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Ergomax Indirect Water Heater (Heat Exchanger)

Ergomax Heat Exchangers

ERGOMAX is a heat exchanger which uses thermal storage and turbulence to heat water instantaneously on demand. ERGOMAX can be connected to any source of hot water such as boilers (gas, oil, electric), solar, geothermal etc.

Boiler water fills, and is circulated through, the ERGOMAX tank, thus eliminating the potential for scaling and corrosion, ensuring that the ERGOMAX/boiler combination will always operate at maximum efficiency. Turbulence is also created within the ERGOMAX tank to maintain an ideal environment for heat transfer.

When demand for hot water occurs (eg. a faucet is opened) cold water enters ERGOMAX's coils and is heated as it flows through the them in a turbulent manner. This turbulence scours the inside of the coils flushing out any potential scaling that could occur, keeping the coils clean.

ERGOMAX has a limited lifetime residential warranty, and commercial limited warranty is 10 years.

ERGOMAX technology, thermal storage and turbulence, results in many benefits:     

  • 99% Heat Transfer Efficiency Saves Energy
  • Performance specifications are located near the bottom of this page.
  • Double-Wall Exempt
  • Output up to 1800 gph
  • Output Temperature up to 195oF
  • Instantaneous - No "Recovery" Needed
  • Prevents Bacterial Growth
  • Buffers Low-Mass High Performance Boilers
  • Fits Through Doorways and in Elevators
  • Requires No Maintenance
  • Lowest Lifetime Operating Costs
  • Transferable Lifetime Residential Warranty
  • Industry's Best Commercial Warranty
  • Made in USA
  • Manufacturers may change product specifications and information at any time without notice.  For additional information, please visit the manufacturer's web site.
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ErgoMax E23 Indirect Water Heater
Accommodates the majority of residential applications. Handles boilers up to approx. 225,000 BTU.
Contact Us for Pricing
ErgoMax E24 Indirect Water Heater
Has the same tank size as E23, but one more coil. Can be used instead of E44. Where demand for hot water is "continuous" and tank size does not matter. Can handle boilers in the range of 200,000 - 350,000 BTU.
ErgoMax E44 Indirect Water Heater
Large homes with spas, smaller apartment buildings. Boilers generally in the range of 200,000 - 350,000 BTU. A single unit can handle apartment buildings up to approximately 20 units.
ErgoMax E45 Indirect Water Heater
Has the same tank size as E44, but one more coil. Can be used instead of E65. Where demand for hot water is "continuous" and tank size does not matter. Can handle boilers up to 450,000 - 500,000 BTU.
ErgoMax E65 Indirect Water Heater
Hotels/motels, apartment buildings, laundries, car washes, restaurants, dairies, very large homes, etc. Can handle boilers up to 450,000 - 500,000 BTU. A single unit can handle apartment buildings up to approximately 40 units.
ErgoMax E109 Indirect Water Heater
Hotels/motels, apartment buildings, laundries, car washes, restaurants, dairies, very large homes, etc. Can handle boilers up to 900,000 - 950,000 BTU. A single unit can handle apartment buildings up to approximately 90 units.


IMPORTANT:  By purchasing this water heater from JupiterHeating.com, the customer is agreeing that the unit will be installed by a licensed, professional heating contractor; that the customer and installer will follow all local zoning regulations, as well as all manufacturer's installation instructions, policies, and warranty requirements; and that the customer has read and understood JupiterHeating.com's Terms of Sale.

Shipping for unit is $200 to anywhere in the continental United States (multiple units are shipped at no additional charge).  The rate is based on residential delivery with a liftgate.  This unit is strapped onto a pallet and shipped via LTL to minimize risk of shipping damage.  Shipping savings may by possible for commercial delivery, or for not needing a liftgate. Contact Us for a custom shipping quote if any of those situations apply, or if you are located outside the continental United States.


