eemax Tankless Water Heater: Complete Technical Guide
The eemax tankless water heater delivers on-demand hot water using electric heating elements, eliminating standby heat loss and achieving energy efficiency up to 99%. These units are designed for point-of-use or whole-house applications, with flow rates from 0.5 to 6.0 GPM depending on model and voltage. This guide covers selection, installation, performance optimization, troubleshooting, and code compliance for eemax systems.
eemax specializes in commercial and residential electric tankless water heaters, offering compact designs ideal for under-sink, wall-mount, or utility room installations. Their units operate without combustion, reducing venting requirements and increasing safety in confined spaces. This guide provides field-tested insights from 15 years of plumbing and HVAC system design, including NEC-compliant wiring, freeze protection strategies, and real-world efficiency data.
What Exactly Is an eemax Tankless Water Heater and How Does It Work?
An eemax tankless water heater is an electric, flow-activated device that heats water instantaneously as it passes through copper or stainless-steel heat exchangers powered by resistive heating elements. Cold water enters the unit, a flow sensor detects movement, and the control board activates heating elements to raise water temperature based on user-set differentials. No storage tank is used, eliminating standby losses.
Each model adjusts power output (in kilowatts) based on incoming water temperature and desired setpoint, maintaining ±2°F accuracy under stable flow conditions. The system uses thermostatic controls and over-temperature limit switches to prevent scalding or component damage. Units operate on 120V, 208V, or 240V circuits depending on capacity, with maximum draw ranging from 10A to 100A.
eemax units integrate modulating technology in higher-end models (e.g., eemaxplus series), allowing variable wattage output to match demand. This prevents short-cycling and reduces electrical stress. Flow rates range from 0.5 GPM (under-sink units) to 6.0 GPM (whole-house models), sufficient for one to three simultaneous fixtures in moderate climates.
These heaters require minimum flow rates of 0.25–0.5 GPM to activate—below this, the system remains dormant. Inlet water temperature significantly impacts performance; in northern climates with 40°F groundwater, maximum output drops by 30–40% compared to southern regions with 60°F supply. Proper sizing requires load calculation based on peak demand and ΔT (temperature rise needed).
For example, raising 40°F water to 120°F requires an 80°F ΔT. A 9 kW unit can deliver approximately 3.0 GPM at this rise, per the formula: GPM = (kW × 3.41) / ΔT. This physics-based calculation ensures accurate selection. Units exceeding 12 kW require dual-pole breakers and dedicated circuits per NEC Article 422.
eemax’s official product line includes self-modulating, fixed-output, and low-watt-density models for hard water areas. The company emphasizes commercial durability with NEMA 4X enclosures on select models, making them suitable for car washes, restaurants, and medical facilities.
How Do You Size an eemax Tankless Water Heater for Your Application?
Sizing a tankless water heater requires calculating peak hot water demand in gallons per minute (GPM) and determining the necessary temperature rise based on local groundwater temperature. Undersized units fail to deliver adequate hot water during simultaneous use, while oversized units waste energy and increase electrical infrastructure costs.
Begin by listing all hot water fixtures likely to run simultaneously—e.g., shower (2.0 GPM), bathroom sink (1.0 GPM), kitchen sink (1.5 GPM). Add their flow rates: 2.0 + 1.0 + 1.5 = 4.5 GPM peak demand. Next, determine your region’s average groundwater temperature using EPA regional groundwater data. Northern states average 40–50°F; southern states 55–65°F.
If your target output is 120°F and groundwater is 45°F, ΔT = 75°F. Using the formula GPM = (kW × 3.41) / ΔT, solve for required kW: kW = (GPM × ΔT) / 3.41. For 4.5 GPM at 75°F rise: (4.5 × 75) / 3.41 ≈ 99.3 kW. No single residential electric unit reaches this—indicating the need for multiple units or hybrid systems.
eemax’s largest residential model, the EE39PLUS-240, delivers 6.0 GPM at 70°F ΔT (from 50°F to 120°F) using 39 kW. This supports two showers and a sink in mild climates but may struggle in cold regions. For northern installations, consider zoning: install point-of-use units under sinks and near showers instead of one central unit.
Point-of-use models like the EE120V (1.5 kW, 120V) serve single sinks with 0.5 GPM output, reducing pipe heat loss and wait time. Install one per bathroom for immediate hot water. These require only 15A circuits and standard outlets, making retrofit easy.
Commercial applications demand higher reliability. The eemax EEM240-18 (18 kW, 240V) supports handwashing stations in restaurants, delivering 2.8 GPM at 70°F ΔT. For laundries or car washes, use low-watt-density models (e.g., EE36LD) to reduce scale buildup in hard water.
