The foundation wall is a solid pourded 10" wall on top of the foundation behind the a standard 8" x 3 1/2 " brick which corbels about and 1" or so I dont know what the structure is 8" Blocck or 2x4 framing.
There is no insulation at all in any of the walls none, the only insulation in this building is 12" blown in insulation in the attic
The baseboard heat is 14" high the fins are 4"x4" square, In one zone down the basement where the bar is there is one section of the 14" baseboard radiatior 40' long also with a 10' long section of standard residential baseboard for the bathroom. also on this floor is where the kitchen is so the gas stove and oven and two large refrigerated units which cools all the beer throws off a lot of heat, this is the zone thats always being heated. Upstairs is where the hall is one large room that does not get used much so the heat is very rarley on this is where the second zone is, there is 110' of 14" baseboard radiators and 15' of the standard residental baseboard in the bathrooms and also in a little hallway type area is a 6'x3' wall radiator.
We took out the old oil fired monster today this beast was 350 BTUs I guess this is why I'm a little nervous to hear such low BTU numbers to replace this thing.
I need to buy its replacement tomorrow A modulating condensing boiler that will heat 4800 sq/ft
I had some concern that the prestiege 250 might be a little undersized but now I'm really confused because your down to thinking that the 110 is capable of heating this ineficient building , I dont know maybe the 175 prestiege solo but in any event are you now saying that the 250 model is way to big even though we just took out a 350 BTU boiler out ?

Don’t worry about the size of the old boiler. It is not relevant. Figure the fuel usage like Dana has done and you can get a reliable estimate of the heat loss for the building. It is not at all surprising that the heat loss is quite a bit oversized for the load.
If you are using 750-1000 gallons of oil per year, there is no way you need a 250K boiler. The math does not work. Lots of 100K BTU oil furnaces and boilers consume more than that every year. 1000 gallons of oil for heat and hot water usually translates to a sub 50 K btu heat loss in Connecticut’s climate similar to your location.

I am currently working on a 7000 sf concrete block building that has (3) 150 Kbtu gas Furnaces and one 150 K BTU gas unit heater. I am sure I could remove 3 of the 4 units and be ok. I kind of laughed when I saw that set up. 600,000 btus of heat
I have another client that is replacing a 245 kbtu boiler in a 4000 sf house with a 75 Kbtu boiler. 75 K is still oversized, but hey it is a step in the right direction. You see a lot of crazy stuff.

So unless you're leaving the place for a whole day a finely adjusted reset curve will usually beat overnight setback on fuel use. (There are of course exceptions that prove the rule.)

You can have most of both by buying an OR thermostat that will boost output as needed to bring the water temperature up in the morning and then fall back to a lower temperature for the majority of the day. Depends on your radiators, but worse case (unlikely), even a 20F boost (~2x the btu output at worse case temps) would mean only a ~5% drop in efficiency for a short period. Compare a daily ~1% loss (an estimate) to a ~10% gain and you see that you want to continue to use setback. Consider disabling it when the weather is close to design temp (warm-up may be too slow).

What eric said- the size of the original boiler is irrelevant. It's pretty common to see old boilers that are 3-4, even 5x oversized for the actual loads.

I'm betting you have CMU wall with hollow cores that has a brick veneer with ~1" cavity, which is why it performs so much better than a solid concrete wall. The R-value of multiple air-films add up- it's literally 3x as efficient as a solid poured-concrete wall on which I based the first-cut calculation.  An 8" CMU is good for about R1.1, the brick is good for another R0.8, the paneling is good for at LEAST R0.2 (if it's thin cheapo stuff, more like R1 if it's 1x t & g) add in another R0.3 for the combined air films in the cavity space and you're at R2.5-R3.5 or maybe even R4-ish. A solid concrete wall is only good for about R1. That's a HUGE difference.

Based on your fuel use history there is no WAY this building has a heat load anywhere near the output of the Solo-250, and it is certainly within the output range of the -110.

With 40' of 4" convector that can deliver 600-700 BTU/ ft @ 130F plus 10' of 2" baseboard delivering ~250 BTU/ft @ 130F water temps your total radiation on that zone dumps about 28K into the zone, which is about the min-fire output of the Solo-110, so I think you're going to be good to go there. But even the -175 will short-cycle on that stub if you run it in condensing mode, and the -250 would be a short-cycling itself into an early grave and low efficiency.

So, if you have to shoot from the hip and buy today, it's the Solo 110.

