Burnham K2WTC - Domestic Hot Water Piping

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107774-01 - 9/17
X. Domestic Hot Water Piping
Install the domestic hot water piping as shown in Figure 10.1. Combi connections are ¾” NPT male thread. The components in
this system, and their functions are as follows:
1. ASSE 1070 or ASSE 1017 Listed Tempering Valve (Required) – This boiler is equipped with a control system that
attempts to regulate the DHW outlet temperature to a DHW set point (default set point is 120F – see Section XIII
for more information). As with all water heaters there are inherent limitations on the ability of the control system to
accurately regulate water temperature to this set point under all conditions. Extremely low draw rates and transitions from
heatingtoDHWaretwoexamplesofconditionsthatcancausethetemperatureofwaterleavingtheboilertosignicantly
exceed the DHW set point. To minimize “spikes” in DHW temperature, a tempering valve is therefore required. Select
and install in accordance with the valve manufacturer’s instructions and applicable codes. Note that some codes require
additionaltemperingdevicesatsomeofthexturesaswell.
2. Flow Restrictor (Optional) - If domestic hot water is drawn from at a rate in excess of the rating in Table 2.2, the
temperatureofthehotwatermaybetoolowtobeofuse.Theuseofaowrestrictorwillhelppreventthisproblemby
limiting the rate at which water can pass through the DHW heat exchanger. If a restrictor is used, select one having a
rating in GPM approximately equal to that shown in Table 2.2 at the desired temperature rise.
3. Pressure Relief Valve (Required) - Limits the pressure in the domestic hot water piping. Use a valve designed for DHW
service, such as the Watts #3L or #53L. Note that this is a pressure relief valve, not a T&P valve. Select a valve with
a pressure setting less than or equal to 145 psi. Pipe the discharge to a safe location using piping the same size as the
discharge connection on the valve.
4. Hose Bib Valves(Recommended)-ThesevalvespermittheDHWplateheatexchangerbeperiodically“backushed”to
remove sediment.
5. Globe or Ball Valve(Recommended)-UsedtoaidinbackushingtheheatexchangerandtoisolatetheDHWpipingif
itmustbeserviced.Inaddition,theupstreamvalvemaybeusedtolimittheDHWowifnecessary.
6. Thermal Expansion Tank(Requiredifabackowpreventerisinstalled)–Ifabackowpreventerorcheckvalveis
installed upstream of the cold connection, a thermal expansion tank will prevent the build-up of pressure in the DHW
piping. Use a thermal expansion tank designed for use in potable water service.
7. Unions – Improve serviceability of DHW piping.
DANGER - SCALD HAZARD
Under certain conditions this boiler can deliver domestic hot water (DHW) at temperatures in excess
of the DHW set point on the boiler control. An installer-supplied, ASSE 1017 or ASSE 1070 certied
tempering valve is therefore REQUIRED as part of this boiler’s installation.
• Select and install tempering valve in accordance with the valve manufacturer’s instructions and
applicable local codes. In the absence of such codes follow the Uniform Plumbing Code (IAPMO/UPC-
1). Also note that additional tempering valves may be required at the xtures themselves.
NOTICE
• DHW feature on this boiler is designed to only to heat potable water (i.e. water from a well or water
utility that is suitable for drinking) having the following characteristics:
a) Hardness less than 200PPM
b) PH between 6 and 8
c) Chloride level less than 80PPM.
Use of water not having these characteristics could result in premature failure of the DHW handling
components in this boiler.
• Internal components near the Hot and Cold connections can be damaged by excessive heat during
soldering. If copper adaptors are mounted directly on the combi, solder adjacent piping to these
adaptors before installing them on the boiler. Failure to do so may cause internal leaks and/or other
damage to the boiler.