any benefit to increasing pipe size before and after Boilers tankless coil?

Discussion in 'General Plumbing Help' started by Alex Vetere, Oct 23, 2019.

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  1. Oct 23, 2019 #1

    Alex Vetere

    Alex Vetere

    Alex Vetere

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    Hello All,
    I have a slant fin L40-PT oil fired boiler with a coil. the taps are 1/2". would there be any benefit in
    using 1/2"-3/4" adapters right in and out of coil? I get i'm limited to the amount of hot water coming
    from coil but, the fact the 3/4" pipe would hold more hot water would possibly help with overall volume after being tempered? Am I chasing my tail here? Thanks, Alex
     
  2. Oct 23, 2019 #2

    Diehard

    Diehard

    Diehard

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    Not totally with you.
    The boiler connections are 1/2" .
    How is it currently piped?
    3/4" CW piping from the source?
    Do you have 3/4" piping currently at least part way to your HW demands?

    Do you have a tempering valve on the boilers HW line. what size?

    Why do you say you a are limited to the amount of hot water coming from coil?What is your low limit set to? 160 degrees F?

    If you use the hw at a rate faster than the boiler can keep up with you can throttle back the HW flow at the boiler or add an aux. tank with circulator to heat it from the boiler water.
     
  3. Oct 23, 2019 #3

    johnjh2o

    johnjh2o

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    What he is asking is if the larger pipe would increase the volume, which it well but it will not increase the pressure.
     
  4. Oct 24, 2019 #4

    Diehard

    Diehard

    Diehard

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    I believe he's looking for an increase in overall volume after being tempered.
    I believe the answer to that is it wouldn't amount to hill of beans.
    If he meant rate of flow, then would have to ask why.

    I have the same arrangement and can understand if he's not getting enough hot water. Those boilers vary but I used to think the average maximum was up to about 3 gpm of tempered water when new and less as it ages.

    EDIT: It's been my experience that those tempering valves are not that good at controlling tempered water temperatures. Different than thermostatic mixing valves.
     
    Last edited: Oct 24, 2019
  5. Oct 24, 2019 #5

    Alex Vetere

    Alex Vetere

    Alex Vetere

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    Hi Guys,

    Thanks for replying. I presently have 3/4" feeding the coil up until about a foot away than reduces to to 1/2", I have about a foot of 1/2" at the outlet of coil than it goes to 3/4". My basement bath has 1/2" feeding it and the other two baths (main floor and 2nd Floor) are fed by 3/4" reduced to 1/2" branches to fixtures. The coil does not presently have a tempering valve on it. I replaced coil approx 3 years ago and have recently cleaned it. I have plenty of hot water for all fixtures during non-heating months (apprx 6months here on LI) . During the heating months the shower never seems to get to a comfortable "hot" and hot water is really affected by the use of other fixtures. All fixtures other than showers have plenty of hot water. I do need to add a tempering valve and would like to add an electric hot water heater to it with a circ w/timer for the extra boost in the winter and in non heating months being able to turn the boiler temp settings down to 140 and let both work together For hot water demand. I was going to just add the tempering valve now (since it doesn’t have one) and see if anything improves this winter but, I may have to also replumb entire boiler because of small Leaks developing, scale, stuck check and a bad xtank. Going to use all new proball valves, circs with checks, taco sr504-4, etc. The boiler’s firebox and heat exchanger are in great shape. If I decide to go through with the replumb this winter I will then obviously add HWH now. My original question was asked because my thoughts were I would have more volume of water with a ¾” tempering valve vs. a ½” valve regardless of coil tap size. Would I keep the tempering valve on coil when adding HWH or just switch it to the HWH? (if ¾” valve is the way to go for coil) …Thanks again
     
  6. Oct 24, 2019 #6

    Diehard

    Diehard

    Diehard

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    Without getting into the subject of your thoughts of adding an electric heater, I'd like to find out more about your system.
    Do you have a control box that when the cover is removed reveals HI, LO, and Diff. dial settings?

    First off, an oil fired boiler with a domestic HW coil is required to have a tempering(anti-scald) valve.

    Secondly, the controls are typically designed to set High, low, and differential temperature settings. In brief, a typical setup would have the low set at 160 F with high set around 180 F. There must be at least 20 degrees difference between Hi and LO.
    The 160 F would be the minimum temperature maintained for the purpose of heating the domestic water. It is also the lowest temperature that would allow the heat circulator to run.
    The 180 F would be the maximum temperature the boiler will reach while calling for heat.
    So basically what that means is the heat will not be allowed to run unless you have the minimum temperature required for the domestic water. Domestic water has priority.
    There typically is a separate differential dial with settings of 10 to 25 degrees. This would control amount above the low limit setting where the heating system is allowed to come on. Or in other words, more available water for heating the domestic water demand.


