Solution for low hanging iron distribution pipes

Dawsonh4

I know this has been covered before, but I was hoping for more specific solutions. Any help is appreciated

We are in a 100+ year old home, 1500 sq ft per floor, 3 floors and an unfinished basement, with a new Bosch (ZBR 28-3) water boiler and Grundfos (29896341P1) circulation pump, attached to large (3" reducing to 1.5" at the end of the run) iron supply/return lines. These supply cast iron rads. Basement is heated only by the exposed heating lines. It all works fine at this point, reasonable heating bills, no concerns.

Time to finish the basement, so those low hanging heating pipes have to be raised to the joists. I have seen a lot about using PEX and home runs, but not sure that it is the best solution. My goal is only to get them out of the way in order to avoid a drop ceiling in the basement. I am fine with keeping the iron pipes and raising them or going the pex route. I was hoping not to get into fishing pex thru walls/floors to get to the upper level if I don't have to. Not exactly sure what to do when the pipes are running perpendicular to the joists.

Thanks so much!

Dawsonh4

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Jamie Hall

Sounds straightforward -- but there is a ringer in the deck (there always is). You want to make sure as you are raising things that the general pattern of circulation isn't too much disturbed. I would try very very hard to avoid a situation where you raise a length, but then either have to drop its continuation or have the pipes to the radiators have to drop and then turn up. I'm not describing that well...

You are no longer dependent on gravity -- you have that pump -- so it you do the minimum amount of rerouting it shouldn't bother the existing balance.

One very serious caution: resist the temptation to notch or otherwise cut into the floor joist above. Don't do it if you can possibly help it, and if you should have to, really evaluate the resulting loss of strength and stiffness. This is particularly true of a notch in the bottom. The strength of a beam reduces in proportion to the square of the depth, and the stiffness in proportion to the cube. (for example, a 2 inch notch in the bottom of 2 x 12 reduces the strength to only two thirds of the original -- and the stiffness to only half)

Dawsonh4

Thanks for the input Jamie.  I understand what you are saying. I assume this is to avoid air pockets.  

I still don’t have a good solution for the iron pipe that runs perpendicular to the joists. Can I using smaller diameter pipe since it’s no longer gravity fed?  Are there other solutions that might be better?

Jamie Hall

The trouble with going to a smaller pipe for part of what was a gravity system is balance -- the smaller pipe will have much greater head loss for a given flow rate, and thus the radiators fed by the smaller pipe will have much less flow (and hence less heat output) than the radiators which aren't affected by the smaller pipe. Will this be a problem? Without looking at the whole piping layout, I wouldn't care to say -- but in general, yes. The solution to it is either a fairly complete repiping, at least in the basement, or to add balancing valves.

There is another solution which sounds daft, but works, if that problem pipe doesn't have takeoffs along its length: replumb it with multiple smaller pipes, plumbed in parallel. Very roughly (VERY roughly!) the flow velocity -- and hence the headloss is proportional to the cross section area of the pipe. So, for instance, you could replace a nominal 3 inch pipe with four 1 1/2 inch pipes, plumbed in parallel. Kind of Rube Goldberg, and only gains you an inch and a half...

Dawsonh4

Would a manifold system be a solution? Could I put the manifold at the end of the 3 inch section?