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oil to gas conversion

FelixCulpa
FelixCulpa Member Posts: 2
I'm a total newbie, but have been trying to learn as much as possible. Let me tell you my situation, then ask questions...



I live north of Boston in a 1947 brick house, about 1600 sq ft, 1.5 ba. My oil boiler is about 30 yrs old, with a tankless HW integrated into it. I have a pressure problem, which is likely caused by the tankless coil. I spent $2500 in oil last year, and this year it projects to be about $3500. I recently had an energy assessment done by Mass Save, and they will be doing insulation and sealing. Their guy says that it will improve my efficiency by 30%.



Looking at all of the incentives laid out by National Grid and Mass Save, such as discounted boilers, rebates, and a 7-yr, no-interest loan, plus the saving in fuel and much better efficiency, it seems like a no-brainer to me to switch. My calculations say that I should be able to provide heat and HW for less than $1000/yr. Add on to that the loan payoff of $70-90/mo., and I still come out ahead on a month-to-month basis.



I am thinking about a high-efficiency (90-97 AFUE) gas boiler with an indirect hw tank.



Here are my questions:

1. What size boiler do I need? I've had two estimates, and they seem to just pick one from a list, with no heat loss calculation done. Given the better insulation I will have...



2. What size HW tank do I need? I'd like to be able to run the dishwasher and take a shower. No hot tub or spa.



3. Has anyone had experience with the HEAT loan? It seems like a ton of steps, and the contractors I've dealt with have no inclination to deal with the paperwork.



4. Should I pick from the list of boilers that National Grid sells at a big discount? They can provide mostly Burnham boilers, the Alpine series look OK to me, though I've read on some boards that they are temperamental. Also, the contractors don't want to lose the mark-up on selling the boilers themselves.



5. Does it make more sense to go with a cheaper cast Iron boiler, save all of the maintenance of the HE models, but lose the efficiency? That's what one contractor suggested.



Thanks very much!

Comments

  • BobC
    BobC Member Posts: 5,230
    edited August 2011
    gas company

    I had Boston Gas send out a contractor to look into converting over to gas heat a couple of years ago. the outfit that came over asked how old the boiler was and then they looked at the boiler in my cellar. A couple of weeks later I got a quote in the mail for a boiler that was much too big and a price tag that was suspiciously high. The companies that install most of these are making money because of the volume they do, I'm afraid a quality install is pretty much hit or miss.



    I'm just south of Boston and I have an oil fired steam boiler (now 15+ years old) that works well but is over-sized. My domestic hot water is by gas. I also thought that gas would probably save me a fair amount on fuel, last heating season the equivalent amount of natural gas costs $2.70 vs the $3.20/gal  I paid for my last fill of oil on Feb 14. When comparing costs remember they charge a lot more for natural gas in the winter and the delivery charges and fees add up FAST. I decided to wait for the old girl to die and then go with a good cast iron boiler with a gas gun in it. In my case oil costs me about $175 more per year than gas would so I'm not going to replace a working boiler just for the fuel cost savings.



    I'm assuming your heat is forced hot water but you still have to know the amount of radiation you have and then figure out your heat loss, which will be less after you get everything tightened up. Then you will know how big a boiler you need. The right boiler correctly installed boiler will last a long time, better to pay a bit more and get exactly what you need.



    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • 04090
    04090 Member Posts: 142
    Is your math off a decimal?

    So if I read you right, you're saying a conversion from an old oil burner to a new gas system would only save $175 annually?



    Do others agree?  It seems to fly in the face of so much that's presented here.
  • lchmb
    lchmb Member Posts: 2,997
    he is saying

    If here were to simply replace the oil burner with a gas burner, due to the difference in BTU value and the pricing available to him he would save that amount. A new properly sized/installed steam system would probably save him more...
  • BobC
    BobC Member Posts: 5,230
    Oil vs Gas - correction

    I was asked about the cost of gas heat last week by somebody so I went back over my calculations and realized i had been using the wrong tables for the cost of gas distribution (R1 vs R3). The net result is that my savings would be more like $300 instead of the $175 I posted  in my previous post. That assumes a yearly use of 485 therms of gas in a boiler that is 83% efficient. That figure does not include the 120 therms used for cooking and DHW. Because it is a steam system there are no federal tax credits available for any steam boiler that I am aware of.



