New Boiler for the house

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vincenzo

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I am looking to get a new boiler for my house here in Massachusetts. My excellent burner tech wants me to put in a Energy Kinetics system2000, he loves them. Reading some other boiler installs on websites like this I am worried about the boiler being oversized for my house. I have a 1500 sq. ft. 2 story colonial built in the 1920's. r-45 in attic, 2 pane windows, insulated front and back doors with storm doors, and has 100' of hydronic baseboard. The house is vynal sided with 1/2 inch of foam beneath it, I insulated the basement sills with foam, but the house has no wall insulation, no basement wall insulation, and is a typical drafty 1920's house. Is a system 2000 too large, or how about a Biasi B3 61000 btu oil boiler with a superstore 45 indirect or maybe a Amtrol 41 gallon indirect. I see the Amtrols need alot less Btu's to work which might help the smaller Biasi boiler, or is the Biasi to small. My area has gas, but I won't be able to switch over to it for 4 more years due to recent road repaving. My current boiler is a Burnham 20-25 years old, 124,000 btu's, inside coil hot water heater, runs at 82-83% efficient. When I have to use this burner alone to heat the house it kills me on oil, a fillup of about once a month is average when it get's cold out.
 
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Dana

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For the record, how many gallons/year do you go through with the Burnham?

A tightened up 1500' colonial with an insulated foundation would typically come in under 25,000 BTU/hr @ 0F, which makes even the Biasi B-3 more than 2x oversized. The smallest System 2000 would also be 2x or more oversized, but comes with smart heat-purging controls that mostly makes up for the oversizing, as do the Burnham MPO-IQ series boilers. A really drafty house that size might hit 50,000 BTU/hr @ 0F, but those would be the rare outlier. you are somewhere in the middle, but insulating the walls could move you to the sub-35,000 BTU/hr range pretty quickly, and in MA there is substantial subsidy money available for that type of work. Got a ZIP code?

An indirect doesn't need a boiler of any particular size to work- it'll still put out WAY more hot water than a standalone gas hot water heater even with the smallest oil boilers driving it. It only "needs" the bigger boiler to meet the specified hot water performance.

If your heating system is cut up into bunch of zones you might be better off with a "reverse indirect" buffer at the center of the system, slaving the boiler to the tank as it's only zone.

Many homes with low heat loads can be heated far more cheaply with ductless mini-split technology than with any oil boiler, but that's a tougher call to make.
 

vincenzo

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I can't say how much oil we use. Because we were using so much, I bought a wood stove and that has been doing a lot of the heating for the past 5 years or so. But I am trying to get away from using the stove as my main heat source and want to start using my burner again. If I remember correctly we were filling up about once a month on average so 6 or 7 fillups a year would equal about 900-1000 gallons a year. My house is not that tight. It has no wall insulation, no basement wall insulation, the basement windows need replacement as well. The house has 2 zones, upstairs and downstairs. I looked into the mini splits, they are very expensive. My next door neighbor just had a Mitsubishi 2 zone mini put in and cost just over $10,000. If I spend that kind of money, I would rather spend it on a new oil burner since the one I have now is so oversized and getting up there in age. Zip is 02062. What do you think about the system 2000, My boiler tech swares by them.
 

Dana

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Your neighbor got hosed. A cost of $10K+ for 2-head ductless is on the very high side. Just last week I reviewed a quote for TWO two-ton three heads per (6 heads total) for a house on Martha's Vineyard for about $15K. These weren't crummy units either, with fully specified output down to -5F (though there are some with guranteed output at -15F.) Over the summer one of my office-mates did three separate cold-climate Mitsubishis (two 1-ton and one 3/4 ton) for about $10K (before subsidy rebates). It's operating cost is about half the cost of heating with his ~80% efficiency oil-fired steam, even at this year's lower oil prices even at suburban Boston's high electricity prices. A typical 1.25-1.5 ton cold-climate single head mini-split would be under $5K, installed, and would heat half your house (even your barely insulated house.)

