New OWB install, suggestions and advice

tabner Posted By tabner, Jan 17, 2019 at 11:56 AM

  1. tabner

    tabner
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    I'm pricing out an OWB and was hoping i could steal some knowledge from this forum. Specifically i have questions on my domestic hot water coil setup.
    I heat about 1900 sq ft with an oil boiler, three zones, baseboard, plus domestic hot water coil in the boiler. Looking to install a heatmaster G100.
    I understand how the plate exchanger works between the pressurized and unpressurized systems, to heat my baseboards, but i am unsure about the domestic hot water, and also about anti-freeze in the system. I asked the dealer and he suggested he would install the plate exchanger per normal configuration for the baseboards, but would also run a line directly into the boiler. He suggests this would have many advantages 1) oil boiler stays at a constant hot temperature rather than heating and cooling (stressing the metal, condensation, shrinking gaskets, etc) 2) it would effectively heat the domestic hot water this way 3) if i were to go away on vacation i would set a circulator pump to continuously run, therefor my oil boiler would be heating the OWB and lines, preventing the need for antifreeze which is expensive and less efficient.
    I have many questions:
    will this require me running two sets of insulated pex into the house? Can you pipe the OWB through the oil boiler without making it a pressurized system? What happens in the summer when i'm not using the OWB but am using the Oil boiler for hot water - will i be back heating the OWB?
    Any and all advice or thoughts are appreciated
     
  2. maple1

    maple1
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    Sounds like something isn't being quite understood here - either on his part or yours.

    'Per normal configuration' - everyones normal is sometimes different, but any normal plate exchanger configuration I can think of would neither involve nor require 'also run a line directly to the boiler'. One side of the HX is in a loop through the OWB (unpressurized), the other side is in a loop through the indoor boiler (pressurized) [i.e., not just the baseboards]. Indoor system otherwise stays & functions as-is. When the OWB is being operated, both loops circulate to keep the oil boiler up to temp & stop it from cutting in. When it isn't, they don't. You can build controls in to circulate both when the OWB is shut down & you want to keep it from freezing if needed. Or do it by manual switch. Or some even just run the OWB pump 24/7 all winter. There isn't any redundancy in doing that though - if one of the loops stops for some reason (power outage?), you could have a very messy costly freeze up.
     
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  3. warno

    warno
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    No need to run 2 underground lines into the home. Just run 1 tied to a flat plate HX then tie the other side if said HX top your oil boiler. The oil boiler will be heated from the OWB. Simply install a set of bypass valves for summer time usage of the DHW.

    For time away the oil boiler should heat the OWB enough to keep it from freezing. It doesn't have to stay hot just warm enough not to freeze. You can put the OWB circ on a timer or use an aquastat to have the circ run on/off to set temp when you're away.
     
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  4. tabner

    tabner
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    Great, thank you both for your replies. I think Maple 1 is right, and i must not have completely understood him. He made it sound like it was a separate/additional connection between the OWB and the oil boiler to heat the DHW coil. But if i'm understanding you correctly, the typical plate HX connection, as it transfers heat into the pressurized system to heat my baseboards - that heat will also circulate fully through the inside of the Oil Boiler, therefor heating my DHW Coil?
    One other quick question, i got the quote last night, and he's quoting me two Circulators - i guess the second one is probably just to circulate water inside the jacket of the OWB? is that standard?
     
  5. maple1

    maple1
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    Yes, circulates the oil boiler. That should be where it circulates. As long as it keeps the oil boiler hot, everything else should work as it always did and the oil won't cut in.

    Sounds like it, on the second circ.
     
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  6. tabner

    tabner
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    alright, sorry to beat a dead horse, but all of a sudden it hit me this morning, i think i understand the problem more accurately now, as well as the solution my dealer is suggesting.
    As long as zones of my house are calling for heat, therefor running circulators, you are running water in the pressurized system through the HX and therefor heating up the inside of the Oil Boiler in the process. Where you would have an issue is if none of my heat zones are calling for heat - but someone is taking a long shower. In this scenario, heat from the OWB is not really working its way inside the oil boiler, because no circulators are running therefor no water is flowing through the HX to bring heat inside the boiler to the DHW coil. So i think what he is suggesting is installing a new zone/loop, with a new circulator, that doesn't run anywhere in my house, it simply circulates pressurized water through the HX and through the boiler, therefor constantly keeping the inside of the Oil Boiler up to full temp, so it's not cycling, and there is constantly hot water.

    Does this make sense? Anyone have any experience with it?
     
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  7. maple1

    maple1
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    Yes, it makes sense, and is where I was coming from.

