Hydronic oil boiler replacement quotes/estimates help please

nother_new_homeowner

Greetings all,

I am in the process of getting quotes to replace my 30yo Burnham boiler and of the three salesmen that have come to give one, not one has done anything close to a heat loss calculation...

SO far two companies quoted the same Burnham mpo 115 and one a Slantfin tr-30... which according to the the heat loss calc I did on the slantfin app are 30k and 50k btu oversized respectively.

Through my reading here and the boiler manufactures websites themselves, I've come to understand how important boiler sizing is, along with proper installation, but if I can't seem to get the first one correct I can't start thinking about the second.

Does anyone have any advice on how I might insist on proper sizing without being a PITA... I understand that these are free estimates and I can't expect hours of work for the possibility that I go with someone else. Should I just keep getting estimates until one does the math?

This isn't exactly a trivial or cheap piece of equipment and under ideal conditions could last 20+ years and I'd like to get this right.

Any advice is appreciated, TIA

Hot_water_fan

Use this: both easier and more accurate.

https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new

EBEBRATT-Ed

@nother_new_homeowner

Check "find a contractor on this site" and post your location someone may have a recommendation

MaxMercy

Not answering your question, but I have a Slant TR-30 that can be downfired to .85gph (according to Slant). I run mine at .85 and it runs fine. They also make a TR-20 which is what I should have bought (2800sq fairly tight house Zone 5).

Jamie Hall

The best heat loss calculator I have found -- it really is a full manual J application -- is this one: https://www.slantfin.com/slantfin-heat-loss-calculator/ . Not green, perhaps -- just the numbers.

Hot_water_fan

@Jamie Hall Just a different approach . They should come close if the calculator is filled out correctly.

DJD775

@nother_new_homeowner Keep in mind that the MPO 115 and MPO 84 is the same boiler with a different firing rate and second set of baffles.
If you can't find a contractor that will size appropriately keep looking. When I was getting quotes for a new central A/C system only 2 out of 6 contractors I got quotes from were willing to do a manual j before install.

rsilvers

That article was good. I also concluded measuring loss makes more sense than estimating it. I made a spreadsheet where I tell it my nozzle size and psi and how many minutes per hour it runs and what the temp is. It then tells me what is needed for the target temp. 

That article says to then multiply by 1.4 to 1.7, which is the information I was missing. 

nother_new_homeowner

@DJD775 I was going to start a different thread about the fact that the 84 and 115 have the same specs besides nozzle size and the internal baffles you mentioned. Looking through the parts list for the two also indicates a low firing rate baffle for the burner, while the burners themselves are the same. I'll have to discuss this with the contractors who quoted them.

Thankfully my current boiler is still chugging along(knock on wood) so I can take a bit of time in weighing my options and getting 2nd, 3rd opinions, and it may be I get a bit more thorough service in the spring rather than the thick of the heating season.

DJD775

You caught the other difference. With the lower firing rate of the 84 you need the low firing rate baffle.