    EDIT: Controls typically look like this but could very well be different set-up.
    Hi-Lo-Diff Settings.jpg
     
    Last edited: Oct 24, 2019
  7. Oct 24, 2019 #7

    Diehard

    Diehard

    Diehard

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    When you sort out what you have and if it's set up properly, if you still feel you need more hot water by way of a storage tank type, you may want to check into what is called, an Indirect Fired Water Heaters vs. an electric water heater.
     
  8. Oct 24, 2019 #8

    Alex Vetere

    Alex Vetere

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    Hi Diehard, Yes I have a L8124a Aquastat, it is presently set to 160-180 with a 15deg diff . .Do you think the circs may not be cutout at low temp during winter causing HW issue?
    I am aware it should have had a tempering valve on it, hope to have that resolved very shortly. I have looked into the indirects and feel that would be a great choice during the heating season while the boiler is very active, I just feel ( and maybe I’m wrong) that during the 5-6 mos of non heating the boiler will have to keep 40-50 gal of Hot water ready to go at all times.. and that seems very inefficient..I do read that heat loss in these are very minimal. Are they much better at heat loss than a Elec HWH? Thank you for your help.
     
    Last edited: Oct 24, 2019
  9. Oct 24, 2019 #9

    Diehard

    Diehard

    Diehard

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    Don't know the answer about the heat loss difference.
    I guess what your really looking at is the difference between the cost of the oil vs the electricity as well as heat loss difference of the two different types of tanks(electric vs the indirect) as well as heat loss from your boiler during the summer months.
    Not totally sure of your meaning here...
    "I just feel ( and maybe I’m wrong) that during the 5-6 mos of non heating the boiler will have to keep 40-50 gal of Hot water ready to go at all times." I have to assume that the capacity of the water heater tank and not the boiler. So you'd have that with either type of tank type heater, assuming your looking at the size tank for either type.

    Talk tomorrow.
     
  10. Oct 24, 2019 #10

    Alex Vetere

    Alex Vetere

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    My thought was during the non heating season I now use Approx 275 gal of oil over
    a 6 Month period to satisfy coil. If I still utilize the coil and piggyback say a 20-30 gal elec HWH with a circ with timer, lower the boiler setting to 140 -160 for the summer. The easily attained temp rise for the boiler ( boiler room gets pretty toasty in summer) in addition to the minimal amount of electricity the HWH would use as both would supplement each other I would actually realize a decent savings. In the heating months I would hopefully solve my cool shower issue and be able to continue to save a couple of dollars. Maybe be able to shut down electric for HWH?
    Thanks again and look forward to speaking tomorrow, Goodnight
     
  11. Oct 24, 2019 #11

    voletl

    voletl

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    Install one of these any brand
    You will burn half the oil. Screenshot_20191024-045235.jpeg
     
  12. Oct 24, 2019 #12

    Alex Vetere

    Alex Vetere

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    Voleti,
    That seems to be the push. Would a 40-50 gal indirect Require less than the 1.6gal a day I’m using now during the non-heating season to keep coil satisfied? 3-4 showers a day, washer, dishwasher.
     
  13. Oct 24, 2019 #13

    Diehard

    Diehard

    Diehard

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    I missed your question, "Do you think the circs may not be cutout at low temp during winter causing HW issue?"

    That actually sounds like the case if you get plenty of hot water during the non-heating season but not during the heating season.
    You should definitely check it out to make sure the heat is not running when below your LO setting. (Not positive but it sounds like the differential setting increases that Low setting for not allowing the heat to run at a temp below the LO setting plus the Diff.)
     
  14. Oct 24, 2019 #14

    voletl

    voletl

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    Yes I have a 50 gallon indirect three and a half bathrooms with a dishwasher two kids it serves all our needs no problem I'm telling you you're going to burn half of what the oil you burn now and you're also going to get a more precise temperature control - and now your boiler doesn't have to run to keep a constant temperature
     
  15. Oct 26, 2019 #15

    wood4d

    wood4d

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    I disagree with the oil use. I put in a propane rinnai because the amount of oil I was using was ridiculous. It may be because I dont use the boiler for heat since I use a wood stove. That would have given me "free" hot water in the winter.
     

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