ErgoMax Unit Comparison:

Tank Volume (US. gal)
Heat Transfer Area (sq ft.)
Domestic Water Connections
Boiler Connections
Weight (lb)
E23 26 19.6 1-1/4" sweat 1" NPT 42" 19.5" 170
E24 26 26.2 1-1/4" sweat 1" NPT 42" 19.5" 200
E44 48 26.2 1-1/2" sweat 1-1/4" NPT 45" 24.5" 235
E45 48 32.7 1-1/2" sweat 1-1/4" NPT 45" 24.5" 265
E65 72 32.7 1-1/2" sweat 1-1/2" NPT 49" 26.5" 385
E109 119 58.9 2" sweat 2" NPT 60" 30.5" 625

Domestic hot water produced per hour in U.S. gallons*:

First Hour
110oF 140oF 180oF 110oF 140oF 180oF
Ergomax E23
100,000 198 131   172 121  
150,000 284 192   258 181  
200,000 370 252   344 241  
250,000 456 312   429 302  
300,000 542     515    
Ergomax E24
150,000 284 192 134 258 181 130
200,000 370 252 177 344 241 173
250,000 455 312 220 429 302 216
300,000 542 373   515 352  
350,000 628 433   601 422  
400,000 714     687    
Ergomax E44
150,000 306 200 137 258 181 130
200,000 392 261 180 344 241 173
250,000 477 321 223 429 302 216
300,000 563 381 266 515 362 260
350,000 649 442   601 422  
400,000 735     687    
450,000 797     773    
Ergomax E45
200,000 392 261 180 334 241 173
250,000 477 321 223 429 302 216
300,000 563 381 266 515 362 260
350,000 649 442 300 601 422 292
400,000 735 502   687 483  
450,000 821 562   773 543  
500,000 946 907   859    
Ergomax E65
200,000 416 270 183 344 241 173
250,000 501 331 227 429 302 216
300,000 587 391 270 515 362 260
350,000 673 451 309 601 422 300
400,000 759 512 352 687 483 343
450,000 845 572   773 543  
500,000 931     859    
600,000 1056     1020    
Ergomax E109
400,000 807 531 363 687 483 346
500,000 979 651 450 859 603 433
600,000 1151 772 536 1031 724 519
700,000 1323 893 622 1202 845 606
800,000 1494 1014   1374 965  
900,000 1666 1074   1546 1026  
1,050,000 1854     1804    

* Based on ASHREA (D.O.E.) tested method with 40oF domestic water and boiler water at 180oF. Boiler must be 200oF to obtain 180oF output volumes. R Factor = 15. Standby loss < 1/2oF per hour.


  1. Multiple units can be installed in parallel to handle demands that exceed the capacity of a single unit. (Use reverse return piping to equalize flow/btu through the units.)
  2. In commercial applications consider installing two smaller units rather than one larger one to provide backup capability. For example, a building has 80 apartments, so a single E109 could handle the hot water demand, but two E65 would provide backup. 
  3. Do not oversize. The flow of water through the coils should be kept high to ensure a high level of turbulence within the coils (eg. high velocity). (This turbulence scrubs the inside of the coils keeping them free of scale.)
  4. ERGOMAX should be compared to units produced by other manufacturers based on performance and not on tank size. 
  5. Using a mix valve with ERGOMAX will eliminated/minimize boiler short cycling (boiler will operate more efficiently) and also provide more hot water.
  6. Add four inches to basic tank dimensions to allow for utility (DHW) and boiler connections.

Frequently Asked Questions about Ergomax

What is an ERGOMAX?  ERGOMAX is a heat exchanger, popularly known as an indirect water heater.

What is an indirect water heater?  An indirect water heater is a heat exchanger and uses heat from an external source (i.e. a boiler, solar panels, etc.) to heat the cold (domestic) water.

How does a direct-fired water heater differ from an indirect?  A direct-fired water heater has its own firebox and must be vented to the outside (like a boiler) and creates its own heat. It operates independently of other equipment.

Which is better -- direct or indirect?  Indirect (heat exchanger) is more efficient and will produce more hot water (from the same amount of heat) than a direct fired unit. (It also has no flue.)

What makes ERGOMAX different?  ERGOMAX are different from other indirects in three ways:

  1. Tank is filled with boiler water, and domestic water flows through a bundle of copper coils.
  2. Turbulence is induced in the boiler water in the tank and in the domestic water flowing through the coils.
  3. Domestic hot water is not stored; it is heated instantaneously, on demand.  

