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Noritz Combi Boiler CB199-DV

Hello, my fiancé and I bought a completely remodeled/redone home in August 2019. The seller has a new Combi boiler system installed that seemed to be working well, with a few mysterious hot water issues here and there. We hadn’t noticed any issues with the hot water supply to our radiators.

Last week, we came home in the evening and the house was 60 degrees F with the thermostats set to 70. I noticed that all the pumps were working in response to the relay but cold water was circulating through the system. We turned off the system and gas and then turned it back on which didn’t fix the issue. Our DHW worked the whole time. The system would turn on the digital display of the radiator and start heating for only 1-2 minutes and then turn off- while the pumps kept running, circulating hot water. Then at 3am the system decided to stay on with the digital radiator display and heat the house.

For the next week this kept happening randomly. I think it may be linked to turning on the thermostat in our garage which has in floor heat and a separate relay/pump.

I don’t think any mechanical parts are faulty being that it’s less than 2 years old (but you never know). I have looked at the installation guide and wonder if the pump/radiator supply and return are on the wrong side of the heating supply and heating return. What is installed doesn’t match the installation diagram. I don’t know if it makes a difference or not. I will post a photo of the system- it was installed in a neat fashion so it may be easy to see any issues.

My only other thought is that the relay box isn’t sending the correct signal to keep the radiator heating/heating supply on per the thermostat(s).

Comments

  • BillyO
    BillyO Member Posts: 274
    does that boiler have a diverting valve internally to switch over from heat to hw ?
  • ricex405
    ricex405 Member Posts: 5
    Yes, there is a 3 way valve. I don’t know enough about the dhw heat exchanger to know if the 3 way valve switches from heat to hw but I’d assume so.

    A public works tech came the night it wasn’t working and said the 3 way valve switches the heat and hw.
  • BillyO
    BillyO Member Posts: 274
    Noritz combi looks very similar to Laars Mascot and HTP EFT wall hung. Could it be possible its made by Kiturami also?
    Hummerr7ck
  • BillyO
    BillyO Member Posts: 274
    symptoms point to bad 3 way valve
  • ricex405
    ricex405 Member Posts: 5
    Could the layout of the plumbing cause the valve to not work/become faulty? It just seems like the loop of hot water out and hot water return has to cross over the in/out from the boiler. Possibly creating negative pressure on the 3 way valve?
  • GroundUp
    GroundUp Member Posts: 1,281
    3 way valves are a common fault in those units BUT, they do have a DHW priority so if you were using any DHW the heating system would get nothing. Has the unit ever been cleaned? Your plumbing looks to be correct. If you could open up the cabinet and get hands on all 3 sides of the diverting valve would tell you where the water is flowing, possibly eliminating other potential problems from the equation. Sure sounds like a 3 way fault though
  • hot_rod
    hot_rod Member Posts: 15,019
    Check all the wiring connections inside. Maybe unplug and plug them back in
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Ironman
    Ironman Member Posts: 6,555
    Where are the return lines from the three zones? I can't see them or where they connect in your pic.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    SuperTech
  • ricex405
    ricex405 Member Posts: 5
    I had the plumber who installed it come out and look at it. He explained that the plumbing moves in the opposite direction than I thought so that was not an issue. He went over voltages with the manufacturer on the phone and it turns out that it is the 3 way valve not working. It’s not switching over to allow hot water into the radiator system and instead is circulating cold water. They are sending me a new 3 way valve covered under warranty. Thank you for all your help.
    BillyOGroundUpDZoro
  • Hummerr7ck
    Hummerr7ck Member Posts: 2
    i,m a heating contractor. the feed & return are reversed,,hence the hot water boiler outlet is on the left,
    GroundUp
  • Hummerr7ck
    Hummerr7ck Member Posts: 2
    oh wow !!.did He install the pumps on the return side.pumps are putting pressure on boiler/pressure switch,,not good. after seeing your mixing valve assuming thats a low temp loop for garage. we always install pumps on supply ..water leaving the boiler-theres a drawing showing this in install instuctions
  • padosi
    padosi Member Posts: 7
    I have a similar problem. Seems like mine is a much simpler setup (pics attached). It is a single family house with heating on two floors. We currently have the room temp setting to 75F on both floors. It randomly stops heating and the temp drops to 65F. Not sure what the issue is, the DWH is working fine. Any advise would be much appreciated as my knowledge in this is very limited. Hopefully the pics are helpful. If not, I can take from a different angle and re-post.



  • padosi
    padosi Member Posts: 7
    Btw, to add to the above post, there are no error codes being displayed.