But rather than chasing highest efficiency equipment, if the boiler still works you'll see much more fuel savings per dollar invested by pounding some cellulose into those empty wall cavities, and doing some blower-door directed air sealing. Spending the money on tightening up and insulating the building has a much higher impact on creature comfort than any heating system could, and in your case, would be money better spent. MassSave covers 75% of the cost up to $2000 of benefit per year (meaning an $8000 insulation job.) There are primarily just two things that could screw that up for you- knob & tube wiring, and if the half-inch foam siding underlayment has foil facers.

Worst casing it on the fuel use, assuming 1000 gallons a year at 85% efficiency in a ~5800 HDD climate (Boston's is ~5600 HDD, Worcester's is ~6800), you're putting 0.85 x 138,000 BTU/gallon = 117,300 BTU/gallon into the heating system. That's (117,300 x 1000) /5800= 20,224 BTU/HDD, or 20,224/24= 843 BTU per degree-hour, for every degree below the presumed 65F balance point.

Norwood's 99% outside design temp is about +9F, which is 56 F below the degree-day base, which implies a worst-case load of 843 x 56= 47, 208 BTU/hr.

At a ratio of 31 BTU/hr per square foot of conditioned space that is a ridiculously overstated worst case. Reality is probably under 40,000 BTU/hr, maybe even under 35,000 BTU/hr. If you air seal & insulate you'll be under 30,000 BTU/hr.

A Biasi B-3 has a D.O.E. output of 67,000 BTU/hr which would be about a 1.4x oversizing factor for that silly worst-case over estimate,which means you're good down to at least -15F with that boiler, and probably a lot colder, since that's truly a heavy handed estimate. The Burnahm MPO-IQ84 puts out about 74,000 BTU/hr, the smallest oil-fired System 2000 would be about 84,000 BTU/hr. They're all at least 2x oversized for the likely real heat load, getting onto 3x oversized for the load after fixing up the place a bit.

A retrofit heat-purge economizer is $500-700 if installed by a tech, ($150-200 as a DIY) and would make huge efficiency gains from that 4x oversized beast in the basement if coupled with an indirect, to allow you to idle the boiler at 140F. Spend the real money on insulating the place there's no real payback on going from a 125K output boiler with heat purge control to an 75-85K boiler with heat purge control. But there's HUGE payback on going from a whole-wall R of about R3 to a whole-wall R of about R13.
 

vincenzo

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Can you explain the problem with the half inch of insulation under the vinyl siding. If I remember correctly, at least one side of it does have the foil on it. I would love to get the walls insulated, but I have read to many times on websites for homebuilding not to get blown in insulation in houses as old as mine because of potential mold buildup in the walls. These houses have to breath a certain way, and the siding along with the foil creates a vapor barrier so the blown in cannot wick itself dry if necessary. Maybe the only thing I could do is get foam insulation installed, but it is very expensive. As far as the boiler goes, you would add a indirect water tank, and install a heat purge economizer. Can you even do that on a boiler that heats hot water with a coil? The boiler is still way oversized.
 

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You can't go wrong with the system 2000. May be the most efficient oil fired boiler (non condensing) on the market today and yes, it will be a bit oversized but it can be slightly down fired. I've been. System 2000 dealer since they were first introduced thirty years ago. In fact, I still have customers with the original grey jacket boilers running just as efficiently today as they did when I installed them.
 

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Can you explain the problem with the half inch of insulation under the vinyl siding. If I remember correctly, at least one side of it does have the foil on it. I would love to get the walls insulated, but I have read to many times on websites for homebuilding not to get blown in insulation in houses as old as mine because of potential mold buildup in the walls. These houses have to breath a certain way, and the siding along with the foil creates a vapor barrier so the blown in cannot wick itself dry if necessary. Maybe the only thing I could do is get foam insulation installed, but it is very expensive. As far as the boiler goes, you would add a indirect water tank, and install a heat purge economizer. Can you even do that on a boiler that heats hot water with a coil? The boiler is still way oversized.

