BTH ULTRA Electric Boilers USE & CARE MANUAL (Revision April 2011), Page 9.
If it is not properly sized, the system pressure will
get above the allowable operating pressure of
30psi (207kPa) and the pressure relief valve will
open. Contact your local heating distributor for
proper selection.
3.4.5 Pressure regulator
An automatic water feeding system must be
employed as required by codes. An automatic
fill valve must be used with a backflow preventer
as required, to maintain minimum system pressure
by supplying water to make up for leakage. The
minimum usual pressure is 12psi.
3.4.6 Air bleeder
Installation of manual or automatic air vent devices
prevents air from accumulating in the system. Air
vents should be installed at all high points to
remove trapped air during initial setup and to
ensure that the system is tight. Regularly purge
the air out of the system while taking care to avoid
personal injuries or property damage caused by
hot boiler water spray.
3.4.7 Pump selection
Performance characteristics of centrifugal pumps
are described by pump curves, which plot flow
versus head of pressure together with other
information such as efficiency and power. Consult
the manufacturer’s pump curves to select the
proper model or ask your pump dealer or your
HVAC wholesaler for a recommendation.
Table below shows required flow in relation to the
power capacity of the boiler and selected
temperature drop in the heating distribution
system. On System with baseboard heaters, 20F
temperature drop is normally recommended and
on radiant floor application a value of 10F is
generally used.
Table 4: Temperature rise vs flow rate (GPM)
BWTD
Model KW 10o
F 20oF 30oF
40oF
BTH ULTRA 6 6 4,1 2,0 1,4 1,0
BTH ULTRA 8 8 5,5 2,7 1,8 1,4
BTH ULTRA 10 10 6,8 3,4 2,3 1,7
BTH ULTRA 12 12 8,2 4,1 2,7 2,0
BTH ULTRA 15 15 10,2
5,1 3,4 2,6
BTH ULTRA 18 18 12,3
6,1 4,1 3,1
BTH ULTRA 20 20 13,7
6,8 4,6 3,4
BTH ULTRA 24 24 16,4
8,2 5,5 4,1
BTH ULTRA 27 27 18,4
9,2 6,1 4,6
BTH ULTRA 30 30 20,5
10,2 6,8 5,1
BTH ULTRA 33 33 22,5
11,3 7,5 5,6
3.4.8 Dual Energy piping
Piping connections between the two boilers can be
made in parallel or in series as illustrated in fig.
5&6.
When installed in parallel, a three way motorized
valve (1”NPTF) is used to guide the heating
system return water toward the appropriate boiler
according to the operating mode in demand. This
way, the oil or gas boiler is not maintained hot by
the return water when the operation is in
Electricity.
N.B.: Make sure to select the appropriate port A, B
and AB when making the connection of the piping
(see fig.6)
3.5 ELECTRIC CONNECTIONS
3.5.1 Main Electric supply
Wiring must conform to the National Electrical
Code and to state or local code requirements.
Wiring must be from a 120/240 Volt (single phase,
60 Hz) circuit protected by a properly sized
breaker. Wire gauge (3 wires+ground) must be
properly sized. Consult the boiler rating plate to
select the proper breaker and wire gage.
Models 6 to 24 kW are certified for CU/AL cables.
Aluminum cables being generally bigger than
copper.
3.5.2 Connecting the thermostat and
pump.
3.5.2.1 Single heating zone
Using a 18 gauge cable, connect a low voltage
thermostat to terminals T and T on the electric
panel (DO NOT apply any power to these
terminals).
Connect the pump directly to the CC 120volts
terminals of the boiler using a 14gauge cable.
N.B. The amperage drawn by the pump shall not
exceed 5A or 1/6HP
