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Can classic cast iron radiators replace baseboard hydronic?

PuttyD
PuttyD Member Posts: 3
Hello,
We are first-time homebuyers purchasing a property in the Berkshires in Massachusetts. The house is a colonial that is over 200 years old but was taken apart and put back together by an architect in 1969. At that time he added two additions. One is a kitchen/dining room addition. The other was a garage that is now the Great Room. The older colonial has a crawlspace. The kitchen addition is over a basement with the mechanicals. The Great Room is a slab.

Currently the main source of heat in the colonial is a 30+ year old oil boiler driving hydronic baseboards. We want to update the boiler to a more efficient propane boiler (thousand gallon tank buried on property), as well as add some mini-split heat pumps.

So, here is my question... We don't love the look of the hydronic baseboards, is it possible to get the same heating efficiency if we replaced them with classic cast iron radiators? Can cast iron radiators work with a new propane boiler and use some of the existing piping?

Thank you!

Comments

  • Grallert
    Grallert Member Posts: 523
    The answer is yes, depending. you can with work replace base board with radiators. You will have to make sure the radiators can be used with water. There are a ton of cast iron radiators out here in western mass but a lot of them are for steam only. There's a difference. You can of course purchase new old style radiators that will work. If you can get the pieces to line up you will end up with a very nice and very efficient system.
  • SuperTech
    SuperTech Member Posts: 1,670
    Cast iron radiators are typically piped different. They are usually piped in a monoflow configuration. Fin tube baseboards are piped in series. If you put in the radiators without modifying the existing piping the radiators at the end of the loop wouldn't be as hot as the ones at the beginning. Flow requirements and supply water temperatures are different as well.

    That being said, I would still consider replacing the baseboards. Efficiency wouldn't be much different, but the radiators provide better comfort. You don't have to pipe them monoflow. You can run home run loops from each radiator back to manifolds at the boiler with PEX. TRVs can be used on each radiator to provide additional comfort.
    Grallert
  • PuttyD
    PuttyD Member Posts: 3
    Thank you for the responses. Definitely gonna look into replacing the baseboards possibly with the Castrads radiators.
    Grallert
  • Jamie Hall
    Jamie Hall Member Posts: 16,589
    edited February 2020
    Cast iron radiators were piped monoflow back in the day -- but they don't have to be. They can also be parallel flow, which would give you much more control.

    May I suggest getting hold of Charles ( @Charlie from wmass ) to take a look at the job? He could probably schedule you in for the summer. If not, try Gary ( @GW ). Either one are among the very best in your area (click on the links to send them a personal message...)
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    The temperature drop at the end of the loop should be the same whether you use cast iron or fin tube because you should be using the same amount of radiant in each room. The delta-t would be no different on the loop if they are properly designed.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Grallert
    Grallert Member Posts: 523
    Keep panel radiators in mind also. These can be very handy where an iron radiator is for what ever reason too large for a space. If it's thought out you will end up with a system that looks right at home.
  • SuperTech
    SuperTech Member Posts: 1,670
    > @Charlie from wmass said:
    > The temperature drop at the end of the loop should be the same whether you use cast iron or fin tube because you should be using the same amount of radiant in each room. The delta-t would be no different on the loop if they are properly designed.

    I gotta go back and re-read Dan's books again. I always thought that was the point of diverter tee/monoflow piping, to try to keep the same same SWT to each emitter.
    Wouldn't it have been easier for them to pipe it in series back then? I have diverter tees at my house, but mine is kinda odd. Two pipe, reverse return.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    The point of a monoflow system is to reduce the size of the pipe to each radiator and to streamline the piping system. If you go in series you can also not balance each radiator individually. this means if a radiator is oversized for the room you can't reduce the flow through it to match the heat loss of the room. Monoflow systems or better yet reverse return piping systems are best for balancing the heat flow through the radiator to the heat loss of the room. Adding central heat two buildings back in the day was more than just the cheapest way possible especially if it was hot water. It was also about allowing a high level of comfort.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
    SuperTech
  • PuttyD
    PuttyD Member Posts: 3
    I am sure there is a lot more info needed to answer my next question. All things being equal and assuming the current amount of slant-fin baseboard in the house provides the correct amount of comfort in each room...is there an easy way to figure out how many radiators and sizes the room would need to replace what is currently installed?

    Just trying to do a rough budget on the actual radiator purchases.

