I will be setting up a small fan to
equalize temperature in 2 different
places. This is actually in a church to
keep the temperature of the organ
chamber, close to the temperature of the
church itself. The reason is to keep
organ pipes in the 2 locations, in tune
with each other. I have googled this,
however, I only come up with a few fancy
electronic units. They would probably
work ok. But, I was wondering if anyone
knows of a simple unit that is capable
of switching 110 to the fan. The fan
will be a small, 300 CFM or so unit,
using just a few amps.
More info, please...how far apart the locations you want/need to use as
controls and what is the existing input(s) you have, if any?
Are you proposing to simply moving church air as makeup or some other
tempered air source?
Do you have any specification from the organ maker/installer/tuner on
the differential required
to be maintained? Has the installation been modified -- if so, would
seem it would have been their job to make sure of ambient conditions
(just a question so maybe you can throw the onus onto somebody else :)
Have good friend who does organ tunings and retrofits -- give more
detail and if like I'll pass on the question to him and ask for
input...where is this located, just in case it might be close?
Alternative solution would seem to me to be to simply ensure continuous
air circulation through the chamber from the other area, but that makes
assumptions about what you're actually moving w/ the fan in your
With a common air supply from the wind chest, all the pipes would tend
to have the same temperature after the organ is played for a while. If
you can make air flow a lot of pipes at the same time, the backpressure
and fan pressure could be low, but maybe that's hard to do, if springs
in the chest hold valves closed until solenoids open them.
Running the blower before the organ is used, or whenever the church is
occupied (with an occupancy sensor) might use less energy. Heliotrope
General makes a 120 V differential thermostat, but the min differential
is fairly large, about 5 F.
With a dT (F) temp diff, 300 cfm would move about 300dT Btu/h of heat into
the pipes, which might lose heat from their surface at 1.5 Btu/h-F-ft^2
to church air at different temperatures. If one part of the church is
50 F and another is 70 and each contains pipes with 300 ft^2 of surface
and each receives 150 cfm of air at say, 70 F, the warmer pipes will be
70 F and the cooler pipes will warm to 55, for a 15 F temp diff. With 60 F
supply air, the warmer pipes would become 67.5 and the cooler ones would
become 52.5, with a 15 F temp diff that would decrease with more airflow but
doesn't depend on the supply air temp. Like this, viewed in a fixed font:
Tc = 50+1125/450 = 52.5
1/150 | 1/(1.5x300)
60 ---------www-----------------www--------50 F
| I = (60-50)/(1/150+1/450) = 1125 Btu/h -->
| Th = 70-1125/450 = 67.5
| 1/150 | 1/(1.5x300)
<--- 1125 Btu/h
A clever controller might measure the pipe temps and route 300 cfm of 70 F
air to the cooler pipes, raising their temp to 58 while leaving the 70 F
pipes unchanged. The chest might also contain a 1500 W space heater.
A small house furnace blower might work. Large organs have blower motors
rated in horsepower. You can't open the door to escape from the chest in
the First Parish UU Church in Concord MA until you turn off the blower or
open a small door slider to lower the air pressure from about 5" of water,
which pushes the 2'x5' door closed with about 300 pounds of force.
The church pipes are mounted right near
the grill where the chamber pipes speak
into the church. The church has it's
own HVAC system with setbacks, etc. The
chamber has no heat, however, when the
organ is off, the shades open. My plan
it to draw church air through the open
shutters into the pipe chamber and deliver
it to the room where the blower is
installed. This way the church air
would be in
the chamber and in the blower room. The
proposed blower/fan will be installed
above the organ blower room, where it
would deliver its air. A duct will go
organ chamber where it will suck causing
church air to enter the open shutters, thus
bringing the chamber temperature closer
to that of the church. This will also keep
the intake air temperature in the blower
room, closer to that of the church.
I am the installer/builder/organist. I
have monitored this for the 20 years
the instrument. It is worse now because
of new setback thermostats in the
church. This was something I have
always wanted to do, but never had the
ambition. Now, it is more important
because of the greater temperature
I guess the onus _did_ get shifted to the organ contractor... :)
Don't suppose there's any convenient way to get a side duct run from
off the sanctuary HVAC system?
Still would seem likely that imply an on/off control and a timer for
the routine service schedule would be adequate.
Well, that is another possible idea.
One of the HVAC systems is right next
to the organ chamber. I could put a
return duct in the chamber. This would
tend to suck church air through the open
shutters, thus equalizing temps. I
am currently waiting for the HVAC guy to
come back from vacation, to
discuss this with him.
Why do you think you need to control the fan? If you are blowing
'church temperature' air into the chamber, then you will equalize the
temperature. Why would you need to turn the fan off?
More detail please.
While you're working on this, why not install the fan and whatever
means you plan to use to direct the air and keep everything quiet.
So your project will be proceeding. Any switch that can control
anything electrical can control 110 volts by means of a relay.
Maybe when you are done, you'll be able to just use a simple
thermostat in the organ room, and won't mind if the fan runs a bit
more than you would have it otherwise. After all, if it runs more
now, and when it turns off 5 minutes later than planned, it will start
again later than it would have. So you'll break even.
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