Oil to Gas Conversion Options

David_16

I live on Long Island and I've made the decision to convert from oil to gas heating. Currently, I have a 19 year old Weil-McLain boiler and indirect hot water tank that need to be replaced.
I have a 2000 square foot house with 2.5 baths with 3 adults (likely down to 2 soon, but as many as 4 at times) with baseboard hot water heating. I already have gas in my boiler room.
I've had a few contractors in and am down to 2 very different proposals from contractors I would be comfortable giving the job to that I'm going back and forth between. For purposes of this discussion, let's consider that the contractors have sized the units properly and that the pricing difference not be a factor in deciding between the 2 options. I would much prefer something that is going to last at least 15-20 years and require as little maintenance as possible.

Proposal 1: Burnham ES2+Diversified TX-40 indirect hot water heater
Proposal 2: Rennai I-Series Condensing Combination Boiler

Both contractors will remove my oil tank and replace an old gas line going to my stove. The Burnham will require a chimney liner and the Rennai will vent through an outside wall.

I know the Rennai will be more efficient and save me some money in annual gas costs, but something about a tried and true system like the Burnham is attractive. I can probably put that in and touch it a maybe handful of times over the next 20 years and be good. What kind of annual maintenance do I have to do with the the Rennai? How long can I really expect to get out of that unit?

Is there anything inherently negative about having a condensing boiler with baseboard heat on Long Island? Will I be good on the coldest of days? How much hot water does it really produce? Can I take 2 showers at once with a properly sized unit?

Appreciate the help in advance!

EBEBRATT-Ed

Some on here do not like combi's. Because they operate more like a tankless water heater and have no storage you have to oversize the boiler for the heating load in order to meet the DHW load.

Going the other way with a boiler and an indirect is what most would recommend based upon what I here. The boiler could be a conventional CI boiler or a MOD CON.

As far as which type of boiler is better.........that is a debate that is far from settled. Mod cons modulate the flame size to match the load and condense to save money on fuel etc etc but the life span?? some have lasted 20 years but 12-15 is more realistic at this point. Not so much due to failures as after that time peroid the MFG has moved on to a different design making parts unavailable. The othere issue is parts availability for mod cons. Some supply houses do not stock parts and there have been jobs where people have waited a week for parts and the parts are big $$$.

Mod cons are a great boiler when they run and are more efficient. But a few parts can wipe out the fuel savings.

A CI boiler (and they don't last as long as they used too) should get 20 years and parts are more available and less expensive.

They both need service and a mod con needs a good technician while CI is a little more forgiving as to service and neglect.

That being said I am not a fan of Burnham.

A mod con is fine with baseboard. But with a mod con operating on baseboard the efficiency is reduced when it is really cold they will not condense and there efficiency drop to that of a CI boiler. Maybe a little more because it will modulate.

And all this is JMHO

others will chime in.

Hot_water_fan

Is there anything inherently negative about having a condensing boiler with baseboard heat on Long Island? 

No

Will I be good on the coldest of days?

Yes

How much hot water does it really produce? 

Depends on the boiler size and how much storage you have - you can install a modcon with a indirect tank, just like you have currently. In that scenario, it’ll be the same exact thing: a btu is a Btu. 

If you have a combi boiler, that’s different. They can handle consistent flows (like showers) but they will run out of capacity with large sudden flows, if that makes sense. 

A point for a modulating boiler with indirect is that they have the highest probability of not being wildly oversized. A CI will almost certainly be oversized - they just don’t come in many sizes and most of the sizes are huge. For example, the ES2’s smallest option outputs 60kbtu and they’ll try their hardest to up sell you. Combis have to be huge to meet the DHW needs. They can modulate down of course, but not as low as a stand-alone, smaller modcon can. 

pecmsg

A condensing boiler is fine for the shoulder seasons. Once you have to supply above 140* water you loose all efficiency 
seeing how your radiators are designed for 180*+. That’s most of the year. 

hot_rod

I would do a heat load and heat emitter assessment first. If you have adequate fin tube to allow you to operate at low SWT for much of the season the mod con option starts to look better.

What size boiler do you have now? How many feet of fin tube?

How many zones do you have? What is the heat load of the smallest zone?

What is the turn down rate of the cast boiler? Oh yeah, its all or nothing I forgot. A modulating boiler helps a lot with zoned systems and wide temperature and load changes.

If you are into number crunching build a graph like this to help determine the hours the boilers could run at temperatures below 180F, for example. I suspect your weather is a bit milder than upstate? So this give you a starting point.