There's a wealth of ignorance out there regarding vapor retarders and moisture control in building assemblies, and it's easy to misconstrue what is really needed.

The issue isn't about wicking, it's about the inability for water vapor to pass from the sheathing to the exterior through foil facers. But if you had sufficient foam-R on the exterior such that the average wintertime temperature at the sheathing was above the average interior air dew point (about 40F, in most houses in this climate), very little moisture would accumulate in the sheathing. If you meet that condition the wall would be able to dry toward the interior, and would never NEED to dry toward the exterior.

In US climate zone 5 climate (MA is all zone 5A) it takes a minimum of 25% of the total R to be on the exterior of the sheathing to provide dew point control. So for full-dimension 2x4 with R15 cellulose that needs to be R5 on the exterior. For 2x6/R23 rock wool construction it needs at least R7.5 or so. This has been enshrined in the IRC building codes, and has long since been proven to work with only latex paint as the interior side vapor retarder.

If the foam doesn't have a facer or if it has a perforated facer, it is sufficiently vapor permeable to dry toward the exterior, and blowing it full of cellulose is not a problem despite insufficient R value for dew point control, particularly under vinyl siding which is inherently back-vented and doesn't inhibit drying. Half-inch XPS foam (blue, pink, green, sometimes gray) has a vapor permeance of about 2.5 perms, which is barely tighter than standard interior latex paint, and more vapor open than most exterior grade paints. Half inch EPS foam is about 5-7 perms, more vapor open than interior latex. But a 6 mil foil facer has a vapor permeance less than 0.05 perms, effectively blocking all drying in that direction.

Installing slow rise foam in those walls is both risky and expensive. It would be cheaper (and higher performance) to pop off the siding and add another layer of foam to bring the exterior R above the IRC prescriptive minimum in order to allow blowing in a cheap fiber cavity fill. With 3.5-4" of closed cell foam in the cavity and a foil facer on the exterior, it creates a moisture trap at the sheathing, since the closed cell foam would only be about 0.3 perms, with very limited drying rates possible toward the interior. But if you filled it with open cell foam with insufficient exterior R you're not really better of than with dense-packed cellulose (and in some ways worse off), since the open cell foam would run about 8-12 perms (the interior paint is more vapor retardent.

Installing cellulose would be preferable to open cell foam, since unlike open cell foam the cellulose can safely wick & store quite a bit of moisture away from the structural wood without losing insulating function, or growing mold, sharing the moisture burden with the timber. MANY 1920s homes have been successfully and safely insulated with cellulose (including mine), and even much older homes. A few years ago I was involved in a deep energy retrofit on a circa 1890 3-story house in Worcester, that had been retrofit insulated with cellulose some time in the early 1980s. When we gutted the walls the cellulose looked as fresh as if it had been installed the day before, and had to be pulled out with a hoe. (As part of the retrofit that house got foam in the stud bays for air tightness on the old wide-plank sheathing, and 4.5" of reclaimed polyiso foam board on the exterior, under new fiber-cement siding.)
 

vincenzo

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You're knowledge of this stuff Dana is tremendous. If you have a couple of minutes, please read this at bobyapp.com/blog/2009/06/myths-about-insulating-old-house-walls. Sorry I can't redirect you there. When I read this article I get paranoid about getting the blown in insulation. If I want to refit my existing boiler with a indirect water tank, should it be a superstore or an amtrol or another brand?
 

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Bob Yapp isn't exactly hitting on all cylinders here- he doesn't appear to have a good grasp on the moisture transfer mechanisms. He IS correct that the most cost-effective energy improvement you'll ever make on the place is air sealing, but seriously:

We create warm moist air in our homes by cooking, taking showers, having plants, breathing etc. That warm, moist vapor is attracted to the exterior walls. This vapor enters the wall through hairline wall cracks, outlets, switches and window trim. In new construction, the plastic vapor barrier under the drywall stops the wet air from getting to the insulation and condensating.

