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Cr 180 thermostat

i just had a Navien Cr 180 condensing boiler installed, the installer left the old thermostats hooked up, they are your basic round thermostat, only temperature can be controlled,Should this furnace/boiler have something different? digital maybe?  i believe at this point all the thermostat controls is the circulating pumps.



  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Navien Cr 180 condensing boiler

    I had the idea that a CR 180 was a hot water heater, not a boiler. I thought the CC-180 was the model that could be used for both hot water and residential heating.

    Assuming you meant a CC 180, the thermostat you use will depend somewhat on the radiation in your house. For a slab at grade with hot water tubing in it,  there is no point having setback, so a "round" ordinary thermostat will be fine if you have outdoor reset. For finned-tube copper baseboard, you could consider applying setback Cast iron radiators are another story, but I do not know enough about these to comment.
  • Ironman
    Ironman Member Posts: 7,111
    edited April 2011
    The CR180 is NOT a Boiler

    JDB is correct that the "CR" is not a boiler, but a water heater. It does not have ASME certification as a boiler and therefore does not have the "H" stamp. It is important that you understand this because your installation may not meet code or insurance requirements.

    The Navien "CH" model is a boiler with a plate heat exchanger that heats the domestic. They refer to it as a "Combi" unit. See attached file.

    There are other issues with using the "CR" unit for space heating. If it's also doing domestic water heating, then provision must be made to hydraulically isolate the hydronic side from the domestic or it will become a breeding ground for legionellae. It would also require a very large pump on the heater side because there is an enormous amount of head (resistance to flow) through the heater. 80 feet of head @ 7gpm, to be exact. This is far beyond the capability of normal hydronic pumps used in residential applications.

    To answer your original question: it does not matter whether your thermostat is elctro-mechanical or digital. It is only signaling the pump relay to turn the zone pump on. The "CR" heater does not receive a signal from the t'stat, it begins to heat as flow is produced through it when a circulator starts. Again, JDB's comment is spot on.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
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