Plenty of other good brands of mod cons. I'm surprised the Burnham bid didn't have the Alpine as option 2. It is a good mod con option, as is any Lochinvar.

Spend $$ tightening up the home as much as possible. That lowers the boiler load and saves fuel costs.

@Mad Dog_2 would know the design temperature for L.I., below is typical January temperatures

Hot_water_fan

@pecmsg generally, you can condense 80%+ of the time even if you need 180F on design day. Most of winters are not as cold as our memories tell us. We remember 0F but we don’t remember the 60 days with a high of 40F

pecmsg

Hot_water_fan said:

@pecmsg generally, you can condense 80%+ of the time even if you need 180F on design day. Most of winters are not as cold as our memories tell us. We remember 0F but we don’t remember the 60 days with a high of 40F

I’m not saying you can’t. Properly sized you’re probably close. How often are they properly sized. 

My point is there is a lot more to it then just deciding condensing boiler. 

Hot_water_fan

I think we agree that you’ll be condensing with baseboard, just the fractions are different. You’d be surprised how mild most winter days are! Supplying 140F or less will be the predominate condition. 

Mad Dog_2

5 degrees off the top of my head but I like to use 0...Mad Dog 🐕 

hot_rod

Mad Dog_2 said:

5 degrees off the top of my head but I like to use 0...Mad Dog 🐕 

Looks like December- February the average temperature is high 20- mid 30. So not a severe condition if it was designed for 0 or 5 above

pedmec

Stay away from the Rinnai. Or for that matter any on demand hot water heaters that try to do heat. Their heat exchangers are for producing hot water and do not last. if i could show you pictures of the failed heat exchangers that are less than 10 years old i would. Stay with a boiler that has a heat exchanger that is specifically designed for heat which can make hot water. lochinvar noble combi is one example. or better yet go with a condensing boiler with an indirect.

David_16

Wow, good stuff here! The insight and advice is much appreciated! I'm learning a lot.

I have 2 zones. The downstairs zone, which is a less space, doesn't get used nearly as much (set to 64 degrees 95% of the time) as the main zone. I have WGO-4 today so that's 145K, but I'm guessing that's oversized.

The Burnham ES2 contractor has done many similar houses and is recommending ES24 which is 105K input.

Sounds like, of the 2 options that I've got, the Burnham+indirect might be the more reliable option to give me what I want, but not the most efficient.

Sounds like, ideally, I'd want to find someone who would to a modcon boiler+indirect. So something like a Peerless Purefire or Burnham Alpine or what else? Looking quickly, the Peerless looks to be more $ than the Burnham. With modcon+indirect I presume I'm going to now drive the cost of this project up further or not necessarily?

I do have to say that the Burnham guy really doesn't like modcons. He said they are not going to be as efficient for this type of house.

The next problem I have is that I've had more than just these 2 contractors out here and not one suggested a modcon+indirect. I have the 2 options I started with here and a couple of others had a Burnham X-2+indirect. Someone else proposed a Lenox CI.

While my current boiler needs to be replaced, it doesn't seem like it needs to be replaced tomorrow, so I do have time to speak with more people, but I'm still hoping to get this job done in December. I just need to find someone reputable that is comfortable with modcon+indirect. But if it's going to cost a lot more $s, I'd probably just go with the Burnham CI+indirect. Between the gas company and federal government, I think there's about $1700 rebates for the modcon vs $575 for the Burnham 85%+indirect so that helps, but I've already accounted for that when I said the price between my option 1 and 2 is not an issue.

Further suggestions at this point?

Hot_water_fan

The Burnham ES2 contractor has done many similar houses and is recommending ES24 which is 105K input.

This is typical - a totally wild guess. 

If you go the Cast iron route, then I’d skip the ES2 and just get a series 2 or equivalent. They come in smaller sizes. 

How much oil did you use last year? That’ll answer the sizing question. 

David_16

Hot_water_fan said:

The Burnham ES2 contractor has done many similar houses and is recommending ES24 which is 105K input.

This is typical - a totally wild guess. 

If you go the Cast iron route, then I’d skip the ES2 and just get a series 2 or equivalent. They come in smaller sizes. 

How much oil did you use last year? That’ll answer the sizing question. 

Why Series 2 over ES2? Just because I can get a smaller sized one?

It looks like I purchased around 600 gallons last year (very warm winter). That's not necessarily what I used depending on what was in the tank when I switched oil companies.

Hot_water_fan

Yup, the Series 2 so you can get something smaller. No sense oversizing - just costs more upfront and wastes more fuel. With an indirect, getting something smaller doesn’t impact DHW. 

