Replacing large steel pipes going to/from hot water boiler to cast iron radiators with PEX
Comments
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The old system was gravity flow. Has it been converted to forced flow with a circulating pump?Bob Boan
You can choose to do what you want, but you cannot choose the consequences.0 -
Is the circulation of hot water pumped? Or is it still by gravity? That's a very important consideration! If it is already pumped, there really isn't that much hassle in replacing the pipes (probably iron, not steel) with PEX, and you can make the switch in the basement.
If it's still by gravity, you can still do it -- but you'll have to add a pump.
And either way, the trick will be to get the system properly balanced. For which reason... I'd very much suggest using a home run system to a manifold with balancing valves.
How recent is the boiler? If it's more than 20 or so years old, it may be time for it to retire...
A word on holes in joists: there are very definite restrictions on where, and how big, they can be. Never more than a quarter of the height of the joist, and less if possible; always in the middle third of the height of the joist; at least a foot between holes horizontally, and never closer than two to three feet from the ends or any support colBr. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Brainstorming here, but could you tear out all of the boiler, its piping and the radiators? Does the mini-split heat-pump system switch to electric resistance heating (which I know really spins the meter), but if it's enough kW to meet code, usually you could operate the pellet stove.
Reclaiming your head room is worth a lot and so is the space reclaimed from the boilers and radiators. Houses cost $100-200 per square foot and with all that space freed up, you might gain tens of square feet.
But I'd start with looking at your cost per BTU for pellets and for natural gas. I'd expect NG to be cheaper than pellets even if pellets are bought by the ton and for NG to be much cheaper if pellets are bought 50 to 100 pounds at a time, retail. Perhaps you should be maximizes use of your boiler and not your pellet stove?0 -
Sorry for delayed response - got tangled up in a nasty 4-car accident. A new boiler was installed right before we bought the house. It’s a U.S. Boiler Co. Model X-205 that was manufactured in 8/16. It’s Max Input is 140 MBH, Htg Cap is 117 MBH & Net AHRI Rating is Water 102 MBH. It has a Grundfos Alpha 15-55 FC circulating pump. I also measured the iron pipes going to each of my 8 radiators. 3 of the runs have1-1/2, 4 have 1-1/4 & the small bathroom has 1”.
And yes the boiler is more efficient to operate than the pellet stove, but getting the temp where you want it is challenging with both. I assume “balancing the system” will be much easier if I install an 8-port manifold & run 1/2” or 3/4” (if there’s any benefits to doing so) PEX with oxygen barrier to the supply & return iron pipes that go to each radiator. And we don’t mind the cast iron radiators & the amount of space they take up at all. Except in the kitchen where they consume what could be 2 large base cabinets. If/when we update out kitchen we’ll most likely get rid of them & put radiant heat in the floor of use a mini-split to take the chill off if it’s necessary to do so. Once I make some energy efficiency “updates” to the double casement & single pane picture & leaded stain glass windows it might not be. Thanks once again for all of your support. Looking forward to running my/our plans by my inspector!0 -
On the right path. Make or calculate the upgrades and do a good heat load calculation. It will show you where the radiant floors are and option and where you may need supplemental heat, btu/ sq. ft. Sometimes kitchens are a tough heat for just radiant floors, not enough surface with cabinets and appliances.
The pencil and paper work is the key to a successful design and install.Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
I don't know of any residential minisplits that have back up heat in them. There are some metal cased commercial inside units that have heaters.
In any event I would not rely on mini HP in MN to keep me comfortable when your real winter sets in.
To avoid drilling floor joists, have you considered fastening the pex on the bottom of the joists near the outside walls. Then a 2" deep soffit could cover the tubing. A removable painted plywood cover would keep everything accessible. Or if you have a center beam supporting FJ's they could run along the side of it.
