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Post in 'DIY and General non-hearth advice' started by boo boo, Mar 23, 2013.

  1. boo boo

    boo boo Feeling the Heat

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    I was thinking on another thread and was wondering on my oil burner that I only use for heating my water and not my baseboard heat. Can I drop the nozzle size from a .75/80 to a lower GPH but leave the angle the same to say like a .50/80 or are there other factors by doing this
    Or am I full of $hit on this and heating water with a lower fire rate will take longer and it will be a wash

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  2. ekarlis

    ekarlis Member

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    Hey Boo Boo:
    I am a retied HVAC tech & maybe I can help you out. Reducing the nozzle gal/hr will defintiely help. For example: 0.65gal/hr @ 100psi would = 91,000Btu/Hr. You should be able to reduce the nozzle by 10% of
    the operating range. Do not change the nozzle pattern (.75 @ 70 degrees). The 70degrees should never be changed. Also, used the nozzle designed for the appliance, like solid or hollow core. All nozzles are rated
    by the manufactures @ 100psi. Let's say you reduce the water temp from 180F to 150F, then you are going to have to check your hot water to make sure it's about 120F. An easier way is to reduce the aqua stat on the boiler
    from 180F to 150F. Make sure your room stats will not engerize the pumps. There a lot of variables & not knowing what equipment you have, it's hard to calculate. You might look at separting your domestic hot water
    from your boiler. How are your electric rates? If they are reasonable (5-6cents/kw), then an electric hot water heater might be the answer. Hope this helps. e.karlis
  3. boo boo

    boo boo Feeling the Heat

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    Thanks for the reply
    Not sure what an aqua stat is but I will read up on it Thanks Changing the nozzle from .75 to .70 I am calculating 65 dollars a year savings. If I need to turn my baseboard heat back on in case my pellet stove goes down should I bring the nozzle back to a .75 or will it be ok?
    Also my electric is high here with all charges the kwh is 0.1027 I would love to have 5 or 6
  4. woodgeek

    woodgeek Minister of Fire

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    wanna be here....

    If you look at the sticker on your boiler (or google the part number) you might find that it has multiple ratings based on different nozzle sizes. In principle, you can use the nozzle for the lowest 'rated' output from the manufacturer without a problem. You might also get a (small) bump in efficiency, quieter operation, etc. If you go too far, you can get condensation on the heat exchanger, and it will soot up a lot faster (and on average perhaps be even less efficient).

    Ekarlis' idea of lowering the aquastat temp makes a lot more sense. Your problem is not efficiency, its parasitic losses. You are getting the heat from the oil into the flame and into the water, but most of your BTUs leak out the sides of the boiler rather than coming out a tap, maybe 70-80% is lost. Turning down the setpoint temp (on the aquastat) will significantly reduce this loss, could be 20-30% savings if you are currently set to 180°F.

    Another thing to look at....a common problem is for the check valves on the hydronic loops to rot out and fail. Then natural convetion can circulate hot water to your radiators at a low rate 24/7, even during the summer. The fix.....at the end of heating season close a manual valve to shut off the radiator loop, and then open it in the fall....if you have such a 'thermosiphon' problem, this will save a ton of oil (literally) and AC in the summer.

    Of course, if you have it shut off in the winter while you heat with wood, you are much more likely to freeze the pipes....my 'thermosiphon' did a great job preventing that.
  5. MasterMech

    MasterMech Guest


    How does that affect the operation of the baseboards should he (or I, ;lol) need the system as a backup?
  6. heat seeker

    heat seeker Minister of Fire

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    When I moved into a house I'd bought, the heating system took hours to heat the place up 3 or 4 degrees. I discovered that the aquastat was set at around 120°. The water circulating in the baseboard radiators just wasn't hot enough to do the job. Also, the inside of the furnace was covered with a stick, yellowish crud that reminded me of sulfur. I raised the temps to 160/180°, and those issues were resolved. So, while you may save some money by lowering the 'stat, you may create other problems.

    Another point: a friend of mine has his 'stat down to 120°, and his chimney liner is coated with the same type of crud I had. I would assume it's corrosive and will damage the liner over time.