David_16

Hot_water_fan said:

Yup, the Series 2 so you can get something smaller. No sense oversizing - just costs more upfront and wastes more fuel. With an indirect, getting something smaller doesn’t impact DHW. 

I'm a bit confused about that statement. If I look at the specs for the Diversified TX indirect that the Burnham guy is recommending, it seems to indicate that it makes a different amount of DHW depending on the boiler size.  

You said number of gallons of oil used would help with the sizing.  So what does 600-700 (probably close to 800 for a cold winter) mean?

Hot_water_fan

Fair enough: that’s true. A bigger boiler will have a higher first hour rating and continuous rating when attached to the same indirect. It’s like when a minivan has a speedometer that reaches 160MPH and another minivan has one that maxes out at 140 MPH. Neither minivan will ever go that fast, but on paper it looks like there’s a difference. The point I was trying to make is that a boiler that’s “small” attached to an indirect will provide tons of DHW anyway- your typical standalone water heater is smaller than the smallest boiler and that’s what almost everyone uses. For example: a typical electric tank is 15,000 btus/h. You’d have a boiler likely 2-4x that size. 

KC_Jones

David_16 said:

Hot_water_fan said:

Yup, the Series 2 so you can get something smaller. No sense oversizing - just costs more upfront and wastes more fuel. With an indirect, getting something smaller doesn’t impact DHW. 

I'm a bit confused about that statement. If I look at the specs for the Diversified TX indirect that the Burnham guy is recommending, it seems to indicate that it makes a different amount of DHW depending on the boiler size.  

You said number of gallons of oil used would help with the sizing.  So what does 600-700 (probably close to 800 for a cold winter) mean?

Don’t get wrapped up in hot water production with an indirect, unless they propose putting in something tiny.  I have a family of 5 with a standard 40k btu 50 gallon water heater and we regularly run 5 back to back showers with zero issues. Even the smallest cast iron boiler will have 1.5x the btu input of what I’ve got.

I will reiterate the above, do not oversize the boiler and don’t pay someone who guesses at their work. If they guess at the very first critical thing, what else do they guess about?

I’m just a homeowner like you, I feel your pain.

LRCCBJ

David_16 said:

Hot_water_fan said:

The Burnham ES2 contractor has done many similar houses and is recommending ES24 which is 105K input.

This is typical - a totally wild guess. 

If you go the Cast iron route, then I’d skip the ES2 and just get a series 2 or equivalent. They come in smaller sizes. 

How much oil did you use last year? That’ll answer the sizing question. 

Why Series 2 over ES2? Just because I can get a smaller sized one?

If you go with the Burnham, tell the contractor that you demand the ES23. 70K BTU will be more than sufficient for your place and it will also produce acceptable DHW.

The contractor will squeal like a pig at your suggestion and tell you that it will never heat your house. Demand the ES23 anyway.

The next step down in the ES2 is 38K. This is likely insufficient unless the house is heavily insulated with very good (and not too many) windows.

HVACNUT

Aren't you supposed to get 3 quotes?
No EK Dealers by you?

Hot_water_fan

You said number of gallons of oil used would help with the sizing.  So what does 600-700 (probably close to 800 for a cold winter) mean?

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

You can use this to size. Since the oil also does DHW, a portion of the oil goes to that, so would be subtracted out from the annual usage. I suspect your heat loss is around 35,000 Btu at 0F. 

David_16

Good stuff! Still learning plenty here and appreciate the continued responses. Please excuse any ignorance or dumb questions. I am here to listen to advice so that I do make a proper, informed decision.

As far as DHW, not really sure why I don't get enough DHW today with oversized boiler and 30G indirect (in winter, I need to keep moving the shower handle towards hotter until eventually I'm max and the water isn't that hot). I guess that's why I'm "wrapped up" up how an ES23 would get me enough DHW, but I guess something may not be set up/working ideally today and will take your words on that.

I know what you will say, but is it really still "guessing" if the contractor has done say 50 installs of the same equipment in the same town in houses that are built identically to mine?

Yes, I have about 6 bids so far. I've just eliminated all but 2 that I've talked to so far. At least the Burnham guy had an ES24. At least 3 people quoted X205s and one even an X206. Burnham guy is also using a Diversified TX-40 indirect whereas some others are going with the TT series, which I think is not quite as good.

Is the ES2 "better" hardware than the Series X-2 in any way?

Seems like I'm going to eliminate the combi option.

I'm not hearing any major negatives about the Burnham other than making sure it's sized correctly and that I'll use more gas vs a modcon, but it sounds like it should work well and be reliable for years and easily meet my DHW needs as well.

That being said, based on the input here, seems like I should still try to find someone who has expertise in something like a Burnham Alpine modcon+indirect. It might put me above what I want to spend though. I've got a few recommendations from people on the town facebook page who went that route, so I'll call a few of those contractors tomorrow and set up appointments.

@HVACNUT What's an EK dealer?

@Hot_water_fan will review that page some. When you say that my need is likely 35K BTU at 0F, am I looking to match the boiler input, DOE or Net ratings? I suspect it's the Net number, but want to confirm. And the negative of getting an oversized boiler is strictly fuel costs? Any estimate of percentage of fuel savings annually if my heat loss 35K and I did an ES23 vs ES24?

Happy Thanksgiving!

Hot_water_fan

I know what you will say, but is it really still "guessing" if the contractor has done say 50 installs of the same equipment in the same town in houses that are built identically to mine? 

Still guessing, because 1. They aren’t identical and 2. When you’re 3x oversized, you don’t get callbacks, so there’s never any feedback. If I forget to feed my dog dinner, it’ll let me know. It won’t let me know if I accidentally feed it twice. 

As far as DHW, not really sure why I don't get enough DHW today with oversized boiler and 30G indirect (in winter, I need to keep moving the shower handle towards hotter until eventually I'm max and the water isn't that hot). I guess that's why I'm "wrapped up" up how an ES23 would get me enough DHW, but I guess something may not be set up/working ideally today and will take your words on that.

That could be a lot of things - a bad heat exchanger, too low of a heat setting, etc. Most gas tanks are around 30-40G with smaller burners and do great. I personally use an electric tank that’s only 15kbtu and don’t run out of water with back to back winter showers. 

When you say that my need is likely 35K BTU at 0F, am I looking to match the boiler input, DOE or Net ratings? I suspect it's the Net number, but want to confirm. And the negative of getting an oversized boiler is strictly fuel costs? Any estimate of percentage of fuel savings annually if my heat loss 35K and I did an ES23 vs ES24?

DOE actually! Net is just output / 1.15. The 15% is just a fudge number, you can use your own. 

https://files.norareport.org/NORA/research/Studies/May%202007-Performance%20of%20Integrated%20Hydronic%20Systems.pdf

This is an older study now, but oversizing was shown to have a large efficiency hit. There are other ways to avoid the hit that aren’t right sizing, but right sizing is the simplest, most reliable way. 

David_16

Is sizing as important with a modcon or does the "mod" part mean that I won't waste as much gas with an oversized boiler? Assuming that my needs are around 40K BTU and I'm looking at an Apline, should I be looking at the ALP105B or the ALP080B?

Hot_water_fan

Correct, doesn’t really matter with a modcon. Their lowest limits are all pretty similar in the 8-15kbtu range. 

hot_rod

Look around here for any local or power company incentives. Look like a $1000.00 for a heat pump water heater if you want efficiency.

https://programs.dsireusa.org/system/program/ny

David_16

hot_rod said:

Look around here for any local or power company incentives. Look like a $1000.00 for a heat pump water heater if you want efficiency. https://programs.dsireusa.org/system/program/ny

Yes, psegli gives $1100 for 95% boiler and something like $300 for 85% and i think another $300 or so for the indirect.  Think I might get a $600 federal tax credit for 95% boiler as well.  

I've factored that into my comparison.  Not sure if I can get modcon+indirect into budget even with the extra rebate.  But, I'm going to have a few more people come so I can find out.

Steamhead

David_16 said:

Is the ES2 "better" hardware than the Series X-2 in any way?

A bit more efficient.

David_16 said:

@HVACNUT What's an EK dealer?

Energy Kinetics. Very nice units. Tell us where you're located and @Roger or one of the other EK people could tell us if there's a dealer near you.

Why does your current boiler "need " replacing? If just because it's oil, I'd look at putting a Carlin EZ-Gas burner in it. Those Golds run nicely with these burners.

David_16

Steamhead said

Energy Kinetics. Very nice units. Tell us where you're located and @Roger or one of the other EK people could tell us if there's a dealer near you. Why does your current boiler "need " replacing? If just because it's oil, I'd look at putting a Carlin EZ-Gas burner in it. Those Golds run nicely with these burners.

@Roger
I'm on Long Island, NY.  My 19 year old Weil Mclain oil boiler has a crack and multiple people told me I should replace it. The indirect is same age.

