Adding a zone

SteveInAurora

I need to replace my 2 zone valves, and thought of a couple 'enhancements' while I'm at it...
The black shows my current plumbing. There are 2 operable zones, plus the basement always runs with either of the other 2.
My main/only restriction is that I don't want to move the top of the current 5 return lines left or right, and don't want to move the return-to-boiler line.
The red shows my "plan".
1. Add a thermostat & valve for the basement zone.
2. One of the halves of the 1st floor zone was extended out to an add-on den. It needs more heat than the main 1st floor, so I want to separate the den into a new zone. It comes in from the left, so I debated running the line across the rest of this and in from the right, where there's more room, or coming in like in the picture.

Any suggestions? Am I doing anything stupid? (haha, that's a setup)

SteveInAurora

Here's a sketch. Not sure which details are most important.
The circulator is a Bell & Gossett Series 100, 1/2 HP, 1725 RPM.

Bob Bona_4

You can verify that one of the split loops on the first floor is soley dedicated to the den?

SteveInAurora

Bob, if I understand what you're asking, no. The den was added on years ago at the end of a loop that covers half the 1st floor. I want to take it back off that loop and run it separately; the easiest source to fork off of is the beginning of the basement loop.

SteveInAurora

Hatterasguy, I agree with your conclusion in #1, and I will have throttle/balancing valves in the lines (left out that detail). I think the basement will rarely run, anyway; it has very little exterior exposure, has the boiler, etc.
Not sure I understand your point about "no reason for the water to make that diversion"; is it just a balancing issue? If both zones are open, there's a 'pull' at the fork on one end and a 'push' at the fork on the other end. Why would the water choose to take only one route? Or, ...??? I would think that any time 2 or more zones are open I could have balancing issues, either way. ???
Your second paragraph point is caused by imprecision in my diagram; there aren't two halves to the den, just one baseboard and the return. I had trouble drawing before-and-after-diagrams-in-one.
I had to look at my diagram 5 times before I caught what you were saying. My bad; good catch.
Thanks for your review!

Bob Bona_4

Ok good. That's the scenario I wanted you to avoid. Sometimes, we get lucky and half the split loop is a nice seperation of spaces conducive to zoning. Other times it's muddled, like part of that loop is serving rooms you want to zone apart. Like yours.

So you're going to cap off one of the split loop returns that serve the first floor and run a new return from the den and zone valve it off. Like Hatt says, be sure you have at least some valving on all 5 of the supplies for isolation for purging if not some crude balancing (probably not an issue).

I'd be looking at an ECM pump to keep things quiet during various zone valve positions.

SteveInAurora

Hatterasguy: I missed your last post earlier, I guess I was typing at the same time.
Here's more detail of the first floor flow. Tried to show 'fins' where it's above the floor and radiating. I show the den part, that was added on decades ago, in blue. It's all one zone right now. The blue part is what I want to make a separate zone.