PDA

View Full Version : controls for freeze protection


kmarroon
04-01-2007, 11:27 AM
I have a system with three air handlers,one of which is in the attic.We are putting in a new boiler with tekmar control. Is there a way to set up a contol of to protect the unit in the attic against freezing. I know the loss of electricty is a liability, but we have a PV system to cover that end of the equation.
crab master
04-01-2007, 01:41 PM
1. Put glycol in the system.

2. Put a freeze stat in the supply duct, if you have supply duct that runs inside the building. If you only have ductwork in the attic then this won't work as you'll get nuisance trips.

3. Put in a programmable controller with the logic that it will only shut down the fan if the outside air and mixed/supply air are both below 38 deg. F for 5-10 minutes and the indoor blower is proofed on. Here you would also want to turn the pump on if it cycles off and open the mixing valve/hot water valve to the ah heating coil so you have full flow. Then also have an alarm generated to someone that can take care of the problem in a relatively quick manner. Send it out via phone call, email, text message, and/or alarm with red light and a buzzer to where someone would likely be in the area to notify someone to handle it.
Blks2000
04-09-2007, 08:29 PM
Which air handler manufacturer? I ask because most of them have a freeze stat as an option.
kmarroon
04-10-2007, 10:04 AM
The units are First Company units, two are 36vdx-3hw,one is a 24max-3hw. Older units that have been in use for about 17 years.
orion242
04-10-2007, 10:53 AM
Spring return actuators and a freezestat. Wire freezestat to kill power to the fan / econ dampers / heating valve. Freeze condition then closes OA damper, shutdown the fan and spring open the HW valve.
Blks2000
04-10-2007, 12:22 PM
For units, that old, you will have to contact them directly
firstco.com
dingman
04-10-2007, 12:28 PM
I agree with this. Just make sure the freezestat is correctly installed and that there isn't severe stratification in the unit, and you'll be good to go!


Spring return actuators and a freezestat. Wire freezestat to kill power to the fan / econ dampers / heating valve. Freeze condition then closes OA damper, shutdown the fan and spring open the HW valve.