Ascent Combi and Ascent Plus Combi Gas – January 2024 17
ZONE CONTROL BY CIRCULATOR: Zone control by circulators requires a circulator relay with end switch (EK P/N: 10-
0464-4, SR504 or equivalent) or individual relays (EK P/N: 10-0464, SR501 or equivalent) for each zone. The boiler
bypass circulator is still used in this case. NOTICE: An additional tee must be installed into the supply for each additional
circulator. The tee is the supply connection for any zone circulators with the returns for these zones connected to the boiler
return. See Figure 2D “Zoning with Circulators” diagram found in this manual.
ZONE PURGING: Valves to isolate and purge individual zones should be installed according to good piping practices.
EXPANSION TANK SIZING: The type and size of expansion tank depends on the total system water volume. The EK1T
Ascent Combi and the EK1T+ Ascent Plus Combi contain 3 gallons of water. NOTICE: Sizing must consider cold start
and hot operation due to system cold start and rapid heat up. Note: Optional trim package, EK P/N:10-1702 includes a
#30 Amtrol expansion tank.
BOILER BYPASS CIRCULATOR
NOTICE: Systems are piped at the factory with the plate heat exchanger mounting installed with a boiler
bypass circulator. This zone must have all valves open for the boiler to operate properly.
The boiler bypass circulator is required for proper operation in both the space heating and domestic hot water
production cycles. In a space heating cycle, the bypass circulator provides integrated condensing protection. In a domestic
hot water production cycle, the bypass circulator provides forced circulation to the plate heat exchanger to allow rapid and
efficient heat transfer to the domestic water. NOTICE: Heat Only systems come from the factory with “bypass” piping
installed in place of the plate heat exchanger to provide the required flow through the bypass circuit.
FILLING WITH WATER, VENTING, and PURGING
When piping is completed and all accessories are installed on the Converter, the system should be filled with water.
The Converter purges itself of air when properly installed. Purge all zones and heating circulators. NOTICE: CALEFFI AIR
VENT CAP CORRECT POSITION IS CLOSED; REMOVE CAP FOR PURGING AND REINSTALL IN THE FULLY
CLOSED POSITION WHEN PUT INTO SERVICE (other air vent caps must be in the OPEN position when put into
service). Each zone should be purged until a steady stream of water without air passes out of the purge hose. Vent all
radiation.
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