Remove Hydronic Heat Black Pipe In Basement

DYIPittsburgh

I know this has already been discussed, but hard for me to take no for an answer.

I have the low hanging black pipe in my basement and want to replace with PEX. Based on a number of posts, I know I can use PEX Al PEX or PEX with oxygen barrier.

General spec:

1. I want to run two zones, separated by floors
2. I prefer not running home runs as there will be a number or PEX lines going everywhere. I would prefer main lines with Ts for each zone (7 first floor and 5 top floor).
3. Return, someone mentioned that I could use one run for both zones.
4. After I run the PEX, my plan is to purchase a new furnace within 6-12 months.
5. I'm not certain on the sizing of the PEX. If I can run main lines with Ts, I believe 1 1/4" should be fine and run 1" off the main lines to the existing pipe going up the walls to the radiators.
6. Benefits of PEX Al PEX vs. PEX Oxygen Barrier (I know both are Oxygen Barrier)

Probably have a number of questions.

As an aside, I've modified the existing black steel pipe in one section to install a bathroom. No issues encountered.







I should note that I am experienced with mechanical, but def not with boilers.

Thank you for any thoughts on this project.

hot_rod

What type of heat emitters do you have, radiators, fin tube? A close up of the fittings, it looks like a monoflo system?

DYIPittsburgh

Hi Bob.

Thanks for the response. Yes, I believe this is mono flow. There are two sections, given the configuration of the basement. The radiators are different sized, but primarily the size in the pic.

DYIPittsburgh

I should have mentioned, I would like to stay with a similar configuration (monoflow), but separate into two zones (two separate monoflow systems). I believe it may be possible to have the return on one monoflow system.

EdTheHeaterMan

The main pipes look like they are out of the way, where do you think you will be pacing the new main pipes? Will you be drilling holes in the joist to put them above the bottom of the joist as the main pipe runs across each joist bay? Or are you just going to attach the main to the bottom of the joust bay? The reason I ask... I did the hole on the joist thing to run PEX to some radiators. as the PEX heats up, you can hear the expansion of the tubing as it creeks and moans thru the holes in the joist. This is one of the reasons that the pipes are hung from straps below the basement ceiling joist. The straps can move without expansion noise.

Jamie Hall

If you plan to make holes in the joists, kindly remember that they are there to hold up the floor. No cuts in the top or bottom third of the joist anywhere on its length. Any holes in the middle third restricted to usually no more than a quarter of the real depth of the joist -- and not closer together than 10 hole diameters. If there is a bearing wall resting on the joists, then no holes period without a structural engineer's examination and approval.

EdTheHeaterMan

DYIPittsburgh said:

Hi Bob.

Thanks for the response. Yes, I believe this is mono flow. There are two sections, given the configuration of the basement. The radiators are different sized, but primarily the size in the pic.

It does not appear to be a one pipe Monoflo® or any other diverter tee system. (see the attached screen shot)

It's hard to tell from the distance and angle of the photos. My guess is that you have a direct return system as most gravity systems were when those radiators were common. The one photo of the modified pipes show that there is a separate supply and return.

You can easily make the system 2 zones by running a 1" main to each of the radiators that are on the first floor. Then plugging off the first floor takeoffs on the original main. You can leave the common return in place.

If you are going to replace all the low hanging pipes, I would suggest that you use 1" pipe or tubing and hang it below the bottom of the floor joist by at least 2". Hard copper pipe will look nicer and be more rigid in the pipe hangers. PEX will bend and flex between hangers and look less professional. the return will need to be 1-1/4" if your boiler AHRI NET or I=B=R NET on older boilers is more than 80,000 BTU. 1" is good up to 80,000 for most systems.

You can then make the connections from the main T fittings to the branch runs to the radiators with PEX where it will be short and arrive at the radiator valves with nice sweeping turns without using a bunch of fittings.

EBEBRATT-Ed

I really don't know why you want to disrupt the whole system. Looks like a lot of work for little gain.

The larger sizes of pex are not as easy to work with as you think

If it is a monoflow system I don't know how you plan on doing that with pex.

You could do two pipe direct or reverse return

In fact you can pipe it a lot of different ways but it is going to require correct sizing to make it work.

Not worth it in my opinion

Looks like monoflow from the pictures.

DYIPittsburgh

Thanks for all the feedback here.

