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Connection For 1" Cast Iron to 1" Copper

Hello all, so i am switching out my 3/4" copper supply and return lines, from my radiators in one room, to 1" copper. The 3/4" connection was originally reduced from 1" cast iron with a dielectric union. I have been told that, going from cast to copper, i didnt need a dielectric union.

so my question to you all is, what would you use at the cast iron 90 elbow to go to 1" copper?

This is for a hot water boiler setup by the way


Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,985
    So the first question is... What is wrong with the current setup?

    Is there a room that is too cold?

    Are the other rooms getting too hot?

    Do you experience noisy operation?

    If you can answer NOTHING or NO to these questions, then it ain't broke... so, don't fix it!
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
    mattmia2PC7060
  • mattmia2
    mattmia2 Member Posts: 7,198
    You can connect copper directly to iron or steel in a closed system like a hot water heating system but unless the radiator is the size of a honda, 3/4' can supply more heat than a single radiator will emit. The only cases where this might not be the case is on gravity system that is still gravity or on a monoflow system.
  • stupidhomeowner
    stupidhomeowner Member Posts: 20
    edited October 2022

    So the first question is... What is wrong with the current setup?

    Is there a room that is too cold?

    Are the other rooms getting too hot?

    Do you experience noisy operation?

    If you can answer NOTHING or NO to these questions, then it ain't broke... so, don't fix it!

    so i don't have enough heat coming into that zone(which has its own pump also). i have slant fin copper baseboards on two walls of the room and am getting ready to add a 3rd wall of the same radiators.

    the old radiators used to be cast iron baseboards and were fed with 1" pipe (i think they transitioned from cast to galvanized). i know i shouldn't have ripped out the old ones but i had to and thought it would be easier to install the slant fin but i didnt add enough i think, and i also reduced down to 3/4" copper.

    i think my piping method is wrong too. i think i ended up installing a 2 pipe direct return but the piping isn't equal lengths going to the 2 existing radiators so im not sure how i want to connect this 3rd one im going to install.



  • hot_rod
    hot_rod Member Posts: 18,239
    If the developed length is different, tube + heat emitter + fittings, you need to add valves to balance flows. The shortest loops will get most of the flow, so those need to be balanced down. 3/4" should be able to handle 60' or so of fin tube.

    Looks like more heaters on one side of the blue zone, that section will under-heat.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,985
    edited October 2022
    The fact that you switched up from cast iron baseboard to Copper tube w/aluminum fin is the cause of the temperature imbalance. They react in different ways. Copper w/alum heats faster and cools faster. It requires a slightly higher GPM to get the most out of them. I will bet the thermostat is in a room with the cast iron rads, that is why the Copper w/alum room is cooler.

    If the thermostat is in the room with the lower price radiators, the rest of the home would get too hot. Changing pipe size and adding more low cost radiators will not solve your problem.

    To solve the problem you need to replace the radiators with cast iron to match the rest of the home

    OR

    Put the copper w/alum radiators in a series loop with a home run to the boiler room. Add a separate circulator and a separate thermostat for that zone. Both options are more expensive than you probably were thinking of, but if you don't spend the money to do it right, then you will be spending less without solving your problem. Any $$$ spent that does not solve the problem is wasted $$$.

    Just the opinion from an old boiler guy with 40+ years experience... Including just your problem.


    Respectfully,
    Me. Ed
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
    bburd
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,985
    edited October 2022
    This might be a good piping diagram for you. Least expensive fix!

    Do not mix different types of radiators/heat emitters on the same zone/thermostat.
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • stupidhomeowner
    stupidhomeowner Member Posts: 20
    This might be a good piping diagram for you. Least expensive fix! Do not mix different types of radiators/heat emitters on the same zone/thermostat.
    so this would be a series loop then, thats what i was thinking also.  this room is actually on its own zone with its own pump already also.

    what's the purple piping for though?
  • mattmia2
    mattmia2 Member Posts: 7,198
    The purple pipe is where he drew red over your blue.