Always consult NEC Article 220 for load calculations and ensure panel capacity supports added amperage. A 36 kW unit draws 150A at 240V—requiring a subpanel or service upgrade. Work with a licensed electrician to avoid fire hazards from undersized wiring.
How Do You Install an eemax Tankless Water Heater Step-by-Step?
Installing an eemax tankless water heater requires plumbing connections, electrical wiring, mounting, and code compliance checks. Incorrect installation causes leaks, electrical faults, or premature failure. Always turn off power and water supply before beginning. Installation time averages 3–5 hours for experienced technicians.
Step 1: Select Location and Mount Unit
Choose a vertical wall near water and power sources. Maintain 12 inches clearance above and below for service access. Use the included template to mark screw holes. Drill into studs or masonry using anchors rated for 50+ lbs. Hang the unit level—misalignment stresses pipe joints.
Step 2: Connect Water Lines
Shut off main water. Install quarter-turn shutoff valves on inlet and outlet lines. Use flexible stainless-steel braided hoses (¼ turn type) for easy removal. Wrap NPT threads with PTFE tape. Hand-tighten plus 1–2 wrench turns. Do not overtighten—eemax’s brass fittings crack easily.
Install a sediment filter (5–20 micron) on the cold inlet to prevent flow sensor clogging. In hard water areas (>7 gpg), add a whole-house softener. Scale buildup is the leading cause of premature failure in electric tankless units.
Step 3: Wire Power Supply
Shut off main breaker. Run conduit from the electrical panel to the unit using EMT or flexible metal. Wire size depends on amperage:
- 30A: 10 AWG copper (NEC Table 310.16)
- 50A: 6 AWG copper
- 100A: 3 AWG copper
Connect black (hot), red (hot), and green (ground) wires to the terminal block. Torque lugs to 25 in-lbs. Install a dedicated double-pole breaker matching unit requirements (e.g., 60A for 14.4 kW). Label the panel.
Step 4: Power On and Test
Restore water, then power. Open a hot faucet downstream. The unit should activate within 5 seconds. Check for error codes on digital displays (e.g., E3 = low flow, E5 = over-temperature). Measure output temperature with a digital thermometer—should match setpoint within ±3°F.
Flush the system for 5 minutes to remove debris. Record amp draw with a clamp meter—should match nameplate within 5%. Verify GFCI protection if installed in damp locations (NEC 210.8).
Why Does Flow Rate Drop or Temperature Fluctuate in eemax Units?
Flow rate drops and temperature fluctuations in eemax tankless water heaters occur primarily due to mineral buildup in heat exchangers, low inlet pressure (<20 psi), or incorrect electrical supply (voltage drop >5%). These issues reduce efficiency, trigger error codes, and shorten lifespan.
Hard water (over 7 grains per gallon) deposits calcium carbonate on heating elements and flow sensors. A ¼” scale layer reduces heat transfer by 50%, forcing elements to overwork. Symptoms include delayed hot water, inconsistent output, and E1 (overheat) codes. Prevent this with annual descaling using a 1-gallon pump kit and 2 gallons of food-grade vinegar or commercial descaling solution.
Low water pressure (<20 psi) prevents activation—most eemax models require 25–80 psi. Check municipal supply or well pump output. If pressure is low, install a booster pump (e.g., Grundfos MQ3-45) rated for continuous duty. Pressure-reducing valves above 80 psi protect internal components.
Voltage drop exceeding 5% (e.g., 228V on a 240V circuit) reduces heating capacity. Measure voltage at the unit under load. Causes include undersized wire, long circuit runs (>100 ft), or loose connections. Upgrade wire gauge or relocate the panel.
Thermal layering in recirculation systems causes fluctuation. If using a return pump, install a thermostatic bypass valve to prevent cold water slugs. Set pump timers to avoid nighttime cycling.
How Much Does a eemax Tankless Water Heater Cost to Purchase and Install?
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A eemax tankless water heater costs $300–$1,800 for the unit and $500–$2,500 for professional installation, totaling $800–$4,300 depending on model, electrical requirements, and regional labor rates. DIY installation saves $500–$1,200 but voids warranty if not inspected.
Unit pricing:
- EE120V (1.5 kW): $320
- EE240-9 (9 kW): $650
- EE36PLUS-240 (36 kW): $1,450
- EE39PLUS-240 (39 kW): $1,780
Commercial-grade models (NEMA 4X) cost 20% more. Prices verified at The Home Depot and direct from eemax distributors as of Q2 2024.