Steamhead

David_16 said:

I'm on Long Island, NY.  My 19 year old Weil Mclain oil boiler has a crack and multiple people told me I should replace it. The indirect is same age.

Is it leaking water?

David_16

Steamhead said:

David_16 said:

I'm on Long Island, NY.  My 19 year old Weil Mclain oil boiler has a crack and multiple people told me I should replace it. The indirect is same age.

Is it leaking water?

Not actively that I can see. I was told when they took the jacket off, there was some water there.
Here are a couple of photos. No one seemed to think it was worth trying to repair, but, of course, they were all trying to sell me a new boiler.

Jamie Hall

If you are not having to add any water to your system more than say a couple of gallons a month, it's not leaking, and probably doesn't need repair.

David_16

Jamie Hall said:

If you are not having to add any water to your system more than say a couple of gallons a month, it's not leaking, and probably doesn't need repair.

I don't think it's actively leaking, but was told that the damage in the pics I posted could lead to that soon. No one who has looked at it thought repair was an option.

pecmsg

Am I the only one that sees a water stain from the fittings running down ?

Mad Dog_2

Are they all quoting the same equipment?   Mad Dog 🐕 

David_16

Mad Dog_2 said:

Are they all quoting the same equipment?   Mad Dog 🐕 

So far, no one has indicated that repair is a viable option, plus it's 19 years old and the indirect is 19 years old and it's oil today, so all that being said I think it's going to be time to replace with gas.

So far, I've got a bunch of Burnham x2 quotes, a Burnham ES2 and the Rennai combi.  No one yet with a condensing boiler plus indirect.  So far, I like the guy proposing the ES2. 

I just spoke to another guy who is going to come Monday.  It sounds like he's also going to propose a CI boiler plus an indirect for the same reasons the ES2 guy is saying to go that route, mainly a condensing boiler is not going to be as efficient with baseboard heating and that a CI will likely require less maintenance.

David_16

One other question in the meantime here.

Let's see I do go with a CI+Indirect with my baseboard heating. Is there much value in an outdoor reset?

David_16

Hot_water_fan said:

You said number of gallons of oil used would help with the sizing.  So what does 600-700 (probably close to 800 for a cold winter) mean?

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

You can use this to size. Since the oil also does DHW, a portion of the oil goes to that, so would be subtracted out from the annual usage. I suspect your heat loss is around 35,000 Btu at 0F. 

This is great, but I'm a bit stuck here and don't know if you have a few minutes to assist. I did as much legwork as I could.
12/17/22 - 1/20/23 I used about 134 gallons of oil.
My WGO-4 looks to be rated 168,000 input and 146,000 heating capacity (data sheet says 86% efficiency, so let's use that number)
Base 65 degrees totals 894.7. Base 60 degrees totals 720.2.
99% outside design temp for my county is 9 degrees.

Not sure I've got the calculations correct.
BTU delivered to ducts 138700*134*.86 = 15983788

65 degree balance point = 744 BTU/degree hour
60 degree balance point = 924 BTN/degree hour

65 differential vs 9 degrees = 41644 BTU/hour
60 differential vs 9 degrees = 47124 BTU/hour

So is my number somewhere around 45K BTU/hour? And I want to size to around 1.4 of that so 63K?

If I've got this all correct, the ES23 would be slightly low at 56K DOE heating capacity? Is the ES23 still going to be large enough? What if my calculations are wrong?

And if I did do the ES23, there would be no difference in the amount of effective hot water produced vs the ES24?

EDIT: I just did another time period 3/21/23 through 4/19/23 I used about 106 gallons and the 65 degrees total is 412.8 and the 60 degrees total is 284.2. That puts me between 71K and 94K for 65/60. Not sure how it could be so far off between the 2 calculations.

As far as calculating gallons, I just took how much they charged me on the end date and divided that by my price per gallon. I do not have any way to know for sure that the tank was full after the previous delivery or that the tank was fill after the delivery I used for the calculation. I can only assume that they fill my tank when they come.

pecmsg

Your forgetting the COP

At warmer ambient that’s above 3:1 so 130, 140,000 BTU,s per hour. 

Steamhead

David_16 said:

One other question in the meantime here.

Let's see I do go with a CI+Indirect with my baseboard heating. Is there much value in an outdoor reset?

How many heating zones do you have?

David_16

Steamhead said:

One other question in the meantime here. Let's see I do go with a CI+Indirect with my baseboard heating. Is there much value in an outdoor reset?

How many heating zones do you have?

2 zones plus the indirect. 1 zone sits at 64 degrees 95% of the time though.