Velocity K2WTC-135, Installation, Operating And Service Instructions

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A. Overview
1. Honeywell R7910B Controller
The Honeywell R7910B Controller (“Control”)
contains features and capabilities which help
improve heating system operation, and efficiency.
By including unique capabilities, the Control
can do more, with less field wiring, and fewer
aftermarket controls and components – improving
the operation of both new and replacement boiler
installations.
2. Advanced Touch Screen Display
Home Screen
Boiler status and setup selections are available
from an easy to use LCD Touch Screen Display.
In the event of a fault condition the user is guided
by “blinking” touch buttons to Help screens that
describe the problem. Operation evaluation
and problem-solving is enhanced by historical
capability including lockout history records as
well as boiler and circulator cycle counts and
run time hours.
3. Advanced Modulating Control
The Control modulates the boiler input by varying
the fan speed. As the fan speed increases,
so does the amount of fuel gas drawn into the
blower. As a result, a fairly constant air-fuel ratio
is maintained across all inputs. The Control
determines the input needed by looking at
both current and recent differences between
the measured temperature and the setpoint
temperature. As the measured temperature
approaches the setpoint temperature, the fan will
XIII. Operation
IMPORTANT
This boiler is equipped with a feature that saves energy by reducing the boiler water
temperature as the heating load decreases. This feature is equipped with an override
which is provided primarily to permit the use of an external energy management system
that serves the same function. THIS OVERRIDE MUST NOT BE USED UNLESS AT LEAST
ONE OF THE FOLLOWING CONDITIONS IS TRUE:
• An external energy management system is installed that reduces the boiler water
temperature as the heating load decreases.
• This boiler is not used for any space heating.
• This boiler is part of a modular or multiple boiler system having a total input of
300,000 BTU/hr or greater.
slow down and the input will drop. The Control
also utilizes boiler return water and flue gas
temperatures to adjust fan speed.
4. HeatMatch
TM
Software
When the boiler is installed with a Sage Zone
Control Panel (Zone Control) into a multiple
zone home the Control uses a patent pending
HeatMatch Software to improve home comfort,
increase component life and save energy. The
Control with the Zone Control detects active
(turned “On”) zones, totals btu/hrs expected
and limits the boiler firing rate to “match” actual
home demand. Instead of simply firing to 100% in
response to a cold supply water temperature the
Control combines heat matching with supply water
temperature control. Additionally, as zones turn
“Off” maximum firing rate is immediately reduced
eliminating the need for supply water temperature
to first increase above setpoint. The result is longer
run times, dramatic reduction in boiler excessive
cycling and higher operating efficiency. Avoiding
extra cycling saves customer fuel dollars (pre
and post purge sends heat up stack) and saves
wear and tear on the boiler. Lowering the boiler’s
firing rate saves fuel dollars by increasing the
amount of flue gas condensation, always the
goal of condensing boiler installations.
5. Built-in Safety Control
The Control includes safety controls designed to
ensure safe and reliable operation. In addition to
flame safety controls the Control includes supply
water temperature, differential water temperature,
and stack temperature safety limits and stepped
modulation responses. Boiler modulation is
adjusted when required to help avoid loss of boiler
operation due to exceeding limits. Additionally,
the Control accepts the field installation of optional
auxiliary safety limits.