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Thread: Questions about hydronic baseboard heat

  1. #1
    DIY Senior Member lordmoosh's Avatar
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    Default Questions about hydronic baseboard heat

    Hello all,

    I am renovating my living room/dining room and have a few questions about the hydronic baseboard heaters. The brand is "RepCo" but I don't know if they exist anymore. I have 4 zones.

    1) The covers are rusting on the inside areas of the covers. There are three 12 foot lengths in the two rooms. The fins look to be in good condition and are about 2" wide. Could I just get Slantfin covers from Home Depot and replace these covers? Anyone know if the current elements are compatible with Slantfin covers? I don't really want to deal with sanding them all and repainting them.

    2) There are no bleeders on any of the baseboards in the house except on 2 units I replaced recently and 1 under cabinet kickspace heater. Should I try to try to desolder the right angle fittings and solder in ones with coin vents?

    3) Two of the zones in the house are 1/2" pipe and two other zones are 3/4" pipe. The current zone (first floor) I am working on is 1/2". I recall reading that the limit for 1/2" is not that long. I would estimate I have at least 80 feet of 1/2" pipe in this zone. I have about 40-44 feet of baseboard heating fins and one Beacon Morris kickspace heater on this 1/2" line. Isn't this line undersized?

    Thanks.

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    In the trades Dana's Avatar
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    1> Any reason why they can't be cleaned up and re-painted? If they can't be refurbed, measure the distances of the fins from the floor and wall, and check against he dimensions of the SlantFin parts to see if it fits:

    http://www.slantfin.com/images/stori...seline_dim.pdf

    http://www.slantfin.com/images/stori...line30_dim.pdf

    2>Don't bother adding bleeders unless you have chronic vapor-lock/low-flow issues.

    3>At 80' of total plumbing including fin-tube it doesn't take a monster pump to get the minimum 1gpm of flow. But it helps to have the whole picture in front of you- total length of pipe, the number of ells & tees, the published "head" of the toe-kick heater, the pump that's driving it, and the boiler's head, then do the math or look at the pump's gpm vs. head or equivalent-length of the plumbing.

    Before you even look at the covers, what's the boiler, and what are the total amount & type of heat emitter on each zone? When systems get cut up into zones like that it can take a toll on the boiler if each zone isn't independently capable of emitting a large fraction of the boiler's output at the high limit temperature, sometimes resulting in 10+ burn cycles/hr on zone calls. This is bad for efficiency as well as for maintenance & longevity, so before hacking on it, do at least the crayon-on-napkin math- you may want to be doing more/different than than adding vents or nicer looking covers.

  3. #3
    DIY Senior Member lordmoosh's Avatar
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    Quote Originally Posted by Dana View Post
    1> Any reason why they can't be cleaned up and re-painted? If they can't be refurbed, measure the distances of the fins from the floor and wall, and check against he dimensions of the SlantFin parts to see if it fits:

    http://www.slantfin.com/images/stori...seline_dim.pdf

    http://www.slantfin.com/images/stori...line30_dim.pdf

    2>Don't bother adding bleeders unless you have chronic vapor-lock/low-flow issues.

    3>At 80' of total plumbing including fin-tube it doesn't take a monster pump to get the minimum 1gpm of flow. But it helps to have the whole picture in front of you- total length of pipe, the number of ells & tees, the published "head" of the toe-kick heater, the pump that's driving it, and the boiler's head, then do the math or look at the pump's gpm vs. head or equivalent-length of the plumbing.

