Tankless Heater Coil, E-624

Weil‑McLain 590‑921‑904 / E‑624 – OEM Tankless Heater Coil for EG‑Series Boilers

The Weil‑McLain E‑624 tankless heater coil is a factory-authorized domestic hot water heat exchanger designed for select cast iron boilers, including EG, P‑68V/B‑68V/A‑68V, P‑68/B‑68/A‑68, and EG‑35/45 water boilers. Manufactured from finned copper tubing, it delivers approximately 4 GPM of potable hot water without requiring a separate storage tank, making it ideal for hydronic systems demanding compact, on-demand DHW solutions :contentReference[oaicite:1]{index=1}.

???? Technical Features Boiler Compatibility: Compatible with Weil‑McLain boiler models listed above Maximum Flow: Approximately 4 GPM DHW throughput under standard ΔT conditions amazon.com +9 thegranitegroup.com +9 ussupply.com +9 Component Package: Preconfigured with coil, gasket, studs, and brass nuts for direct installation thegranitegroup.com +5 supplyhouse.com +5 supplyhouse.com +5 Size and Fit: 11″ long × 7″ diameter — unit clearance requires 14″ boiler door access (EG/PEG‑40–45 series) weil-mclain.com +1 weil-mclain.com +1 ???? Installation & Service Guidelines Hydronic Connection: Installed in the boiler jacket via designated opening; gasket compression uses supplied hardware Service Clearance: Requires 14″ clearance for removal on relevant boiler models to allow coil replacement supplyhouse.com +13 weil-mclain.com +13 amazon.com +13 boilersupplies.com +7 weil-mclain.com +7 thegranitegroup.com +7 Flow Control: Recommended to include a check valve or tempering valve to prevent cold boiler water from circulating backwards into the coil during heating cycles weil-mclain.com Gasket Integrity: Replacement of sealing gasket is critical to prevent leaks and maintain efficient coil operation ⚙️ Contractor Notes This E‑624 coil allows the boiler to deliver domestic hot water directly, eliminating the need for an external indirect tank. It is best suited for systems where delivering ~3–4 GPM meets household DHW needs. Proper installation requires torque sequencing, clean surfaces, and ensuring water circulation does not inhibit boiler or coil service. Confirm boiler model compatibility before ordering, and maintain the correct service clearances as specified.