    In my case to change over to gas on my steam system, just for the savings in fuel, would take 19 years for ROI (return on investment). That includes a cast iron boiler with a gas gun (smith G8 and EZ-gas) and a chimney liner. When my 15+ year old boiler starts to fail I will switch to gas because the additional costs incurred by switching will be paid for in 3 years, that is a great ROI. A 15 years old V75 boiler is probably not far from that day, but I can always hope for the best. The tech who cleaned the boiler last month said it looked to be in great shape for it's age.



    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • lchmb
    lchmb Member Posts: 2,997
    thoughts

    1. what size. The only way this can be answered is by a heat loss. Taking the size of the existing boiler does no good because odds are it's over sized. Find someone who will do the heatloss, it's worth the search.

    2. Tank size, I generally install 40 gal tanks with a mixing valve. Run the tank at a higher temp and blend to 120 out, never had an issue.

    3. Sorry cant help you with that..

    4. After you find the company willing to do the heat loss, discuss the option's with them. See if they have a recommendation, Sometime's a "big discount" doesnt alway's pay in the long run.

    5. A mod/con boiler does require yearly service. But then again, if you read the literature with a cast iron boiler, it also requires yearly service. I service both and have seen both have problems. Look at all options givin by a company and research each unit. See what other people think that have installed them...Internet is an awsome place to search..
  • FelixCulpa
    FelixCulpa Member Posts: 2
    Update

    Thanks lchmb, I appreciate it. Here's where I am now:



    I decided to make the conversion

    I chose the HE Mod/Con Burnham Alpine 105 (from National Grid), based on a heat loss calculation

    I chose the SuperStor 45 for the HW

    I am applying for the HEAT loan (7 yrs, 0% interest)



    Here are my calculations --

    Gas company says $1.39 per therm, 1.38 therms per gallon = $1.92 per gallon equivalent by my calculations. Oil right now in my area is $3.80



    My est. oil use for the winter is $3500



    If above calcs are correct, gas will cost me about $1750 without any improvements. Subtract 40% more efficient boiler (at least), 30% better insulation, 10% better from hw system, and my total for the year becomes: $662. I think that's waaaay optimistic, but still, i know my cost will go down. A lot.



    The total cost for everything -- boiler, HW tank, gas line, removal of oil tank, permits, electrical, insulation, house sealing, etc., etc. is $10,700 after rebates.



    I know I'm going to beat the 7-yr payback of the loan, no problem, and probably do much better. I'm going with the mod/com boiler because everyone I asked had a different opinion about which way to go, so I'll take a chance with the better efficiency.



    Thanks everyone for your help.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Mod-con boiler

    I am not a professional, but I do have a mod-con boiler with outdoor reset.



    For me, it was pretty clear I should go with a mod-con because my biggest heating zone (I have two zones) is radiant heat with copper tubes in the concrete slab under the house. The maximum supply temperature to that slab is 120F, and on design day, it is only 112F. The other zone is much smaller, but is heated with fin-tube baseboard. I increased the size of the baseboard so on design day, the supply temperature is 130F instead of the more usual 180F so that I will get condensing with that zone also.



    In my view, there two advantages to a mod-con, and you want to be sure you get both advantagesl One is the modulating feature coupled with the outdoor reset. This provides increased comfort with that slab (much less overshoot of temperature). This permits longer cycles for more efficiency.



    The other advantage is the condensing feature. This, in theory, could get you something like 10.1% more efficiency, but you will not get that much; you could get a lot of that. But to get it, you want the return water temperature to the boiler to be as low as possible -- surely less than 130F, and to get that you need as much radiation as possible. For in-slab radiant, you can be pretty sure you will have enough radiation. For the other means (baseboard, for example),  you might be lucky, or you might need to make some changes. In my case, it was easy to replace the 3 foot baseboard pieces with 14 foot baseboard. In other situations, it might not be so easy.
  • sgall
    sgall Member Posts: 37
    I am new to a lot of this

    myself but your boiler seems very big for your square footage of your house.  I am doing a similar conversion and my heat loss was 80,000 for an old house twice as big as yours. 
  • Brick Deteriorate, Venting, Acidic Condensate, 95% Efficient Alpine

    My dad is a heating contractor and I just put an Alpine 105 with 40gal weil mclain hot water heater. I spoke to at least 15 heating contractors before installation and read as much as I could also.



    My house is 1920 brick, about 2000 sq ft including fully finished slab first floor, second floor and unheated attic, 3 zones plus one for the domestic hot water.