In old houses with plaster walls, there is no vapor barrier under the plaster so the wet air hits the insulation and condensates. This wets down the blown-in insulation making it a wet mass at the bottom of the wall cavity creating an inviting place for termites and dry rot. Then the moisture enters the exterior sheathing and wood siding causing permanent exterior paint failure.

Ignoring the fact that "condensating" isn't a word in English, he is conflating air-leakage with vapor diffusion, which are not the same thing. Air leakage can move orders of magnitude more moisture than vapor diffusion, and air-sealing/air-retardency is key to getting good performance, which is why dense-packing would be preferable to 2.5lb density "2-hole method". With dense-packed cellulose in the cavity it's sufficiently air retardent that vapor diffusion becomes the primary moisture transfer method, and it's much slower than air.

Installing plastic vapor barriers in new construction causes as many moisture problems as it solves, ESPECIALLY when the vapor barrier is not detailed as an air barrier (which it usually is, in Canada, and almost never is in the US), which allows convection to accumulate the moisture, but blocks drying via vapor diffusion.

The word he's looking for is "condensing", but even that isn't what's going on- it's adsorbed moisture into the wood that makes it susceptible to mold. Wood and paper take on moisture as adsorb, not condensate, and you won't see liquid water until it is saturated (well over 30% moisture content). Adsorb is a different physical state than liquid or vapor- it's a molecule-thickness layering on the microscopic structures of another material, and does not behave as a liquid. The only way the insulation becomes wet is if there is COPIOUS air leakage from the interior, but the more likely proximate cause (almost always), is bulk water leakage, usually at unflashed windows. If you had replacement windows installed they SHOULD have installed proper flashing, which needs to be verified, but that's an orthogonal issue. (If you have deep roof overhangs bulk water intrusions would be rare even without flashing.)

He goes on:

The other big issue is "pillowing". Today we have dense pack cellulose insulation as well a foam. The installers cannot control the pressure of these products being jammed into your plastered wall cavity. They should only be used with open walls which means losing all your original plaster. Foam expands and the pressure used to install dense pack cellulose properly cannot be controlled within a closed wall.

Utter BS, but with a caveat. Any competent cellulose installer inspects the integrity of the walls ahead of time. Installers absolutely can and DO control the pressure of the equipment. There are some walls where the lath nails are too far gone or the plaster too thin/weak to dense-pack to 3.5lbs density, but even a paper bag can handle 2.8lbs density without failing. A competent cellulose installer warns you if that's going to be a problem, and adjusts accordingly. Competence & experience is key- so vet the installer carefully.

It's true that the pressures can't be controlled with slow rise foam pours, and that IS a blow-out risk, but it's still do-able (if expensive.) The better installers will do an initial shot not intended to fully fill the cavity, use infra-red cameras to track the expansion, then top it off with a smaller shot for the finish, mitigating the risk of catastrophic blow out or pillowing.

He is correct that insulating a house with painted clapboards usually results in paint failure. With a cellulose insulated wall that would be due to the lower siding temp (= higher moisture content of the clapboards). Back in teh 1930s/40s/ 50s when low density fiberglass and rock wool became standard products paint manufacturers and insulation manufacturers had finger-pointing matches that never fully resolved, but that's when the whole notion that vapor diffusion as the primary culprit took hold. But since the 1980s when polyethylene sheeting vapor barriers became the rage it didn't fix things, it made things worse, with "sick building synrome" etc, but it didn't improve paint longevity much. It's been studied to death by building scientists at this point- it's the inability of the siding to dry quickly enough, not moisture drives from the interior that causes the paint failure on siding. On replacement siding primering the back side of the clapboards limit the amount of moisture that wicks into the siding from direct wetting, but isn't a perfect cure. There are more effective means in new construction:

Best-practices on new construction is to build a "rainscreen", which is to build in a vented air gap between the siding and the next layer, which allows both the siding and wall assembly to dry evenly. It also forms a capillary break, to keep moisture from wicking from the rain/dew wetted exterior to the interior layers- liquids don't wick through air.

But you don't even need a rainscreen. Vinyl doesn't take on moisture, and is inherently vented- the air gap is already there, it's effectively it's own rainscreen. In a MA climate, simply building with a rainscreen (or vinyl siding) is sufficient protection for the sheathing to be able to use standard interior paint as the interior side vapor retarder, no sheet plastic necessary (provided you don't have a foil facer or some other vapor barrier between the siding and the sheathing to block outward drying...) A bit further north you'd have to take other measures, but I won't get into the details here.

His economic assumptions are also a bit provincial, and back-dated to 2009 when that article was posted:

The other factor that must be examined is payback. Lets say you spend $4,000 to have your old house walls insulated. In my experience you would probably save about $200 per year on heating and air conditioning costs

Yapp is located in Hannibal Missouri, which is US climate zone 4, not 5, so he has far fewer heating degree days, in a state where electricity costs are (or were at the time) well under 10 cents/kwh (instead of 18-22 cents, like MA), and natural gas prices run about 40- 50 cents/therm (instead of $1-1.50 as in MA). NOBODY heats with oil there, which is still significantly more expensive than heating with $1-1.50/therm gas even at this year's $2.20/gallon spot price. So, his pre-2009 experience in a low-cost energy state has no bearing on your local energy markets.

If you want to chase down the science on this stuff, Building Science Corporation has a searchable vast array of well written articles available on line, and unlike Yapp, they do real science- they actually test and measure things, both in test-assemblies and in-situ in real occupied buildings. Another decent source is Martin Holladay's green building blog (some of which is behind a pay wall, but a great deal of which is gratis).

In MA you can usually get the walls insulated for under $4000 after subsidy, and if you're heating with oil you'll be saving more like $600-800 /year (more, if oil heads back north of $4/gallon again.)

As far as indirect tanks go, think local- the HTP SuperStor is from a company located in New Bedford. If the thing fails you can drive on down and launch it through the window at the front office! :) (Or maybe get better local support than you might get from another vendor.)
 

vincenzo

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Thanks for all the info. Tomorrow I will check to see if I have the foil on my siding, I am pretty sure I do. After, I will decide if I am going to convert my boiler to an indirect Or just put in a whole new system. Thanks again.
 

Tom Sawyer

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System 2000. Lol, no really, you won't be disappointed and if you ever get not gas in the area, it can be converted easily.
 

vincenzo

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The system 2000 is one of the boilers I could install. That is what my excellent boiler tech is recommending. A Biasi B3 with a superstore ssu45 is another, although my boiler tech says they are finicky boilers. Gas is available at my house now, but the road was repaved last year and I have to wait another 4 years to be able to cut into it. Either one of these boilers can be converted to gas. I was thinking of converting the boiler I have now to a superstore with a Intellicon controller like Dana suggested to hold me over for 4 years. Then I can convert over gas and I already have the hot water tank installed. Maybe by then, there will be improvements to these products that I can take advantage of.
 

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The Biase is a good choice also but the 2000 will give you the most bang for the buck.
 

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The smart controls on the System 2K make it a better choice, given your oversizing factor. You could add heat purge control to the Biasi, but it would still underperform the System 2K by a bit.

If you're considering hooking up the gas main in only four years there are better choices in the modulating-condensing boiler world than the system 2K, that can be sized to modulate well with nearly continuous high efficiency burns with your 1920s radiation & zoning scheme.

Dropping a $150-200 Intellicon onto the oil boiler now would still pay off (usually in the first year), and if you size the indirect for the biggest tub you'll ever need to fill almost any boiler would give satisfactory performance.

