Queequeg- chiller question

[OG Tree Grower]

I have a 1 hp chiller cooling 700 litres of res, i know it's overkill but it was pretty much free so if like to use it.I can't get the thing to stop short cycling, I've tried several things like increasing the differential from 65-70 but I don't want to stretch it much further as I don't like them above or below that, I've added another cooling coil to a passive res I wouldn't normally cool, I've relocated the chiller a few times to see if ambient temps would change anything and it doesn't help much.
Do I have any other options other than a properly sized chiller?

 

[OG Tree Grower]

I should add the heat exchanger it self is small for a chiller this size and I believe this is a big part of the problem because my res stays 68-70 and the heat exchanger will go down to 64 because of the cooling cool inside the small exchanger , then it kicks off, 2 seconds later it warms up to the res temp and kicks back on. I can't use a bigger pump because I'm already at the max flow rate for the chiller and the heat exchanger leaks if I try to hook up a bigger pump to equalize temps between my res and heat exchanger.

 

[queequeg152]

is your chiller shutting down at the thermostat or at the high pressure cutoff switch?

there might be a problem with the chiller itself if its the latter... maby a dirty condenser coil or failed fan/missing fan shrout.


if its the former... u just have to much chiiller for reservoir duty.

why dont u just install a solenoid and divert the flow into a fan coil?

u would basically wire 2 thermostats or a single 2 stage thermostat ... first stage being your res. when the res thermostat is satisfied it opens up and the second thermostat powers your solenoid and fan coil.

excess capacity will be dumped into the air... either your home or your grow room.

how many btuh is this thing rated for?

how bad is the cycling? like 1 min on 10 min off?

 

[OG Tree Grower]

It's shutting down at the thermostat, and thanks that's a good, easy solution.

I'm not sure on the actual btu , it's a home made job. The compressor is 1 hp but the heat exchanger is the weak link, it's just 6" pipe with a stainless coil inside. I was thinking I could make the heatexchanger longer and put the thermostat closer to the intake side as a last resort. Should fix the problem

1-2 min on 7-9 min off

 

[queequeg152]

so the CHILLER heat exchanger is the one u are referring to? not your res. heat exchanger?

what you mention sounds like a typical( and wholly appropriate) non flooded type tube shell heat exchanger.

basically u flow the refrigeraant through the tube... and the jacket is full of water.

a flooded tube shell has the jacket full of refrigerant, and water flows through the tubes. theres usually something like a float valve inside the flooded evaporator to regulate the flow of liquid refrigerant.

anyway the flooded is usually seen in higher effieicy tube shells.... but for something thats probably topping out at around 24kbtuh max, a non flooded type its entirely effective and efficient enough to get the job done.

ive even seen them done with a pvc shell, and convoluted( dented or ribbed) titanium tubing wound into a single spiral ( like a home brew type beer chiller). i think this was for a salt water aquarium chiller... the water being fairly corrosive is what necessitated the titanium.

u should be very carefull with any modding of this heat exchanger. a heat exchanger of this type is prone to issues with oil flow... basically the oil charge in the system can become trapped inside the coils of your heat exchanger.

normally to combat this in very large setups there are measures to prevent the trapping of oil with oil mist seprators etc... but in a cheapo hacked together cap tube set up... oil startvation is more likely even with highly miscible POE oil...

what happens is the velocity of the vapor leaving the evaporator is not high enough to move the oil film off the evaporator tubing walls, eventually collecting to the point where the compressor is starved of oil.

without seeing this heat exchanger its hard to say whether or not its actually under sized, but 24kbtuh is not alot... it probably IS sized appropriatly believe it or not. 6" diameter pile makes me thing its probably got like 25-50 feet of 3/8 id tubing inside which should be plenty provided the flows are correct and there is atleast a little bit of baffleing action.

 

[OG Tree Grower]

Yes the chillers heat exchanger.

To be clear, my main res pumps nutrient through the chillers pvc tube and comes in direct contact with the ss316 cooling coil , it then goes into my veg room and cools another res while being pumped through another ss coil or heat exchanger if you will.

 

[OG Tree Grower]

I can easily mod the heatexchanger without messing with the refrigerant coil by simply adding a longer 6" pvc housing and relocating the thermostat to the intake side , further away from the actual refrigerant coil.

The reason I think it's oversized is because it usto cool a 10k grow without issue and ran it only ran 70-80% of the time during lights on

 

[queequeg152]

adding length to the pvc will do almost nothing. check the temp across the heat exchanger. its probably fine sized the way it is.

its just over sized. u have add more heat to the unit if you want it to run longer... or add more nutrient volume.

 

[Drop That Sound]

Hey OG, how does that temp controller on your chiller hookup? Does it bypass the old thermostat, or is it just going to a pump somewhere? Can't see any wires. If it does control the power to the unit isn't there compressor delay setting and other timings you could change? People are turning freezers into refrigerators with em..

 

[queequeg152]

Hey OG, how does that temp controller on your chiller hookup? Does it bypass the old thermostat, or is it just going to a pump somewhere? Can't see any wires. If it does control the power to the unit isn't there compressor delay setting and other timings you could change? People are turning freezers into refrigerators with em..

i use a very similar controller in my seed starting setup. its a very common johnson controls line voltage thermostat, no different than your average baseboard heater thermostat... EXCEPT that the sensor is remote not built into the units PCB.

the one i have has male and female plugs wired in... it was origionally sold as a home brew kegerator controller, but most are just hard wired.

u can set them for heating and cooling via a jumper... if i recall correctly u just set the temp and deadband. the short cycle prevention is not ajustable. its set at like 1 min? i might be off there though.

 

[OG Tree Grower]

Not positive , I will look into in in a few week when I get back down that way

If memory serves me right all it has for programming is set point , differential temp adjustment and some sort of afg shutdown feature. Again I might be wrong and I'm thousands of miles away from there right now but I will update this when I can get there