    If you already have the return to the far end it wouldn't hurt to put the new section between one of the existing sections and the return as long as you put a balancing valve on the shorter section somewhere after it branches off the supply before it combines at the return. you would get a little more output that way because 2 of the sections would start at the boiler supply temp instead of each series section getting progressively cooler water.
  • stupidhomeowner
    stupidhomeowner Member Posts: 20
    edited October 2022
    mattmia2 said:

    The purple pipe is where he drew red over your blue.

    If you already have the return to the far end it wouldn't hurt to put the new section between one of the existing sections and the return as long as you put a balancing valve on the shorter section somewhere after it branches off the supply before it combines at the return. you would get a little more output that way because 2 of the sections would start at the boiler supply temp instead of each series section getting progressively cooler water.

    hey there, so all the radiators are 10' sections. as far as a balancing valve, im not sure if i would be able to fit those onto the 90 elbows coming into the radiators. i have end caps at each end of the radiators and from the valves I've seen, there's no way i would fit them within the space of the endocaps.

    I've been told that a total of 30' of radiators in that space (especially being on its own zone and with its own pump) would not drop temp much going from radiator to radiator. not enough to be of concern at least. what do you think? how much of a drop would be a concern? more than 20 degrees?

    if you wouldn't mind, would you be able to map out the piping your talking about though, im trying to picture it in my mind but i cant.
  • mattmia2
    mattmia2 Member Posts: 7,198
    You can use a standard ball valve or a globe valve as a balancing valve. If I used a globe valve I would put it on both branches because the valve itself will be restrictive so just having the valve there might make the shorter pipe the higher resistance.

    You can put the valve below the floor somewhere or before you start with element in the fin tube horizontally.
  • hot_rod
    hot_rod Member Posts: 18,239
    Ideally you would no before hand what flows are needed in the various zones. Then if the system requires balance valves you could go with automatic valves built to the gpm require

    Your system will be more if a trial and error logic. But you can avoid some problems with a more adjustable piping method as you are learning.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • stupidhomeowner
    stupidhomeowner Member Posts: 20
    hot_rod said:
    Ideally you would no before hand what flows are needed in the various zones. Then if the system requires balance valves you could go with automatic valves built to the gpm require

    Your system will be more if a trial and error logic. But you can avoid some problems with a more adjustable piping method as you are learning.
    What do you mean by adjustable piping method? 
  • hot_rod
    hot_rod Member Posts: 18,239
    hot_rod said:
    Ideally you would no before hand what flows are needed in the various zones. Then if the system requires balance valves you could go with automatic valves built to the gpm require

    Your system will be more if a trial and error logic. But you can avoid some problems with a more adjustable piping method as you are learning.
    What do you mean by adjustable piping method? 
    The piping that Ed showed with the emitters in series

    although not knowing where the expansion tank connects, I might not use circs in the return as show as “optional”
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • stupidhomeowner
    stupidhomeowner Member Posts: 20
    edited October 2022
    hot_rod said:
    hot_rod said:
    Ideally you would no before hand what flows are needed in the various zones. Then if the system requires balance valves you could go with automatic valves built to the gpm require

    Your system will be more if a trial and error logic. But you can avoid some problems with a more adjustable piping method as you are learning.
    What do you mean by adjustable piping method? 
    The piping that Ed showed with the emitters in series

    although not knowing where the expansion tank connects, I might not use circs in the return as show as “optional”
    So do you think I should use 1” and get rid of the dielectric union or just use the existing 3/4” that I installed and run a series loop?

    Also, the expansion tank is in the boiler room.

    im thinking the series loop won’t be a bad ideas as I will use less piping which would make me think the badly insulated crawl space will have less of a chance to drop the temp in the supply line.  We shall see, there is a stretch of 3 70f days this weekend in Chicago so that’s my last chance to shut the boiler down and tear into the system and redo it
  • hot_rod
    hot_rod Member Posts: 18,239
    yeah, without knowing how much heat the space needs, it is a tough question.

    In a series loop, the first radiator gets say 180F, as it goes through more radiators temperature drops. So the last radiators have a lower output. Too low?? You would need to crunch some numbers to get the correct answer.

    That is one reason why you see split loops, to assure enough temperature at each radiator to make the heat load.

    The same answer for pipe size, you need to know how much flow, which equates to BTU delivered, to size pipe.

    WAG, I think series with the piping you have could work. Hows your luck these days :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream