Oil prices are choking us to death. Convert to gas?

Discussion in 'Boiler Forum' started by Highgear, May 3, 2013.

  1. Highgear

    Highgear New Member

    Messages:
    3
    Location:
    Connecticut
    I'm in the beginning stage of trying to figure out the best way to convert to gas. We have a 12 yo. Weil-Mclain Gold series oil fired boiler with on demand HW. The house 1600 sq. feet with one bath, three kids and two adults. At this point our family is very tight in the funds dept. What would be our best option, convert what we have or buy new. Our first and only estimate was $6400 for a Navien unit and $7600 for a Rinnai unit....both kind of out of our price range. Any other good options out there?

    Thanks Guys!
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
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    Keeping a boiler hot all year to provide hot water is not particularly efficient. An indirect WH is often a good choice, but not all boilers can stand cooling off in between calls for heat on the indirect, and still must idle at a moderate temperature. A modern mod-con will cost a good deal of money. If you have natural gas available, it might work out to just add a traditional gas WH and shut down the boiler for the summer. One thing most people do not realize is that the state of the art on heat pumps has evolved so that they can often be a great alternative to older methods and would provide a/c as well. It would help if you related what brand/model you actually have in place. Chances are, it is significantly oversized, and there may be some add-on controls that could help make it more efficient. The first step is to figure out what your actual heat loads are. There are lots of threads here that describe how to get a reasonable WAG based on oil use, boiler efficiency, and heating degree days. Your existing boiler is probably 2-3x oversized for your needs, and this alone is likely a big part of the expense - the more oversized, the less efficient primarily because it will often short-cycle.
  3. Tom Sawyer

    Tom Sawyer In the Trades

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    Location:
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    Keep the boiler, change the burner. Carlin makes a nice gas power burner that will fit. Put temperature reset and an indirect for hot water on too.
  4. Highgear

    Highgear New Member

    Messages:
    3
    Location:
    Connecticut
    jadnashua, our boiler is a Weil-Mclain P-WGTO-3. I'll have to see if I can save some money by asking my father in law to get his retired plumber buddy to help him with the conversion. My father in law retired from Yankee Gas, but did not do residential.

    Tom, what is a indirect for hot water? I would like to know these things so that I can convey them.

    Thanks!
  5. Tom Sawyer

    Tom Sawyer In the Trades

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    Google superstor and amtrol boiler mate. The wgto3 may be slightly oversized but its as small as that particular model goes. The carlin conversion burner can be down fired to compensate foe differences in heat loss vs input. Also google taco pc700 or Beckett heatsmart and intellicon. My preference is the pc700 but all three will get the job done. I doubt that tearing the boiler out and installing a mod con is the most cost effective way to go. You are probably looking at many years before the reduced operating cost overtakes investment. You can hit NORA's web site and download their free comparison software if you want.
    Last edited: May 4, 2013
  6. Dana

    Dana In the trades

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    Consider this another vote for installing a conversion burner w/ indirect hot water heater and smarter heat-purging controls. Odds are pretty good you can get this done for under $3K, maybe even under $2.5K.

    An indirect hot water heater is a tank with an internal heat exchanger that allows the boiler to heat up the volume of potable water:

    [​IMG]

    1 Hot water pipe (to taps)
    2 Heat trap
    3 Cold water inlet
    4 Hot tap water storage tank
    5 Heat exchanger (filled with boiler water)
    6 Stored hot tap water
    7 Pump
    8 Hydronic heating pipe (to house radiators)
    9 Boiler for house heat

    ----------------------------

    The "smart" contollers like the Taco PC700 or Intellicon 3250 HW+ or Becktt Heat Manager improve the system efficiency by keeping the boiler at a lower temp during standby mode, but they have somewhat different approaches/algorithms by which that is achieved. The Taco senses the outdoor temp and uses that to determine the appropriate average boiler temp, whereas the Intellicon (& Beckett, which is an Intellicon design) "learns" to anticipate the end of a call for heat based on recent burn cycles, and turns off the burner early, purging heat from the boiler into the system to finish off the call for heat, an purges it further down to the (user programmed) low-temperature limit at the beginning of a call for heat.

    When the boiler is grossly oversized for the load (as yours almost certainly is) the outdoor temperature hardly matters, since even at the boiler's safe low temperature limit it will always be hot enough to heat the house. The Weil-Mclain P-WGTO-3 has an output of 100,000BTU/hr, and for a 1600' house that would come in at a very high 60+ BTU per foot of conditioned space. Assuming it's a house and not a tent, that's probably about 400%-500% of the heat rate you'd ever need to keep the house warm, even at the 99% outside design temp (somewhere between +2F and +15F, depending on where you are in CT.) When it's that oversized, you're probably slightly better off with the Intellicon. Were it less than 200% oversized for the load there would be a comfort benefit to the Taco.

    While burning oil the lowest temp you can run the boiler without running into corrosive condensation problems is ~140F, but once you've converted to gas you can run it as low as 130F without issues. Running it at the lowest temperature possible has an efficiency benefit from both a standby loss and distribution loss point of view. The smart controllers allow you to run it at lowest possible average temperature without efficiency robbing short-cycling, and without destructive exhaust condensation. At 4-5x oversizing you can expect to get a 15%+ reduction in fuel use by using heat purging smart controls. Newer-better boilers incorporate these types of smart control, as well as internal plumbing to run the system at even lower temperatures (for lower distribution losses).

    If you replace the boiler, it's important to determine the true heat load, since oversizing it costs more up front, runs less efficiently and higher maintenence & comfort issues. Most 1600' houses in CT will have a design condition heat load of under 30,000 BTU/hr, and many will be around or under 20,000 BTU/hr. Both the Rinnai & Navien combi-units are on the big side these types of heat loads, and may short cycle unless you have high-mass radiation. If you have a mid-winter oil bill with a "K-factor" stamped on it and a zip code (for design temp & weather data) it's pretty easy to calculate a hard upper-bound on where your heat load lies.
  7. LamdaPro200

    LamdaPro200 In the Trades

    Messages:
    10
    Location:
    New York
    Down firing isn't going to help with the short cycling. I'm in a zero degree climate with 1650 sqft of heating space. R11 Walls, Double Pane windows and my heat loss is 36,000 Btu/hr. If your keeping the boiler the fix would be to add a buffer tank to allow the boiler to at least get to steady state efficiency. I wouldn't add the Taco PC700. Way expensive in comparison to the Taco SR-501OR Fuel Mizer which will provide outdoor reset.

    Here is the problem with conversion burners. First, do they work, yes they do. Once you convert the boiler outside the mfg installation instructions you have voided the reminder of warranty you have. Second, since you now have a boiler that is no longer UL rated and operating in a condition it wasn't tested for, rated for, certified for your home owners insurance may not cover any damage, ie, fire, water damage etc god fobid caused by the boiler. Do your do diligence and check with your insurance company prior to converting to make sure you are making the right decision.

    I am not saying not to convert it, I'm saying check and cover all dimples on your a**.

    If your budget is an issue. I'd look at doing a Crown AWR sized to the heat loss, an indirect as others have suggested and add the Taco SR-501OR. The AWR can handle boiler return water temps of 120 without any issues with thermal shock to the iron.
    Last edited: May 9, 2013
  8. Dana

    Dana In the trades

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    Thanks for the reference on the Taco SR-501OR Fuel Mizer! Specs-wise it looks like a better mousetrap than some of the other retrofit ODR controls.
  9. Tom Sawyer

    Tom Sawyer In the Trades

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    Location:
    Maine
    With the water capacity of the WTGO boiler and its cast iron, there is no need for a buffer tank. Changing the burner does not void the boiler warranty.
  10. BadgerBoilerMN

    BadgerBoilerMN Master Hot Water Mpls,MN

    Messages:
    303
    Location:
    Minneapolis
    I am an advocate for indirect water heaters but for the tight budget a conversion burner and conventional storage water heater like half of the country.
  11. LamdaPro200

    LamdaPro200 In the Trades

    Messages:
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    Location:
    New York
    Sorry Tom but have to disagree with you on both counts. Suggest you read the warranty. Specifically (3) and (6). A Gas Conversion burner is not approved by the boiler mfg.

