I'm trying to design a system that will cool a room down to 55 to 65 degrees. I know high temp systems are not designed for this, but I'm hoping you guys are willing to help anyways. It will not hold any perishable items or cause any safety issues. It is just a project I need to complete. It will only run for short periods of time a few times a year. I was hoping someone could help me that has heat pump knowledge or control knowledge. I want to make sure I'm not missing anything.
As you guys know, there are problems associated with bringing the temperature down this low with a high temp designed system. I was originally going to just install a freeze stat on a straight cool system to prevent ice build up on the coils. I started to think that I might be able to incorporate a heat pumps defrost system into my application. I would basically run a heat pump defrost cycle in reverse. I'm working with an old Trane heat pump split.
Here are some of the problems I can think of:
-Trick the defrost board into thinking it is in the heat cycle.
O signal will not go directly to the defrost board. It will go to a relay (see reversing valve operation).
-call for defrost
Condenser coil sensor will be moved to the evap coil. The outdoor ambient sensor will be removed and a resistor mimicking a certain temperature will be installed. I don't really know what the exact purpose of the outdoor ambient sensor has with the defrost system.
-reversing valve
90-341 relay installed to control operation. Normally closed set of contacts will have 24v (R) going to reversing valve. The coil of the relay will be controlled by the orange output from the defrost board. When there is a call for defrost, the o signal will actuate the relay and open the contact points. This will cut power to the reversing valve putting it into the heat cycle.
-outdoor and indoor fan operation
The condenser fan will be wired directly and bypass the defrost board fan relay. The blower fan control wire (G) will go through the defrost board fan relay. It will break power to the blower relay when a call for defrost is made. The blower motor will be controlled by a 90-340 relay with a time delay board. I'm hoping a lot of the heat will be removed from the coil while the blower is on its delay, after the defrost cycle ends.
I just started thinking about this and haven't really thought about all the different issues. I might just stick with the freeze stat. Is there anything that I"m missing, or would it be better to just keep it simple?
Thanks
As you guys know, there are problems associated with bringing the temperature down this low with a high temp designed system. I was originally going to just install a freeze stat on a straight cool system to prevent ice build up on the coils. I started to think that I might be able to incorporate a heat pumps defrost system into my application. I would basically run a heat pump defrost cycle in reverse. I'm working with an old Trane heat pump split.
Here are some of the problems I can think of:
-Trick the defrost board into thinking it is in the heat cycle.
O signal will not go directly to the defrost board. It will go to a relay (see reversing valve operation).
-call for defrost
Condenser coil sensor will be moved to the evap coil. The outdoor ambient sensor will be removed and a resistor mimicking a certain temperature will be installed. I don't really know what the exact purpose of the outdoor ambient sensor has with the defrost system.
-reversing valve
90-341 relay installed to control operation. Normally closed set of contacts will have 24v (R) going to reversing valve. The coil of the relay will be controlled by the orange output from the defrost board. When there is a call for defrost, the o signal will actuate the relay and open the contact points. This will cut power to the reversing valve putting it into the heat cycle.
-outdoor and indoor fan operation
The condenser fan will be wired directly and bypass the defrost board fan relay. The blower fan control wire (G) will go through the defrost board fan relay. It will break power to the blower relay when a call for defrost is made. The blower motor will be controlled by a 90-340 relay with a time delay board. I'm hoping a lot of the heat will be removed from the coil while the blower is on its delay, after the defrost cycle ends.
I just started thinking about this and haven't really thought about all the different issues. I might just stick with the freeze stat. Is there anything that I"m missing, or would it be better to just keep it simple?
Thanks