Installation costs vary:
- Point-of-use (120V): $500–$800 (plumbing + electrical)
- Whole-house (240V, new circuit): $1,800–$2,500
- Service panel upgrade: +$1,200–$3,000
Labor rates range from $85/hour (Midwest) to $150/hour (California, Northeast). Electricians charge $65–$100/hour for running conduit and breakers.
ROI averages 8–12 years via energy savings. eemax units achieve 99% efficiency vs. 60% for standard electric tanks. Annual operating cost: $240 (eemax) vs. $400 (tank-type) for a family of four—saving $160/year.
Rebates are limited for electric tankless units. Check DSIRE database for state-specific incentives. Some utilities offer $100–$300 rebates for high-efficiency electric water heating.
What Problems Might You Encounter with eemax Tankless Water Heaters?
Common problems with eemax tankless water heaters include scale buildup, electrical tripping, freeze damage, flow sensor failure, and inadequate sizing. Each has distinct symptoms and solutions, preventable with maintenance and proper installation.
Scale buildup occurs in hard water areas, reducing flow and efficiency. Descaling annually with vinegar restores performance. Units in areas with >10 gpg hardness fail 3× faster without treatment.
Electrical tripping stems from GFCI incompatibility or ground faults. eemax units draw high inrush current (up to 2× rated amps for 0.5 seconds), tripping sensitive GFCIs. Use time-delay GFCI breakers (e.g., Siemens QD260T) or install a non-GFCI circuit if code allows (NEC 210.8 exceptions for dedicated appliances).
Freeze damage destroys heat exchangers if water remains in the unit below 32°F. Prevent this by draining during winter shutdowns or installing freeze-proof models (e.g., EE240FP) with built-in heaters that activate at 40°F.
Flow sensor failure causes no-heat conditions. Symptoms include no activation despite water flow. Replace the sensor assembly ($85–$120) or entire control board ($220). Avoid abrasive pipe flushes that damage the sensor.
Undersizing leads to cold water sandwich or insufficient flow. Always size for peak demand and local ΔT. Use multiple point-of-use units if whole-house models are impractical.
Which eemax Model Is Best for Residential vs. Commercial Use?
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For residential use, the eemax EE36PLUS-240 (36 kW, 240V) is optimal for whole-house applications in moderate climates, while the EE120V suits point-of-use needs. For commercial use, the EEM240-18 (18 kW, stainless-steel housing) or EE36LD (low-watt-density) are preferred for durability and scale resistance.
Residential selection depends on household size:
- 1–2 people: EE240-9 (9 kW)
- 3–4 people: EE36PLUS-240
- Cold climate (40°F inlet): Add recirculation or use two units
Commercial environments demand robust construction. The EEM series features NEMA 4X enclosures, corrosion-resistant housings, and commercial-grade flow meters. The EE36LD uses larger-diameter heating elements (low watt density) to reduce scaling in hard water—critical for laundries and restaurants.
Hospitality and healthcare settings benefit from ASSE 1070-compliant models that prevent scalding. The eemaxplus series includes thermostatic mixing valves and digital diagnostics.
Always verify local code acceptance. Some jurisdictions require ASSE 1083 certification for commercial installations.
How Do You Maintain and Descale a eemax Tankless Water Heater?
Maintain a eemax tankless water heater by flushing annually with vinegar or descaling solution, inspecting electrical connections every 2 years, and replacing inlet filters quarterly in hard water areas. Neglecting maintenance reduces lifespan from 15 to 5–7 years.
Descaling Procedure (Annual):
1. Shut off power and water.
2. Connect a submersible pump to the service valves (included on most models).
3. Fill bucket with 2 gallons of 5% acetic acid (white vinegar) or commercial descaler.
4. Circulate solution for 45 minutes.
5. Flush with clean water for 10 minutes.
6. Restart system and check for error codes.
Use only food-grade vinegar—muriatic acid damages copper coils. In areas with >10 gpg hardness, descale every 6 months.
Inspect wire terminations for oxidation or arcing. Retorque to 25 in-lbs if loose. Check ground integrity with a multimeter (<1 ohm resistance).
Replace sediment filters every 3–6 months if water is turbid. Clogged filters trigger low-flow errors (E3).
