Cast iron boiler replacement with Navien High Efficiency Condensing Boiler NFB 200H

OLuckys3095 · September 16

Hello!

I am going to replace an old lochinvar solutions boiler with a new NHB 200H Navien Boiler. The existing system is piped as a series loop zone supply and return system. I am going to be converting it to a manifold system with individual supply and return runs. I need advice on what's the best way to do this. The original system has 4 zone valves. The boiler supplies 20 baseboard registers in a 4 apartment building. My setup with the new boiler will have 2 pumps, a 1558 pump on the return side of the boiler and a 2699 pump on the supply side of the boiler. Can I stick with the 4 zones and have each apartment ran off one single thermostat? I will install new t stats in each apartment if so with new wire. Also need some help on the wiring side of this. Zone valves to transformer? 4 Zone valves = 1.28 A with a single 24V Transformer? Control wire to boiler from transformer? Pumps wired into boiler? Any thoughts on the naviclean kit? New venting, new gas line connections. I will be installing two new non side arm water heaters as well. So this boiler replacement is only for baseboard heat.

Jamie Hall · September 16

EEEK. Is that poor boiler really sitting in a pit? Asking for trouble.

Step 1. Make sure you have the sizing right. Mod/cons are wonderful gadgets, but they do need to be sized correctly for the load. So… a building heat loss is in order.

I'm curious. Why two pumps in series like that? That makes no sense at all. You are going to be running primary/secondary, I hope, so two pumps will be needed — but not in series as you suggest.

Snowmelt · September 16

how many zones ? Is it easy to vent to outside ?

hot_rod · September 16

the boiler you have is a 135,000, 107,000 output. If that has been been adequate, why are you considering a 200?

offdutytech · September 16

Assuming that a load calc has been done and that BTU range works for your load there's a few things to consider.

Not a fan of Navien and their heat exchanger design. There are better boilers in the price range give or take $. Viessman , Burnham / Velocity Boiler Works are my go to. When compared to Navien it's a much better product. Both manufactures have similarly price ranged products. Might spend a few bucks more but it pays in the end. Choose a brand that's well repped in your area.
I would flush the system prior to installing a modcon such as sentinel or similar product.
Definitely install a mag filter when installing a new boiler to help further filter the system and protect the heat exchanger.
Hydraulic separator makes easy work of primary /secondary piping. You can get one with a mag separator if you like.
Get a zone control panel such as a Taco,Tekmar, etc. Cleans the wire up and makes troubleshooting much easier.
If you stick with zone valves Taco sentry are a great upgrade from the honeywell and easy to override if needed.
Follow and read the install instructions.

OLuckys3095 · September 16

This is how im planning on piping zone valves/pumps minus the side arm tees and domestic pump. This a triangle tube boiler i did a while back during the piping phase, almost completed.

OLuckys3095 · September 16

Yes boiler is currently sitting down in the cinder blocked out pit. Im going to be adjusting / Framing a support wall for the new boiler to be hung

OLuckys3095 · September 16

I believe the boiler wasn't properly sized, not pushing enough, so the client im working with has his mind set on the navien 200

Jamie Hall · September 16

https://forum.heatinghelp.com/discussion/comment/1865085#Comment_1865085

Contrary to popular belief, the client isn't automatically correct. That said, try at least to be sure that the installed radiation can support the full output of the chosen boiler.

offdutytech · September 16

Sometimes it's better not to take on a job and walk vs be married to a problem. Why risk your reputation where sizing or equipment will be a headache for you.

hot_rod · September 16

At the very least count up the heat emitters in each unit

If you have 50’ of fin tube in each unit X 550 per foot you can only put 110,000 into the units

Even a 1 million btu/hr boiler would not add more heat The heat emitters are what you might size to, if they have been adequate in the past

Here is a multi function hydraulic separator, Sep 4

It does air, dirt, magnetic and hydraulic separation in one unit

This shows zone pumps, it could be one pump and 4 zone valves

OLuckys3095 · September 16

Thank you I appreciate the insight! I will definitely take all of this into consideration moving forward

OLuckys3095 · September 17

Can you elaborate on the low header loss common piping. Where the autofill connects

hot_rod · September 17

the expansion tank and fill could connect at any of the 4 connections

Most often at one of the bottom, return connections

But not right off the bottom as it collects debris from the dirt separator inside

pump and zone valves on red line, the upper right

Cast iron boiler replacement with Navien High Efficiency Condensing Boiler NFB 200H

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