    Before you even look at the covers, what's the boiler, and what are the total amount & type of heat emitter on each zone? When systems get cut up into zones like that it can take a toll on the boiler if each zone isn't independently capable of emitting a large fraction of the boiler's output at the high limit temperature, sometimes resulting in 10+ burn cycles/hr on zone calls. This is bad for efficiency as well as for maintenance & longevity, so before hacking on it, do at least the crayon-on-napkin math- you may want to be doing more/different than than adding vents or nicer looking covers.
    1 - The covers are rusting on the inside. I'd have to pull them out and spend a lot of time sanding and painting them and then hope they go back in ok. The dampers don't open/close as nicely as the new covers (maybe they need some WD40?) Also Some of the covers in areas of the house are missing accessories like the metal pieces that join two separate baseboards together. I can't find any information on RepCo to buy replacement pieces. I figured it would save time (but more costly money wise) and look better if I got replacement covers.

    2 - I don't know what "chronic vapor-lock/low-flow" means but I do have a hell of a time bleeding the system when I refill it after doing some work on it. I've tried different methods like filling each zone one at time but the second floor is especially troublesome to bleed. The second floor has no air bleeders and is a pain to get water flowing completely through the pipes. I think eventually it fills up over time as the auto air bleeder at the boiler does its job. I figured it might be worth adding manual bleeders around the house as I go along to help me solve these kinds of problems if they occur. I do have bleeders on three other radiators on the same zone, would that be considered good enough to clear this particular zone of air?

    3 - I will do research and get back to you with these details.

    Regarding the energy efficiency... I don't know if the system is optimal but our energy bills are pretty good. I am always sealing and insulating as I renovate the house but I can't really complain about my gas bills (water boiler is natural gas). With that said I would love to make them even cheaper if possible.

    Thank you.
    Last edited by lordmoosh; 09-10-2013 at 12:59 PM.

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    In the trades Dana's Avatar
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    Purging air after opening up the system is always a PITA, even with bleeders, but ideally you'd only need to do that once a decade or less. Only if it has a bubble sufficient to block flow (=vapor lock) that seems to recur at random times is it worth cracking open the system simply for the purpose of adding bleeders or vents. But if you're adding radiation, by all means, install the bleeder at that time.

    In a tight well insulated house a 2-3x oversized boiler serving a modest sized load at 70-75% efficiency instead of 85% due to short cycling it would be hard to tell from the billing, especially at the current/recent retail price of natural gas, which is at or near historical lows in most of the US (an artifact of shale gas being wholesaled at less than the cost to produce it, making their real money off the propane & butane liquids.) But short-cycling definitely shows up in wear & tear on the boiler. Over the total life cycle of the boiler the difference in operating cost due to the lower efficiency would pay for some up-sized radiation on the zones, as would extending the boilers life to 30 years instead of having it get flaky and having to replace all of the ignition stuff at or before the ripe-young age of 15.

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    DIY Senior Member lordmoosh's Avatar
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    Quote Originally Posted by Dana View Post
    Purging air after opening up the system is always a PITA, even with bleeders, but ideally you'd only need to do that once a decade or less. Only if it has a bubble sufficient to block flow (=vapor lock) that seems to recur at random times is it worth cracking open the system simply for the purpose of adding bleeders or vents. But if you're adding radiation, by all means, install the bleeder at that time.

    In a tight well insulated house a 2-3x oversized boiler serving a modest sized load at 70-75% efficiency instead of 85% due to short cycling it would be hard to tell from the billing, especially at the current/recent retail price of natural gas, which is at or near historical lows in most of the US (an artifact of shale gas being wholesaled at less than the cost to produce it, making their real money off the propane & butane liquids.) But short-cycling definitely shows up in wear & tear on the boiler. Over the total life cycle of the boiler the difference in operating cost due to the lower efficiency would pay for some up-sized radiation on the zones, as would extending the boilers life to 30 years instead of having it get flaky and having to replace all of the ignition stuff at or before the ripe-young age of 15.
    I have not had a chance to measure the pipes and count the fittings yet but I did look at those Slantfin PDF files and see that they may not work with my heating elements. The diagrams say the Slantfin dummy covers are about 3" from the floor to the center of the element pipe. I think my pipes are like 2-2.5" on center from the floor (depending on the room you are in). I have some slack in the pipes so I can raise the heating elements up. Here are my questions:

    1) How much vertical slack does there need to be for heating elements? Some of the older heating elements in the house have an inch or more slack but the Slantfins I recently installed have less, one heating element does not have much slack at all at one end maybe 1/8".

