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Defrost Termination
I have an older Heatcraft walkin freezer that has had many hands in it. The timer is a 208v. The X wire is disconected from the timer because it is powered at 114v all the time. There are two evaporators in the freezer. Both evaporators have two DTFD’s. One Ranco and one SL5709. It looks like the Ranco is OE and the SL5709’s are add ons. The Ranco DTFD’s terminate on the block 3,4,X. The SL5709s are wired separately. The fan wire is not used on the SL5709s. I havent traced anything yet but I am wondering why they chose to use two DTFds for each evaporaror. By the way I know at least one Ranco is bad. Any ideas are appreciated. Thanks, Rich
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2 Replies
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It has to have a protection on both evaps because it cant be guaranteed that both evaps will be at same temp when the heaters are on.
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You must have one of the low overhead units with a center evaporator. The 114 volt feedback is through the coil. They are not using a neutral. That wire is to terminate defrost after the coil is above defrost and minimalize added heat into the box. It trips a solenoid in the Paragon timer. Provided it’s the right timer.
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