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Boiler Sizing and Other Questions


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I found a used boiler on auction that I am considering making an offer on. Steam boilers are not exactly my forte and I would appreciate any insight or suggestions from folks that might be more familiar with steam appliances.

First off, here is the equipment I am looking to power with steam:

- 300 Gallon Mashtun - pipe-in-pipe heat exchanger with 60+GPM circulator pump (10BLL)

- 150 Gallon Plated Pot Still - fully-jacketed (5BBL)

possible later expansion

- 300 Gallon Stripping Still, or smaller continous sripping still

Working under the assumption that I need 50,000 BTU per 1BBL of boiling capacity I need about 750,000 BTU..

The used unit I found is a 20HP (I beleive thats about 700,000 BTU) Hurst natural gas boiler bought new in 2004 and used for 3 years.

Thats a bit shy of my estimate, but I am also looking at pre-heating mash water via the still condensor, or an in-line water heater, so perhaps thats not a big deal.. Obviously thought I want to be able to run both the still and mush tun at the same time..

I guese my questions would be:

I understand its suggested to get one boiler to run everything and not dedicated boilers for each piece of equipment. Would those folks currently using steam agree with this?

Is this unit large enought the have reasonable boil times? Is it possible to oversize the boiler?

Is anyone familiar with this brand (Hurst)

Based on the description provided, how much would a reasonable offer on this unit be? What would a great deal be?



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Hedgebird, sounds like you are from the beer side of things. That is a lot of steam. I imagine you searched "steam boiler" ? There are several good threads on this site. But quickly, check your local zoning to see what maximum size you can have without a "Fireman's" permit? Also check with your landlord and his/your insurance company for their maximums. I had to walk a Jr. inspector through his own regs and show the error of his interpretation. 700,000 is on the edge in most municipalities. Though it may also be of no consequence.

Also, be sure to have a good plumber who really does have experience with large steam units, not just say that they do. Boilers are fickle enough, let alone buying someone elses boiler, which by your statement, seems to have been sitting around for 5 years.

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Yes, it seems like a "lot of steam" to me as well! But everything I can find indicates it would not be too large.. Most of the sizing recomendations I could find for this type of stuff are from breweries, and hence the BBL measures in my original post..

Information I found on this forum..

I found a sales listing:

125 Gallon Christian Carl still being sold with a 400,000 BTU Gas Steam Boiler

And a comment:

I note a range of boiler sizes in terms of gallons of still capacity per boiler HP ranging from 8 gallons/HP to 20 gallons/HP

That range would mean the 20HP boiler I am looking at would be good for between 160 and 400 gallons while I have 450 total potential gallons to heat up.

I also found a sale listing for a "150,000btu natural gas steam boiler" that was purchased and never used. Perhaps it ended up being too small?

Thanks for the heads up on zoning and insurance maxes on steam boilers; that is not something I considered and will need to look into. I am not familiar with a Fireman's Permit and Google is suprisingly unhelpful for that term!

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Fireman's permit may be an old expression. Sometimes the word "Engineer" is used. But here is excerpt from Massachusetts: "Section 46 of Chapter 146 of the General Laws as appearing in the 2008 Official Edition. Said boilers shall be operated and maintained by a dually licensed second class fireman. This license must be renewed every five (5) years and shall require thirty (30) hours of training from an approved school by the department of public safety”.

Also: I'll admit I only undersand what I understand. I have not heard the use of "HP" or "Drive". That may be more with maintaining higher pressure, tall buildings, etc. We are concerned with slow rise in temp and pressure less than household, 7.5 PSI (lb per sq. inch) or .5 bar.

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One thing you may want to think about is that if you have one boiler running everything, when it goes down, (and they go down), everything stops. with Dedicated boilers or staged boilers you can keep up production. That was the advice I got from a distiller I took a class from.

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It's not just about the size of the boiler, pipe size and steam pressure make a difference, bigger pipes allow you to use lower pressure. In distilling in general you can use a low pressure boiler ( less than 15 PSI )

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In addition to all the good points, above, to amplify on what miller mentioned, make sure it's a 15 psi boiler, also referred to as atmospheric pressure.

If you use a high pressure boiler (which are often around 150 psi) you may need any of the following: a special inspection from the Fire Marshal, and an operating engineer's license, as Bob mentioned. It may be called something else in your jurisdiction. If you're in a rural location, none of these regulations may be applicable. Where are you?

I think the 20 HP will probably be fine. For a boiler that size new, it's in the $20,000 range, plus or minus $5k or so. "Great" used price for me would be $5k to $8k. I think the big unknown variables are the condition and ease of maintenance. I suggest you find a local expert to inspect it for you.

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Thanks for all the feedback everyone. Ill make sure to work with a steam-experienced plumber to review my calculations and install the equipment. Rickdiculous, thanks for the feedback about staging. Its good to know that not everyone agrees with the idea of having just one boiler. Miller, thanks for the heads up on presure levels; it was definatley good to read a bit more on that. Jedd, thanks for the price range estimates! This type of info is very helpful and hard to come by.

From doing more research I found its helpfull to differniate between "steam generators" and "steam boilers".

"The advantages using a steam generator compared to conventional steam boilers:

Easy to operate - normally no requirement for boiler authorization

Rapid start-up and establishing full steam pressure

Compact and easy to adapt in the existing machinery arrangement

Price attractive - especially at low steam rates."

Also for refrence:

Nice Range of BTU boilers with prices listed:


Good Discusion on Boiler Sizing, PSI levels:


After thinking things over more I am leaning towards going with a new, 350,000-400,000 BTU boiler. Something similar to:


- This is cheaper than even the "great" price on the larger used unit.

- Initially I will only be heating 150 gallons not 300 anyways..

- I can probably time things so still and mash are not heating from scratch at the same time.

- I can expand later with a second matching (staged or dedicated) steam unit if/when things get busy.

Thanks again everyone!

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