With some retrofit weatherization you can probably get it within range of the -060, but as long as you have the radiation to get condensing efficiency out of the Solo 110 (which you do), you can improve the building on some other schedule. (Insulating the basement walls with reclaimed foam and installing low-E storms over the single-pane basement windows would be well worth it, even if you didn't touch the rest of it.)

Well I was under the gun and had to buy it today so I did !
I went with the solo 175
Considering I was very close to buying the alpine 285 and then the solo 250 I think the 175 was a big jump down ..........call me old fashion but I guess I would rather be safe then sorry
I want to thank everyone who responded and took the time to really help me size this boiler up and the effort and the figures and calculations that went into it.
I owe Badger special thanks and I especially also owe Dana many thanks for his impressive caculations and for not getting to frustrated with me for the lack of the necessary stats on my part that were needed

I was afraid you were going to do that. If you can take it back you should.

From a "...rather be safe than sorry..." point of view, the 175 is going to make you sorry, not safe.

The 175 is GUARANTEED to short-cycle on zone calls at condensing temps, and it's at least 2x oversized, possibly 3x oversized for the actual load.

The only question was whether it could squeak by the -60, which it might. The -110 is a sure thing from both a capacity and short-cycling point of view.

Yes, it's a big jump down, but that's always going to be the case when you are replacing something that was installed when oversizing by 3x+ was the norm. The output of the 110 would put you at over 40 BTU per square foot of conditioned space on a building that has a very low window/floor ratio. Your real loads can't be more than about 3/4 that, even if you cracked open some windows.

The fuel use numbers don't lie, nor are they an opinion. ( L'aritmetica non e un opinione.) With the 110 you're at least 30% oversized, and may even be 100% oversized (in which case the -60 could have covered you just fine.)

I expect that you would find it cost effective to add a buffer tank (to eliminate short cycling). If not, consider putting some amount of bypass flow on zone valves to increase the min radiator btu capacity (assuming you don't want a zone to be completely off).

Dana ........You do understand there is 4800 sq/ft of space to be heated and in that space there is a 12' high ceiling in a building that has NO insulation of any kind in or on any of its walls the only insulation is 12" on the attic floor

So, let me get this straight.

You don't have the funds for a proper Manual J, but you don't mind spending hundreds of dollars for an over-sized boiler (and attendant over-sized fittings and trim) guaranteed to short-cycle; dramatically lowering efficiency and shortening the life expectancy of the boiler by half??????

Posted By tom37 on 29 Oct 2014 01:33 PM
Dana ........You do understand there is 4800 sq/ft of space to be heated and in that space there is a 12' high ceiling in a building that has NO insulation of any kind in or on any of its walls the only insulation is 12" on the attic floor

Sure, I understand!   That WAS the correct building in the street view link, right?

The lower 2400' semi-basement is about 50% below grade, but has higher wall losses than the upper floor due the fraction that is R1 poured concrete construction. But that lower space has effectively zero ceiling losses once you start heating the upper floor to a higher temp.

The upper floor walls may have no insulation, but they're about R3-R4, not R1. That means it takes 3-4 square feet of wall area to equal the loss of one square foot the exposed above-grade foundation.  So just the three vertical feet of exposed foundation wall is the heat loss equivalent of 9-12 vertical feet of the brick-clad section. (Which is why even partially insulating the poured concrete wall down there is worthwhile- it's well into double-digit fractions of your heating energy use.)

Even though you were not fully conditioning the upper floor previously when only heating the lower level to temp, you WERE  heating it to SOME temperature via the ceiling losses of the lower section.

The total heat load when fully conditioning both spaces will be under 2x the heat load you were seeing when only fully conditioning the first floor, which we determined (way back on page 1 of this thread) to be on the order of 35,000 BTU/hr or less. 

There is an outside chance that the full heat load keeping the whole place at fully at 70F when it's 5F outside could be as high as 70K, but it's probably less than that, maybe 55K. That's why it wasn't clear whether the Solo-60 was going to cut it. But there's really no way your heat load is going to be as high as 100K (and even that would be covered by the Solo-110.)

Even my crazy straw-man analysis I posted on 24 Oct 2014 06:56 PM (page 2 of the thread) using wildly overstated fuel use and wildly understated HDD for last year came in at only 59,800 BTU/hr.  Your heat load might actually be that high when you're heating the whole place to 70F, but I'd be surprised if it were much more than that.

