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I. PRODUCT DESCRIPTION
This indirect water heater (IWH) is designed to generate domestic hot water in conjunction with a hot water boiler, or other
suitable heat source, using forced boiler water circulation. This indirect water heater consists of a stainless steel tank in which a
smooth stainless steel coil is located. Boiler water is pumped through the coil and heats the water in the tank. This product is not
intendedforuseinpoolheatingapplicationsorforheatinganyotheruidotherthanwater.Itisalsonotintendedforuseingrav-
ity hot water heating systems.
This manual shows installations where a hot water boiler is used as the heat source for the IWH, however other heat sources (such
as solar collectors) may be used provided that the following conditions are met:
1)Theheatsourcemustbeabletoprovideacontinuoussupplyof180FwatertothecoilattheowratesshowninTable2.1.
Iflowertemperaturesand/orowratesareused,theperformanceshowninTable2.1maynotbeachieved.
2)ThethermostatprovidedwiththisIWHmustbeinstalledandwiredinsuchawaythatitwillinterrupttheowofheat
source water passing through the coil when its contacts open. Failure to control the heat source ow using this thermostat
could result in unreliable operation or personal injury or death due to scalding.
3)Theuidpassingthroughthecoilmustbewaterorothernon-toxicuidhavingatoxicityratingorClassof1aslistedin
Clinical Toxicology of Commercial Products (latest edition).
4) The heat source must be used in accordance with its manufacturer’s instructions and those of the authority having jurisdic-
tion.
IMPORTANT NOTE
All models have a stored volume of less than 120 Gallons. When installed in accordance with these instructions, stored
potable water temperature in the tank is limited to a value of 210F or less by a temperature and pressure relief valve.
The maximum possible heat transfer rate across the coil (heat input) is less than 200,000BTU/hr with 210F potable
water provided that boiler or heat source water temperature is limited to:
MS2-030 – MS2-075: 250F
MS2-119: 220F
All models are therefore outside of the scope of both ASME Section IV, part HLW and ASME Section VIII when
installed in accordance with these instructions and with the boiler or heat source water temperature limited as shown
above.
II. SPECIFICATIONS
Notes:
Ratings based on 77F DHW temperature rise (135F outlet temp) and 180F boiler supply temperature. The ratings in Table
2.1wereobtainedattheheatsource(boiler)outputratesandheatsourceowratesshownabove.Otherresultsshallbe
obtainedunderdierentconditions.
Pressure Ratings:
Maximum Allowable Tank Working Pressure - 150 psi
Design Hydrostatically Tested to 300 psi
TABLE 2.1: Mega-Stor®II Series AHRI Performance Ratings
Model
First Hour
Rating
Continuous
Draw Rating Standby
Loss
(°F/hr)
Minimum
Boiler
Output
(MBH)
Boiler Water Through Coil
(Gal/hr) (Gal/hr) Min Flow
(Gal/min)
Head Loss
(ft w.c.)
MS2-030 162 138 1.4 87 8.0 2.6
MS2-040 192 162 1.1 101 8.0 2.8
MS2-050 236 193 0.9 121 8.0 2.9
MS2-075 307 238 1.0 150 8.0 4.5
MS2-119 497 417 1.4 264 14.0 4.2
