Need validation on Heat loss done for a new boiler

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Naren Rao

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All,
First of all this is a great forum, and I have read the detailed responses from the pros has brought me to the point where I can just get validation on my analysis.

Background - Moved in 2 yrs into this 5500 sqft house, has a 1992 installed original Peerless boiler (w 2 stickers 183K BTU and 209K, IBR 157 and 182) assuming running at 61-65% real efficiency Combustion efficiency measured (via testo) at 81-82%. No indirect water tank, water is heated through propane tankless, 3 Zones heat. Located in Somers NY 10589

Problem - Guzzling 1900+ and 2100+ gallons in past two winter seasons. Deducting 500 gallons (oil fired Bock replaced w tankless now in place). Still 1500+ gallons/year. Performed detailed heat loss through Slantfin ipad app w design temp 0 deg (120K w NYC design temp at 15) and home temp at 68. 140K heat loss. Looking to lower yearly oil costs .

1) How accurate is the Slantfin heat loss at 140 K (Hearth.com heat loss was 175K)
2) The Peerless boiler seems oversized - is it ? Option - 0.75GPH nozzle and downfire ? or replace
3) If replace Peerless with Biasi B-5(IBR 108) or B-6 (IBR 133) triple pass w higher AFUE - 20% oil savings ?
4) Install outdoor reset - 5-10% oil savings ?

Am I on the right track w this replacement
 

Tom Sawyer

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How much money do you want to spend and how many years do you want to take to pay if back? The peerless boiler is not as efficient as a new Biase or Buderus but then again you won't pick up more than perhaps 5 to 8% on a change out. It is over fired though so dropping the nozzle down to a .75 or even .60 will increase run time and efficiency. The best thing to do is install an intellicon or similar device.
.
 

Dana

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Downloading monthly base 65F heating degree day data from degreedays.net for a station in nearby White Plains, it looks like the average of the two heating seasons was about 5500 heating degree days, maybe as much as 58oo HDD, burning an average of 2000 gallons/season. To be conservative, lets assume 5500 HDD, which will deliver a ~5% error to the high side when estimating the heat load based on fuel use. Since Somers is probably a couple degrees cooler than White Plains, the calculated load will overshoot by a bit more than 5%, but still less than 10%.

2000 gallons @ 138,000 BTU/gallon burned at 82% combustion efficiency is 226.32 million BTU went into the heating system.

Divided by 5500 heating degree days is 41,150 BTU per degree day.

Divided by 24 hours in a day is 1715 BTU per degree-hour.

With a presumed heating balance point of 65F (that's why you use base 65F for heating degree-days), and using NYC's outside design temp of 15F, that's 50F heating degrees.

So the heat load is about 50F x 1715= 85,750 BTU/hr @ +15F.

At 0F (which is colder than your 99th percentile bin) that's 65F heating degrees, for a heat load of:

65F x 1715= 111,500 BTU/hr.

Slantfin's tool is a fairly crude I=B=R methodology tool, and typically overshoots reality by 20%, but often by more than 25%. Taking the calculated 140K @ 0F and discounting it 20% you end up at 112K, which is where we ended up on a fuel-use calc. Seems to be converging in that neighborhood.

Somers is a bit cooler than White Plains, which has a 99% outside design temp of +12F, but nowhere near as cool as Poughkeepsie's +6F. Call it +10F.

That means the design condition heat load is really about 95K rather than 111.5 K.

In order for true heat load to be 140,000 BTU/hr @ +10F means you aren't really heating the place to anywhere near 68F much of the time (do you keep one or more zones at 50F all winter?).

Unless the boiler is in a separate building or outside the house in an extremely leaky garage you should ignore the IBR output number. If it's in the basement (usually is), it's inside the building envelope, and the standby & distributions still largely accrue to the house rather than being wasted, even if the basement isn't a fully conditioned space. The D.O.E. output number would be the correct number to use.

The Biasi B5 has a D.O.E. output of about 122K BTU, which is more boiler than you actually need, but not grotequely oversized for a 95K load.

The Biasi B4 has D.O.E. output of about 97.5K, and would pretty much do it, except during Polar Vortex events.

