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Thread: Hot water baseboard system , questions.

  1. #1
    DIY Member GG_Mass's Avatar
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    Default Hot water baseboard system , questions.

    Hello,
    I've Googled this for a while but could only find general type of knowledge as in 'how it works', but :

    We have a hot water baseboard (heated by oil) system. The same boiler is also in charge of heating up our water for personal use. I understood from my Oil supply company that an auxiliary water tank was installed after the fact into my system, to provide more 'ready to go' heated up water.
    my questions:

    1. Being that my heater(for the baseboards), is not working at this time, is there water pressure up to the baseboards ? Just as there is to the faucets, ? Or, only when the heater starts working, triggered by the thermostats, only then water is pumped and circulated to the baseboards ?

    2.The water comping up our supply lines (kitchen,etc.) get used up and the exit out the drain lines. What happens to the water that circulates through the baseboards ? does it ever get discarded ? Or, is the same water in the system since the system was installed ?

    3. Is there any interaction between the water in the personal use lines and the heating lines ? Or , these are two different systems all together, and their only common place is the boiler that heats them up ?

    I'm sure these are very general questions, I hope that after the first round of answers I'll be able to sharpen them up a bit.
    Thanks in advance.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Your hydronic heating system is (normally, and yours almost certainly is) a closed system under pressure (typically somewhere around 15psi to keep the water from boiling at a low temp like the cap on the radiator in your car). Because your boiler is heating your domestic hot water, it probably maintains some nominal temp all year long. That hot water circulates through a heat exchanger (either a coil or plate) in the indirect WH, when the aquastat for the IWH drops below a certain point. This also triggers the boiler to likely raise it's temperature and turn on its pump until the IWH has been reheated. There's likely separate valves to prevent that hot water from circulating into your baseboards, and that may have a separate pump to circulate it as well.

    Unless your heating system has a leak, the water that gets put in to fill it the first time is the water that continues to circulate until you trash the whole thing.

    Your system MIGHT have a automatic fill valve, and if it has a leak, might be adding new water over time. That can mask any problem until that new water which contains dissolved minerals and oxygen rusts out the system! So, from a practical matter, it's sometimes better to shut the valve to the automatic fill. If there's a leak, the pressure will drop and the boiler will stop, but you'll know it and then be alerted to fix the system rather than it running for years, adding water and corroding things inside along the way. After the original fresh water was installed, eventually, it reaches an equilibrium, all the oxygen is used up (things rust) and the minerals deposited somewhere in the system, then there's essentially only H20. It will have some dissolved metals and things in it, so you wouldn't want to drink it, but it is in equilibrium with the system, and things aren't changing anymore.

    Hope this helps...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Member GG_Mass's Avatar
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    I see, that's interesting.
    So , if I understand correctly, at any given point, there's water pressure up to the baseboards.
    And, these are two different water flow systems which should not mix.
    I took another look at the system, and the 1" pipes (heater) come out only from the boiler itself, whereas the 1/2" pipes (which then get fitted to 3/4") seem to only come out from the hot water tank.

    Being that I have two heating zones in the living area, and we have the water tank that gets heated, is it safe to assume that there should be an aquastat, downstairs, solely devoted to that hot water tank ?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    There's typically an aquastat IN the indirect. Look for a small cable coming out of the tank going over to the boiler...that's the aquastat. It is often inserted into a well from the outside, usually in the bottom third or so.
    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 Member GG_Mass's Avatar
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    I see.
    There's a unit I suspect is the one, , with both F and C values , I'll take a picture of it later and post it, to make sure I found the right control for the water tank temp.
    Thanks.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    On some installations, only the sensor is in the IWH, and all of the actual controls are in the boiler. This may be more common than having an actual fully functional aquastat in the IWH. On mine, the thermocouple is just inserted into a well on the IWH, and it feeds into the boiler's control board, so the adjustment of tank setpoint is all done in the boiler. The thermocouple acts like a variable resistor (volume control like thing) that the electronics in the boiler reads to determine the temperature and then decide when to fire. In this way, you can adjust when to turn the boiler on more easily. Mine is setup to allow it to cool off more before it refires to limit the burns and make them longer which is more efficient. If it senses a drop in temp fast, it can start earlier, rather than dealing with long-term heat loss from just sitting there. A mechanical in-tank aquastat will often have a fixed on/off differential - say, turn on when it gets down to 130 and off when it gets to 140. BTW, it's not uncommon to run the IWH hotter than a conventional tank, but ANY tank, however heated, generally needs a tempering valve to limit the delivery water temperature in a residential environment (commercial situations may need hotter water that the 120-degrees allowed in residential situations.

    FWIW, if you have something like a dishwasher or a need for very hot water at a washing machine, you might take the water off before the tempering valve, but water out of the taps should be limited by the tempering valve. Most residences aren't plumbed with separate hot water lines for those devices, making that impractical. Both my DW and WM can heat the water, should they need to, to function properly with hot water for cleaning purposes. The only one that gets used in this manner regularly is the DW, as super hot water in the WM isn't needed very often for most people.
    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 Member GG_Mass's Avatar
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    Here are some pics:

    One from a few feet back, and one centered on the unit I think is the aquastat for the water tank.

