Hyprotherm FLRH-350 Boiler

Coal Boiler

Hyprotherm FLRH-350 Outdoor Boiler

FLRH-350


$10,997


(Front Loading Residential Heater)
HyproTherm Wood and Coal Boiler
AKA Hyprotherm 350


** The cylinder you see on the side (flange not installed yet) is optional for an aftermarket oil, K-1, propane or waste oil burner. The handle on the ash tray compartment is for shaking the optional cast iron shaker grates.

FLRH-350 SPECIFICATIONS:

- Water Capacity; 350 gallon
- Firebox Thickness: 3/8" standard (50% thicker than most others)
...with a - HALF INCH THICK option, where you also get a 1/2" water jacket bottom!
Water Jacket Thickness Bottom: 3/8” or 1/2" with firebox upgrade (No one else in the world does this!)
- Water Jacket Thickness Sides and Top; 3/16” up-gradable to 1/4" (1/3 thicker)
Our LARGEST Firebox on a front loading boiler. The FHRH-400 has the exact SAME firebox but more water and BTU storger for greater heating capacity.

Firebox Capacity: 41 cubic feet
- Firebox Dimensions: 3/8” thick @ 69.5”L x 31-3/4”W x 31-3/4”H
- Overall Dimensions: 108”L x 46”W x 87”H
- Shipping Weight: 3,580 lbs
- Fuel Door; 26.5” x 26.5” with a 2' x 2' opening
- Grate System: Flat, one inch thick solid steel grates (Optional Shaker Grate Upgrade if Burning Coal)
- Ash Clean-out: Removable Ash Pan
- BTU: 392,175 BTU @ 180 degree
- Heatable Area: 9,800 sq ft approx, if well-insulated

> The standard insulation on our furnaces is unbeatable and a non-degrading K-factor insulation.



In the U.S., with rare exception, our boilers are for Business applications only.

They are built to heat businesses, buildings, garages, workshops,
commercial and other spaces, plus domestic hot water systems,
pools and hot tubs.

Our traditional outdoor furnaces generate economical,
natural and safe heat.

They are compatible with most existing and new heat systems,
including hot water, forced air, hydronic heat, radiant floors and baseboard heat pools and hot tubs and more.
.

Please see https://outdoorwoodfurnaceboiler.com/EPA_regs.htm




FLRH-350 Wood and Coal Boiler

Up to 9,800 sq. ft. burning a good hardwood like Oak, well-insulated building in a cold climate like PA

$10,997

20-year ON-SITE WARRANTY

1.

20-year ON-SITE WARRANTY!

- VERY IMPORTANT, with Hyprotherm you won't have to pay shipping back to the factory to get it repaired! We come to you for any major repair. FYI, other manufacturers will charge you to ship it back to your home after it is repaired, as well! (10-years on water jacket)
430-ton Press Brake

2: 430-ton Press Brake

We are the only manufacturer that uses a press brake to form a firebox and water jacket; both individually formed from a single piece of metal.

Most everyone else uses 6 flat slabs of steel, with no inherent strength and that requires 12 welds because welds are the weak spots.

This new firebox and water jacket is formed using a 430-ton Press Brake, meaning less welds which means less potential for leaks because leaks often start at welds; Almost as few welds as on a cylinder; Only 4 welds vs. 12 welds on a typical firebox. Three times less! 

3: Not only is the firebox thicker; the water jacket bottom is THE SAME THICKNESS as the firebox because it is the most vulnerable part); 3/8" standard and the 1/2" THICK firebox option gives you a HALF INCH THICK water jacket bottom as well!
NO ONE ELSE DOES THAT - ANYWHERE!!  The cost for this is  $897 extra. You may want to consider that upgrading the thickness of the water jacket may be a better option for less money ($525), where we make your water jacket 1/3 thicker, upgrading it to 1/4" thick, which is what I did on my personal boiler. 

Proprietary Electronics and Circuit Boards

4: It is the best boiler because it has ALL Off-the-Shelf PARTS; nothing proprietary that you have to get from us.

5: It is the best boiler because it has No electronics; NO circuit boards, NO computerized parts (like the circuit board on the left and on the Wood Master and Central Boiler and many others)! 

Smartphone Monitoring

6: Do you really need a Smartphone or Laptop to monitor your outdoor boiler?

I say that you should not have one if you cannot go outside and open the rear door and look at the thermometer and glance at the water gauge to see what is going on!

It is just something else to go wrong with a lot of extra expense that seems to be never covered under warranty.  They always say that a power surge took out the circuit board and you get stuck with a $300.00 bill and the technicians cost to install it.  

Not so with HyproTherm.  Every part on our boiler is available almost anywhere and everywhere; on eBay, at Grainger, your local plumbing supply; even in Canada!

One inch thick Solid Steel Grates

1 inch Solid Steel Grates

7: Solid Steel grates are much stronger; resistant to bowing and deformation like you may get with other thinner grates.