The B6 had a D.O.E. output of about 152K. That still isn't crazy-oversized, but do you REALLY think you need to be covered all the way down to -25F? According to Weatherspark's data sets for Somers it got down to negative single digits exactly three times last winter, the coldest of which was -6F on 4 January. At -6F you're looking at 71 heating degrees for a heat load of 71F x 1715= 121,765 BTU/hr, which a hair below the full output of the B5.

Reads to me like the B5 is the biggest boiler that makes any kind of sense, since you'd still be covered at the 99.7th percentile temperature bin, but it's probably not crazy to at least consider the B4. With the B4 you would just keep the thermostats at a constant temperature 24/7 during mid-winter rather than using setbacks since the recovery ramps would be long and slow. The B5's capacity is only outstripped at temperatures seen maybe a dozen times in the life of the boiler, and you'll probably be in bed when it does. The duration of those heating load peaks are not long enough to matter- the thermal mass of the house would keep it from losing much ground for hours even if you're 5000-10,000BTU/hr shy of boiler output relative to the load. The day it hit -6F that temp occurred at 6AM, and by 9AM it was already above 0F.

To save big money on oil you'll pretty much have to either get off oil, or get serious about weatherizing & insulation details. A 95,000 BTU load @ 10F for a 5500' house is 17 BTU/ft^2 which is on the high side even for a 2x4 framed house. Bigger houses typically have lower exterior surface area to floor area ratios, which lowers the BTU/ft^2 ratio. Air leaks in the basement & attic (driving stack-effect infiltration) and uninsulated foundations can collectively account for about 20-25% of the total load on a 2-story house that is otherwise insulated.

But there may be other low-hanging fruit to chase- every house is different, with many exceptions to prove the rule. With an insulated foundation and a fairly air-tight envelope a 5500' house would usually to come in around 12 BTU/ft^ 2 @ +10F , assuming an insulated 2x4 framed house with clear-glass storm windows (or clear sealed-glass double-panes.) Those would be fuel-use measured loads, not a Slantfin-calculated load.
 

Naren Rao

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Thanks Tom Sawyer.

Was looking to buy the Biasi w Riello online around $2200 + Tekmar outdoor reset, and my plumber would charge me 1500 to swapout the boiler. Around 4K. I am sure my oil company would like to do the work at 8-10K. Anyway is there a way to know what nozzle could be in there as my oil company services it.

I looked at the testo printouts and temp of flue stack is running way too high. Sounds like my heat is going out through the flue than to the airhandlers. its also short cycling.

2013 readings - 485.8 Tstack, 10.08 CO2, 82.2 EFF, 53.1 ExAir, 7.6 Oxygen, 8 ppm CO, 12 ppm CO Airfree, 68 Ambient temp, 61.9 Instrum temp

2014 readings - 600.1 Tstack, 11.73 CO2, 81 EFF, 31.6 ExAir, 5.3 Oxygen, 23 ppm CO, 31 ppm CO Airfree, 0.0927 inH2O, 56.7 Ambient temp, 54.7 Instrum temp
 

Naren Rao

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Wow just wow Dana, I am absolutely floored reading your response to my question. thank you so much. Am confident to go ahead. Just a sorry state here where all the local guys come, see a big house, suggest 210K, and one went all the way to 275K BTU. Oh they saw a 500 sqft 2 story addition built. Absolutely no heatloss, no sizing why 200+.

Can I bother you to see the analyzer read how badly is my boiler running at.
 

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Depending on the condition of the house & boiler you might still get better bang/buck out of air sealing & insulation than buying a right-sized, better efficiency boiler.

I'm confused by the statement:

"Sounds like my heat is going out through the flue than to the airhandlers. its also short cycling."

Is this boiler hooked up to a hydro-air system or something? (In which case the boiler either has to be sized for the coil in the air handler, or there needs to be bypass plumbing to manage the too-cool return water temps when down-sizing the boiler.) Leaky ducts or unbalanced duct designs can also introduce substantial air-handler induced air infiltration, often more than 10% of the entire heat load, which may be an other cheap way of cutting fuel use.

