problem adding (wiring) a pumpdown cycle

[vettehead]

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...?

[smilies]

You didn't mention what the LPC is set for?

[KB Cool]

You did install a low pressure control to energize your contactor? Right

[tnbasshunter]

Yes, what is lpc set for and sounds like you may have bad contactor. With tstat closed check voltage at contactor coil. Coil may be week. GL

[crackertech]

The first thing I would do is lose the hot sh!@.Then work on the lls.:)

[vettehead]

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...?

[smilies]

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.

[thermofridge]

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.

[beachtech]

i posted in the other thread that was started :o :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. :o

t-stat should control only the LLS and low pressure control should control the contactor outside :)

[Freezeking2000]

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.

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.

[jpsmith1cm]

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.

[dangpgt97]

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.

[beachtech]

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.

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 :)

[vettehead]

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.

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..?

[rango]

Can we see a drawing of your circuits?

[dangpgt97]

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 :)

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.

[vettehead]

Can we see a drawing of your circuits?

I would love to.... just don't know how to post a sketch:rolleyes: Inform me how to upload a sketch and I'll try. I have it on paper and cant wait to get back there tomorrow to giter done. (and get my paper)

[leakcheck]

Loads in parrallel. Switchs, safeys, and, non load bareing controls in series.

[vettehead]

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!

[leakcheck]

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.

[pecmsg]

:rolleyes:

[ckartson]

When you said In series hopefully you also mean in parallel with the contactor.Also make sure that the llsv is not in the same circuit a the lpc. You want the tstat to operate the llsv and the lpc to cycle the compressor.

[ckartson]

sorry vettehead I had not read the full thread before answering, Glad you got it!

[thermofridge]

You're welcome Vette. When you get to the point that you can draw a wiring diagram for the electrician for a walk in freezer, then you have the basics down. Around here very few of the electricians understand control wiring so we always supply them with a diagram. Try this one, draw a diagram for a split groundwater heat pump with a gas furnace backup with coil in supply plenum. Sounds easy but there are some catches.

[vettehead]

Yea I've had to draw for electricans in the past. That is what I did with this problem. Once you got me the idea, I sat down and drew it. I would like to post the diagram for the benefit of somebody who asked, but I haven't seen one wiring diagram on the site and wouldn't know how to do it. I suppose I could scan the image, attach a file name to it and then, either upload, or add a link to a future posting.

[pecmsg]

vettehead
Go to the Educational Forums > System Components > Commercial Refrigeration & Supermarkets > from there the Heatcraft or Russell sites have wiring diagrams.

I sent you a fax last night with a simple diagram.