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  1. #1
    Join Date
    Jul 2009
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    23

    What's wrong with my steam to hot water conversion?

    HVAC experts--I'd appreciate your help since we have paid the contractor, who agreed to fix the problem but I don't think he will have unlimited patience to do it.

    Background: My house is heated with steam radiators. An addition at the back is heated with 2 Sunrad radiators off the main steam pipe. Because the long steam line and higher heat loss of the addition, it is always cold. The 2 radiators do have enough BTU to heat the space. The problem is if I crank up the heat the main part of the house would be too hot--too much waste.

    Problem: We hired a contractor to convert the 2 radiators to hot water on a separate zone. The radiators have 2 pipe connections, he ran about 50 feet one-way of 3/4 copper pipes from my unused water coil in the steam boiler to the 2 radiators (in a series connection), with a circulation pump at the return end of near the boiler. But the result is a minor disaster. The first radiator is fine. But after the first radiator, the water is already cooled down so the second radiator doesn't get really hot. As a result the room is 10 degrees colder than when we had them on steam.

    Again, the 2 radiators do have enough heating power for the room because on steam they were able to heat up the room in the coldest days. After the hot water conversion only 1 is working 100% and other at most 20% since there isn't much convection going on. The contractor came back once to increase the hotwater temperature and insulate the copper pipes, that only improved the heating slightly.

    The boiler can produce enough hot water, and the radiators can radiate enough heat for the room. From the simple physics, obviously not enough volume of hot water is sent to the radiators. Is the size of the copper pipe 3/4 inch too small? Is the water pump too small (the contractor said that is the same pump for the whole house)? Can I add one more pump to push the water to the radiators (in addition to the current one that sucks the water from the radiators)?

  2. #2
    Join Date
    Feb 2009
    Location
    north of 49
    Posts
    233
    Quote Originally Posted by ilnyc View Post
    HVAC experts--I'd appreciate your help since we have paid the contractor, who agreed to fix the problem but I don't think he will have unlimited patience to do it.

    Background: My house is heated with steam radiators. An addition at the back is heated with 2 Sunrad radiators off the main steam pipe. Because the long steam line and higher heat loss of the addition, it is always cold. The 2 radiators do have enough BTU to heat the space. The problem is if I crank up the heat the main part of the house would be too hot--too much waste.

    Problem: We hired a contractor to convert the 2 radiators to hot water on a separate zone. The radiators have 2 pipe connections, he ran about 50 feet one-way of 3/4 copper pipes from my unused water coil in the steam boiler to the 2 radiators (in a series connection), with a circulation pump at the return end of near the boiler. But the result is a minor disaster. The first radiator is fine. But after the first radiator, the water is already cooled down so the second radiator doesn't get really hot. As a result the room is 10 degrees colder than when we had them on steam.

    Again, the 2 radiators do have enough heating power for the room because on steam they were able to heat up the room in the coldest days. After the hot water conversion only 1 is working 100% and other at most 20% since there isn't much convection going on. The contractor came back once to increase the hotwater temperature and insulate the copper pipes, that only improved the heating slightly.

    The boiler can produce enough hot water, and the radiators can radiate enough heat for the room. From the simple physics, obviously not enough volume of hot water is sent to the radiators. Is the size of the copper pipe 3/4 inch too small? Is the water pump too small (the contractor said that is the same pump for the whole house)? Can I add one more pump to push the water to the radiators (in addition to the current one that sucks the water from the radiators)?
    What are the supply and return temperatures? The temperature leaving the water coil and the temperature of the water returning to the boiler? In other words, what is the temperature drop?

  3. #3
    Join Date
    Feb 2009
    Location
    north of 49
    Posts
    233
    Oh....and by the way! If the requirement of "being an expert" is a pre-requisite of posting to your question......I withdraw my questions

  4. #4
    Join Date
    Dec 2009
    Location
    Nashville, TN
    Posts
    35
    With out looking at what you have we can only speculate, but I would suggest that the supply to the radiators should have been parallel instead of in series. The majority of the heat from the water is being expelled at the first radiator.