    Thanks.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    A heat loss needs done. One should be done anyways whenever you work on your heating system. Would need to know your choice of boiler be at standard chimney vent or high-efficiency condensing boiler. The designed water temperature for the zone you live. All these things need to be known for a proper answer. The quickest way to get an idea to match what you have is to figure 600 BTUs per linear feet of existing baseboard and match the radiators to that.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,275
    The thing is, if you replace your boiler with a condensing boiler, you can size your new cast iron radiators for a lower water temperature (not hard). This will give you very high overall efficiency and save you a lot of fuel over the years of operation you live there. Is the slab radiant or heated with baseboard?
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • GW
    GW Member Posts: 4,232
    Thanks Jamie for the mention. I don’t travel very far, the windshield doesn’t pay very well. Normally 20 minutes max from the shop, or a bit further if it’s a meat ball.

    I dig the one pipe conversation.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • MarkZeh
    MarkZeh Member Posts: 10
    Jamie, hello, read your great responses to PuttD. I have a similar situation.
    Recently purchased an old victorian from 1908 where the original cast iron rads were sadly replaced by baseboards. At this point the BBs are fairly beat up and need to be replaced anyway, so moving back to cast iron rads. Current BBs are fed by a 3/4" copper line with same as cold return to system. The living room has 20' of BB @ 580 Btu/hr-ft brings me to 11,600 Btu/hr heat output. Looking to come close, or slightly exceed, that amount of heat output I have selected 2 - 20 section slim line rads @ 6800 Btu/hr each totaling 13,600 Btu/hr, figure they can be slightly throttled down with the incoming valves if necessary.
    Question: when re-installing cast iron rads, you advised parallel piping. Understand that the cast rads should not be piped in series so as to avoid heat run-through on rads. So for parallel piping, am I simply branching/slitting the hot line, then re-pipe o each rad so that the hot water hits both cast rads close to the same time? Then pipe the two rad cold returns making a single connection point returning water back to system?
    Logic correct and reasonable?
    I have to repeat this logic in a few areas in the house to bring place back to its 'cast iron rad victorian' glory days LOL
    Many thanks to all who chime in with suggestions and tips.
    best regards, Mark
  • Jamie Hall
    Jamie Hall Member Posts: 16,589
    That's the basic idea, @MarkZeh . You want the flow to be able to go to either radiator without going through the other one. It's not so much a matter of timing, however, as of flow, since the system will be flowing water much of the time. It can be astonishingly difficult to get equal flow to both radiators just with piping, but you don't need to (and, very likely don't really want to -- since you will likely need different heat outputs from each one). However, this is not a problem -- each branch can have its own flow control valve (even TRVs, if you like) without interfering much with the flow to the other branch.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • MarkZeh
    MarkZeh Member Posts: 10
    Jamie, huge thanks. Sounds very reasonable, can always attempt to make branch offs equal length to improve on equal flow. Doubt 15 seconds or so in delta will make a diff once rads heat up. Most probably will perform extra work in 3/4" pex. Guessing know, but just asking an expert: any issues branching a 3/4" copper pipe with 2 - 3/4" pex outflows to the 2 rads. My take is that at least the water flow to each rad will be equivalent.
    many thanks again
  • Jamie Hall
    Jamie Hall Member Posts: 16,589
    No, in terms of pipe size -- but be sure that you use PEX-Al-PEX, which has an oxygen barrier in it. Big box store PEX doesn't, and that will give you problems with the system. Also make sure that your aquastat shuts things off at or below 180, which is the rated temperature for PEX.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    MarkZeh
  • MarkZeh
    MarkZeh Member Posts: 10
    Jamie, again, huge thanks. Total clear, will most probably stick with copper to copper on first floor and back room where basement give me great access to all hydronic piping for those 2 zones. If 2nd and 3rd floor piping becomes and issue then I'll go with Pex-Al-Pex tubing and adjust the aquastats so that they run below 180. The 2nd and 3rd floors run off of 2 separate zones anyway so should not be an issue.
    thanks for the great tips!!
  • MarkZeh
    MarkZeh Member Posts: 10
    Jamie, as I read more and more on doing this job more Qs arise. What are your thoughts on Pex-Al-Pex vs. Pex B? I do not have the special crimp tool for PAP but only the std pex crimp tool for std pex which work on Pex B. No sunlight exposure as well.
    thanks
  • Jamie Hall
    Jamie Hall Member Posts: 16,589
    The question isn't so much PEX A or B or C as it is oxygen barrier. None of the three cross linking methods (that's what the A or B or C stands for) provides, by itself, an oxygen barrier -- and that's the problem.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • MarkZeh
    MarkZeh Member Posts: 10
    Jamie, thanks, on that aspect I am totally clear, must have the O2 barrier. Question: preference between Pex-Al-Pex or Pex-B with O2 barrier. Any reason to go in either piping direction?
    thanks
  • mattmia2
    mattmia2 Member Posts: 3,668
    Pex-al-pex is semi rigid so once you put it someplace it stays in that shape but pex is easier to pull through a building(at least for small sizes). Pex needs to be secured frequently but in such a way it can expand and contract with temp or it will sag and such. The layer of aluminum is probably a more solid oxygen barrier than the barrier layer in pex. Both can have problems if not terminated properly.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    The oxygen barrier that is in any pex tubing is separate and aside from the aluminum. The purpose of the aluminum is to provide rigidity to the tubing when it becomes heated. I prefer pex A. When properly installed I trust the fittings more. I very much dislike the small copper rings as PEX has a lot of expansion and contraction with changes in temperature. If I use compression rings I only use the full sleeve stainless steel ones. I do understand that there is a significant price difference in the tools to use either the stainless steel sleeves for the expansion rings.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 3,668
    edited October 4
    I much prefer propex connections. For smaller sizes a hand tool that can use the actual Milwaukee dies and a couple sizes of Milwaukee dies isn't that expensive.(although the brass transition fittings are a bit pricey)

