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Convectors

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Tom_133
Tom_133 Member Posts: 888
Gentlemen,



I am struggling with a new project. Homeowner is a builder and already knows what he wants but in the next breath has absolutely no idea!!



7000Sqft house built with 12" brick exterior walls and seriously high ceilings (some 22') and a ton of windows. I did a full heat loss and the entire building is 201K btu of loss.

Currently the building has convector heaters on one half of building, they are double finned 4" fintube on1 1/4" copper pipe that have been abandoned in the past because the boiler was installed by the pilgrims (its waaay too big and old)!! The house was retrofitted with 3 gas furnaces to keep it warm. Very inefficient.



The new owner wants to go geothermal, after a long conversation about the cost exceeding his budget he now wants to do a pellet stove, with a condensing boiler backup piped into a thermal tank and install 3 coils into the furnaces.



Ok, so enough back story and to my actual question, after looking at some websites and not getting anywhere (eyes glazed over) I need help figuring out what these style convectors put out for heat at different temps? I want to know what water temp I can set them for and still cover my load. If it's easier I need a little guidance understanding the charts in this PDF, They are the WA style with 6" cabinets
Tom
Montpelier Vt

Comments

  • Zman
    Zman Member Posts: 7,574
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    Charts

    On those charts, the average water temp for each chart is in the upper right corner.

    If you are using a condensing boiler, you might want to use the 130 degree chart.So that the return water temps will allow the boiler to condense.



    As an example.

    A model W-A 26 that is 4" deep and 40" long would produce will produce 2125 BTU/HR. at 130 average water.



    The real trick is in sizing the coils for the ducts. They will need to be fairly thick and you will have be sure the circulating fan can overcome this.



    Even though the pellet boiler will not achieve higher efficiency at lower water temps, it is a good idea to size the radiation for low temps in case solar or geothermal is added at a later date.



    Hope that helps.



    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • icesailor
    icesailor Member Posts: 7,265
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    No Envy:

    I don't envy you Bro.

    Nothing worse than working with an expert that knows far more than you. I love GC's that are plumbing and heating experts who try to tell us how we can run pipes and pass an inspection.

    First of all, that giant inefficient boiler was designed and install by old dead men who knew what they were doing. So, with inefficiencies taken into account, it heated the building. From my theoretical point of view, it might be safe to consider the boiler to be 70% efficient, or it could have been made so with some insignificant modifications. Therefore, for the sake of discussion, if the boiler is rated at 1,000,000 BTU's, it is still pumping 700,000 BTU's in the building. So, if the RS (Rocket Scientist) decides to replace said boiler with 3-150,000 BTU boilers (450,000 BTU's), the new boilers are seriously undersized. How many Pellet Stoves is he going to use and how much for pellets? I hope you understand the exercise. Why do you think that they use fan coil cabinet heaters in commercial spaces with unusual heating demands? To force circulate the air.

    Unless you have already, you need to get the IBR manuals for heat loss and piping design from the GAMA. You should be able to figure it out as to how it works. What you describe is really a small commercial job and requires more knowledge in design. The GC/Customer is treating you like one of his employees who know less than he does. This mess needs to be designed by a ME. Let the GC argue with him. Will you be paid for all this uncompensated time while you use YOUR expertise to solve the impossible? It took me far too long to stop me from these fools errands for people who didn't know what they wanted or needed. You do all the leg work, give him all the information, and he shares it with everyone else.

    If I could have been paid for all the uncompensated time I spent while trying to solve these problems, I could have retired with a lot more money.

    Let him hire a "Professional" to figure out his design and fight with him over what he wants and thinks will work. Then, you give him a price to do the install. And you won't be at fault when it doesn't work as promised.
  • icesailor
    icesailor Member Posts: 7,265
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    All that may be true:

    Z-Man,

    All that may be true, but it sounds like a very careful heat loss design hasn't been done for all the spaces. Some of the described spaces sound extremely difficult to heat properly. Cooling isn't mentioned but you mention it. That creates another 5 gallon bucket of worms from the description. If you need heat emitters with double rows of 1 1/4" fin tube cabinet heaters, it probably needs high emitting fan coils. I can see it now. All the wall spaces covered with that ugly fin tube cabinets but the owner/GC doesn't want to listen to a fan coil unit. So, what to do?