But say it really is 70,000 BTU/hr (even though that is extremely unlikely).  That means the Solo-110 output is only 50% more than you actually need. But at 50% oversizing you wouldn't lose ground until it drops below -25F.  

Hell, even if your heat load is 90K (which would require leaving some windows open) you'd be good to -5F-0F or so before it couldn't keep up.

But if it turns out the heat load really is as high as 70K, the Solo-60 is off the table.  The chance of it being that high are really really remote, but non-zero. The chances of the load being as high as 90K are essentially zero, which makes the -110 the "...better safe than sorry..."  choice.

If the Solo-60 wouldn't cut it under the current state of insulation, putting 2" of foam on the upper half of the basement zone walls (to at least a foot below grade) would probably bring it into range.  If it were my building that's probably where I'd be going with it- smaller boiler with some modest building envelope upgrades.

But if you don't have the time to deal with insulating, the Solo-110 is surely enough boiler, and you have just enough radiation to run it at better than 90% combustion efficiency without short-cycling it to death.

As yet another sanity check, my ~2400' house (with 1500' of conditioned basement, and another 150' of conditioned crawlspace) has a comparable sized footprint but MANY more corners than that (which means a higher wall area to floor area ratio) and has more than twice as much window area to boot. Most of my roof is R15-R20 to your R40-ish.

Even before the (full dimension 2x4) walls were insulated and the house tightened up (it's probably still leakier than a brick clad CMU building that has only 10-12 windows) the measured heat load at +5F was a shade under 50,000 BTU/hr. A manual-J might have put it at 55K, but the gas bill doesn't lie.

This house probably has more exterior surface area than your building, and prior to some retrofit insulation & air sealing it had comparable wall losses, but higher attic & infiltration losses, and it still has higher window & door losses than your building.

With some air sealing and insulation (including 3" of foam on the foundation walls) the load is now in the 35K range @ +5F, and the revised heating system is maxed out between 42-44K at the water temps I'm running, but it keeps up just fine at -10F.

It'll be under 30K if I get more than half way down my project list before they cart me away. :-)

As-is your building really might already be within range of the Solo-60, and it surely could be without breaking the bank.

Tom,
I always like to look at things on the bright side. First, you ignored free advice from at least 3 people who gave it to you straight. Hey I have had people that paid me to figure this stuff out and then ignored my advice, so you saved at least 500$ right there.

Second, If somebody steals all your windows, you can still heat the place in the winter.

Third, you probably are not going to add a buffer tank or anything like that, so you are going to short cycle the hell out of the boiler. That means you may get to chose a new heating system again in less than 10 years, so at least you wont have to live with the mistake for that long .

Fourth, If you sell the building to a Finnish American Club, they could turn the whole upstairs into a Sauna, and not need to add any new heat source.

Or, you could return the 175, and buy a smaller boiler.
Cheers,
Eric

Yes, lots of good advice has been ignored here. If you don't return the boiler, at least do the calculation to determine the proper buffer tank size to avoid short cycling...assuming you have enough real estate for the size that will be likely required.

Well, this is quite the hootenanny. Hey, everyone, hope all is well!

First, I agree with every word said about insulating this place. Whatever can be done is hugely better than nothing and would be likely to affect the boiler choice pretty quickly. I also think additional radiation in the basement zone would be helpful but I haven't dug into that with real analysis.

tom, what temp were the two zones kept at for most of last winter? was the top floor truly unheated or maintained at 40, 50?

I think there is some erroneous assumptions on heating degree days driving some questionable math here. My back of the envelope math says you'd basically have to ignore floor loss and infiltration to get under a solo 110 in a shell like this, or insulate. No way 5000 square of uninsulated anything is topping out at less than 20BTU/sq ft at a regular design condition in new england... no way at all. I'm prepared to eat those words but I think correcting HDD for your actual conditions will show the mistake.