    When I replaced some of the galvanized pipe in my mom's house I concluded that copper sweat fittings were so much less expensive than pex fittings that even though the tube was significantly more expensive, copper with sweat fittings was the least expensive way to go. I just used pex a in a few specific places where making up copper would be difficult or I needed some flex.
  • MarkZeh
    MarkZeh Member Posts: 10
    Charlie from wmass/Mattmia2, many thanks for your advice. Most likely will stick with copper for the area that are accessible within the basement. Unless I can get my hands (borrow) the special PAP expensive crimping tool I will most likely go with Pex B and take all precautions to secure properly and not kink tube.

    "I very much dislike the small copper rings as PEX has a lot of expansion and contraction with changes in temperature. If I use compression rings I only use the full sleeve stainless steel ones."

    Totally agree with Charlie on the copper rings, have always used the sleeve SS crimps. As a modicum of insurance, any plumbing I've done with reg Pex that was either within a wall or a difficult area to access I always use 2 crimps at each connection joint. Few $$ more but better be safe than sorry in my book.
    thanks again
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195


    " agree with Charlie on the copper rings, have always used the sleeve SS crimps. As a modicum of insurance, any plumbing I've done with reg Pex that was either within a wall or a difficult area to access I always use 2 crimps at each connection joint. Few $$ more but better be safe than sorry in my book.
    thanks again"

    The crimp rings I use only fit one on per joint. I use only viega or uponor pex products supplemented with compatible Sioux Chief specialty fittings .

    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • MarkZeh
    MarkZeh Member Posts: 10
    Charlie, many thanks. Clear on the fiting. Reviewing both Viega and Uponor web sites. Swapping out some beat up BBs with older style cast iron rads. JUst want to do the plumbing conversion correctly. You reco monoflo Ts for the branching? any recos on the specific Pex tubing, fitting and crips. I always listen well to the pros.
    thanks
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    Monoflo is fine if it allows enough btu flow. Reverse return piping is best for balancing system, and home run system is best for individual control of radiators. 
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,275
    Reverse return or a home run system. Generally speaking a homerun system can be done with 1/2" pex. You would bee surprised how little flow those CI rads actually need. Do the math for sizing. 

    I've done both reverse return and home run systems, and they all have performed equally well, with surprisingly little need for balancing on the homerun system. That rads really aren't very sensitive to flow. The farthest one and the closest one all heated well. 

    If the space layout is good, I prefer reverse return, which you can do with hard pipe or pex. Maybe it's the oldschool in me.....
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • RobertJordan
    RobertJordan Member Posts: 2
    You should consider having an energy audit. Mass Save does them for free. Contact CET - Center for Eco Technology, I think it stands for. Air sealing will probably be warranted. Insulation in the attic. Insulation in the walls might be problematic, unless you are residing. There is too much chance of moisture building up in the walls if it isn't properly dealt with, despite what Mass Save might recommend.