Outdoor reset doesn't really save fuel unless the controller also does heat-purging of the boiler. Heat-purging economizers like the Intellicon 3250 are often a better approach, since rather than shifting the high-temp limit, it purges heat to the programmed low limit on new calls for heat, and "learns" the system behavior, cutting the burner and starting heat purging the boiler heat into the zone when it senses that the thermostat will soon be satisfied. The average temp will still vary with the load ( as with outdoor reset),but it will be fewer burns, of longer duration, getting maximal use out of the thermal mass of the boiler.

BTW: Naren Rao desi naam hain- Hindi bolte?
 

Naren Rao

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LMFAO - Of course YES!!! I can speak Hindi. Came as a complete shock.

"Sounds like my heat is going out through the flue than to the airhandlers. its also short cycling." - On the topic, my thought is at 61 efficiency, the other 40 must be going through the flue. 40% of 1500 gallons burnt is significant I would think.

Yes its Hydro air - w 3 airhandlers 5 zones, and 2 airhandles further zoned into 2 each, and 1 airhandler dedicated zone for master bedroom, bath, closet. (Specifically This zone when it requests heat I believe the furnace short cycles....)
 

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So you both are saying install Intellicon 3250 on new boiler or current Peerless setup. If this accomplishes lowering the oil usage then I am all for it. Can either of you kindly confirm.

Ofcourse I will look at the ductwork and see if leaks exist. What is an unbalanced duct. Can you kindly advise

Thanks both
 

Tom Sawyer

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If you really can get the Biase boiler installed for around four grand then you absolutely should.
 

Naren Rao

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If you really can get the Biase boiler installed for around four grand then you absolutely should.

Dana mentioned that I have Hydro air setup (air handlers) so need to be careful sizing the boiler to it. Just have to figure out what BTU size. 2 airhandlers are quite antiquated. They are First Co - Model 48vDX-4HW - Max Heating BTU at 140F water = 67,000. Does this mean 3 airhandlers = 67+67+67=200K Boiler?
 

Dana

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The FirstCo air handers typically have aquastat controls either internally or on the exterior that only turns the blower on when the incoming water temp is above some number. With an oil boiler there is almost always is bypass plumbing in place to manage the cool return water temps. The bypass branch feeds boiler output water into the returning water stream to raise the temp of what is going back into the boiler. That temp needs to be 140F or higher to avoid corrosive exhaust condensation. Any time you down-size the boiler or lower the turn-on temp at the air handler the flow needs to be adjusted at the bypass to keep the temp at the boiler above 140F.

With hydro-air you absolutely DON'T want to use outdoor reset, it increases air handler power use more than it reduces oil use, and the return water temperatures will vary with the weaather. With an Intellicon you may have to play around with the air hander aquastats and low-limit settings on the Intellicon, but it'll still heat-purge down to whatever out program it to. ( Again 140F min recommended.)

The BTU numbers on the air handlers are it's output with 140F incoming water, which is below the safe RETURN water temp for the boiler. But with bypass plumbing protecting the boiler you can set it up for any temp you like. The heat output capacity goes down at lower temp, up at higher temp. With 140F incoming water the temp of the air coming out of the air handler is typically 125-130F, with the exit air at the furthest registers in the rooms a few degrees below that (assuming the ducts don't leak.) Since the air handlers are also oversized for the loads, you could probably still deliver the heat with 125F water and still have exit air at the registers at comfortable 110F or so.

The design heat load at my house is about 35K, with maybe 20-22K of that being served by a hydro-air system, the rest being radiant floors and low-temp radiators. The 140F output of the air handler is something like 50K, but I'm only giving it with 125-130F input water, and it has plenty of capacity due to the oversizing factor. If you right-size the boiler you may have to adjust the aquastats down, but they'll still deliver the heat.

If the boiler is short-cycling on zone calls during continuous calls for heat from the thermostat you can increase the aquastat setting on the air handler to improve air-handler output. If it short-cycles simply because the thermostat is satisfied, stopping the call for heat, keeping the air handler temp low but controlling the boiler with a heat purging economizer should help at least a little bit. If the AIR HANDLER is short cycling, it means that the boiler's high temp setting is marginal for the air-handler's aquastat setting, but that would be unusual when you have a boiler as big as yours unless somebody tweaked the aquastats to some odd combination of settings.

