To: Customer
Crane Hwy. NW.
Glen Burnie Maryland 21061
410-760-XXX
Written By Scott Meenen N3SJH
As of April 2000 the time clock that controls the hvac system including
the
Air conditioning compressors and the large blower for the main
air handler has failed.
This clock is a very primitive device that allows setting for
a week to be adjusted with mechanical stops that must be added or removed
to include, exclude or adjust weekend operation. The time settings on this
clock must be set advance of any occupied times to ensure that the building
is at occupied temperature at occupied times regardless of weather conditions.
We propose replacing the current time clock with a Honeywell
7300A commercial thermostat that will control all the functions of the
system including the boiler in heat mode and the perimeter heating loop
that currently has NO (normallyopen) controls other than
manual intervention.
This repair will consist of discarding the time clock and adding
a bank of relays to the box that contained the time clock. These relays
will control the following functions: 1st and second stage cooling for
the main air-handler, blower operations for the main air-handler, boiler
operation, perimeter heat operation.
The thermostat will be located in the boiler room next to the
location of the existing time clock and will require the addition of a
remote sensor to be place on the first floor on a partition in a
section of the building that is served by both the air-handler and the
perimeter heat.
The advantage of using a honeywell 7300 thermostat is as follows:
minimal operation of main blower (restricted to occupied times and morning
“warm-up” or “cool off”), Minimal use of second stage cooling (old open
belt drive system), Minimal use of first stage cooling (limited to occupied
times and “morning cool off”), minimal use of boiler (limited to morning
“warm up”, occupied times and unoccupied freeze protection ), Minimal use
of perimeter heat (the most wasteful circuit) except when main air-handler
cannot keep up, the times can be set to when people will actually be in
the building and adding or deletion of weekend programs is easy and does
not require the changing of mechanical “stops”.
Investment costs:
· 7300A Thermostat $140.00
· Q7300 Sub base $120.00
· Remote Sensor $50
· Optional remote sensor (with 3 hour occupied control) $65
· 6 Idec relays (24 volt single pole ) $50.00
· 6 relay sockets $30.00
· Relay track $3.00
· 24 Volt Transformer 40 VA $20.00
· 8 conductor 18AWG cable $5.00
· 3 Conductor 18AWG 100 ft cable $30.00 (for Remote Sensor without
3 hour occupied)
· 1900 Square electrical box and plaster ring for thermostat.
$3.00
· RBM Switching relay for boiler $10.00
· Total Materials $431.00
·
Labor to Install all items NOT including wire for remote sensor $100.00
Labor to install wire for remote sensor time/materials or provided
by customer.
Terms: Customer must provide draw for materials before work begins.
Materials will become property of customer upon purchase.
Labor will be due upon connection of remote sensor and successful testing
of thermostat and control relays.
Winter 2000-2001; Switch and second sensor was added to
allow sensing of coldest location in winter and warmest location in summer.
The second sensor has a "3 hour occupied" feature.
Bid to replace a defective motor starter with a used
Cutler Hammer control.
Bid to install Replacement Lenoxx
heat pump system.
Bid to install Trace engineering
backup power system.
Bid to install a low ambient kit
on a Rheem Ruud air conditioning system coil.
Bid to install a Carrier
06D COMPRESSOR Go to or return to the bids index
page For
a list of all files go to the site map Goto or return to
the G&S Mechanical Home Page