Why do other indirects scale up and corrode?  Other indirects hold domestic water in the tank and heat it by immersing a coil connected to a boiler in the tank. The heat from the boiler water in the coil heats the domestic water in the tank. As hot water is used, fresh cold water enters and refills the tank. This constant refilling of the tank with fresh water provides a steady supply of minerals which precipitate out when the water is heated and attach themselves to the hottest part of the tank -- the coil -- forming a constantly growing layer of scale, reducing the heat transfer from the hot boiler water to the cold domestic water. Also, the constant temperature swings within the tank from hot to cold cause the tank (steel) to expand and contract. These thermal stresses cause cracks to form in the glass lining(which does not expand) allowing the steel to be attacked by oxygen in the water, causing corrosion.

Why won't ERGOMAX scale up or corrode?  The ERGOMAX tank is filled with boiler water. So, except for a very small amount of makeup water, no new minerals or oxygen enter the tank. No minerals means no scale build-up; and no oxygen means no corrosion.    ERGOMAX tanks do not need glass lining as they hold boiler water, and thermal stresses are minimal as ERGOMAX operates on the same temperature differential as the boiler. Also, turbulence within the ERGOMAX tank prevents stratification and cold spots.

How does turbulence affect energy consumption?  Energy consumption is reduced because heat transfer is much more efficient within a "turbulent" environment than within a "static" environment.

How is turbulence maintained within the ERGOMAX tank?  A mechanism located at the top of the tank forces the incoming boiler water to flow in spiral formations throughout the entire tank, creating turbulence.   

How many coils does an ERGOMAX contain?  The last digit of each model number represents the number of coils in that unit, so:  

  • Model E23 has 3 coils
  • Models E24 & E44 have 4 coils
  • Models E45 & E65 have 5 coils
  • Model E109 has 9 coils

Why are all ERGOMAX coils 50' long regardless of model?  Coils of this length have maximum heat transfer with minimum pressure drop.

How many GPM can each coil handle?  Each ERGOMAX coil can handle 3 - 3 gpm on a continuous basis. Peak usage can go as high as 4-5 gpm per coil, but this output rate should not be steady-state.

How is turbulence created within the coils?  The total cross section area of all coils is less than the cross section area of the incoming pipe, causing the domestic water to flow faster within the coils and creating a turbulent flow (eg. like a wide river flowing through a narrow gorge).

Why is turbulence inside the coils important?  Turbulence inside the coils scrubs the inside of the coils, preventing formation of scale.

How does turbulence affect heat transfer?  Turbulence creates an ideal environment for heat transfer. An example will illustrate this phenomenon: You come home very tired and want to soak in a very hot bath. How do you get into the bath? Very slowly, not to cause any ripples. Once you are in the bath, you can lie in this very hot water so long as you do not move. When you start to move, you feel the heat. This movement creates turbulence which "washes away" a thin layer of water next to your skin (known as a boundary layer) which acts as a layer of insulation preventing heat from the rest of the bath water to get to your sk in. Similarly, turbulence within the ERGOMAX tank and coils prevents this boundary layer from adhering to the inside or outside of the coils, hindering the heat transfer process

What is an ERGOMAX unit's heat transfer efficiency?  ERGOMAX units operate at 99%+ heat transfer efficiency which stays constant over time.

Why is ERGOMAX 99+% heat transfer efficiency higher than that of other indirects?  ERGOMAX is much more efficient because the built-in turbulence inside and outside the coils creates an ideal environment for heat transfer. Also, ERGOMAX copper coils transfer heat at a much higher rate than other metals. Other indirects, using coils made from other metals which conduct heat at a lower rate, operate in the mid to low 80% range when new, and steadily lose efficiency as they scale up over time.

What is thermal energy and how does an ERGOMAX unit store it?  Thermal energy is heat. The hot boiler water in ERGOMAX tank contains heat (Btu) which is used to heat the incoming domestic cold water.

