Economizer, thermovalve

[benji]

Hey guys i know its been a while, been hectic never the less i have a problem or rather an issue where there is no liquid in the economiser, but the liquid make up solinoid is energised and there is liquid feed to the economiser. i have previously changed the power head of the thermo valve and orifice and it worked. the economiser started filling up and controling but now there is no ammonia in the economiser :rolleyes: ANY IDEAS?

[US Iceman]

Is there any ammonia in the high pressure receiver? What is the liquid level in this?

[Grizzly]

Yep!
I would follow up on Icemans suggestion.
If there is insufficient refrigerant in the receiver then there would be no liquid seal within it.
Resulting in flash or hot gasses supplying the economiser make up.
Grizzly

[benji]

yes there is liquid in the receiver its a high side float system but it is controlling on level. i fitted a gauge on the pilot line today to monitor the pressure or liquid supplying the economiser. adjusted the thermo-valve but still no liquid which means no sub-cooling.

[US Iceman]

If you have liquid in the high pressure receiver how can you not have liquid at the economizer? The liquid for the economizer comes from the receiver, unless your system is set-up in a unique configuration I have never seen.

It sounds like your economizer is using a heat exchanger where a TXV feeds the heat exchanger to cool the liquid refrigerant flowing through the heat exchanger.

What is the liquid temperature entering and leaving the economizer?

Stop adjusting the TXV. You have other problems.

[benji]

on your liquid make up line to the economiser you have a thermovalve ok. there is no heat exchanger on the system, the liquid coming from the receiver goes into the economiser, gets sub-cooled and back out to the accumulator via a pmfl1-82 with a needle valve controling the flow to the accumulator. the temperature leaving the ecconomiser supplying the accumulator is exactly the same

[NH3LVR]

By thermo-valve could you mean a Sporlan Levelmaster?
It is almost the same but has a heater in the well with the bulb.

[US Iceman]

If the economizer is not a heat exchanger type, then it is a flash type economizer. This means the economizer pressure is at the side port pressure of the screw compressor. If you have liquid in the receiver and you are not getting liquid to the evaporator, what is the economizer tank pressure and what is the evaporator pressure?

If the compressor is unloaded so that the side port is uncovered the side port pressure will be at suction pressure, which is almost the same as the evaporator pressure.

If the flash tank is at suction pressure, no flow would result into the evaporator and could appear as if there is no liquid available from the economizer!

The economizer should have a back-pressure regulator on it to control the economizer pressure to provide sufficient pressure to push the liquid into the evaporator.

[benji]

it is a TEVA (danfoss) and yes there is a heater on the top side of the economiser

[benji]

Well yes it doesn't have a back pressure regulator but there is a discharge of hot gas supplied to the HP receiver putting downward pressure on the liquid feeding the accumulator through the pmfl 80-2 danfoss control valve and the hp piloting this valve is controlled by the hp float so when the level in the hp receiver rises the pilot pressure to the pmfl 80-2 is de-energized and thus the piston in this valve is forced upwards by the hp pressure in the receiver, thus feeding the accumulator. The economiser gets its feed from this line as well through a Hansen hs8a solenoid valve then through the thermo-valve, then into the economiser. The pressure on the intermediate is 1.0 bar same as the side port of the screw which is obvious.

[RANGER1]

benji , you have to check heater in TEVA power element bulb as this heats up to open valve , to control level in economizer .
If it is ok ( which is unlikely ) check solonoid by manually jacking open , perhaps even clean strainer before it .
When you changed orifice in TEVA is it correct size ? What size is it ? ( check on old orifice , it will have eg TR 80 for example ) .
When you changed orifice did you remove old alumimium sealing ring . If you have 2 in it orifice wont open enough due to power element pin not having enough travel.
The system you have would be seperate vessel whith HP liquid running through a coil being subcooled . Vessel has level in it contolled by danfoss TEVA ( equivilent of sporlan levelmaster ). Suction goes to screw comp economizer port .

[benji]

yes the heater is staying on, meaning its calling for liquid. The orifice is TR12 and yes i did remove the alluminium washer. Could it be that the system is short on refrigerant and there is not enough liquid to supply the economiser, the bulls eye level sight glass is iced to the second one which means theres enough liquid in the accumulator...... Because it being an HP float system and the level is controlled by this HP float it will drain off all the access liquid from the HP receiver when the level risers, supplying the accumulator leaving nothing for the economiser? any ideas....

[RANGER1]

Solonoid , strainer on economizer liquid feed restricted ?
Do you have t/syphon oil cooler off liquid reciever ?
If you do its unlikely level is low in reciever or oil temp would rise dramatically .
Is economizer feed into comp definately 1 bar ? Can you jack open check valve or pressure regulator on this line ?
Could it be full of oil , maybe oil logged .
Are you getting any subcooling of liquid line at all ?
You have a sight glass on liquid reciever , is it roughly at centre of SV danfoss float ?
Have you adjusted TEVA , if so i would suggest putting back to factory setting .
Can't think of much else at the moment

[benji]

yes the liquid is in the center of hp float. yes im getting sub-cooling but not much. Its possible it could be full of oil. Well to my knowledge, you suppose to be getting a rise in pressure of one bar on intermediate pressure at the moment its at suction pressure which is at -40 on the gauge, which could mean low on refrigerant. When your liquid enters the economiser it should start flashing resulting in rise in pressure on the intermediate which is not happening.

[RANGER1]

The economizer appears to be low on refrigerant , not the liquid reciever .
Its a critically charged system with all excess ammonia in accumulator .
If reciever is low t/syphon oil cooler will not work .
Drain oil first to see what you have .
Maybe pull TEVA out with heater still on and you should be able to blow through it with compressed air or similar or something is wrong . Go from there .

[benji]

Thanks mate i think its low on refrigerant i know the thermo-valve is working its new the only thing thats bothering me is the accumulator, it has 3 level sight glasses and two are iced up maybe its just because the liquid is just below the first sight glass and the compressor is sucking off the vapor thats why the second glass is icing up too. i don't want to over charge the system although the intermediate should be sweating back which its not.

[RANGER1]

Let us know what you find for interest

[benji]

Will do thanks for your interest.

[benji]

Hey guys it was a shortage of refrigerant!

[RANGER1]

Thats good but i can't understand it , any theories ?

[US Iceman]

Hey guys it was a shortage of refrigerant!

That's what we have been trying to say.;)



Is there any ammonia in the high pressure receiver? What is the liquid level in this?




If there is insufficient refrigerant in the receiver then there would be no liquid seal within it.
Resulting in flash or hot gasses supplying the economiser make up.




The economizer appears to be low on refrigerant...


Look for the simple things first.:) The answer was right in front of you all the time...



yes the heater is staying on, meaning its calling for liquid.

[benji]

The hp receiver sits above the economiser. The supply of liquid comes from the receiver through a 1 inch pipe and goes through the economiser to the bottom and comes back up and out to the accumulator through a control valve. The supply for the economiser is half inch which taps into the 1 inch line above the economizer, It then goes through a solenoid valve then through the thermo- valve and into the economizer. Because its gravity fed there is not enough refrigerant to supply all of this, there for the smallest vessel will suffer.