinnai tech. His first thought was the "water flow servo and sensor assembly" which I purchased and replaced. Nope.



    I did not replace the boiler controller or any other gas supply parts-yet.



    I spoke to another rinnai tech who walked me through the process of checking switch positions. His conclusion was that the unit was suffering from short cycling causing condensation and fouling the burners. He advised cleaning and rotating the burners. Shortly thereafter the hx started leaking. I shut the system down, put in an electric tank and took a break.



    I was very fortunate to meet another rinnai tech while playing golf. He stopped by, looked at the installation, saw no installation problems but  agreed that short cycling was probably an issue. Somehow he managed to get me a new hx. I purchased a new burner assembly when I saw the condition of the old one.



    I've put it all together it fires but still cycles hot/cold under domestic load only.



    I just reviewed the error code history many of which are not listed in my manual or online at rinnai.  They include 1,2,3,4,5,6,8,9,10,11,12. Some can be easily explained.

    Of those three are in my manual. 10 is airsupply or exhaust blockage.I have completely disassembled and reassembled the stack. 11 is no ignition. Probably occurred while rebooting with the gas off. 12 is flame failure which is probably the main issue.



    Two other codes are found online but I'm not sure they relate to this unit. 1 concerns burner operation during freeze protection mine's inside. 2 concerns power interruption.



    It may sound crazy but it's cheaper for me to buy some more parts than to bring in a tech with the added bonus of really getting to know my system! What's next?



    Thanks for humoring me!



    I did send a pm.



    Here's a picture.
  • nygrosity
    nygrosity Member Posts: 7
    picture?

    picture?
  • CMadatMe
    CMadatMe Member Posts: 3,085
    edited November 2011
    Come On

    Seems to me that your upset with Rianni when you installed a piece of equipment that isn't meant to do the job. What did you expect? You also used the wrong equipment for the heating. The Taco X-Pump was the right choice not the RMB. Your installer didn't see anything wrong with this installation? He needs glasses. RMB piped wrong among some other smaller issues I see from the pic.



    In every post you mention what something is going to cost you. Seems to me that you took that same approach on the intial install and got what you paid for.



    Your missing a pump to move water thru the Tankless and out to a properly piped RMB.



    http://www.taco-hvac.com/uploads/FileLibrary/RMB02.pdf
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • meplumber
    meplumber Member Posts: 678
    I have sat here quietly listening.

    I have read your posts and just watched. Jack was my Rinnai rep for years and his advice his golden. He knows the products like few others.



    However, after looking at the picture, I believe that my colleague Chris is dead on. You got what you paid for.



    And now you are mad at Rinnai? You should be mad at your installer.



    Slow down and listen. There are MANY problems with this installation that are causing your problems with the Rinnai.



    It is a shame to put that poor tankless water heater in the situation that you have put it in. Water heaters and boilers are not the same thing. The problems that you are having are a result of trying to use a water heater as a boiler.



    Keep an open mind and maybe we can help you get this straightened out.
  • CMadatMe
    CMadatMe Member Posts: 3,085
    I Just Noticed

    What looks like a Taco Replacement Cartridge box in the pic. Seems like oxygen is making its welcome heard on this system as well. ME is dead on. Your issues are with the installer. You should be thanking Rinnia for giving you a free hx. The failure issue wasn't caused by a defective product but rather a defective installer.



    System needs to be re-piped at a minimum.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • nygrosity
    nygrosity Member Posts: 7
    geez

    Golly fellas, I believe I've stated numerous times that the initial design is flawed! I didn't design or build it but I sure am having to live with it.



    Where in my posts did I suggest I was upset with rinnai? Of course I've

    been disappointed with the fact that my warranty is void, who wouldn't

    be? If anything I tried to temper an earlier posters rant. I'm not going to be overly critical of the installer either, we were trying to do something unique after all.



    It's water under the bridge.



    I'm not going to continue to use the rinnai in this configuration.



    I'm trying to make it work as a domestic water heater again.



    This may be getting a bit emotional for me. Ever notice how that can happen more in emails than in person?
  • CMadatMe
    CMadatMe Member Posts: 3,085
    Not a Rinnia Problem

    This is a hydronics design problem. You need to repipe and until then you will not make the problem go away. This is not a unique installation in my opinion, pretty simple actually.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • nygrosity
    nygrosity Member Posts: 7
    hydronics off

    Once again, the rinnai cycles hot/cold under domestic use only, hydronic system off, plumbing isolated.
  • meplumber
    meplumber Member Posts: 678
    I missed that somewhere in the posts.

    I must have missed that somewhere in your posts.



    I am not trying to be hard on you. We are just trying to help you fix the situation.



    The picture that you showed looked like a Rinnai being used for heating and hot water.



    Which would cause the problems that you described in your posts.
  • CMadatMe
    CMadatMe Member Posts: 3,085
    I Also Missed

    That he did install a XPB. Still piped wrong but atleast he has isolation. Xpb needs to piped this way http://www.taco-hvac.com/uploads/FileLibrary/XPB03.PDF and then he needs to add a 3-way valve. In then end he should look similat to this.



    http://www.noritz.com/u/plumbing_diagrams/nr98/7a1_nr98_dhw_rad.pdf
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
This discussion has been closed.