Adding Zone(s) to old two pipe heating system

13bravo

Hey All, New to the site and am hoping I could pick your brains...I'm having a new boiler installed and was also looking to add a zone but am getting conflicting responses from the plumbers that have come in.

I have a 30yr old Weil CG-7 and will be replacing it with a CGA-7. We have a two pipe hot water system that runs the the length of the house in the basement with branches out to 8 convectors (4 on 2nd floor across three bedrooms, 3 on the 1st floor, and 1 in the basement). I want to put the 3 bedrooms on their own zone. Each radiator has its own branches that come off the supply line and the return line.

Is it as simple as running a new supply and return from the boiler, disconnecting the bedroom branches form the existing supply/return and connecting them to the newly added supply/return? Will that cause any issues with balancing? I have some contractors tell me you won't get even heat this way, need to run a new monoflow line connecting all the 2nd floor bedroom boilers. Others say, no issue, simple matter of doing what I wrote above, disconnect branches for the bedrooms and reconnect them to new pex supply/return lines and add zone valves/pumps. A third said you would need to add special "joints" at the tees (couldn't understand what he was talking about.

At the end of the day, I'd like to add more heat to the bedrooms, as my wife really struggles dealing with the cold, without having to heat the entire house up every night. I've also considered adding thermostatic valves one each of the convectors but would prefer adding the zones, am just afraid the system would become unbalanced as some have said.

Thanks in advance for your thoughts!

13Bravo
U.S.H.A.!

Jamie Hall

If indeed you have separate supply and return lines from each convector that you can access, then it's actually pretty simple.

However, it isn't perfectly straightforward. The comments from the first and third plumbers suggest to me that you may indeed have separate lines, but the system may have been a monoflow system. If so, the new plumbing is a wee bit more complicated. To verify that, would you post a picture of one of the Ts where a line to a convector leaves the supply main, and another where the return comes back? And does it come back to the same pipe, just further along?

It still can be done -- not to worry -- and it's not that complicated.

13bravo

Hey Jamie, really appreciate the quick reply. Definitely two pipes...here is an image of the two pipes...left is the supply, right is the return. The branches you see in this pic are related to two separate convectors, I happened to have this pic already but will go take another that shows it better.

13bravo

Here is a view from the side of the supply pipe. You can see a branch coming off of it heading towards the camera and then another branch from the same direction going past it and into the return just behind the supply. You also see another branch coming out of it heading away from the camera and a parallel branch coming form same direction going into the return. Does this help?

13bravo

Ugh, sorry, screwed up on adding the pic. Take two...

13bravo

Here is my rather lame attempt to map them out and diagram them...keep in mind, I struggle with stick figures so hopefully y'all cut me some slack...

13bravo

13bravo

The second floor image doesn't have pipes layed out because I had trouble finding them...they might be hidden behind ceiling drywall OR those two might be connected on the same branch, not sure...but my gut tells me I don't think so, they are probably just hidden in the garage ceiling.

EdTheHeaterMan

I count 5 rad's on the second floor. I count 4 rad's on the first floor. there is no rad in the kitchen.

If this is accurate, I would disconnect all the first-floor rad's and plug or cap off the branch risers near the main.

Then run a separate set of main pipes in 1" copper (3/4" may also work depending on the load) and connect the first-floor rad's to the new main.

A 3/4' zone valve will handle about 30,000 BTU capacity. A 1" zone valve will handle about 50,000 BTUs. each valve manufacturer will be a little different, but these are good rules of thumb to use.

Now use zone valves on the near boiler piping to separate the 2 mains before the common piping. Your system appears small enough to use this method.

A good resource for this information ishttp://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf

Jamie Hall

This^^. Piece of cake.

13bravo

Hey Ed, thanks for the reply and insight. I'm assuming it wouldn't change anything but there are a total of 8 radiators (4 upstairs, 3 on 1st floor, and 1 in basement which wasn't pictured). The diagram is misleading because it shows pipes going to the bathrooms but those radiators were removed last year when we renovated the bathrooms (replaced with in floor electric heating) and the pipes capped.

OK, so it sounds like it is "as easy as" running a second supply and return main. I was concerned based on the feedback of some of the plumbers that there might be a balance issue and could struggle with getting hot water to the farthest radiators upstairs.

Ed / Jamie,

Sounds like you guys don't think there would be an issue with that? House is ~1900sq ft livable and is semi-detached so shares one wall. The one who took my request seriously was afraid heat wouldn't get up to the farthest rads, recommended installing a new monoflow loop just for the uppers (and connecting all the uppers to each other). Not needed in your opinion?

Thanks in advance!

13Bravo
U.S.H.A.!