It would take a bit of analysis to know for sure, but it's likely that even the smallest HTP Versa combi-heater would cover your space heating & hot water loads at condensing efficiency, and is often cheaper than a mod-con boiler + indirect.
 

vincenzo

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I am surprised that the system 2000 would be more efficient than the Biasi setup because it is 22,000 btu's larger in size. Is there anything else that I could do to my current boiler to make it as efficient as possible other than the things already discussed here, and maybe just ride out these next 4 years. The boiler is a Burnham,with the following specs I got off it's sticker.
D.O.E. htg cap.
124
water mbh
107.8
LT oil gph
1.05
Seems to me like I am stuck between a rock and a hard place here. If I put in a system 2000 then when I switch over to gas it would not be as efficient as a nat gas only burner. If I switch over to a indirect now along with a intellicon and then I install a gas only boiler later I end up spending more money than just waiting and installing a Versa combi-heater as Dana said.
 

Dana

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I am surprised that the system 2000 would be more efficient than the Biasi setup because it is 22,000 btu's larger in size. Is there anything else that I could do to my current boiler to make it as efficient as possible other than the things already discussed here, and maybe just ride out these next 4 years. The boiler is a Burnham,with the following specs I got off it's sticker.
D.O.E. htg cap.
124
water mbh
107.8
LT oil gph
1.05
Seems to me like I am stuck between a rock and a hard place here. If I put in a system 2000 then when I switch over to gas it would not be as efficient as a nat gas only burner. If I switch over to a indirect now along with a intellicon and then I install a gas only boiler later I end up spending more money than just waiting and installing a Versa combi-heater as Dana said.

The Biasi has essentially zero smarts to the controls, whereas the System 2000 has the most sophisticated controls, purging heat into either the zone radiation or the indirect at the end of a call for heat based on which is currently cooler. Even though it's getting on to 3x oversized (for your "after insulation upgrades" picture) compared to the 2x oversizing of the Biasi, it'll beat it since it's cooler during idle. With a retrofit heat purging controller you'd be able to get significant improvement out of the Biasi, but it still lacks the sophistication of the integrated package that System 2000 brings to the table.

At 124,000 BTU/hr (=124 MBH) D.O.E. output your current boiler is about 3x oversized for your heat load right now, and 4x or more oversized for the "after" picture. At this level of oversizing an Intellicon 3250HW+ will pay for itself very quickly. It's cheap, and you can write off that cost as the cost of waiting.

It's also possible to down-size the oil burner jet on the beastie-boiler to something less than 1.05 gph at the same time as you add the indirect, lowering the oversizing factor to pick up another few percent of as-used AFUE for small money. Is it the the V8H3 or V8H4 or similar? It's a no-brainer to down-jet a V8H3 to 0.75 gph, and it'll probably still have reasonable stack temps with a 0.68gph jet, at which point it's about the same output as the smallest System 2000, but with dumber controls. (A competent burner tech should be involved in any re-jetting of the thing, but it's not much more labor than a typical annual tune-up.) You probably need the higher-BTU jet now for domestic hot water performance, but wouldn't need it once you have the indirect in place. You probably have to idle the boiler at a low limit of 150-160F for reasonable performance with the tankless coil, but with an indirect for hot water you can safely program the low-limit of the Intellicon to 140F (maybe even a bit lower if you have a stainless flue liner.) Lowering the standby temp by 10-20F delivers a significant efficiency boost.

The above measures on the old boiler will likely save between 15-25% on annual oil use (750-850 gallons/year instead of 1000), which isn't the 30% reduction you might hit with a System 2000 (~700 gallons/year instead of 1000), but it's not as much money, and it's not necessarily money wasted, since a good indirect should last 20 years.

