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Indirect tank vs. oil burner on-demand coil vs. NG Tank

doooglasss
doooglasss Member Posts: 18
edited November 2017 in Domestic Hot Water
I currently have a Burnham KV74, oil fired burner with on-demand DHW. The flow rate (unknown to me) is terrible to the point where only one person (in a house with 3 full baths and 3 people) can shower at once. I'm in NY so as winter approaches the issue is compounded by the inability for the on-demand coil to increase the water temp enough to make it comfortable - you have to reduce pressure to achieve hot water flow.

A co-worker has a 80 gallon indirect tank he has offered to me for free. I'm trying to mentally explore my options as far as up-front cost/complexity and reoccurring costs (efficiency) are concerned. In my mind NG is the way to go, but I have heard bad things about standalone tanks - low efficiency ratings and bad reliability. Everything I read online says indirect tanks are the winner for long term reliability.

Let me start by saying my oil burner and tank are located in my garage which is closed-cell spray foamed. My heating manifolds are located in a utility closet in the middle of my home so I have limited PEX in the ceiling I could re-use for this application. Depending on plumbing requirements the tank might have to also go in the garage.

Scenario 1:
--Take free 80 gal tank (I have space to keep this in a conditioned part of the house)
--Buy circulator & DHW mixing/anti-scald valve
--Connect output right to my hot water manifold (same room, simple)
--Wire it in to my Uponor X-165 zone control for DHW override of heat demand?
--Cap the Burnham KV74 tank off - leave it full of water or drain it???)
--Am I missing parts I need on the plumbing side such as zone valve or flow detection device?

Scenario 2:
--I have natural gas piping ran to my conditioned water closet
--Buy standalone natural gas self-heated tank
--Same questions apply about capping off the KV74 tank
--Big question: Could I use this for my suspended tube radiant heat setup and eliminate a boiler? Or is the replenishment rate not high enough to keep up with that task?

My current heating configuration is suspended tube radiant with multiple zones, Tekmar 360 mixing valve control. Last year on the coldest of days with high winds / snow on the ground I remember seeing demand temps between 140-160.

Scenario 3:
--I just renovated my home so it isn't an option, but it's what I want. I really hate paying for 300 gallons of oil per month.
--Buy a quality NG boiler and utilize indirect tank or high flow rate on demand DHW (4+ gpm ?)

Sorry if that was long- any advice is appreciated!

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 20,404
    I'd go with Number 1. You'll need some parts...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Grallert
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,087
    Your going to have to get a few quotes to help you decide.
    They are all viable options. You will never be happy with a tankless coil in a boiler.

    Best option also the most expensive is #3
    #2 I wouldn't be afraid of this option. gas water heater are fairly cheap and supply plenty of hot water. I have a 10 year in my house it's going on 14 years old (fingers crossed) I shut it off when I go on vacation and a week later the water is warm. Efficiency isn't that bad

    #1 as Jamie said is also a good option.

    Some things to consider:

    How long will you stay in the house?
    How old is your boiler? Will it need replacement in the near future anyhow?
    How old is your oil tank?
    What is the efficiency of your boiler? Have you had any issues with it?
  • Brewbeer
    Brewbeer Member Posts: 616
    I have an indirect and love it, for no.1 you can't beat a free 80 gal indirect if it's in good shape, and it will be there when you are ready for no. 3. Probably will need to do some boiler work to change it fron always hot to stand by, that will help with summer fuel savings. For no.2, a stand alone water heater will need to be properly vented, which could be a challenge, and you don't want to run your radiant system off a water heater.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
  • doooglasss
    doooglasss Member Posts: 18


    #2 I wouldn't be afraid of this option. gas water heater are fairly cheap and supply plenty of hot water. I have a 10 year in my house it's going on 14 years old (fingers crossed) I shut it off when I go on vacation and a week later the water is warm. Efficiency isn't that bad


    So are you using your NG water heater with a heat exchanger to heat your home as well? Also what climate do you live in? Long Island gets pretty cold January & February.

    How long will you stay in the house?

    This is a question I've been asking myself throughout this renovation. I'm going to guess 10-12 years- but I've seen lots of people say that then live there way past the date they set.

    How old is your boiler? Will it need replacement in the near future anyhow?
    How old is your oil tank?

    Burnham KV74 says "06/9" on the sticker so I'm assuming September 2006? Oil tank is above ground in my garage. House was built in 1954 and there is evidence of a tank that used to be under ground so we can assume it was replaced at one point or another.

    My only motivations for replacing it is cost savings. Oil prices fluctuate, but using COD prices today I'm looking at a $650 fill up which I do twice off-season and once a month during our 4-5 cold months. I have to assume NG is much cheaper and I can run it at condensing temperatures with this radiant system.