FAQ
#### What are the most common error codes on eemax tankless water heaters?
Common eemax error codes include E1 (over-temperature), E3 (low flow), E5 (sensor failure), and E7 (ground fault). E1 often results from scale buildup restricting flow—descaling resolves 80% of cases. E3 indicates clogged filters or pressure below 20 psi. E5 points to a failed thermistor—replace the sensor. E7 requires electrical inspection for grounding issues. Always power cycle the unit before troubleshooting. Consult the model-specific manual for reset procedures and diagnostic modes.
#### How much electricity does a eemax tankless water heater use per month?
A eemax tankless heater uses 200–900 kWh/month depending on household size and hot water usage. A family of four using 60 gallons/day at 120°F consumes approximately 550 kWh/month with a 36 kW unit. At $0.15/kWh, this equals $82.50/month. Compared to a standard electric tank ($110/month), savings are $27.50. Usage drops 30% with low-flow fixtures and timed showers. Install a kWh meter (e.g., Emporia Vue) to monitor real-time consumption.
#### Are eemax tankless water heaters compliant with NEC and plumbing codes?
Yes, eemax units comply with NEC Article 422, UPC Chapter 6, and IRC P2901. They require dedicated circuits, proper grounding, and GFCI protection in damp locations. Units over 12 kW need dual-pole breakers and conductor sizing per Table 310.16. Plumbing connections must include shutoff valves and thermal expansion tanks if on closed systems. Local amendments may require ASSE 1017 tempering valves. Always obtain a permit and schedule inspection.
#### How do eemax electric models compare to gas tankless brands like Rinnai or Navien?
eemax electric models offer simpler installation (no venting), 99% efficiency, and lower emissions but require substantial electrical service. Rinnai and Navien gas units deliver higher GPM (up to 11 GPM) and perform better in cold climates but need Category III stainless-steel venting and gas line upgrades. eemax suits homes with 200A+ panels; gas models work where electricity is limited. Gas has lower operating cost in areas with cheap natural gas. Choose electric for tight spaces, gas for high-demand homes.
#### Should I install a eemax unit myself or hire a professional?
Install simple point-of-use models (120V) yourself if experienced with plumbing and electrical work. For 240V whole-house units, hire a licensed plumber and electrician. DIY risks improper wiring (fire hazard), voided warranty, and failed inspections. Professionals ensure NEC compliance and can handle panel upgrades. Labor costs $500–$1,200 but provide insurance and permits. Most manufacturers require certified installation for warranty validation.
#### How long does a eemax tankless water heater last with proper maintenance?
With annual descaling and filter changes, a eemax tankless water heater lasts 12–15 years. Units in soft water areas reach 15+ years; those in hard water fail at 5–7 years without maintenance. Heating elements typically last 10 years. Control boards last 8–12 years. Commercial models with NEMA 4X enclosures last longer due to superior sealing. Register your unit for the 10-year limited warranty—requires proof of annual maintenance.
#### What tools are required to install or service a eemax tankless water heater?
Essential tools include adjustable wrench, basin wrench, pipe threader, voltage tester, clamp meter, T20 Torx driver, ¼-turn fitting tool, submersible pump for descaling, and digital thermometer. Electrical work requires conduit bender, wire stripper, and torque screwdriver. Safety gear: gloves, goggles, and insulated tools. Diagnostic models need a Bluetooth adapter (eemax Connect) for app-based troubleshooting. Keep OEM service valves and Teflon tape on hand.
#### Can a eemax tankless heater work in cold climates like Minnesota?
A eemax tankless heater can work in cold climates but requires careful sizing. With 37°F groundwater, a 36 kW unit delivers only 3.8 GPM at 120°F (ΔT = 83°F). This supports one shower and a sink, not simultaneous use. Use multiple point-of-use units or pair with a heat pump water heater. Install freeze-proof models (EE240FP) with built-in heaters. Insulate pipes and locate the unit indoors. Avoid outdoor mounting unless specified.
Conclusion
The eemax tankless water heater offers high-efficiency, on-demand hot water for residential and commercial applications, with models ranging from 1.5 kW point-of-use units to 39 kW whole-house systems. Success depends on proper sizing using ΔT calculations, NEC-compliant electrical installation, and annual descaling to prevent mineral buildup. These units eliminate standby losses, achieve 99% efficiency, and last 12–15 years with maintenance.
Key considerations include groundwater temperature, available electrical capacity, and water hardness. In cold climates or large households, zoning with multiple units outperforms single whole-house models. Professional installation ensures code compliance and warranty validity. For maximum ROI, combine with low-flow fixtures and off-peak usage.
Next steps: Calculate your peak GPM and ΔT, verify panel capacity, obtain 3 quotes from licensed installers, and select a model with modulating controls for stable output. Register the warranty and schedule annual maintenance.