    Additionally, this Limited Warranty does not cover claims you make if the failure, malfunction, or unsatisfactory
    performance of, or damage to, your Product resulted from or is attributable to:
    (1) Inaccurate or incomplete information or data supplied or approved by any party other than Weil-McLain;
    (2) The failure to properly size the Product for its use;
    (3) Installation not done in accordance with manufacturer’s instructions;
    (4) Services provided by and workmanship of the installer of the Product;
    (5) Components that are not supplied by Weil-McLain;
    (6) Improper or negligent operation, adjustment, control settings, repair, care, or maintenance of the Products, or the failure
    to adjust, set the controls of, repair, care for, or maintain the Products;
    (7) Operation with combustion air contaminated by chemical vapors, with improper fuel additives, or with water conditions
    that have caused deterioration or unusual deposits in the heat exchanger; and
    (8) Freezing, accident, fire, flood, or other acts of God; abuse or misuse; unauthorized alteration; or power surges or failures.

    As for the buffer. If you have a fixed input boiler firing every day of the heating season the same specific btu/hr and your emitter system cannot absorb and remove the created btu/hr because the heat loss is severely less then what the boiler is producing you short cycle. Your system side delta-t shrinks meaning your return water temps are awful warm.

    WGO holds 14 gallons of water - Chances of all zone open at once, about 2% of the heating season. Let's say your pulling out 5gpm on the typical 10 degree delta in the real world 5 x 500 x 10 = 25,000 btu/hr so you have 75,000 btu/hr or so left sitting in that boiler.

    14 - 5 = 9gpm of 180

    (9x180) + (5 x 170) = 14 Gallons of 176 Degree Water sitting in the boiler one minute after it reached high limit

    (9x 176) + (5 x166) = 14 Gallons of 174 ( 2 Minutes After)

    (9x 174) + (5 x 164) = 14 Gallons of 171 (3 Minutes After)

    (9 x 171) + (5 X 161) = 14 Gallons of 167 (4 Minutes After)

    (9 x 167) + (5 x 157) = 14 Gallons of 163 ( 5 Minutes After)

    (9 x 163) + (5 x 153) = 14 Gallons of 159 (6 Minutes After)

    Boiler Fires - 6 Minute Run time until it hits 180 again and that is not getting you to steady state..Using 5gpm was conservative.
  12. Tom Sawyer

    Tom Sawyer In the Trades

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    Location:
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    You can disagree all you want but having done countless such conversions in the past ten years or so I'm telling you that there is no need for a buffer tank and the boiler is old enough that changing the burner ain't gonna effect anything at all having to do with the warranty unless someone grossly over fires the boiler. You guys all seem to want folks to shell out a lot of money that they will never see a return on.
  13. Dana

    Dana In the trades

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    Location:
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    Cheaper than an indirect would be drainwater heat recovery heat exchanger, which would give you continous showering capability (no recovery time necessary) with the embedded coil, even with all zones calling for heat, and would allow you to set the low-limit to something like 140-145F and still get reasonable hot water performance, as long a filling big tubs isn't a priority. With a showering family of five it would have a reasonable ROI on raw fuel savings from the energy returned too, ignoring the standby loss issue.

    An indirect would cut way down on summertime standby losses by letting it cold-start, but those are likely pale in comparison in terms of the total magnitude of the savings if you have five people taking daily showers.
  14. LamdaPro200

    LamdaPro200 In the Trades

    Messages:
    10
    Location:
    New York
    Each is welcome to their opinion. I never said a gas conversion burner could not be done. I said to understand that you void the warranty or what is remaining and to check with your homeowner insurance to ensure that god forbid that converted boiler was the cause of something that they would be covered. Are both not the truth?

    What hurts our industry are installers that do not provide the consumer all the correct information, options and professional opinion that allows them to make their choice instead of choosing the choice for them. If your not making consumers aware that once you converted the boiler with a gas conversion burner that the mfg warranty on that piece of equipment is void then your not doing your job. Same goes for making sure they check with their homeowners insurance. Our job isn't just to turn a wrench, collect the check and walk away. It's to inform, educate, help the consumer make the best decision based on the application and provide the installation we contract for.

