Combi Boiler Install

Hello! New to the forums and new to plumbing! So naturally I have a couple of questions that even all of my research couldn't get an answer on.

Here is a rough diagram of my project (Although there have been a few slight changes). I'm using a Navien 180 NCB-E. Its not perfect by any means and its not up to plumbing diagram standards but it should be easy enough to understand and the city has accepted it as my blue print for my permit.

I think it should look pretty good. If you have any suggestions please let me know. Some of the changes I made include:

Lowest drain valve on return line will be a wye strainer with a drain valve hooked up to it
Shut off valve after circulator pump will also have a purge valve
Right before the expansion tank will be a "Drain Valve" that will actually act as a fill valve for adding inhibitor
There will be a shut off valve on the main cold/DHW supply lines

That is all the changes I've come up with so far. Here is a question for the guru's though:

My older style expansion tank is corroded and I'm replacing it with a simple 4.4 gallon amtrol tank (https://www.supplyhouse.com/Amtrol-141363-THERM-X-SPAN-T-12-Expansion-Tank-4-4-Gallon-Volume)

How should I go about this for purging purposes? The tank has a 3/4" MNPT end. The taco 4900 air separator has a 1/2" FNPT end. I was thinking of using a closed 1/2" nipple with a 3/4" x 1/2" bushing and then a coupling to connect the tank. Should I also add in an isolation valve and purge valve to be able to do maintenance on it, or should the shut off valve after the tank, the shut off valve at the start of the supply line, and the drain valve be good enough to purge the tank each year? These tanks don't come with a drain valve like my old one did so there doesn't seem to be any good way to completely drain these.

Also any suggestions on where to put check valves throughout the system? Thanks!

diagram?

Diehard said:

diagram?

Click to expand...

Updated. Sorry I must've messed up uploading it.

View attachment 17791
seee if this works

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The boiler has its own feed line for the boiler. I figured I'd just use that. It even has its own pressure regulator and check valves but from what I read most people install one anyways. That would've been my setup if I didn't use the systems auto feed though. Should I have the PSI gauge on the return line and a temp gauge coming off of the supply line? That's a good idea to put a ball valve before the circulator! will make it easier to replace in the future especially since I'm using the one that was already on the system. Do I need a ball valve for the bypass though? I didn't figure it needed one since the prefabbed manifold that you can by doesn't have one. And I'm guessing I should still do a ball valve and purge right at the expansion tank even if I don't do a direct water feed.

Oh I should ask too, is this a decent air separator? Or is there a particular style plumbers use the most? https://www.supplyhouse.com/Taco-49-075T-2-3-4-Brass-4900-Series-Air-Separator-Threaded

And are there any additional air vents I should place around? There are none on the baseboards and I'm not getting into installing them around there, but if there are any additional ones I can put in the loop near the boiler let me know.

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mdk0420 said:

The boiler has its own feed line for the boiler. I figured I'd just use that. It even has its own pressure regulator and check valves but from what I read most people install one anyways. That would've been my setup if I didn't use the systems auto feed though. Should I have the PSI gauge on the return line and a temp gauge coming off of the supply line? That's a good idea to put a ball valve before the circulator! will make it easier to replace in the future especially since I'm using the one that was already on the system. Do I need a ball valve for the bypass though? I didn't figure it needed one since the prefabbed manifold that you can by doesn't have one. And I'm guessing I should still do a ball valve and purge right at the expansion tank even if I don't do a direct water feed.

Click to expand...

you need gauges on the supply and return, psi and temp gauges
you also need a bleeder valve on every radiator you install, on supply and return
if not you will air lock up

I thought it should, but it worked fine without the bleeder valves before with just a $10 simple air scoop at the start of each zone (Used to be a dual zone but I cut off the upstairs since it is another apartment). Way to much moving stuff around and having to unsolder and resolder each one. It's not a very big apartment though either. There are 5 baseboards in total and roughly 100-125ft of 3/4" in the whole loop. I'll add them when I move and everything is more accessible unless it becomes a major issue right away.

I'll put some gauges up in the line as well. Do the internal PSI/Temp sensors count or is it just better to still have 2 gauges on each end?

Also thinking more about it, I feel like having the ball valve on the bypass might make things easier for purging air out of the system. And it's a fairly inexpensive and easy enough setup to do.

Edit: I just read through and I've been calling them radiators (which I guess they kind of are) but its the baseboard with copper finned type. Doubt that really matters since it still collects air and such though,

https://www.supplyhouse.com/Wal-rich-1701202-1-8-Combination-Coin-Key-Air-Valve-Nickel-Plated
https://www.supplyhouse.com/Elkhart-30602-1-2-x-1-8-Copper-Bushing-FTGxF

What is the zone valve for? Only one zone in the house now. Also odd spot to put one isn't it? I always seem them on the return lines near the boiler.

a zone valve is a low voltage actuating valve
that is wired to a wall thermostat and to the boiler
the placement of zone valve really depends on what system you are using
if you have multiple zones, you would want the valves at the base board with a 3 way on the end of the run
to keep the water circulating and the wait time for heat at a minimum
look at this drawing,

mdk0420 said:

What is the zone valve for? Only one zone in the house now. Also odd spot to put one isn't it? I always seem them on the return lines near the boiler.

Click to expand...

not odd at all. if your vale is in the boilr room, you have a longer wait time for heat.
the ''loop'' is cold
if a 3 way valve is on the ''loop'' the loop stays hot, less run time
it all depends on how the home is piped, since their are numerous ways to pipe it
drawing of 3 way on a single zone

I'm using existing plumbing which is pretty much the same setup as the bottom picture. It used to have an old cast iron boiler that kept some hot water ready, but now it's an on demand system. It'll only fire when heat is called for or if DHW is called for (It gives DHW priority). My setup wouldn't be able to make use of a valve since it's just a single zone (It used to be a dual zone to heat the upstairs but it had a circulator pump for each zone instead of valves). It's only one thermostat for the home as well. The apartment is only around 700 sq ft and it doesn't take much to heat it up. The setup your showing looks more efficient but I'm only replacing the old boiler with a new combi boiler. No rerouting of the main piping or anything crazy.

I just want to make sure that when it comes to any maintenance that all the common failure parts will be almost plug and play. I want to make sure I have all the isolators, drains, check valves, etc that I need to make it like that. Spending quite a bit on the union fittings to make that possible but I feel like it'll be worth it later down the road when I have to replace an air separator or the pressure regulator, etc. I also want to make sure that I have adequate filtration. I was thinking of even adding a water filter on my water lines at the start of the home's supply, but it doesn't look like any of the small filters really help all that much besides catching some debris. The home doesn't really have hard water but better safe then sorry right? I definitely don't want a whole water softener system. Just a simple filter that hangs on the line.

Before I complete my big order of all my stuff, I need to know if there are any check valves that I need? I can add a water filter and such later on. It looks like I got a lot of isolators and drains, hopefully everywhere I might need them. But I have no check valves exactly for whats built into the pressure regulators, the boiler, and the back flow preventer. Not sure if the circulators would stop back flow from happening or if the air separator would either.

Using the diagram I posted, are there any check valves you can think of that I might need? Thanks!