Navien CH-240 ASME NG

I have a Navien combi. It feeds an air handler in the basement and the other in the attic for a hydro air solution. The question I have is in regards to the "Remote Control". First of all, is the Remote Control required. 2nd, if required, does it need to be "ON" if the heat is controlled by a seperate thermostat (1 for the lower level and another for the upper level). I was under the impression that one could set this up so that the thermostat would control whether the boiler kicked on to provide heat to the respective air handler. Is that not possible? Do you actually need to leave the "Remote Control" on? If so, why is it keep circulating hot water when their is no call to heat from the air handlers (the thermostats are off)?

Thanks in advance.

Some (all?) of the Navien units have a small tank, and that is kept at a fairly constant temperature - that may be what is running. Often, but not always, the system circulators are controlled by the thermostats, so if they are not calling for heat, they normally wouldn't be on. If you do not have a check valve in the system, you might get some convectional flow, but I would be surprised if that was enough to turn the boiler on.

The remote control allows you to vary the water delivery temperature, but I do not think you must have one to make the system work, it may be more convenient, but often, you'd set the thing up for your specific needs, then that wouldn't need to be tweaked unless the circumstances changed.

So, how are the circulators wired? What turns them on and off? Without knowing a bit more about how your system is setup and what controls you're using, it's really hard to tell with the info you have given so far.

Thanks for the reply.

I'll try to get a photo of the system setup (piping). Also, there's a Taco switch relay(SR502) hooked up also (the basement is zoned separately from the 1st floor). The unit in the attic simply services the top (2nd floor). I'll also try to get some photos of how they are wired and the settings in the Navien (dip switches etc).

CH model Navien combi

I very familiar with the Navien CH combi boiler.
The taco SR 502 is a two zone circulator switching relay that also has a XX terminal output that is used to activate a boiler (dry contacts)
The Navien has several DIP switches that need to be set to the required positions based on type of install.
I can't speak on all your other settings, but there is a bank of 6, and next to that a bank of 8 on the board. On the bank of 8, the installer must switch up (on) number three which makes the CH combi require a external signal to activate the heat mode of the boiler. If this was not done, the boiler will maintain constant heat.

The XX of the taco panel must have a low voltage 2-wire stat wire connected the the Navien R&W or the T&T (the different markings depends on the age of CH)

Now the sequence of operation is the t-stat calls for heat, starts the zone pumps (not sure how your fans are controlled) the xx closes and starts the heat side of the combi boiler.

Regarding the Navien remote, you do not have to use, but if it's connected, it must be turned on. The benefit of the remote is additional temp selections available versus the limited defaults that are set on the dip switches. There are some other settings done on the remote for the install such as outdoor reset system pressure, and a few other things that may or may not be used or required.

zl700

I'm going to try and get some photos of my setup linked.

In the meantime, here's the link to the Taco manual http://www.taco-hvac.com/uploads/FileLibrary/SR502(102-082).pdf

I don't see XX but do see X1 and X2 on this document.

Which of these should my setup be following, the Cold Start Boiler application or the Tankless Coil Boiler application.

Thanks in advance for any guidance.

Its the X1 & X2 with no jumpers on them from the line voltage side
Use the cold start example (the TT is the combi connection)
With no jumpers they are dry contacts that go to the CH R&W or the T&T (whichever you have)