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I was at a call that has a RINNAI 2532C, The boiler is feeding therm. mixing valve for domestic hot water and brazed-plate heat exchanger to give heat for a baseboard loop. There is a bronze pump that continuously circulates the boiler water through the heat exchanger. My question is, can a  brazed-plate heat exchanger be used with this boiler ? and when I run the tub after a few seconds it runs out of hot water, but the shower stays hot.


  • Jack
    Jack Member Posts: 1,047
    Has this worked for the several years

    It must have been in? That model has not been manuf for probably five years or so. You say the pump "continuously" recircs to the unit. How is that pump controlled? What kind of flow rate do you have at the tub? At the shower? Sorry to play 20 questions with you, but I need a bit more info. Btw you can read output flow from the Rinnai by holding the red button for at least two seconds and then simultaneously hitting the Green and then let them both go. Same sequence with the green gives you exiting temp. Did you clean the inlet filter on the cws?

    Generally, this was the worst type system,imho, as you are driving a high temp to power the hx while then supplying that same hi temp to the tempering valve for dhw. The minimum flow to initiate operation on todays Rinnais is .4gpm but on that unit it is .6gpm, so you have to be making either really hot water or have a high flow rate. That was the last model that Rinnai allowed to be used as a closed loop heating device. Are you getting any error codes? Tech service is 1888-RINNAIS.
  • Mordy_NY
    Mordy_NY Member Posts: 2

    The unit is in a rented apt. with new tenants, the landlord "claims" the unit work from the time it was installed which was about 3 years ago. I was called to the job because the tenants had no hot water and the unit would lockout periodically on a code 12. So I opened the burner and saw allot of rust and scale , so I cleaned it out with compressed air and all so cleaned out the clear vent tube of dirt and rust.

    So I checked the length of the vent and realized it was long run and it did not have a condensing trap.

    I all so checked the in coming gas press. and it was 7" W.C. static and about 4 " while the burner was firing. I REALIZE THAT'S A PROBLEM !!

     The pump is not controlled by any thing, there is only a on/off switch on the wall. With the pump off I'm getting 0 gpm with the pump on any were from 0.3 to 0.9. I set the remote to 180.  It took about a 100 sec to fill a 5 gal. bucket with the tub and about 4 min with the shower.

    Whats bugging me, is that I'm getting around 170 deg water out of the heater when the water turns cold. I replaced the mixing valve &  the check valve at the HX. I'll try to post some pics of the piping to get a better idea what I'm talking about

                                                                                                                     Thanx a  Bunch !!!
  • Jack
    Jack Member Posts: 1,047
    I wouldn't put a nickel

    into this unit until the internals are squared away. Rust on the burners? If they have had condensation coming back onto this unit the biggest problem is that the moisture boils off the finned hx and seals up the fins. That causes hot spots and ultimately leads to hx failure. On the burners, if you have had condensation getting back on them it is best to remove the burner tray, remove the strap that holds the burners in the rack (4 screws) and individually clean them with water/compressed air. I will take each burner and tap it, gently, face down on a horizontal surface to get that white precipitant out of the burner. Make sure you identify the 3 low fire burners by the flame rod and sparker. Set them aside and when reassembling the rack put those three on the far left so they become high fire only burners and you put the 3 from the far left in the FR/sparker position. On the "clear tube", we have a problem. If you look at how that equalizing tube connects to the burner tray and gas valve you will see that in the burner area the sensing port is elevated about 3/8". That is to prevent minor debris/moisture from being able to get into the tube. If you call Rinnai tech and tell them you have signs of moisture at the bottom of the tube at the gas valve they will insist/demand/require a new gas valve, and correctly so. One other thing I have found when improperly vented and no drain tubes present the moisture goes down the fins, then the burners and if there is a great deal of it, it passed down to the air diffusing plate between the inducer and the bottom of the burners. The air difussion holes heal up and now we have the full monty. You can't get air to it, the gas valve is toast, the hx is compromised, but not leaking...yet.

    Due to improper installation, this unit may likely be compromised beyond reasonable repair. The question is, how much in parts and labor to save a unit that even when repaired is not "like new" as the customer would expect. If you want to talk this over, give me a call at 617 834-8751. That is my cell
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