Boiler sizing

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  #1  
Old 02-22-18, 04:18 PM
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Boiler sizing

I was recently given a fairly new Budarus logano g215/7 boiler. My house is a 2300 sq ft ranch with a finished basement, located in Northern VT. I am aware that this unit is much larger then i need to heat my house. I was planning to install unit in my garage and use it to heat my 26x40 garage as well as my entire house (roughly 5700 sq ft total area). When i spoke to my friend that works at a plumbing supply house he told me it was not a wise idea. my question is will the the extra expense i may pay in fuel every year be more then what it would be to buy a smaller boiler that might be better suited to perform my heating needs. Also does anyone know if it is possible to remove a section or two to size the boiler to fit my needs.
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Old 02-22-18, 05:22 PM
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P,
First of all what size boiler do you need. If you removed sections the casing wouldn't fit and it's a lot of work to dismantle and reassemble and reseal boiler sections.

Although a large boiler how much larger is it than what you need. There's 25 gals. of water so it would depend on how much water would be in the one you need.

Being oversized the boiler would tend to short cycle but they are very efficient and heat up fast.

A 4 section burns 1.4 gph, this 7 section burns 2.5 gph so it all depends how you use your heat.

You're looking at about 1 gph difference during run time. Again it depends on what size you really need.

If all you are worried about is fuel consumption that's about a 4700.00 boiler vs a few bucks extra a year on fuel vs spending a whatever on a new boiler.

You have decide if it's worth it to you.

Just my thoughts.
 
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Old 02-23-18, 03:47 AM
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If you are going to install this boiler or any boiler in your garage you should check the codes relating to boilers and burners installed in an area with potential flammable liquids present. Where I live that installation would require a separate and totally isolated room with it's own combustion air make up venting. Looking at the specs of this boiler , it is a very efficient unit . If you wanted to downsize the oil nozzle for a lower firing rate, I would contact the factory or a local rep for their input and their recommendations and follow them to the letter. Even If your garage has a minimum amount of insulation this unit is way oversized for your heating needs. I would run a heat loss calculation or have someone do it for you to see just what size boiler is recommended for your area and proceed cautiously.
 
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Old 02-23-18, 07:54 PM
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Reducing the firing rate of this boiler by 50% to say 150,000 BTU hour will increase efficiency and make boiler appropriate for this application. It will also lower installation costs by using a smaller vent.

Boiler are heat exchangers and reducing the thru put increases efficiency by lowering stack temp.

With a free boiler, heat load calculations are a waste of time. Run boiler and clock degree days per hour. https://www.ebay.com/itm/Generator-H...RXrhNb&vxp=mtr

Simple math will show what it will run at design temp or lowest expected outdoor temp. Then you can calculate optimum nozzle firing rate.

Many carry “short cycling” to absurd points. Cycles of 2 or 3 minutes are more efficient that 4 or 6 minutes. With 1,000's of cycles per year a few more is not a significant factor. Most burner parts MTBF's (mean time between failure) are based on run time, not number of cycles.
 

Last edited by doughess; 02-23-18 at 08:45 PM.
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Old 02-24-18, 04:24 AM
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As I said before, call the factory if you plan on down sizing the oil nozzle . Do not down size without the "phone call". If you were firing natural gas there would be no problem, but for #2 fuel oil???
 
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Old 02-24-18, 09:36 AM
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Donít be foolish,

Sell the boiler and get what you can for it and do the heat calculation requirements for it. Then pay the difference for a properly sized boiler. Youíll sleep better at night knowing you have the correct sized boiler for the application, and with the sale of the gifted boiler to offset the cost, your well ahead of the game.
If you can get gas, I would do that, the removal of the fuel tank will also give you more room in the basement to install the new equipment. New units are much smaller now. The maintenance cost are less for gas than oil. If. You miss a year with gas, no big deal , but with oil, youíl have a no heat call for sure.
 
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Old 02-24-18, 11:57 AM
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Foolish ???

The words “properly sized boiler” sounds nice but in the real world are simplistic when 85% of US homes have boilers that are twice the size needed.

In this thread “Patriotsfan” free boiler puts him in the 85% group, but he has a simple answer use a smaller $6.00 nozzle to properly size boiler.

The boiler BTU output is actually determined by the burner firing rate, not the manufacturer's label rating. Label rating should be considered maximum. Some show a range in BTU's or oil gph.

For $6.00 per nozzle Patriostsfan can determine what is “proper”.
 
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Old 02-24-18, 12:28 PM
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That 85% was from untrained personnel. No excuse for it today. De-rating a boiler is highly frowned upon, and usually limited to abut 2/3 the rating. I tried it with my Pensotti 4 section hydronic boiler and the efficiencies were not good, so I put it back up to where the recommended settings were from the OEM. It just runs so much better there. I went to the Carlin factory school in MA and saw all the many boilers they run in experimentations settings there, with a lot better instruments to measure peak efficiency than we could ever afford. Itís their job to get the best output they can confidently advertise. Fuel is the big expense, not a free boiler.
 
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Old 02-25-18, 06:37 AM
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hvac01453 That 85% was from untrained personnel.

The 85% reflects the large number of US homes build before 1970's oil crisis. Until then oil at $0.15 per gallon was cheap. Builders put big boilers in homes that had no or little insulation. By 1980 when oil was $2.00+ people became cost conscious and started reducing heat loss.

In established areas oil consumption went down as people added insulation, storm windows, etc. resulting in over-sized boilers. Installing smaller nozzles is an easy way to lower stack temperatures and increase efficiency.

I went from 1800 gallons/year in l970 to less than 600 gph. My Weil-McLain boiler label reads 1.80 gph but am firing at .80 gph with a stack temp of 350F. Over the years that is many thousands of dollars in fuel savings … enough to pay off the mortage!

Reducing nozzle sized works, both in theory and practice. If some cannot make it work that is their problem. It works for those with modulating burners that adjust firing rate based on actual load.

Unfortunately for consumers, many “professionals” are still using obsolete concepts. Oil company profits rise with oil consumption so they just love to give customers plenty of heat.
 

Last edited by doughess; 02-25-18 at 06:58 AM.
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