    But we can't read his mind from here. :)
     
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  8. Eureka

    Eureka
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    That is how you want it, exactly because of those reasons. Without circulating through the oil boiler it will have a large lag on a call for heat. Also, depending on the setpoint temp of the oil boiler it would likely be firing unnecessarily while your OWB is happily producing heat outside.
     
  9. warno

    warno
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    That's probably the best route to do go. Not much money to run a line tied into the oil boiler and the FPHX with a circ to run it all.
     
  10. E Yoder

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    Agree, pull the cooler return water off to go through the flat plate heat exchanger maximizing heat transfer, return into the boiler nearer the supply side.
     
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  11. tabner

    tabner
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    Thanks again all, for the help. Sorry to continue with novice questions - but i really don't want an 11k investment that doesn't heat right.
    E Yoder - i was just reading a different thread, and you had a post in there which raised some other questions for me.
    My current oil boiler heats my house fine. i have the thermostat on it set to a high point of around 170/180, but for some reason every time it fires it heats up to 205-210. The gauge is new, so i have always assumed my thermostat is just a little off calibration. Is this possible/common?
    Anyways, the post that got me curious, is that baseboards are often designed to heat with 200 degree water running through them, but an OWB is probably going to be piping in 185/190 max, minus a little heat loss in the lines and HX, and aren't i going to have 175 degree water in my baseboards? Anyway to check this/make sure it's going to heat my house prior to actually installing it?
     
  12. maple1

    maple1
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    We have no idea what your baseboards are designed for. 200 would be an outlier - more apt to be not more than 180. But we don't know anything about your design or how well it was done.

    Your oil settings have more than just one number to them. There is hi-limit, lo-limit, and differential. There is no way I would have mine set to heat up to 205-210. The heat loss would be too much. I would have mine set to cut in at 160 and cut out at 180. If you have an IR temp gun you can double check your gauge by shooting the boiler outlet pipe with an IR gun.

    So, if you wanted a better idea about how capable your baseboard is - set your boiler back to max 180, and see how it does heating your house at that. If you don't know how to adjust your boiler, you could try posting a pic of your aquastat & dial settings.
     
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  13. maple1

    maple1
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    but i really don't want an 11k investment that doesn't heat right

    Since you mentioned that - have you fully costed everything?

    Underground piping is a very important thing to get right, and the right stuff is expensive. In the $10-20/foot range. If the wrong stuff is used, that will likely lead to disappointment with your investment - maybe not right away, but over time it very likely could.
     
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  14. leon

    leon
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    Before you spend your hard earned money you need to invest in 3 paper back books; CLASSIC HYDRONICS, PUMPING AWAY and HOW COME.
    These three paperback books will give you 40+ years experience at your fingertips and you will know what you need to know about hot water heating.

    Your home thermostat or multiple thermostats control the amount of heat delivered to each zone..
    1. Your boiler has a triple aquastat with a low limit temperature at 160 degrees typically that activates the oil burner when the boiler water reaches the low limit temperature.
    2. Your boiler has a high limit temperature that shuts the oil burner off at the high limit which is typically set at 180 degrees
    3. your boiler has a differential temperature that operates your dump zone which only happens when your boiler overheats and needs to shed heat.

    You need to have a heat loss study done for your home as YOU Need to know what improvements can be made to improve your heating systems efficiency and to also show where you are losing heat out of your home.

    When a heat loss study is done the person doing the work measures every room and every window and also notes whether the windows are single pane windows and how much insulation you have in your attic and basement walls. The person doing the heat loss study also brings along a blower that mounts in one of your exterior doors and then turns it on and uses an infrared camera to see where your home is losing heat and then notes that on your heat loss worksheet.

    If the person doing the heat loss study just measures the length of your baseboard and writes down the BTU value of your boiler and does nothing else find another firm to do your heat loss study.

    The next step is when you contact a home repair business to obtain an estimate for the cost of upgrading your homes insulation, windows, doors and weather stripping as well as adding more insulation in your basement walls.

    Having the heat loss study done will tell you how much it will cost and ALSO tell you much money you will save on your energy costs AND you will know that when the repairs are done you will have an immediate return on your investment. as you are saving energy.

    DO NOT SPEND any money until you have a heat study done as all you may need is more hot water storage and more insulation.
     
