In floor heat

Hvacdoc

I have a Navien NCB 240 with in floor heat my brother added on a living space and extra work area to the barn/shop. What to add a 2nd Navien to make up the needed btu since tue ncb is 1.5 yrs old since install but has not run. So it’s brand new. (Just spray foam the barn this summer). Navien says I can cascade a Navien NPE. Water heater on to it.  But can’t find no info of that is correct that I can do it. or how to pipe it properly. 

Hot_water_fan

Why do you think you need a second? That’s a huge boiler!

EdTheHeaterMan

Hot_water_fan said:

Why do you think you need a second? That’s a huge boiler!

Exactly

Unless "my brother added on a living space and extra work area to the barn/shop." is a really really big addition.

GroundUp

What?

kcopp

Sounds like he has a combi boiler and wants to add a tankless WH to the set up. Some MFG allow you to pipe these in a manner that if the combi cant handle the DHW supply the Tankless will kick in. If navien says its doable you should contact their tech dept and or a contractor in your area who is very familiar w/ them.

Hvacdoc

You need to remember the combi 240 is not 240,000 btu. It’s only 199,999 for DHW. heating is only 130,000 btu. 

Hot_water_fan

You need to remember the combi 240 is not 240,000 btu. It’s only 199,999 for DHW. heating is only 130,000 btu. 

I’m aware. Do you know your heat loss? 130,000 goes a long way in a spray foamed building.