RTHD , oil return issues .

[CumulusMech]

I have an RTHD under contract , about five years old . Machine has shut down on loss of oil pressure twice . On the initial alarm I added two gallons of oil . Two weeks later another alarm .
The machine opperates at approximatly 60 to 70 % demand this time of year . Oil pressure drop across the oil filter is approximately 5 psig or less . Oil pressure is approx 119 psig . Oil heaters working . Condensor tubes clean . Leak checked , and charge recently weighed back due to a previous leak . Oil return gas pump is cycling normaly .
I have recently observed the liquid level sensor fluctuate between 2 and -2 causing the approach to increase and decrease by 3.5 F , the expansion valves appear to be opperating well . If my refrigerant level is not consistant would this not cause poor oil return and thus cause my oil reservoir sensor to go " dry " causing the machine to trip on loss of oil ?. I believe the replacement liquid level sensor is of new design , perhaps for a reason such as this one ? .

Your thoughts on this would be greatly appreciated .


CumulusMech

[Healey Nut]

So you added two gallons of oil , did you actually check the oil level before you did that to see if it needed it . If it didnt leak out then it didnt need it . Adding oil to an RTHD that is losing oil will make it worse and loose more oil as you will get oil logging in the evap . By adding the oil your problem is going to snowball .

[Healey Nut]

Another thought , you say the gas pump is working . How do you know ? just because the solenoids are alternating does mean its working ,the check valve could be blocked /stuck etc.
Did you hook up you laptop and run trendview to check "The Heartbeat" this is proof that the gas pump is working .

[CumulusMech]

So you added two gallons of oil , did you actually check the oil level before you did that to see if it needed it . If it didnt leak out then it didnt need it . Adding oil to an RTHD that is losing oil will make it worse and loose more oil as you will get oil logging in the evap . By adding the oil your problem is going to snowball .

Hi Graham

Thank you for your response . At the time of the alarm I was monitouring the oil level sensor . I observed the sensor go dry and then the machine shut down on oil pressure failure . The only solution to that problem was to add oil . Perhaps I added too much , perhaps one gallon or less too much . If that creats oil logging it must be a very sensitive machine . The machine btw is 300 tons . Now that I think of it , when my refrigerant level is at 0 i achieve a 1.5 F approach , which is bang on . If my refrigerant is oil logged I would see a change in approach on the evaporator .
I geuss I am hung up on the refrigerant level sensor . If the level fluctuates , like a thermostatic expansion valve temperature swing as it hunts , then could there be a problem with oil return ? .


Peace

[BillLohr]

You might want to check the condenser water temperature as well. RTHD's don't like the ware too cold. Had same problem which raising condenser water temp. corrected. As has been noted in previous threads need bypass and maybe fan control to control water temp.

[Healey Nut]

So you added 2gallons of oil and never checked the level ?????????? Big mistake with an RTHD . These machines are critical when it comes to oil / refrigerant charge .

[CumulusMech]

Another thought , you say the gas pump is working . How do you know ? just because the solenoids are alternating does mean its working ,the check valve could be blocked /stuck etc.
Did you hook up you laptop and run trendview to check "The Heartbeat" this is proof that the gas pump is working .

I have TechView , but our company laptop has the the port locked out . Its a subject of great frustration . Once i get the service manager to get off his hands and address this issue I will do this . The only access to info is the IOM off the net , thats it .
I think its time to buy my own laptop . I just get tired of dropping thousands of after tax dollars to support someone elses company and profit . I geus I have a bad attitude .


BTW the condensor entering temp is a constant 85 degrees .

[CumulusMech]

So you added 2gallons of oil and never checked the level ?????????? Big mistake with an RTHD . These machines are critical when it comes to oil / refrigerant charge .