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  8. #8
    In the Trades Tom Sawyer's Avatar
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    Te boiler is an ultimate, oil fired, cast iron with two heating zones and one zone for domestic hot water. The hot water tank is a super Stor SS40 gallon tank with an internal coil that has boiler water circulating through it which in turn heats up 40 gallons of water for domestic use. The temperature of that domestic water is controlled by an aquastat mounted in the tank. F and C are fahrenheit and Celsius. That aquastat should be set at about 120. The white Rodgers control mounted on the boiler is the high limit operating control for the boiler. It should be set between 180 and 210 max.
    Last edited by Tom Sawyer; 09-08-2013 at 05:25 PM.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    DIY Member GG_Mass's Avatar
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    I see.
    If I get it right - The White Rogers sets the limit of the hot water flowing to the baseboards ?

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    In the Trades Tom Sawyer's Avatar
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    Yes and no. The boiler is what is referred to as cold started which means that when you turn up the thermostat the burner comes on and the pump circulates water throughout the zone that called. The burner will continue to run until the set point of the aquastat is reached ( 180 to 210 depending on where its set ). The circulating pump will run until the thermostat is satisfied. The burner will come back on when the temperature drops below the controls differential which is usually set at 15 to 20 degrees.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    DIY Member GG_Mass's Avatar
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    Quote Originally Posted by Tom Sawyer View Post
    . The burner will come back on when the temperature drops below the controls differential which is usually set at 15 to 20 degrees.
    And that setting of 15F-20F is factory configured to a certain controller of the system, if I assume right ?
    (I have no intent of messing with that setting , just trying to gather more generally helpful information).
    Thanks.

  12. #12
    In the Trades Tom Sawyer's Avatar
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    It's usually adjustable from 0 to 25 degrees. Yes, leave it alone. You might want to think about having a Beckett heat smart or intellicon reset control installed. It senses outside air temperature and adjusts the high limit so that on warmer days the boiler does not have to go to 180 or so to heat. It modulates temperature based on outside air temperature and boiler temperature. Costs a couple hundred bucks and will pay for itself in a couple years. Most installations will save you around 15% fuel cost.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    In the trades Dana's Avatar
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    Neither the Beckett Heat Manager nor the Intellicon units directly sense the outdoor temp, and is not the same as outdoor reset. Instead, they control the burn cycles based on the system behavior on the recent burn-cycle history. The peak temp at the boiler WILL hit 180F (or higher, if set higher), but it heat purges the boiler to a lower (programmable) low limit, as well as turning off the burner in anticipation of the setpoint being satisified by "learning" the system based on recent burn cycles. But by always heat purging the AVERAGE water temp is lower, and the number of burn cycles lower, even though it'll still be banging on the high limit with these controllers. The heat-purge-before firing and early cut-out anticipation approach consistently leaves the temperature of the boiler at a lower average temperature, resulting in lower standby loss. And by maximally utilizing the thermal mass of the system, it limits both the burn time and the total number of burn cycles, both of which enhance as-used efficiency.

    Outdoor reset is somewhat different, adjusting the actual high-limit based on the outdoor temperature, not the actual heat load, which is only partially linked to outdoor air temp. The Beckett/Intellicon approach only responds to the heat load, and is agnostic of the outdoor temperature, only knows about the heating system water temperatures, and internally calculates the amount of heat that it took to statisfy the calls for heat on recent cycles.

  14. #14
    DIY Member GG_Mass's Avatar
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    Outdoor reset is somewhat different, adjusting the actual high-limit based on the outdoor temperature, not the actual heat load, which is only partially linked to outdoor air temp. The Beckett/Intellicon approach only responds to the heat load, and is agnostic of the outdoor temperature, only knows about the heating system water temperatures, and internally calculates the amount of heat that it took to statisfy the calls for heat on recent cycles.
    It sounds like the Heat Manager is somewhat 'smarter' then the outdor-reset, would you agree that it is also better performing ? The test unit being - getting the same level of temperatue over time for less oil burnt ?

  15. #15
    In the trades Dana's Avatar
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    The Beckett Heat Manager is actually a dumber version of the Intellicon 3250HW+, and was designed by the same people. Either will edge out a straight-ahead outdoor reset for net efficiency on oversized systems. The distinguishing characteristic of the Intellicon is that it can correctly deal with the differences between heating zone calls and calls for heat from the indirect hot water heater, and would be the appropriate retrofit unit for you.

    Most of the time the radiation on oversized systems is capable of delivering the average winter heat load at water temperatures below the temperatures at which the boiler can operate without destructive condensation in the flue (or heat exchangers on the boiler, for boilers that aren't cold-start tolerant), so the with outdoor reset the temperature curve spends 90% or more of the time flat, at the safe low-limit, and unless it's allowed to rise to a higher limit, results in a greater number of cycles. Efficiency is still pretty good, in some cases as good as the Intellicon, and the room temperature overshoots are somewhat (but only somewhat) better managed. If you wanted to manage the comfort levels with outdoor reset using a an reset controlled thermostatic mixing valve is nicer to the boiler and can run at lower radiation temps than you'd be able to run the boiler, but that's a bigger system-design hack than just adding smarter boiler controls. (A boiler-control outdoor reset or an Intellicon does not require any plumbing.)

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