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problem adding (wiring) a pumpdown cycle

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vettehead

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Discussion starter · #1 ·
This customer of mine has lost two compressors in the last seven years.
(Med. temp remote unit 1 HP 208/230, 1ph, R12 coverted to Hot Shot.) Happens in winter. I'm suspecting flooded starts due to liquid migration back to compressor. Yes CC Heater is good. Told him I would install a LLS with a pumpdown cycle to help prevent the problem again. Thought I could simply wire the LLS (Sporlan dual voltage MKC-1) in series after the thermostat. However the contactor never pulled in despite LLS powered open and 40 psi low side. Tstat has 240 volts at terminals when 'open' and Yes I wired the LLS for the 240 volt version. This unit was assembled by another company long before I got there so I dont have a traditional schematic to follow. My electrical knowledge is being tested here. (Admittedly not my strongest suit) Here's the weird part... the contactor will pull in when I manually push it in and will remain pulled in until, the tstat opens again. I can't figure out how to wire the LLS. Cant see why I cant just wire in series after the Tsta. Any clues...?
 
Discussion starter · #6 ·
LPC is properly set. Prob is power isn't even making it to the LPC because the contactor isn't being pulling in. For an experiment I wired TStat back to original and all works well. (I have LLS powered temporarily through another source). It's not the LPC.

I'm wondering if one side of contactor coil is constantly powered w one leg on 110 and other side goes through Tstat. And once I introduce the LLS into the circuit it creates a shunt circuit where not enough voltage can pull the coil in. Electrical sharpies does this make sense...?
 
#7 ·
Are you saying you have the LLSV and the contactor coil in series? That is wrong. The tsat needs to control the LLSV only, and the contactor coil energized through the LPC. You still did not mention LPC values.
 
#8 ·
It wont pull in the contactor as you have it wired. Before you started, control power went from one line ,through the tstat then back to the contactor coil,correct? Then you tapped that line after the tstat and wired it to the solenoid. You dont have 240 volts to the solenoid. The easiest way to fix it is to use the power from the evaporator to power the solenoid. Tap off evap. power,take one line through tstat then to one line of solenoid. Take second line from evap. to second line of solenoid. Then make sure your low press. switch is set correctly.
 
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#9 ·
i posted in the other thread that was started :eek: :confused:

seems like a voltage drop somehwere is causing the issue. not enough power to pull in the contactor, but enough to hold it when you give it that push. :eek:

t-stat should control only the LLS and low pressure control should control the contactor outside :)
 
#10 ·
smilies said:
Are you saying you have the LLSV and the contactor coil in series? That is wrong. The tsat needs to control the LLSV only, and the contactor coil energized through the LPC. You still did not mention LPC values.
Click to expand...
Line 1 to one side of the t-stat then other side of t-stat solonoid coil other side of coil to line 2.

Compressor contactor one side of the coil to line 1, other side of coil to LP controll and other contact on LP control to line 2.

Defrost timer breaks l.l. solonoid coil.
 
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#11 ·
OH!!!

Yeah. Loads in series are a VERY bad idea on an AC circuit.

There are 2 circuits required on the control.

You need to have one for the LLSV and one through the safeties that runs the compressor.
 
#12 ·
Did you add a new contactor? I had this happen to me on a siemens contactor brand new out of the box. Old contactor went out replaced with a new siemens and it wouldnt pull in for whatever reason unless i nuged it just a hair. Checked voltage and everything. Put in a total line and it worked fine ever since. Just a bad one for whatever reason.

If its wired right one line should be a direct hot line to the one side of the coil and the other through the lp control, safties
for pumpdown. If the contactor isnt new and it pulled in before id be looking at corrosion, burns or something on the lp control contacts. Would have to be.
 
#13 ·
dangpgt97 said:
Did you add a new contactor? I had this happen to me on a siemens contactor brand new out of the box. Old contactor went out replaced with a new siemens and it wouldnt pull in for whatever reason unless i nuged it just a hair. Checked voltage and everything. Put in a total line and it worked fine ever since. Just a bad one for whatever reason.

If its wired right one line should be a direct hot line to the one side of the coil and the other through the lp control, safties
for pumpdown. If the contactor isnt new and it pulled in before id be looking at corrosion, burns or something on the lp control contacts. Would have to be.
Click to expand...
found some of them siemens contactors bad, the coil plastic melts and won't allow the contacts to close all the way. easy to pull it apart and visually see if that has happened :)
 
Discussion starter · #14 ·
thermofridge said:
It wont pull in the contactor as you have it wired. Before you started, control power went from one line ,through the tstat then back to the contactor coil,correct? Then you tapped that line after the tstat and wired it to the solenoid. You dont have 240 volts to the solenoid. The easiest way to fix it is to use the power from the evaporator to power the solenoid. Tap off evap. power,take one line through tstat then to one line of solenoid. Take second line from evap. to second line of solenoid. Then make sure your low press. switch is set correctly.
Click to expand...
That's it!! I beleive this will work. BTW...LPC is cutting in about 12 psi, and off at 4-5. It was never an issue with the LPC because I could never get the contactor to pull in when I (mistakenly) wired the darn LLS in after the Tstat. Therein lied the problem...I had two coils in series after the Tstat. The LLS and the contactor coil. Not good I now learned. Wont have the same type problem stealing the power from the evap fan circuit because those loads (fans and LLS) will be in parallel.... correct..?
 
#15 ·
Can we see a drawing of your circuits?
 
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#16 ·
beachtech said:
found some of them siemens contactors bad, the coil plastic melts and won't allow the contacts to close all the way. easy to pull it apart and visually see if that has happened :)
Click to expand...
Thanks for the tip beach appreciate it.

So you were basically wiring this so one line went through the thermostat then to the llsv then the other wire from the llsv to the lpc on the roof then to the contactor? That could cause some problems. So the contactor having a weak pull in was probably due to the voltage having to go through the llsv? Is that right. Also considering the llsv didnt have 220 out to it that wouldnt have worked.

I think you get it now just do what thermofridge said.
 
Discussion starter · #19 ·
Yea ..got it now. Went there today, wired it up as I sketched it out and WahLa ..off and running she goes. Adjusted LPC to proper sets and everyone is cool. BTW,,Customer explained he shuts off the small basement WIC in winter to save on utility. Fine ...except to do this...he pulls the disconnect which kills power to the CCH and allows refrigerant to migrate to compressor outside. Very cold here in suburban Chicago this year. For future, I informed him to simply raise the TStat to 75 if he doesn't want to use the WIC. With pumpdown now incorporated, liquid migration issues should be OVAH!!

Special thanks to Therofridge for the insight on how to get it wired. I owe ya a beer!
 
#20 · (Edited)
cch

Very nice yea lol. Im sure chicago is just as nice as Toledo, Oh in the winter and with no CCH say bye bye to oil after defrost !

ahh misread yea deffinately migration issues if no pump down is achieved also.
 
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