You may have other plumbing runs to cover in this manner also.0 -
On those windows. Make sure your updates don't damage the value of the windows -- particularly the stained glass ones. There are very very good solutions to making old windows have good insulation value and become essentially draught free which completely retain their value and, for a pleasant surprise, cost a good deal less than replacement with even mid-range modern windows.Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
My brothers own/operate the Western WI electrical & refrigeration company my dad started (the one I worked for during HS & college summers) & they say their Twin Cities-based suppliers/wholesalers don't even stock AC-only mini-splits anymore. So every mini-split sold/installed up here in the Frozen Tundra is a heat pump these days & there are several that will keep producing good heat when the temps drop as low as -20 F. My last house had 220V electric in-floor heat cables in the basement cement floor of the big addition we built & a high-efficiency natural gas forced air furnace with a heat pump coil & an electric heat coil in its plenum. Xcel has some really good off-peak rates up here so we heated the cement slab up & used the heat pump &/or electric heat coil when off-peak rates were low & let the heat from the cement slab & the natural gas furnace keep things warm when off-peak rates weren't available. That was about as efficient as you can get. I won't be knocking out the cement floor in the basement I'm remodeling to do that again, but am planning put in-floor heat cables in the bathroom & possibly the big rec room if I decide to go with tile or laminate. And I'm not a bit worried about drilling holes thru the 2"x10" ceiling joists in my basement as our building code gives me plenty of room to drill ones big enough for four 1/2" PEX runs & I hate "boxed in" pipes & ducts in basements because they often exist because the folks who installed them were too lazy to do things the right way & yes that was not acceptable when working for my dad!0
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Yeah there's no way those original windows will ever get replaced as long as I'm alive! The previous owners replaced all the double casements in the second story with vinyl "pocket" replacement windows that have double pane insulated glass - which is fine because somebody painted all the wood trim up there white before we bought it. But on the main floor all the amazing wood trim, doors, stairways, open doorways, columns & built-ins are what sold us on the house. My girlfriend & I both grew up in old houses & love the character & warmth that only natural woodwork can provide! Some of the old windows have combination storm windows outside & I'm planning to buy some of the new friction fit inside storm windows for the two big picture windows to make them a little more efficient. And the big oak front door is so awesome that I removed the old single pane of glass & replaced it with an energy efficient double pane with Argon gas between the panes that cost more than a new insulated steel or fiberglass door would have cost. As they continue to tear-down old houses in our neighborhood & build new ones & rip the tops off 1-1/2 story bungalows so they can build full second stories with modern building materials, houses like our will always attract buyers who are willing to pay a premium for old home character with updated, energy efficient mechanical systems!0
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Hello,
I'm in a century-old St. Paul, MN house, and considering the same project of removing the iron pipes to the radiators to gain headroom in the basement. My plan is to install a manifold at the boiler and then run PEX to the iron pipes that go up from the basement rather than fish the PEX through the walls.
I'm interested to know if you completed this project and how it went. I'm DIY proficient, but I'm from the south and have no experience with plumbing hot water radiators.
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Perhaps the biggest task for a DIYer will be the fitting transition at each radiator. You may run 1/2" pex to some or all and the radiator, and connection will need to be reduced. Those large 1- 2" pipe and fittings can be a bear to work with.
Some radiator testing I have done with small pex S&R. 2" bushed to 3/4" at the radiator.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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Hundred year old pipes need to be replaced. Unless you're okay with leaks. Pex or small soft copper is a good idea. Best way IMHO opinion is to manifold and run individual tubes to each terminal.
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my gravity system was installed 1918. Redone in 2012. The risers are still original. So your saying I need to replace them?
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Think about how you're going to join on to the riser before you cut it and where you have space to cut out the remnants of a pipe or cut off a fitting by scoring and splitting or shattering it if it doesn't unscrew, make sure you are working someplace where you have room to work.
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What did you redo? Did you stick with gravity?
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@Brandon_MN I did pretty much what you are looking at not too long ago. Kept all the old pipes in the walls to avoid any interior work. In the basement I removed the main horizontal pipes and connected right to the eblow on the risers going up. Some of the risers had more than one rad, those got 5/8" feed, the rest 1/2". All pipe home run to two manifolds in the utility room. Ran all the new pipes through the joists so I now have a completely flat ceiling.
It does look a bit wrong to see 5/8" pex connected to 1 1/2" black pipe. The funny part is that the system works way better than it ever did before. Some of the rads that were far on the old gravity main would never get enough heat, with the new setup I can dial in the flow to these and get nice even heat everywhere.
Best part is no more pipes that I can bang my head into.
Undoing some of the old pipe was not fun, did break a pipe wrench with a 6' cheater bar but got all the pipes out of the fittings.
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You can leave the larger steel or iron pipe risers in the walls (as long as they are not leaking) and connect the 1/2" PEX in the basement to make your home runs to the balancing manifold(s). You can even make separate zones in the basement as long as there is only one supply riser per radiator.
Since the PEX tubing can be secured to brackets and easily routed to each manifold then the job can look very professional if you take your time and plan it out properly. (as shown by @Ironman's work in @hot_rod's comment above.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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oh my, a Bumblebee😆
Nice clean piping work.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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One more thing to watch, you loose the supports for the rads when you take out the piping. Any main floor rads that are not connected to other rads through the left over piping will need to be supported to the walls.
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and the piping, there are both you may need to add support to
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1st floor 2nf floor zones. Raised the mains between the floor Joice, insulated everything in the basement, used most of the old risers!
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You need to make sure that you use O2 barrier pex, not regular plumbing pex.
The tubing that we used in the picture is actually Pex-Al-Pex which has a rigidity similar to soft copper, so it requires less support and remains where it’s bent, unlike regular pex. The aluminum wall provides the O2 barrier.
I have tools for just about every piping method, so that gives me more options than most. Viega makes MegaPress fittings for hydronic use that can be pressed onto iron pipe so it doesn’t have to be threaded. They’re the green labeled ones. If you have a stubborn fitting that won’t come loose, you can simply cut it off and press the necessary fitting on. Most larger supply houses that carry the MegaPress fittings will usually rent the press tool and tongs.
Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
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