    What is the efficiency of your boiler? Have you had any issues with it?

    82% efficient on the label. No real issues yet.
    Brewbeer said:

    Probably will need to do some boiler work to change it fron always hot to stand by, that will help with summer fuel savings.

    I currently wired my boiler to run constant circulation through a small primary loop year round. The only item that triggers it is a built in aquastat I have set to 140 low & 170 high (creeps to 180 though on warmer days). If I let the boiler drop below 120/130 or so I actually have a visible external leak. I'm sure I have to replace a gasket, but it was my understanding that running an older boiler like this was a poor decision?
    Brewbeer said:

    For no.2, a stand alone water heater will need to be properly vented, which could be a challenge, and you don't want to run your radiant system off a water heater.

    I was looking at the power vent systems that I could use PVC for. I have a straight shot to my roof (next to a 4" waste pipe) that I could fit a 2" PVC vent through. For a feed I can either pull air from inside the house or pipe it outside about 12" above ground just need to remember to clean it or put something there to prevent snow pile up on side of the house.
  • HVACNUT
    HVACNUT Member Posts: 4,856
    Burnham states a manufacture date on the rating label. There V8 series has been out at least 12 years, so your V7 is 12, if not more.
    Your near boiler piping manifolds must be able to handle the load of an 80 gal indirect.
    You can also get a large capacity, power vent NG water heater. Good recovery, and efficient. Set the tank temp to 140 and install a thermostatic mixing valve tempered down to 120 domestic hot.

    ***Do not zone the indirect with a zone valve. It needs it's own circ sized to the specs of the tank.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,087
    06/09 would be June 2009 I think. So the boiler is 8 years old
  • bob eck
    bob eck Member Posts: 930
    Do you have natural gas available? Some gas utilities and some states offer rebates for going to high efficiency gas boilers.
    If so you could consider a condensing gas boiler with the indirect water heater.
    Not to jinx you but Burnham had a lot of V7 boiler fail by leaking cracked sections.
    I don’t think your Boiler was built in 2009
    You can call Burnham with the S/N and they can tell you when the oil boiler was built. 866-659-3927
    If you have natural gas look at using a 50 or 75 gallon power vented tank type water heater.
    You could also look at using a natural gas tankless gas water heater. The 199,000 BTU input TGWH can deliver 5.0 to 5.5 GPM at a 70 degree temp rise.
    Both of these water heaters can be vented with pvc pipe and fittings sidewall or vertical.
    HTP has a unit called the Crossover. High efficiency 20 gallon natural gas water heater vents with PVC pipe and fittings. One model 76,000 btu input one model 100,000 btu input. Delivers 100-130 GPM
    Check it out at htpproducts.com
    If staying with oil use the indirect water heater get it piped in right and you can get it set up for priority.
    How old is the indirect water heater. Get the S/N and call the manufacture they can tell you how old it is.
    If you need a new oil boiler look at the Burnham MPO oil boiler or the Trio oil boiler from F W Webb Company.
    You can see the Trio oil boiler at www.trioboiler.com
    Both boilers are well built.
    The Trio oil boiler is approved for burning fuel oil or you can switch to natural gas or LP gas by chainging the burner. When going from oil to gas with the Trio boiler you do not loose the warranty. If going with the Burnham MPO oil boiler you can not switch it to burn gas.
    Find a good professional heating contractor and they can help you to get the best system for your house.
  • doooglasss
    doooglasss Member Posts: 18
    Thank you for your words of advice. I agree with you that my burner was not built in 2009- I believe it to be older than that. I have confidence it will last me through this heating season, but I don't know how much longer beyond that.

    I have natural gas plumbed into the house and I am currently using it for kitchen stove, outdoor grill and clothing dryer. I had the piping and meter installed oversized with the intention of installing a NG wall-mounted boiler and trying to use a combi unit with on-demand DHW.

    I would like to ditch oil all together at this point, however, I don't have the funding to buy a nice boiler and definitely don't have the funding to pay someone to do the work. I am capable of doing it myself and will read code, but I guess I am just trying to explore my options and where I can and can't save money. There is a significant cost difference between a large NG water heater and respectable brand combi-unit boiler.
  • i07nyc
    i07nyc Member Posts: 8
    I did my system last year. I was in a similar conundrum. I went with the indirect with separate circulator. My efficiency is directly tied to the efficiency of my boiler which is higher than a stand alone. I know people who have on demand and either they love it or hate it. For our lifestyle of quick draws on hot water the on demand did not sound like a good idea. I have a 45 gal hydrostor and have never come close to running out of water. Other plus is when the tank has to be replaced it'll take me 20 min to do. 4 pipes and an Aquastat. No gas lines or chimneys to mess with.