 Shaker grates made from cast iron and are available as an option, mostly for those folks burning a lot of coal, where the coal is inclined to have clinkers.

Our smallest models have one grate, the next two sizes up have two grates and our largest models typically have three grates.  

Pull-out Ash Tray / Pan

8: Pull-out Ash Tray

Most manufacturers make you open up the firebox door to clean out the ashes with a shovel.  You will quickly find out that you are not going to get anywhere near the firebox because it will be 800 F or more!

They want you to open the firebox door and you will need to leave it open to let the heat out and I call that wasting heat.  You will need to kill the fire to be able to shovel out the ashes and then you have to start a fire again, in the dead of winter.

With our furnaces you do it the easy way.  Even with a fire raging, you can pull out the ash tray, dump the ashes into a fire proof container and slide the tray back in without missing a lick.  Two handles on the ash tray make it easy.  Every ash tray is the same length as the firebox.

9: It is the best boiler because it has one pump installed WITH flanges; many others don't give you any pump PLUS we give you an extra set of ports for another pump to heat another building. (Shown Below)

10: They all come pre-wired with a reliable RANCO aquastat as shown below.

Hyprotherm Boiler pre-wired with Ranco Aquastat

Hyprotherm Front Loading Boiler

ALL MODELS
except for Econo 85

- Full-sized rear door for easy access!
- Totally pre-wired with Ranco Aquastat, fan switch, 4 electrical outlets, a pump, a second port for another pump, and a 75 CFM forced air induction fan .
- The blower (see next photo) feeds oxygen from the bottom, up through the grates just like a blacksmith's forge.
- Water level gauge and an analog thermometer included (upper left)
- Second set of ports for another pump (below thermometer).
- Built in hot water coil to heat your domestic hot water (saving you $35-$65 per month plus up to $400 in parts costs).
ASH TRAY CLEAN-OUT!

75 CFM Forced Air Induction Blower

75 CFM Forced Air Induction Blower

Feeding oxygen up through the grates (which most boilers don't have) from the bottom, just like a blacksmith's forge with a solenoid activated damper, so that no wood is burning (being wasted) when the aquastat turns the fan off!

Two return ports shown!

Copper Domestic Hot Water Coil

11: A built-in copper hot water coil, that sits in the big tank of water to heat your domestic hot water; saving you $35-$65 a month in energy costs plus $300 in installation costs of parts that are needed with other manufacturers' boilers.

12. Our boilers have the best of the newest insulation; a combination of ceramic wool and a product from Knauf. This was done after insulation engineers told us that fiberglass insulation was only good for a home, where you are trying to keep 75 degree heat in.

It is a different story when you are trying to contain 800 + degrees in a firebox; thus the new and better insulation. 

We put a layer of SolarGuard on top of the insulation from Knauf to give R-10 additional insulation by using a reflective barrier that controls heat in 3 ways; reflective, radiated, and conductive.  See this video for a demonstration of its great properties.

All of our YouTube videos are on this page. CLICK HERE

SUMMARY:

Our boilers have flat cast-iron grates standard, a 3/8" thick firebox; that is 50% thicker than common 1/4" fireboxes OR a half inch thick option; 100% thicker than common 1/4" fireboxes) and includes a pullout ash tray for easy clean-outs, the standard pump, a second set of ports for another pump or building and the built-in heat exchanger for the domestic hot water - as well as an automatic, solenoid activated damper on the forced air fan/draft, in the back and a chimney cap AND last but not least, a 3/8" or 1/2" thick water jacket bottom option; the most vulnerable part; now at least 3 times thicker.

Remember, there is no negative to getting a bigger furnace because it is not like purchasing an air conditioner where if you get one too big, it becomes inefficient. It is simply like getting a bigger fuel tank so that it will hold more fuel and you will need to fill it less often.


** Most companies do not even have grates or a way to clean out the ashes, other than opening the loading door and you are not getting anywhere near it because it is 800F - 2000F. So you have to let it cool down from and then restart a fire - in the dead of winter!

This is how we do it! A removable tray! The EASY WAY!

Remember, there is NO SALES TAX when we ship out of state!

Remember, the 20/10 year parts AND labor ON-SITE warranty, which is probably the best feature because at least 85% of the manufacturers out there require that you ship the furnace back to the factory to get it repaired. Then they have to ship it back to you and while the repair may be free, they charge you for the shipping both ways AND you have to disconnect the furnace, reinstall it and be without it for at least 2-6 weeks.

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Hypro Therm Furnace Mfg LLC

With rare exception, in the U.S., our boilers are for Businesses, shops, outbuildings, Pools and Hot Water heating only. 

SEE THIS PAGE

It is ultimately up to YOU, the consumer to check with YOUR local/state dept. of Environmental Quality to see what regulations apply to you.

Our BOILERS are built to heat businesses,  buildings, garages, kilns, workshops, commercial and other spaces, plus domestic hot water systems, pools and hot tubs.

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8/1/25