    2) I need to pipe my kickspace heater in the kitchen so I will have to drain the boiler. Would you guys think its worth it to desolder the return elbows at the baseboard heating elements and solder in elbows with coin vents?

  6. #6
    DIY Senior Member lordmoosh's Avatar
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    bump bump

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    In the trades Dana's Avatar
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    Fin tube baseboards are designed as convectors, with air inlet at the bottom, exit at the top. The required clearance to the floor depends on the location of the air inlet, which is a function of the sheet metal cover design. (1/8" seemed unusual though.)

    If you're ripping the thing apart, putting in vents for air-purging convenience never hurts. "Worth it" or not is up to you.

  8. #8
    DIY Senior Member lordmoosh's Avatar
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    Quote Originally Posted by Dana View Post
    Fin tube baseboards are designed as convectors, with air inlet at the bottom, exit at the top. The required clearance to the floor depends on the location of the air inlet, which is a function of the sheet metal cover design. (1/8" seemed unusual though.)

    If you're ripping the thing apart, putting in vents for air-purging convenience never hurts. "Worth it" or not is up to you.
    I am not talking about clearance between the finned tube and the floor (which is about a couple of inches in my case). I am talking about how much slack/play should there be when you move a fin tube up and down (how much slack between the fins and the hangers). Thanks.

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    In the trades Dana's Avatar
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    The amount of slop doesn't much matter, as long as it doesn't impede air flow.

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    DIY Senior Member lordmoosh's Avatar
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    Quote Originally Posted by Dana View Post
    The amount of slop doesn't much matter, as long as it doesn't impede air flow.
    1) I am planning on piping in the kickspace heater soon which will require me to drain the heater. I plan to add a brass t fitting 1/2"x1/2"x1/4" in-line on the second floor (I did not see a 1/2"x1/2"x1/8" brass t fitting so I will need to reduce the 1/4" to 1/8") and put in a coin vent. I don't really want to mess around with desoldering this close to winter. I want to do this to help me bleed the second floor after I finish soldering the kickspace heater. The second floor gave me a lot of trouble the last time I drained the heater. Would having the bleeder in-line help me?

    2) Also it looks like two Maid-O-Mist number 67 auto air vents are leaking at my heater. One of them was leaking before so I just closed the cap all the way. Now a second one in a different spot is leaking which I also closed. Should I simply replace them with the same brand/model? I notice the maid-o-mist one is like $9 and another brand is like $23.

    http://www.pexsupply.com/Jacobus-Mai...-1-8-Auto-Vent
    http://www.pexsupply.com/Bell-Gosset...-Male-Threaded
    http://www.pexsupply.com/Taco-417-3-...ent-11389000-p
    http://www.pexsupply.com/Cello-CP12-...Tee-12353000-p
    http://www.pexsupply.com/Cello-TB12-...hing-1849000-p

    PS - I still plan to measure the pipes I just need to get around to it.

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    I have a preference (limited experience, though) for Spirovents. You might want to look at them. They're not inexpensive, but seem to work a long time, and are a bit more efficient at scouring air from the system.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member lordmoosh's Avatar
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    Is there a spirovent that fits in a 1/4" thread? I don't want to hack up the system at this time.

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    DIY Senior Member lordmoosh's Avatar
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    Quote Originally Posted by lordmoosh View Post
    Is there a spirovent that fits in a 1/4" thread? I don't want to hack up the system at this time.
    bump. I would like to do this on the weekend so I need to put the order in today or tomorrow at the latest.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Spriovents are plumbed in a main line, not as a 'top hat'. It has a SS comb that sits in the water stream that literally combs micro air bubbles out of the water stream.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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