    What's wrong with honesty? My car will still drive without the right tire pressure but it doesn't mean I'm getting the best gas mileage I can.
  15. gennady

    gennady New Member

    You can cut your bills in the half without converting to gas. Install I series taco 3 way valve with outdoor reset, bumble bee taco delta T circulator , or just retrofit radiators with thermostatic radiator valves. You will be amazed with comfort and savings.
    Last edited: May 29, 2013
  16. Dana

    Dana In the trades

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    Yes, I would truly be amazed if it actually cut oil use by fully half.

    Were it actually that effective, you made those adjustments to the system AND changed to gas, the net savings would be more like 3/4, (and thus cost effective, even in buck a therm land.)

    But I sincerely doubt the net savings would actually be half. A quarter I'd believe, a third, maybe, if you're starting out with the worlds crummiest hydronic system designs.
  17. gennady

    gennady New Member

    Well, a half at least. With conversion to gas fuel bill can be cut over 4 times down on really screwed up systems. On average 3 times down. And no zoning at all.
    Last edited: May 30, 2013
  18. BadgerBoilerMN

    BadgerBoilerMN Master Hot Water Mpls,MN

    Messages:
    303
    Location:
    Minneapolis
    "You can cut your bills in the half without converting to gas. Install I series taco 3 way valve with outdoor reset, bumble bee taco delta T circulator , or just retrofit radiators with thermostatic radiator valves. You will be amazed with comfort and savings."

    Good idea, but for the same money we can usually install a condensing boiler and cut you heating bill in half, for real.

    The conversion would cost less and if sized and set up correctly would certainly be the best ROI. Any such conversion should be done by an experienced technician using a combustion analyser. As for warranty, we are design, install and service all makes of boilers here in Minneapolis and find the manufacturers more than fair with warranty issues on residential boilers. The only component covered after the first year on most models is the heat exchanger, which will last long burning gas than oil, regardless of model or manufacturer.

    Go for it!
  19. gennady

    gennady New Member

    Taco bumble bee.

    Taco bumble bee on primary and secondary loops are standard on our installations. and radiator thermostatic valves are very strongly recommended as an option. On steam conversions TRVs are not even an option. We will not do conversion without them. So bumble bee and I series Valve with outdoor reset actuator cost few hundred dollars and half day of work. So it is by far not a new boiler. But it will reduce pressure on home owner , and what is more important, when he will decide to go for new boiler bumble bee and TRVs will stay with new system.
    Last edited: May 31, 2013
  20. Tom Sawyer

    Tom Sawyer In the Trades

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    3,128
    Location:
    Maine
    a couple factors nobody seems to want to address is the payback and the longevity of the system. Condensing equipment is a pain in the ass plain and simple. It's complicated, uses proprietary controls and WILL cost more in upkeep and service than non condensing equipment. I find the guys pushing this stuff generally do not have much of a customer base, do not actually install or service equipment and live in a fantasy worlds where everyone has a wad of cash to spend. As a consumer you have to understand that while you may save a few bucks in fuel cost, it may very well take 10 years or more to realize the savings over the cost of the equipment and by then guess what? The equipment is on its last legs or, someone else has come up with something better. I know of many folks that have spent in excess of 15 grand tearing out their oil system to convert to gas and while gas is currently ( note the word currently) cheaper than oil, there is no guarantee that it will stay that way. Worse yet are the poor suckers that tear out their oil system and install propane. We service close to 8000 customers, both oil and gas and by far the most cost effective thing to do is to upgrade the current system. A 10 year old oil boiler can and will perform quite well with a minimum investment. Mod con's have their place but intelligent research must b don before laying out the cash. And, I love to see all the math and numbers being thrown out but 90% of them are based on erroneous, or missing data.

    If your old boiler is running at say 80% efficiency and your new equipment is running at 90% you save a whopping hundred bucks a year if you were spending a grand on oil. At 8000 dollars plus for a new boiler.....well, you can do the math.
    Last edited: May 31, 2013

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