Tape the seams of the air handler with FSK tape (aluminum duct tape), and if you have access to some or all of the duct work, use duct-mastic goop on all of the seams and joints- it pretty messy stuff, but it works, sticks to almost anything, and is more permanent than tape solutions.

I no longer assume the origins of a name mean the person can use the language. In the US only maybe half the desi folks I run into can speak Hindi/Urdu/Punjabi, something I figured out decades ago when dating a New Delhi born Punjabi whose English sounded more like a Buffalo NY (where she had lived since she was a small child) than Lahore (where her parents were born, pre-partition) . Her Hindi was OK, not great- she seemed reluctant to use it. My real introduction came from watching Bollywood movies, not the few phrases I picked up back in the 1980s. My (not-so-desi) wife has become an avid Bollywood fan and I've probably sat through 100 of hours of screen-time by now. She doesn't understand when I tease her with sappy chick-flick lines like, "Tu mere zindagi hai! Jaan-nu!". :) I'd have to study to come up with a useful vocabulary, but more is sinking than I would have predicted year or so ago when she first started her NetFlix-Bollywood habit, which makes it more fun for me.
 

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Thanks again for a extremely detailed response. So hopefully the last question, having reread all your responses, this is what I will proceed to buy

Biasi B-5 w Riello Burner (No outdoor reset) - Are these straightforward to install, my plumber is not "master" yet but has installed Burnham, WM boilers. Also its a swapout
Intellicon 3250 (I would need an electrician for this ?)
Tigerloop Oil filter (informed this highly recommended)

Following Airhandlers will be supported
FirstCo - 67K BTU (External aquastat set at 140)
FirstCo- 34K BTU (External Aquastat set at 140)
Trane GAM5b0C48M41SA - This is a brand new airhandler w hydronic coil (no BTU seen on the sticker). It replaced a FirstCo airhandler but have no idea why the AC guy chose this. Its 3.5 Ton. The air flow from this air handler is amazing into the zones but not too hot. will measure it tonight w a Kintrex Infrared thermometer
 

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If the exit air temp of the Trane air handler zone at the registers is marginal even with the bigger boiler, it could turn into a comfort issue while the thing is running with a smaller boiler. Down to about 100F air out of the registers it's still reasonably comfortable, but when it gets to be 5-10F below body-temp there is a wind-chill effect that makes it pretty tepid. Try measuring it in a couple of modes- one with just the Trane calling for heat, another with all three air handlers running.

If the thing is just running too much air there are different speed tap settings on the motor, and slowing it down would increase the air temps. But if the air handler is also being used for air conditioning slowing it down could result in ice-up conditions on the AC coil during the cooling season.

If you understand the boiler controls, retrofitting an Intellicon is not difficult. I don't know if NY codes demands that all electrical work on the boiler controls be done by a licensed electrician or whether any boiler-tech/plumber installer can do it.

BTW: I understand that the Hydrostat 3250 controller is sometimes sold with Biasi boilers. Despite the "3250" in the product name, it's not just a re-branded Intellicon. It has more features than the Intellicon (most of which you wouldn't use with a hydro-air system) but it also has a heat-purge mode and independently programmable high/low limits, that would work in a similar, if not identical fashion. With that controller in purge-control mode it won't let the boiler drop below the low-limit even in standby mode (no cold-starts from lower temps during the shoulder seasons), but that's not a fatal flaw.
 

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BTW: I understand that the Hydrostat 3250 controller is sometimes sold with Biasi boilers. Despite the "3250" in the product name, it's not just a re-branded Intellicon. It has more features than the Intellicon (most of which you wouldn't use with a hydro-air system) but it also has a heat-purge mode and independently programmable high/low limits, that would work in a similar, if not identical fashion. With that controller in purge-control mode it won't let the boiler drop below the low-limit even in standby mode (no cold-starts from lower temps during the shoulder seasons), but that's not a fatal flaw.

So should I bypass the Hydrostat and install intellicon anyway to manage it smartly by "learning" then
 
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