  5. #5
    Join Date
    Feb 2009
    Location
    north of 49
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    233
    Quote Originally Posted by kontrolsfreek View Post
    With out looking at what you have we can only speculate, but I would suggest that the supply to the radiators should have been parallel instead of in series. The majority of the heat from the water is being expelled at the first radiator.
    Absolutly.....but is is piped the way it is in parallel. And being piped in parallel feeding 2 rads on a 50ft loop, there should not be, as he described, an 80% temperature drop between the 2 rads. It should be the other way around and a one pipe parallel should be able to achieve that.

  6. #6
    Join Date
    Jul 2009
    Posts
    23
    Quote Originally Posted by trout lake View Post
    What are the supply and return temperatures? The temperature leaving the water coil and the temperature of the water returning to the boiler? In other words, what is the temperature drop?
    The temperature drop is a lot. The heat is being delivered to the room, mostly at the first radiator.

  7. #7
    Join Date
    Jul 2009
    Posts
    23
    Quote Originally Posted by kontrolsfreek View Post
    With out looking at what you have we can only speculate, but I would suggest that the supply to the radiators should have been parallel instead of in series. The majority of the heat from the water is being expelled at the first radiator.
    Agreed. But question is still what is wrong with my current configuration? The parallel configuration sounds better, but one can think of the left half and right half of the same radiator are in a series configuration. The real issue here is not enough gallons of hot water reached the radiators per minute. I have no clue if he cut corners on the size of the piping, or created some bottleneck in the loop, or sometime I even suspect the pump isn't working because it makes no sound at all.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,074
    Quote Originally Posted by trout lake View Post
    Absolutly.....but is is piped the way it is in parallel. And being piped in parallel feeding 2 rads on a 50ft loop, there should not be, as he described, an 80% temperature drop between the 2 rads. It should be the other way around and a one pipe parallel should be able to achieve that.

    From his description. I don't think its piped parallel. Sounds more like series since he said the water temp is too cool after the first radiator.
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  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,074
    OP:

    You need a good contractor to straighten out that mess.
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  10. #10
    Join Date
    Jul 2009
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    23

    The radiators are in series

    as I said in OP, they are in series. The question is if there is an easy way of mitigating the problem.

    Why are you sure parallel vs serial is the root of the problem?

    Let's say he changes the connection to parallel. At the boiler, it is still one 3/4 pipe going in and one 3/4 inch pipe coming out, same pump also. So if the flow rate is the same, then same amount of heat is being delivered to the room, which is not enough. So I would get the 2 radiator perfectly balanced but what does that achieve if the amount of heat is not enough?

    The contractor obviously messed up somewhere. But he is not bad. I can have him back to make appropriate changes. But I don't think he will be back twice, nor I am asking advice on how do deal with him. I am asking for advice how to change the system.

  11. #11
    Join Date
    Dec 2005
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    Current whereabouts unknown
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    the issue here may be the hot water coil is being used as the heat source. There is a way that a hot water zone can be piped from below the water line of a steam boiler but it isn't something i can go into here. As someone already said, you should find someone that really knows steam heating and have him look at what you have
    It matters not how strait the gate,
    How charged with punishments the scroll,
    I am the master of my fate:
    I am the captain of my soul.

    -- William Ernest Henley

  12. #12
    Join Date
    Dec 2005
    Location
    Current whereabouts unknown
    Posts
    639
    .
    It matters not how strait the gate,
    How charged with punishments the scroll,
    I am the master of my fate:
    I am the captain of my soul.

    -- William Ernest Henley

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,074
    Take a garden hose.

    Connect to outdoor faucet. Turn water on. See how much comes out. Then slightly kink it. See how much less water comes out. Put a second kink in it. See how much less comes.
    You are increasing the resistance to water flow with the kinks. Same thing with serial piping.

    PS: Your rads have one heat rating with steam. they have a much lower heat rating with just hot water.

    And your plumber doesn't sound real Sharp on circulator selection.

    What temp is the boiler set to for this loop. What is the entering and leaving water temp of the coil(in F).
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