How does thermal storage translate into energy savings?  Thermal storage allows the boiler to run less often, saving energy. When domestic hot water is needed, the heat stored in ERGOMAX tank (hot boiler water) is used to heat the cold water entering the coils. When the demand for hot water uses up all of this stored heat, the boiler is activated to supply more hot boiler water to ERGOMAX tank to continue heating the domestic water. This makes the boiler run less often. Combined with the built-in turbulence, this capability results in minimal energy consumption to heat domestic water. The thermal storage in ERGOMAX also acts as a buffer to minimize/eliminate short- cycling in low mass boilers during periods of low demand.

How much domestic hot water is stored in each ERGOMAX unit?  Very little, each coil holds less than 1/3 of a gallon.

What is the recovery rate of an ERGOMAX unit?  With ERGOMAX, there is no need to worry about "recovery," because an ERGOMAXunit will never run out of hot water as long as the boiler/circulator are functioning and hot water demand does not exceed the boiler's capacity to produce heat.

What equipment comes with an ERGOMAX unit?  All units come with an aquastat, a 30 psi ASME safety valve, and a drain valve. E24 through E109 models are also equipped with a temperature/pressure gauge.

What is the tank made of? Is it glass-lined?  AS36 steel. A glass lining is not needed since the tank contains only "dead" boiler water.

What maintenance does a ERGOMAX unit require?  None.

Does ERGOMAX have a sacrificial anode rod?  No. None is needed as no fresh water enters the tank (it holds only "dead" boiler water).

Does an ERGOMAX need a separate flue?  No. It has no firebox and produces no exhaust.

Does an ERGOMAX unit make any noise?  No. Normal operation is completely silent. If any noise, vibrations or gurgling is heard, there is probably some air trapped in the piping or the tank. Open the safety valve until all of the air is evacuated. NOTE: Installing an automatic air vent on the tank will prevent trapped air from accumulating at the top of the tank and causing corrosion.

What is the tank standby loss?  Less than 1/2oF per hour.

Can water conditioners, antifreeze, etc., be used with ERGOMAX?  Yes.

How long is the residential warranty?  ERGOMAX are covered by a Limited Lifetime Warranty to the original purchaser, which can be transferred to the second owner during the first 10 years following installation (see the Warranty). Note: Residential use is considered to be a single home or duplex.

How long is ERGOMAX warranted in commercial applications?  Ten (10) years, 100% for the first 5 years, then prorated 20% in each of years 6-10.

Legionnaire's Disease has been traced to domestic water systems and, in particular, storage tanks where stratification occurs. Can such bacterial growth occur in an ERGOMAX?  No. ERGOMAX does not store potable hot water, but heats it only as it is needed, instantaneously, so no bacterial growth can occur in ERGOMAX. NOTE: The ideal temperature for bacterial growth in a traditional indirect units, direct fired units or storage tanks is 120oF.

Does ERGOMAX come in a double-wall version?  No. ERGOMAX is exempt from the BOCA and IAPMO double-wall requirements. Under BOCA, heat exchangers utilizing non-toxic heat transfer fluids are exempt from the double-wall requirement. (See BOCA - 1993 Edition, Section P-1507-13.2). Under IAPMO single wall heat exchangers are permitted, so long as a) the heat transfer medium is either potable water or a substance recognized as safe by the FDA; and b) the pressure of the heat transfer medium is less than the operating pressure of the potable water system. The ERGOMAX tank is filled with boiler water at low pressure. The higher domestic water pressure will cause the safety valve on the ERGOMAX tank to open should a leak from the coils into the tank occur.

Can ERGOMAX units be used with "low-mass" boilers?  Yes. Since the ERGOMAX tank is filled with boiler water, it acts as a buffer and prevents low-mass boilers from short-cycling.

Can ERGOMAX units be used with "cold-start" boilers?  Yes. However, as with other indirect units, if a reverse acting aquastat is installed in the boiler it will prevent boiler water from circulating into the ERGOMAX tank until the boiler water is up to temperature. This allows the boiler to "catch up".

Can ERGOMAX units be used with steam boilers?  Yes, but only with low pressure steam boilers. By tapping in below the water line on the boiler (at least 9 inches below the water line), hot water can be drawn off to supply the closed loop to the ERGOMAX tank. NOTE: Care should be taken not to draw any sediment into the ERGOMAX tank from the bottom of the boiler.

Information Source: ErgoMax