thermostats reach in coolers
im more familiar with the thermostats where the sensing bulb hangs in the return air stream and of course senses the temp inside the box (cooler). then there are the kind that the bulb touches the evap coil. and works off of coil temp im starting to see more of them on newer equipement or maybe its just me. whats the pros and cons there has to be something for them to choose one over the other one. while building these units, also i see some pieces of equipement once it reaches temp the evap fan shuts off. whats the benefit toward that. if it stayed running it provides defrost for the evap coil while off on temp. also keeps the air constantly blowing over the product in the cooler. but im sure there is a benefit to it, looking forward to hearing your input/ knowledge....
coil sensing cold controls are cheaper, smaller, and give you built in defrost: they are usually fixed cut in at around 40 to 44 degrees coil temp ensuring the ice is gone before restarting the system. Cut out is adjustable, but you can't set a temp - you pick from 1 to 9 or something and have to tweak it until everything's just right.
The only time i've seen the fans stop when the unit satisfies is in a domestic style fridge/freezer where the evap is in the freezer compartment and the fridge is supplied cold air through a duct. Or on a cooler in defrost with heaters.
A co-worker is installing some new Heatcraft refrigeration equipment in a large walk in freezer. He was telling me that the evap fans in the freezer are designed to turn off after the thermostat satisfies. He said it has something to do with a government grant or rebate or something the business owner got for getting high efficient refrigeration equipment. It doesn't make much sense to me, especially with how temperamental ecm motors that i've seen seem to be when short-cycling in a freezer environment, but whatever. I just thought I'd share. Normally you'd want the fans to run all of the time in a cooler, and all of the time except for defrost (and shortly after defrost) in a freezer.
Originally Posted by ammoniadog
De energizing the fans during the off cycle makes the unit use less energy. Whether it's right or wrong is up for discussion. Citations from the health dept generate money in my pocket.
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In most cases when the question "why would the manufacturer do that?" the answer is money. Most cases.
i have seen the same thing on true reach in freezers. first time I saw it I was stumped. I actually had to look at the wiring diagram. When I called tech support I questioned them about this. He told me me has has instructed techs to jump the fans out so they always work except when in defrost.
I like the idea, but in high traffic areas I don't see the cost savings.
Of course when the store closes and no one is opening the door, you are saving money.
I've seen plenty of True reach-in-coolers cycle fans with the thermostat, too - its usually the TUC models (undercounter) but also seen some reach-in-freezers do it. I've seen some new Delfields that do it as well, with a funny looking mullion coil evaporator with two 4" axial fan motors. My manager always tells me to modify it to make the fans run all the time on coolers.
I like trentons 2 speed ecm on their evaps, at least some air is moving in the box.
I prefer coil sensing in small reach in applications. When they function correctly its like a reassurance to have a frost/ice free coil like mentioned already. I also find it to give better overall box temp control range.. for the last 16 months i was finding a lot of what i refer to as idiots installing A30-261 air sense stats in place of defective coil sensing types. Constant freeze ups or excessively high temps on these caused constant call backs. My question to the moron installing them was how does he initially attempt to set these up after installing. He says he turns then all the way to the right then back a hair. :banghead: ...
Originally Posted by anthonyac1
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Coil sensing type. For reach in I agree. Expecially with high usage.
Fan cycling can be done for a number of reasons, but primarily for energy savings. How much is saved in a small reach in is debatable but in walk-in coolers and freezers it can be significant. Fans can be cycled on freezers to reclaim the energy represented by the frost on the coil, that is, turn off the compressor but cycle fans to use the frost to chill the room air. Even a cooler can get energy savings by cycling fans, especially when the box to shut for extended periods but also if the door is opened a lot. Turning off the fans when the door is open helps to prevent excessive frost and loss of efficiency of the coil. Although the frost can be "reclaimed" as above if the system is adaptive, a time based system will have extended defrost, times to get rid of the excess frost, adding heat perhaps not meeting room temperature. As to coil or air thermostat, why not use both..........?
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Originally Posted by BDOLIN
That would be a design question.
It seems that restaurant chains want the absolute least expensive equipment, compared to equipment that will need service less frequently. You see the same dynamic in retail HVAC.
So, the answer to your question is that a single method is less expensive, and that allows more competitive pricing to the cheapskate... (ahem) the "value conscious" customer.
I'm certain that a failed ECM motor more than makes up in replacement cost for any energy saved when it fails, and is two to three times as expensive to replace as an evap motor from say, 2004.
There is no silver bullet. It's mostly BS when one uses the words "saving" and "energy" in the same sentence.
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