    It sounds like the GC is an expert and knows far more than anyone here.

    I find many GC's to be our worst nightmare. I had the pleasure of working for or with some really good ones. Then, there are the others.
  • Tom_133
    Tom_133 Member Posts: 888
    edited May 2014
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    Dead on

    Thanks Carl, Does that number on the chart account for the double fin tube or just a single row?



    Icesailor, you are absolutely correct, I do feel like an errand boy. I chalk some of this up to educational expense. I do learn a lot from doing this but also need to learn how to say no thank you to being a mildly informed free sounding board. The building heated well with the 3 furnaces (all about 90K btu's) and I don't know how long that monster Weil McLain has been offline but it will take a full day, a plasma cutter and 2 guys to get it out of there. My plan is to use a 120 gallon thermal accumulator and feed the condensing boiler into it and the pellet stove into it and set the tank temp as low as I can get away with. Thanks for helping
    Tom
    Montpelier Vt
  • Zman
    Zman Member Posts: 7,574
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    Charts

    Tom,

    I think if you look carefully and the specs for the different models you will be able to determine which line is the double coil. I think it will have a different model number. I was just giving an example of how the chart works.



    Ice,

    What about AC? It looks like you have good rant going, I was just answering the question.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Tom_133
    Tom_133 Member Posts: 888
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    Picture

    Here a pic of one of the units
    Tom
    Montpelier Vt
  • icesailor
    icesailor Member Posts: 7,265
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    No rant:

    No rant here. Just fond memories of life in the fast lane.  Mention was made about learning and being a sounding board. I should have a PhD from all I learned while trying to do the engineering for all these people that think they know far more about our trade than we do. The posting reminded me of that comment, "Been there, Done that". "I've" Been There, Done that.

    I figured it out a long time ago. It was reinforced over and over on HH.com, FIRST DO A COMPREHENSIVE HEAT LOSS!!. No mention of one in the posting. Because the GC is smart, and he isn't. So, they don't need one. Until something doesn't work and someone like you or I come in and do the first one.

    If you want to get really good at understanding why things don't work, figure out how they work and then, fix them.  Maybe you've never had someone with a 6.000 sq. ft partially insulated building and they want to heat it with a 91,000 BTU Mod Con gas boiler with radiant PEX. They have already bought the materials from PEX Supply and they just want you to install it.
  • icesailor
    icesailor Member Posts: 7,265
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    Learning Curves:

    So, from what little I've seen, you have one complicated system on your hands. Whatever that baseboard is feeding, there must be a lot of loss in the room and/or not a lot of wall space. Two rows of 1 1/4" fin tube is not found in your average tract or beach cottage. Unless it is along the bluff in Newport, RI. The supply and return are on one end, there's a electric zone valve to control the flow. That single 110 volt receptacle with the plug on the floor, opens the valve when the boiler gets a call. Whenever I was faced with something like this. I learned to be able to calculate the emitting characteristics of the fin tube and build a scenario of what was needed in the room. Then, what is the heat loss of the room. You have to do every room to get a pattern on how the old dead estimator calculated the loss and how to cover it. Once you know the loss, and understand how the water temperature determines the output of the emitter. Then, you adjust the water temperatures from the chart to come up with some water temperature the designer used. It may be all well and good to try to use 130 degree water in the system, but the old dead guy would have used a whole lot of baseboard. Which would have run up the cost. Those old dead guys were tight as a crabs butt, And that was watertight.

    I've looked at a lot of steel and copper heating mains and branches. I've never found one to be oversized for the application. If there was a 1 1/2" main in the house, the emitters connected a 1 1/2" main to flow the correct amount of water.

    Its worth learning.