O k for this area if you use base 65 for heating degree days, you get 6720 HDD, if you use base 60, you get 5392 HDD Assuming that you used 3000$ for oil last year, the lowest potential cost/gallon is $3.0, and $4 is likely the highest so the consumption is between 750 and 1000 gallons of oil. Oil has a heat content of 138,000 btu’s per gallon so you used between 103 and 140 Million btu’s of oil. Efficiency is somewhere between 83% and 55% These are the extremes of the range. Based on this, your actual delivered BTU’s are between 114 M btu’s and 56 M btu’s Admittedly that is a huge gap. So I set up a spreadsheet with the following variables: Oil usage 750, or 1000, Furnace efficiency 55% or 83% Heating degree days 6720 (Base 65) or 5392 (Base 60) and propagate all uncertainties. Here is what you get. The highest heat loss possible is 62,000. Assuming you want to be conservative and multiply this by 20%, you get 74,000 BTU’s. This is easily within the territory of a Solo 110. My guess is that the correct number is just under 50KBTU’s so the solo 60 would do it. I would be nervous recommending the 60, but would be quite confident recommending the 110. 49713.54 37285.16 32942.71 24707.03 61957.53 46468.15 41056.19 30792.15 So the worst case is using heating degree days base 60, a design temp of 0°F heating set to 70 anyway using a 83% efficient boiler and buying oil at 3$ per gallon. Doing all that, I get a heat loss MAX of 62,000 btu’s I would say that a 110 is a conservative bet. But this all dependant of the initial figure of 3000$ per Year for oil. Now if you gave me a list of 18 months of delivery dates and # gallons delivered, I would narrow this down quite a bit. Sorry for the lack of paragraphs- I have never gotten it to work on this computer

Base 60 is WAY too high for unoccupied space (that's appropriate for many occupied spaces) and your HDD assumption changes your analysis in a hurry when you drop it down to 50 degrees or less. He is certainly not higher than 3500 degree days here and he may even be less... base 40 only returns 1930 degree days in bedford. That's quite a difference. If the upstairs was truly not heated he might even have a degree day base for the upstairs lower than that.

Tom already mentioned what they paid for oil as well, they are at the higher end of the range at around 1000 gallons. No Question about that.

step back a second. Have you EVER calculated a heat load on an uninsulated building that came in at 12 BTUs/sq ft?? that's a number that's hard to hit WITH insulation for most buildings!!!! No way. Even under 20 is, frankly, absolutely insane. I've done loads for many such buildings. I expect final loads to fall in the 20-30 BTU/sq ft range with leaky building ranging slightly higher in the mid 30's. Here in New England. Pretty consistently. This is a large building, it MIGHT be under 25BTUs/sq ft because of the lower PSF totals that result in larger buildings, but if it is, it's only barely so.

And my basic envelope math on the loads again say if you want to stay under a 110 you have to be real generous about the basement floor losses and infiltration. No way. at R4 for the upstairs walls (60x40x12) you're at 42,000 BTUs right there with no windows or doors... add the basement walls in and you've basically maxed out the 110 already, with no ceiling, floor, infiltration, windows, or doors. I think dana is wrong to calculate the basement walls at R1 (you do still have air films at least, I never calculate a wall at less than R2) but if you do, it only proves my point further.

There is absolutely no way the solo 60 should be anywhere near this conversation. That is complete and utter madness. There is only SLIGHTLY less vehemently no way a 110 is going to heat this place fully at design temp. The 175 was almost 100% definitely the right choice here.

Hopefully Tom will be willing to provide some actual run-time & temp numbers a couple of months from now.

I'm still here reading .......... I haven't left !
The upstairs space with the 12' high cielings we might have turned the heat on once or twice so that would be 1 or 2 days of heat last year other then that the thermostat
was turned down very low to around 40 45ish
The other heating zone in the basement where the bar is and where there are 3 7x7 or 8x8 registers sucking out cigerete smoke with 8' cielings the thermostat is set to 70 and gets turned down to 60 at 11:00 pm then gets turned back up to 70 around 9:00 or 10:00 am again
I dont know what those exhaust regeisters pulls for CFMs but if you hold a doller bill up to the register it barly holds on to it

That exaust fan gets turned on at 1:00 pm and gets shut off at 11:00 pm and its on a dimmer type switch so its runs full speed maybe 70% of the time the other 30% runs about half spped

Rob is right and nice to hear from.

Insulating the attic is the fastest payback followed by a properly sized condensing boiler.

The only question for me is; what is the indoor design temperature? We do a lot of work for Church groups and find a meeting hall of any kind can be challenging but rarely needs to be at 70F. If you keep it at 60, effectively lowering your heat load, you then can size down the boiler. When you get 100 people in the place an open window will feel good in the coldest weather.

Again, a proper Manual J allows for modeling for different designs and supplemental heat may be added for the few cold days when you may have an event. You may also prioritize one zone to meet the load condition while sacrificing temperature in the other. IBC has a boiler that will control zones sequentially with a weighted average on time.