Tayters
13-07-2011, 10:42 PM
Gentlemen I need some advice with a Dunham Bush water chiller. Not the type of thing I've had much experience on so here goes....
System in basement, part wound recip compressor, 3 heads, 1 unloader, shell/tube evaporator, condenser on roof up 4 stories, R22, 1989 vintage.
I repaired a gas leak a few weeks back and recharged, now there is an oil pressure fault.
The compressor sight glass seems empty (or full but the glass looks clear not yellowey so I think empty), system will run (suction 60psig, oil pressure about 80psig. discharge 200psig) then oil pressure wobbles before reaching suction pressure then out on oil pressure switch after a couple of minutes.
I have attatched a schematic of the oil return system and a couple of low grade photos because this is the bit I'm stuck on.
Refering to the diagram, the oil sight glass is full, sol. valve energised (valve checked and is open), 30psig at 1/4" stub, rotalok open but this 30psig appears too low to get oil pass the NRV into the hot gas line. When the system was running previously the hot gas pipe at the shell/tube was very hot all the time indicating discharge gas of some pressure constantly there. No ports to check so not sure what pressure though.
So I'm not sure if the pressure regulating valve from the discharge pipe (looks like an EPR or CPR but no markings on it) is at too high a pressure. Even if it was I'd have thought there would be more pressure on the oil return line but I'm not sure why the oil line (it's a 1/2" pipe) goes into this hot gas line anyway.
It seems the low pressure on the oil line is the fault but why it's that low I don't know. If the float was stuck in the oil sep. then why would the sight glass still be full. Maybe the oil sep is empty I suppose and oil has just collected at the sight glass as it is on a lower piece of pipe. I've given the sep a clout but no difference in the pressure at the stub - assuming here also there is a float in the oil sep. It's a small can - just bigger than a tin of beans so unsure exactly of it's construction and no details on the Danfoss site.
6869
6868
6867
There are 2 refrigerated systems making the pictures a bit hard to decipher hence the drawing. You've guessed right, the other system leaked out years back. Not sure if there was anything else wrong with it. At the riser end, the inlet to the oil sep T's directly from the elbow on the riser - no traps, it's just made up with a 1 5/8" T piece and one end reduced to 1/2"
Hmm, as I read that back with a calmer head it seems oil sep empty so oil outlet closed therefore accounting for my 30psig. So oil has got stuck somewhere in the system. Still unsure of the hot gas and oil return systems.
I'm reluctant to just go poking oil in it as there are no massive oil stains anywhere and this thing has been running to some degree since 1989 (another 30 years and Jon will no doubt be working on it!)
Any advice would be much apprieciated folks.
Cheers,
Andy.
System in basement, part wound recip compressor, 3 heads, 1 unloader, shell/tube evaporator, condenser on roof up 4 stories, R22, 1989 vintage.
I repaired a gas leak a few weeks back and recharged, now there is an oil pressure fault.
The compressor sight glass seems empty (or full but the glass looks clear not yellowey so I think empty), system will run (suction 60psig, oil pressure about 80psig. discharge 200psig) then oil pressure wobbles before reaching suction pressure then out on oil pressure switch after a couple of minutes.
I have attatched a schematic of the oil return system and a couple of low grade photos because this is the bit I'm stuck on.
Refering to the diagram, the oil sight glass is full, sol. valve energised (valve checked and is open), 30psig at 1/4" stub, rotalok open but this 30psig appears too low to get oil pass the NRV into the hot gas line. When the system was running previously the hot gas pipe at the shell/tube was very hot all the time indicating discharge gas of some pressure constantly there. No ports to check so not sure what pressure though.
So I'm not sure if the pressure regulating valve from the discharge pipe (looks like an EPR or CPR but no markings on it) is at too high a pressure. Even if it was I'd have thought there would be more pressure on the oil return line but I'm not sure why the oil line (it's a 1/2" pipe) goes into this hot gas line anyway.
It seems the low pressure on the oil line is the fault but why it's that low I don't know. If the float was stuck in the oil sep. then why would the sight glass still be full. Maybe the oil sep is empty I suppose and oil has just collected at the sight glass as it is on a lower piece of pipe. I've given the sep a clout but no difference in the pressure at the stub - assuming here also there is a float in the oil sep. It's a small can - just bigger than a tin of beans so unsure exactly of it's construction and no details on the Danfoss site.
6869
6868
6867
There are 2 refrigerated systems making the pictures a bit hard to decipher hence the drawing. You've guessed right, the other system leaked out years back. Not sure if there was anything else wrong with it. At the riser end, the inlet to the oil sep T's directly from the elbow on the riser - no traps, it's just made up with a 1 5/8" T piece and one end reduced to 1/2"
Hmm, as I read that back with a calmer head it seems oil sep empty so oil outlet closed therefore accounting for my 30psig. So oil has got stuck somewhere in the system. Still unsure of the hot gas and oil return systems.
I'm reluctant to just go poking oil in it as there are no massive oil stains anywhere and this thing has been running to some degree since 1989 (another 30 years and Jon will no doubt be working on it!)
Any advice would be much apprieciated folks.
Cheers,
Andy.