  15. tabner

    tabner
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    Thanks Leon. I'm going to Amazon one or two of those books right now. I certainly don't want to ignore your advice on the energy audit, but for what it's worth, i can say that my home is pretty efficient. It's 2 x 6 construction, built in 87. Vinyl siding and double pane windows. Faces due south with sky lights and a long roof line for max solar warmth. I heat about 1800 sq feet. three zones (three floors, finished basement plus two floors). My oil boiler keeps up with no problem, plus DHW. I printed my oil usage from my HVAC company - i have spent 4200$ total in the last 3 years. I do however expect that to go up because we are having our first child so i am planning on higher thermostat settings (keep it at a cool 64 in the house right now) and more hot water (plus i don't trust oil prices).
    I believe i do understand how the aquastat works with regard to a low and a high. I will take pictures and post them this afternoon - but i believe it is set to a low of ~140 and a high of ~170, and yet the temp and pressure gauge on the side of the boiler gets up over 200 every time it fires. I don't have an IR, but i do have a pretty sensitive high temp electric thermometer, maybe i'll see if i can get a decent reading on the output pipe with that.
    Maple1, as far as pricing, i was quoted about 8800 for a heatmaster G100, plus 80 feet of insulated pipe at 9$ per foot, plus two circulators and some misc, so 11k total. Wondering if E Yoder would chime in here, since it looks like he installs this brand. pricing seem right? Unit seem right size?
    Thanks again for the patience and advice.
     
  16. salecker

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    Read the sticky on the top of this forum on underground lines before you spend any money on them.
     
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  17. maple1

    maple1
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    i was quoted about 8800 for a heatmaster G100, plus 80 feet of insulated pipe at 9$ per foot, plus two circulators and some misc, so 11k total. Wondering if E Yoder would chime in here, since it looks like he installs this brand. pricing seem right? Unit seem right size?

    That depends on exactly what type of pipe it is (they are all far from equal), what size it is, and if the circ is right sized for the job. The most common cause for an unsatisfactory performing OWB setup, is underground not done right.
     
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  18. tabner

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    Reviewed quote - Underground pipe is described as "1" pex underground insulated 5 wrap".
    Also attached are 4 pics from my current oil boiler, as you can see, aquastat is set quite low. I tried to get a pic of the sticker on the top of the boiler to see BTU's/Model. The two photos of the gauge with temp/pressure one is taken right when the boiler kicked on (so lowest temp), and one right when it kicked off (highest temp).
    Only two things i can think are either aquastat isn't calibrated accurately. Or the gauge i'm looking at takes an internal core temp of the boiler which is different than the aquastat, which is looking at water temp on the input and output of a zone?
    IMG_20190121_121813361.jpg IMG_20190121_121844504.jpg IMG_20190121_122053165.jpg IMG_20190121_122122647.jpg
     
  19. maple1

    maple1
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    If the aquatstat is in the side of the boiler (in the stream of incoming return water), and the guage at the top - you might have a difference there, possibly. Is the stat in a well? Or does it have an external sensor? If external, where is the sensor mounted?

    'Insulated 5 wrap' - that is not good stuff. You should be using closed cell foam insulated piping, Thermopex or Logstor or the like.
     
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  20. Eureka

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    Yeah don't get the 5 wrap, get the foam filled for sure. I'd also recommend going with 1-1/4" (actual ~1.0625 O.D.)
     
  21. leon

    leon
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    Please tell me this first; Is the triple aquastat located in the top of the steam chest or on the side? If it is on the top of the steam chest it is directly over the firebox.

    As Maple1 mentioned you may have an external sensor which is a clamp on aquastat that is secured to your piping near the boiler. If it is a Honeywell clamp on aquaststat it is a narrow gray box attached to a pipe.

    Your differential temperature is too high you can lower to 10 degrees, you nealso ed to lower the low limit temperature to 140 degrees Fahrenheit, you can do that safely with no issues.

    Your home is well pretty well insulated but having the heat loss study is a must do item before you go further.

    I am sending you a PM.
     
  22. maple1

    maple1
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    I don't think a heat loss study is needed here. There is already an heating system in place that sounds like is heating the house fine. So a G100 should heat it fine too. As long as the install is designed & done right.

    If planning a new system - yes.
     
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  23. maple1

    maple1
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    I also don't think I would touch those settings until you figure out why the difference between hi limit & temp guage, and maybe more importantly verify the temp guage is right. Then I might consider lowering hi & low by 10 each & see what happens.
     
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  24. tabner

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    Thanks all, I will investigate the aquastat more, and follow up with more info/pics.
    Just off memory right now, it is a grey Honeywell box, on the side of the boiler. It is not permanently attached, or sunk into a well in the boiler, or something like that. It's more like a unit bolted, or piped on. I will check it out when i'm home and see more specifically how it is attached.
     
  25. maple1

    maple1
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    That might explain something then.
     
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