Old Radiators Repipe

J_man

Assessing and designing for a historic 90 year old house. Abandoning the failing sub-slab 1.5" iron pipes for a couple of 3/4" new S/R. I'm assuming this can be done, though I have not worked with radiators like this before (see pic - just painted, too).



Is it recommended to remove the 8 radiators and flush/clean them somehow? Or is it better to not do that? We will be running much of the new lines on the outside of the building. What is the consensus on accomplishing that? House is smallish, but concrete walls, lot of mass.Buderus GA244 boiler, 8 years old. Other red flags I need to do or look out for?



Much appreciated. Thank you.

Rich_49

3/4

S & R piping is not your best option for this system .   This piping should be large enough to get supply water to all the radiators .   Is there a way to employ a manifold near the boiler and run 1/2" home runs to each radiator ? If not I would lean toward 1 1/4 " or larger S & R piping to insure adequate flow .  I see that you have TRVs in the system also , you'll be able to use a nice ECM circ like a Taco bumble bee or other for constant circulation with a 30-40 * Delta T .  If you use the smaller pipe you will not be able to use an efficient circulator and will more than likely be stuck with a fixed speed pump which will not be conducive to comfort or heat transfer . Larger S & R , TRVs , ECM pump will allow all parts of the system to run at their most efficient , will provide better comfort and lower fuel bills . Outdoor reset may also be an option .

  Flushing them can probably be accomplished from the individual S & R piping in the basement when you cut them free and probably would be a good idea , then you'd be cleaning the piping to remain and the rads .

J_man

two pairs of 3/4 S/R

Thanks, Rich. Homeruns are not possible. I plan on splitting the radiators in half, feeding each half on 3/4 S/R. So, two pairs of 3/4 S/R. That is pretty much the largest pipe I think we can feed. I like the continuous circ on outdoor reset; they may be using that already.



Most of the rads have already been cut loose to replace flooring; no way to flush with existing lines. I just don't know what to expect on the inside of these radiators, sediment-wise, and the best way to clean them out, if necessary. Do the rads act as sediment traps?



Any issues with running glycol 40%? I know slightly less heat capacity, but necessary for freeze protection.

Rich_49

30%

should be fine if you must use glycol .  Use bypasses at the TRV so the water will be right there when needed .  Don't know how poorly the home's thermal envelope is but you may be able to use no glycol on a constant circulation situation .

Plumdog_2

sounded like...

he wants to put the pipes on the Outside of the building. Much as I hate glycol, I would not attempt this feat except in warm climates where no heat is needed.

Rich_49

forgot reading that

but I was speaking of utilizing the existing piping and having all within the envelope . Did not think anyone would even think I meant to not use glycol in any piping on the exterior . 



 " Flushing them can probably be accomplished from the individual S & R piping in the basement when you cut them free and probably would be a good idea , then you'd be cleaning the piping to remain and the rads ."

Armadillo

In my 2-pipe steam conversion I implemented counter-flow return piping, that is, I reversed the flow of the returning steam mains [left and right of the 2 story building each have a return serving 2 floors]. To accomplish this I cut and capped the mains where they met the old steamer boiler, and ran 1" PEX-AL-PEX to the FAR ends of the old return mains from the new separator, a Caleffi HydroLink. The 2 return legs have each, 3 stages of filtration [a bit overkill], the last stage each is a magnetic cyclonic filter that really does take out very fine ferrous particulate. I find myself blowing down the Y-strainer filters every visit, so easy! If I had to do it again I'd consider some sort of side-stream cartridge filter as well. We left all the rads in place and put on bleeders and drilled out the steam trap seats with a drill and ShopVac [sucking up the bits of metal best we could]. Counterflow return piping with Pex-al-pex is fast and easy, just make sure to buy and use a tool for the Pex-al-pex ends that shaves off the inner edge of the cut pipe so it's like / not a 90. If you do not prep your cut ends like that the O-rings on the compression [not crimp, compression] fittings get cut and damaged. I put stops in strategic places too. If I had to do THAT again I'd consider using raw slant-fin for parts of the long counterflow returns runs, maybe cool that return water even more and heat the unheated basement a little. Slant-fin would not convect much though; the return temps are not very high. I used to boilers that are mod-con and staged, or, will be when I finish the staging part. The primary side of the separator takes 1 1/4", again, I used 1 1/4" Pex-Al-Pex to speed the install process quite a bit. I used old-guard Grundfos pumps, the electric has been so high that I am trying the Bumblebee pumps this Fall [4]. I suspect the new pumps will pay for themselves maybe 1 a year, but have not done all the math. Part if my reasoning is the existing secondary pumps were wired ON 7x24... and the primary pumps were both on when making heat [wire OR'd boilers thermostatically controlled vs having the staging working]. I could not fiddle with the high-tech staging in January, just had to make heat. I also adopted the use of Permatex® Anaerobic Gasket Maker, especially in places where brass Pex-al-pex fittings meet black pipe threads, or where black meets brass stops. I don't want to start a pipe-dope war but we had some leaking, small drips...to fix, I wish I used the stuff all over in the first place.. The 1/8" plugs at the rads? They had been there over 100 years and wouldn't budge. We sawed them off flush, then center-punched, and drilled progressively larger holes in them until we could clean out and tap the old threads [pin punch, chisel, hammer, tap]. We rebuilt and repacked existing steam valves at the rads; we had ordered fresh valves but for various reasons we had troubles and it was cccold out!! If you want to replace rad valves, have a SawsAll handy, and also a Spud-wrench. We installed a water softener to fill the system with too. I wish I had more radiation now, more surface area.... I knew that going in.