Please read my second thread . Also could you please explain what you mean by critical oil and refrgerant charge . If I am over or under by a pound or two the machine is going to crap out ? . The charge was just weighed in . How can one gallon of oil logg refrigerant ?. You are beggining to concern me . And if the liquid level sensor is working properly then the oil scimmer can return oil back to the compressor . I must be missing something .
BTW , I did try to check the oil level . I ran the machine at 40% for 20 min , shut the machine down for thirty . However , I must have had a pessure diferential as the sight glass remained full and I could not achieve a level , and yes I must have passed some oil to the condensor , it could not have been much as the condensor valve was open long enough to check quickly and then isolated . Thats when I had to add the oil . There had to have been one alarm prior to this or I would not have checked . I will verify this in the history .

[Healey Nut]

What has the liquid level sensor got to do with oil return ???
The oil charge is much more critical than the refrigerant charge ,if you weighed it in then you should be ok . But just guessing at the oil level and adding oil without accurately checking the oil level in the sump is asking for trouble . Has someone closed the oil sump vent valve by mistake ??
Checking the oil level with a standard refrigerant sight glass is a PITA . I have a 10" long glass which gives an accurate reading every time no fooling around up and down with the glass .
Without techview and the ability to use it properly to troubleshoot all the oil system components your flying by the seat of your pants on this one .

[maxpower]

I have an RTHD under contract , about five years old . Machine has shut down on loss of oil pressure twice . On the initial alarm I added two gallons of oil . Two weeks later another alarm .
The machine opperates at approximatly 60 to 70 % demand this time of year . Oil pressure drop across the oil filter is approximately 5 psig or less . Oil pressure is approx 119 psig . Oil heaters working . Condensor tubes clean . Leak checked , and charge recently weighed back due to a previous leak . Oil return gas pump is cycling normaly .
I have recently observed the liquid level sensor fluctuate between 2 and -2 causing the approach to increase and decrease by 3.5 F , the expansion valves appear to be opperating well . If my refrigerant level is not consistant would this not cause poor oil return and thus cause my oil reservoir sensor to go " dry " causing the machine to trip on loss of oil ?. I believe the replacement liquid level sensor is of new design , perhaps for a reason such as this one ? .

Your thoughts on this would be greatly appreciated .


CumulusMech

If you had some contact info in your profile you could receive some more info you could read..

[CumulusMech]

Sorry , your right , I did not do my homework . Sooo , to heck with this liquid level sensor theory . Well then , I will get the port operational and check the machine out . I will try and examine the check valve as well . I will also look into this sight glass as the one I obtained was the standard 1/2 inch .

[maxpower]

put your email address in your profile. I could send ya some stuff.

[CumulusMech]

put your email address in your profile. I could send ya some stuff.

.
My information is up .

[maxpower]

you have mail. happy reading..

[klove]

put your email address in your profile. I could send ya some stuff.

While you're in the mood to send stuff..........




Many thanks!

[maxpower]

hmm I see a money making thing here..lol!

[maxpower]

you have mail. happy reading..

my lazy reply..haha

[CumulusMech]

Thanks maxpower . Part two got snapped up by yahoo , something about it needed to be cleaned or something . if you have the time maybe you could resend it ?
Thanks Graham for your input . If I get stumped , like flying by the of my pants, I will invite you over . For now I would like to try .

Regards to all

CumulusMech

[Healey Nut]

No problem Cumulustech ,you know where I am .

[Doesn'tPhaseMe]

These machines are critical when it comes to oil / refrigerant charge .

Absolutely 100% correct. I remember other guys going through this and the factory said DO NOT ADD ANY OIL. What guys would have to do is get an electric refrigerant pump only used for 134a and pump liquid refrigerant out of the evap into the oil seperator and let the oil heater seperate it and refill the oil level that way. Unfortuantely this process takes time, like overnight and is a PITA.

I also remember there was something about the liquid level sensor and the way some were piped in that could cause erratic reading. I cannot find the service bulliten but make sure all the piping to and from it goes up hill and does not create any type of traps. Also these machines need to be level, if it settled that could also effect your liquid level sensor. I never had one loose oil but I can't see the liquid level effecting your oil level either.