Navien Boiler & Switching Relay Question

Cyclist77

NHB & NHB-H are the units I have a question regarding. If I want 4 heating zones and Indirect DHW will Taco Switching Relay work on either unit? I believe the NHB has been replaced by the NHB-H but they are still available.

As this is research time I appreciate your responses!

Thanks

hot_rod

Are the zones going to be zone valves, my preferred method, or zone pumps?

A ZVC is a zone valve control, for zone valves

A ZSR is a zone switching relay, for pumps

Either type can activate the boiler

Lots of info here about wiring Caleffi relay boxes.

https://www.caleffi.com/en-us/blog/zone-relay-controls

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Cyclist77

Currently setup with circulator. As I read the info on each Navien boiler I cannot make out if the NHB would work.

hot_rod

So 1 circulator and 5 zone valves? The manual for the boiler should show piping options?

Regardless if you use 5 pumps or 5 zone valves, you want a relay box. You need to determine your piping method then select the correct control box.

I imagine you will want a hydraulic separator, or some sort of primary secondary loops..

I prefer the hydraulic separator, a Sep 4, as you get 4 functions in one device. Air, dirt, magnetic and hydraulic separation.

Some examples here.

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Cyclist77

I am pretty clear on the piping it is the Navien unit I have a question about. Not sure if the NHB will work with a switching Relay or do I have to go with theNHB-H

hot_rod

the manual shows you various piping and wiring diagrams. Either build your system to match their example, or configure your own control logic. The relay board just send a closure to start the boiler up. All boilers have an “enable” set of contacts. So a two pair wire from that boiler contact to the relay box TT

It looks like the boiler control can do some control of the zones for you. But you need to define your piping and zoning method

It may vary from model to model, this NHB shows relays for 3 zone pumps. You might have 4 and a DHW pump? I don’t know if this is the model and size boiler you are considering?

I don’t see any connections for 24v zone valves? So if you zone with valves you may need a relay box

It is a personal preference, some installers prefer stand alone control, some try to run the controls all from the boiler. Relay boxes are from 2-6 zone versions. I always buy a version with an extra connection, just to have a spare relay if one fails. So a 5 or 6 zone box would cover what you describe.

Maybe hire MrEd to draw up a wiring schematic for exactly what you need. It’s nice to have “as built” piping and wiring diagrams. It easier to follow a diagram than a essay.

For the next person that needs to work on it. Or when you forget😏

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