    Just my 2¢.
  7. woodgeek

    woodgeek Minister of Fire

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    Usually it doesn't. Most aquastats have two setpoints, a low and a high, and when there is a call for heat from the zone, runs up to the high setpoint for radiation, and falls back to the low setpoint for standby (and it will cycle on/off near both setpoints using a differential). Without a call for heat (a DHW coil doesn't call, just robs heat), it rides the low setpoint. These are called 'triple' aquastats and their operation is complex....but you can google it if you want details. In my case, the house was so much better insulated than when built I could actually pull down the hi temp a little too, and it made the 'clicking' of the radiators less.

    [Aside: Technically, your system is supposed to be sized so that it can run the radiators at a steady state temp just less than the High setting at design load for eff operation. In practice, I don't think that happens, and the unit cycles on and off at the high ('safety') setting even when the radiation is running. If it short cycling, you prob should leave the High setting higher, or reduce the nozzle size. IF the boiler is way oversized, not much you can do, its gonna cycle]

    I really don't like these things.
  8. ekarlis

    ekarlis Member

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    Boo Boo:
    There is a chemical that you can add to your boiler water to prevent it from being corrosive. I think Home Depot carries it. The aqua stat is on the right or left side of the boiler(2"wide x 6or 8" long) usually a Honeywell control.
    It has a slot that requires a screw driver to adjust..A triple aqua stat is much larger & you can not miss it.
    Hope this helps
  9. MasterMech

    MasterMech Guest

    I see, so my indirect tank setup wouldn't gain much if anything from messing with the aquastats since it's plumbed in as a zone?
  10. woodgeek

    woodgeek Minister of Fire

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    How hot do you keep the indirect...you might still save on parasitic losses on the boiler? I do not know from indirects.
  11. MasterMech

    MasterMech Guest

    The indirect stat was cranked down to 120.
  12. boo boo

    boo boo Feeling the Heat

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    Lots of good information here.
    What I have learned about my system.

    My indirect tank for my hot water is also on a zone of its own set at 120 or just above. My tap water using a meet thermometer is almost 140 more like 137. I will leave that set where it is. Prior to getting a pellet stove and using my baseboard heat the tap water was hotter to the touch during the winter months last year because of the boiler running more.

    My boiler system. Last summer After the first year having this house we knew the boiler needed attention as the previous owners did not care for it. I have experience with forced hot air systems but not forced hot water. I went through it and it was sooty really bad and the tank filter was like tar.
    When I took out the nozzle to see the size It was a .75/80 took it to plumbing and heating supply and got two more one for emergencies.
    Now looking at my boiler plate as Bill Nye (woodgeek) suggested I find the firing rate is .90 and I have a .75 in there.
    Could this be the cause of the black soot or could it be from the previous owner not cleaning it for 5 years?

    Also my acuestat was set at 180 high and 160 low any suggestions there?
  13. woodgeek

    woodgeek Minister of Fire

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    I don't get indirects....presumably when it calls for heat, the bottom is less than 120, and then it fills the top with 160 degree water from the boiler....so you get 140 deg water from the tap (which seems unsafely hot). Ugh. If the boiler has a triple aquastat set to 180/160 (the least eff setting imaginable, but one that minimizes callbacks to the techs, so their default), then it seems your parasitics are quite large. You could set the low a bit lower, maybe 180/140 and still be aok. You could also try 160/140 and run that (which might make the water less scaldy), and just check that it doesn't short cycle.

    As for the soot, dunno. Could be no cleaning for a long time, or it could be a too small nozzle, or a bad air setting, or all of the above. Have a pro tune up and inspection, and ask their advice, the trick is finding someone who knows what they are doing.

    And tell me you have a CO monitor near it.
  14. boo boo

    boo boo Feeling the Heat

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    Thanks
    I Set it to 170/150 and will monitor it for a few days.
    Yes I am going to get a pro to come and go through it and check the air and combustion flame and all the settings I don't know about. I like to do my own maintenance but when it comes to setting things like the damper and air flow in the flue I don't have a clue.
    And yes on the Monitors one in the basement and one on the first floor

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