I added a couple pictures as this looks similar to the monoflow in your screenshot.

Re the sizing. If I understand correctly, I can run 1" supply to the first floor (with diverter Ts) and 1 1/4" returns. For the 2nd floor, I will need 1 1/4"? I can use the same return lines for both first and second floor?

Re the joist, if I make 1 3/8" holes 1/8' clearance, will this alleviate the sound discussed above? Also mentioned was the idea to run copper and Ts from Supply/Return using PEX (not sure if I got that right?) I would prefer PEX Al PEX, but not completely sold on that.

Any thoughts between PEX Al PEX, Copper or Steel Pipe - removing the large diameters and replacing with sizing discussed above. If needed, I could move closer to the walls and only hang 1" or 2" from the joist. I would prefer to hide the pipe within the joist. There is a chart that shows code hole requirements that I would follow.

DYIPittsburgh

DYIPittsburgh

1987 Unit / 187,500 BTU / Cap 149 LBS/HR. I believe this unit is 80% efficient.

As mentioned about, I'd be replacing this unit in the next 6-12 months and wanted to first fit it with the new piping.

DYIPittsburgh

I didn't understand that monoflow is literally one pipe for supply and return. So, def not monoflow.

DYIPittsburgh

Further, I now stand corrected on the term "diverter T". As this is not a monoflow system, I would use only Ts for branching from main supply and main return.

EdTheHeaterMan

NOT a one pipe MonoFlo® system. You have separate supply and return main pipes. That is a direct return system.

EdTheHeaterMan

DYIPittsburgh said:

1987 Unit / 187,500 BTU / Cap 149 LBS/HR. I believe this unit is 80% efficient.

As mentioned about, I'd be replacing this unit in the next 6-12 months and wanted to first fit it with the new piping.

This number is the minimum relief valve capacity. It has nothing to do with the boiler capacity

The boiler information is too small to read but I believe that the 187,500 Input number is the maximum amount of gas that can be burned safely and the I=B=R NET rating is close to 128,000. So based on the standard 20°∆T from the supply temperature to the return temperature, the most water you need to pump is 13 GPM, and that can be done with 1-1/4" pipe. So using the common return would need to be 1-1/4". My guess is that you will need 1" main to all the radiators on the first floor and a 1" main to all the radiators on the second floor.

EdTheHeaterMan

DYIPittsburgh said:

1987 Unit / 187,500 BTU / Cap 149 LBS/HR. I believe this unit is 80% efficient.

As mentioned about, I'd be replacing this unit in the next 6-12 months and wanted to first fit it with the new piping.

Be sure to have a load calculation completed before you select the new boiler. The old boiler that came with the house was probably an oversized, hand fired, gravity system that was converted to oil heat. If the plumber who put in the gas heater just picked the Bryant Boiler based on the old one... Then that one is oversized too.

If your new replacement is a Modulating Condensing boiler, then you may only need the smallest one available. A load calculation will let you know this.

If all you need is the smaller one, then the main return pipe may need only be 1". But we will not know if you don't do the load calculation

Also look at this comment to another with your same idea. https://forum.heatinghelp.com/discussion/comment/1748197#Comment_1748197

ethicalpaul

> If the plumber who put in the gas heater just picked the Bryant Boiler based on the old one... Then that one is oversized too.

Nah, Ed, surely he bumped it up one size "just to be sure"

pecmsg

ethicalpaul said:

> If the plumber who put in the gas heater just picked the Bryant Boiler based on the old one... Then that one is oversized too. Nah, Ed, surely he bumped it up one size "just to be sure"

As did the plumber before!

hot_rod

I'd start with a heat load calc
Then a radiator assessment
Then a design to see what SWT is actually needed
Then chose a repipe option.
This info will indicate required tube size.

Spend money on lowering the heat load where possible. Everything gets smaller, pipe size and fuel costs

Yes pex can be run through joists in a way that does not make noise. 1/3/8" holes with isolators in every hole. Loop at ends for lateral movement.

Download an actual hole drilling chart for where holes can be drilled.

One option here.
https://structuretech.com/notching-boring-dimensional-lumber-joists/

DYIPittsburgh

Sorry for the late response.

Appreciate all the feedback. I'll run the calculations as suggested, but seems very doable using Ts for branching from main supply and main return. I'll need to look into the "isolators" and a few other items that were suggested.

Thanks again!