Until you've actually quoted the installed cost of a Versa combi vs. an indirect + mod-con boiler you can't really say for sure. It's not always cheaper to go with the combi, but it's usually easier to design around, and can fit in a smaller amount of space (not that space is likely to be at a premium here, if it' has an oil boiler hogging up the room. ) The raw hardware cost of the Versa combi is a bit higher than a mod-con + indirect, and it may or may not be a good fit for the whole system design.

Regarding that, how many zones, and how much radiation per zone? If it's old-school radiators, measure up the EDR (equivalent direct radiation) on each zone using this document as a guide.
 

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I have 2 zones, upstairs and downstairs. I don't have radiators, but about 100' of hydronic baseboard, and yes, the boiler does have a stainless liner on it. Can the intellicon be used to control the hot water coil, or will it just work with a new indirect. Getting back to the insulation for a second, are you saying that I should remove the tin foil faced insulation before I get the blown in cellulose?
 

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I have 2 zones, upstairs and downstairs. I don't have radiators, but about 100' of hydronic baseboard, and yes, the boiler does have a stainless liner on it. Can the intellicon be used to control the hot water coil, or will it just work with a new indirect. Getting back to the insulation for a second, are you saying that I should remove the tin foil faced insulation before I get the blown in cellulose?

With 124,000 BTU/hr of boiler output and 100' of baseboard that's 1240 BTU/hr per foot. The baseboard can only emit about half that at typical 180-200F boiler output temps- it'll never balance.

If you jet down to 0.68 gph the output will be something like 78-80,000 BTU/hr, so it'll almost balance with both zones calling for heat, if you crank the high-limit temp to 210F or 215F, and the burn cycles will be reasonably long when both zones are calling for heat. With an Intellicon retrofit and jetted it'll exercise the thermal mass of the boiler and improving average efficiency by quite a bit, despite the imbalance.

The shorter zone has to be less than 50', which means it's probably short-cycling quite a bit on zone calls right now. A single 50' zone of baseboard is good for about 25,000-35,000 BTU/hr of cast-iron boiler output. But at condensing temps it can emit around 10- 13,000 BTU/hr. Not all boilers can modulate that low, but some do. Measure the zone radiation to within a foot or two, since that affects which mod con gas-burners will be able to balance at condensing temps, and which ones won't.

The Intellicon will still work with the boiler as-is with the tankless coil, but the benefit is less due to the higher low-temperature limit usually necessary to provide decent domestic hot water perfomance. If you get acceptable hot water performance out if it with the low-limit set to 140F that would be great, and the full benefit of the smarter controller would be there, but most tankless coils are pretty crummy in winter with the boiler temp under 155F-160F or so. What is yours set to?

If you install the cellulose with a foil-faced foam on the exterior of insufficient R-value for dew point control you run a risk. But rather than removing it, add more foam. You only need R5 to be protective. If it's foil faced polyisocyanurate (off white/pale beige) with half-inch you're at R3, so you'd almost be there. Adding another 3/4" of polyiso (nominally R4-4.5 ish) would put you there with some margin. While the labeled-R of the 1-1/4" combined layering would be over R5, it takes a bit over 1" for polyiso to actually perform that well during mid-winter temps. It's R-value isn't constant with temperature- peaking at above the labeled R at an average foam temp of ~55F, but falling below its labeled performance when the average temp is under 40F (which it will be in mid-winter.)
 
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I think I am leaning towards getting an indirect along with a intellicon for now, waiting the 4 years then switching over to gas. One last question, is it o.k. for the boiler I have now to go cold over and over again once I put the indirect in. I can remember once or twice it shut down and went completely cold due to a clogged filter and it leaked a big puddle of water all over the floor. I don't know if this boiler is made to do that.
 

Tom Sawyer

In the Trades
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When the cast iron sections cool, they contract and the rubber gaskets that seal the sections leak. So, don't let the boiler go cold. You could replace the gaskets but you might as well buy a new boiler by the time you pay for that job.
 
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