    Now I see the steam coming out of the house onto the brick wall and worry about deteriorating mortar. One reason these boilers are not exhausted through the chimney is because the exhaust is acidic steam. The acid is like muriatic acid which dissolves the lime in mortar and freezing and thawing causes mortar to crack and allows rain to get in the cracks causing more freezing, thawing and cracking.

    I did not have any contractors comment on the brick except to say they wanted me to handle getting the vent holes cut for the venting because they would not be able to do it.

    If anyone has any suggestions or advice on how this acidic vapor will affect our houses over time, I'd like to hear them. I have not seen anything written about this except in discussing venting through a chimney where they describe the problem of high efficiency boilers having more acid and water vapor with less heat loss to help dry out the condensate. I assume some of the same problems would happen to the side of the house where the boiler is vented.
  • lchmb
    lchmb Member Posts: 2,997
    suzanne

    I dont believe you will have an issue with the venting. I have a number of home's that are brick sided and serviced every year with no issues.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    The acid is like muriatic acid

    Acthally, it is mainly carbonic acid which is a lot weaker than muriatic acid (an impure form of hydrochloric acid). I am told its pH is between 3 or 4 which is weak enough you could put your hand in it for a little while. My guess it is about as acid as the vinager used on salads. This is not to say it will have no effect on mortar or bricks, but I would guess it would be slow.



    The gargoyles on Notre Dame cathedral in Paris are made of limestone. The first set lasted several hundred years. The next set lasted only about 50 years. That just from acid rain. So long term, the acid rain we get is likely to wear out your concrete, mortar, etc., perhaps as fast as condensate from a condensing boiler. Still not a great idea to let it dribble on a concrete floor. I know my vent blows "steam" out the side of my garage and if the wind is wrong, it blows it back onto the outside wall. This happens only if the boiler is modulated all the way down. When it is really runing at a high rate, the "steam" blows straight out.
  • vents placed 12 inches apart or you get frost

    I am near Boston on the ocean, so brick already has it rough with wind blowing away any loose mortar sand, freezing and thawing with snowstorms, I understand venting inside a chimney would concentrate the water more. I guess I will just  have to see this winter if ice builds up on the side of the house where it vents the steam.

    I noticed in the instruction book it warns about frost if 2 vents are placed less than 12" apart,

    I'm impressed! So few people have worked on brick houses here in New England and you have also been installing condensing boilers long enough to say there is no harm, being that they are so new. You must have started when they first came out.

    Wonder if they were always direct vented or if chimneys were used and people had bad experiences.
  • vents placed 12 inches apart or you get frost

    I am near Boston on the ocean, so brick already has it rough with wind blowing away any loose mortar sand, freezing and thawing with snowstorms, I understand venting inside a chimney would concentrate the water more. I guess I will just  have to see this winter if ice builds up on the side of the house where it vents the steam.

    I noticed in the instruction book it warns about frost if 2 vents are placed less than 12" apart,

    I'm impressed! So few people have worked on brick houses here in New England and you have also been installing condensing boilers long enough to say there is no harm, being that they are so new. You must have started when they first came out.

    Wonder if they were always direct vented or if chimneys were used and people had bad experiences.
  • vents placed 12 inches apart or you get frost

    I am near Boston on the ocean, so brick already has it rough with wind blowing away any loose mortar sand, freezing and thawing with snowstorms, I understand venting inside a chimney would concentrate the water more. I guess I will just  have to see this winter if ice builds up on the side of the house where it vents the steam.

    I noticed in the instruction book it warns about frost if 2 vents are placed less than 12" apart,

    I'm impressed! So few people have worked on brick houses here in New England and you have also been installing condensing boilers long enough to say there is no harm, being that they are so new. You must have started when they first came out.

    Wonder if they were always direct vented or if chimneys were used and people had bad experiences.
  • 3 of the same post

    Sorry, not sure how the site posted this 3 times. maybe someone can remove the extras.
  • 3 of the same post

    Sorry, not sure how the site posted this 3 times. maybe someone can remove the extras.
  • 3 of the same post

    Sorry, not sure how the site posted this 3 times. maybe someone can remove the extras.
  • lchmb
    lchmb Member Posts: 2,997
    edited October 2011
    direct vent

    I have been working on condensing boilers/furnaces for 12 years now and have a number of brick sided home's that I service. I have never observed an issue with the flu gas's affecting the side of the house. In some case's I do see ice build up and it affects wood more than brick...
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