Fosters Double Freezer Help?????

[paddyaircon]

:confused: Can anyone help me? i have a fosters freezer that every three months fails from eitther, 1- overheating compressor, 2- failing to reach setpoint, 3 producing excees water in cabinet that freezes.
i have replaced compressor with manufacturers part, installed clean up dryers new liquid drier blown out caps coils and pipe work, had new evap and condensor fans controls all as they should be. AM not amateur at this lark but thgis one unit is doin me in ! After repair unit runs great down to -21 but after 3 or 4 months the gas is degraded and unit pipe work driers and internals smell of burnt oil. I have replaced the oil with correct type. kitchen ambient is 25 c so holds no probs there. Are fosters kit that bad or i jus picked up someone elses cack job? runningh pressures 15 psi suction and 250 - 280 psi head help !!!!!!!!!!!1

[Latte]

:confused: Can anyone help me? i have a fosters freezer that every three months fails from eitther, 1- overheating compressor, 2- failing to reach setpoint, 3 producing excees water in cabinet that freezes.
i have replaced compressor with manufacturers part, installed clean up dryers new liquid drier blown out caps coils and pipe work, had new evap and condensor fans controls all as they should be. AM not amateur at this lark but thgis one unit is doin me in ! After repair unit runs great down to -21 but after 3 or 4 months the gas is degraded and unit pipe work driers and internals smell of burnt oil. I have replaced the oil with correct type. kitchen ambient is 25 c so holds no probs there. Are fosters kit that bad or i jus picked up someone elses cack job? runningh pressures 15 psi suction and 250 - 280 psi head help !!!!!!!!!!!1

Hi Paddyaircon,

Couple of things, can you tell us the model number of the unit and confirm gas although assume its R404
you say you have changed the oil, this is not normally possible on a foster ?. What oil did you put in.

What driers have you put on, liquid no problems but clean up ? do you mean a suction, if so what type/size.

Fosters Kit is 99% good and reliable, as long as its blown through with ofn, vac'd well (Prefereably with a micron gauge attached) it should all go OK.

Any more info would be appreciated

Regards

Raymond

[Electrocoolman]

Intermittent Condenser fan?

[taz24]

:confused: Can anyone help me? i have a fosters freezer that every three months fails from eitther, 1- overheating compressor, 2- failing to reach setpoint, 3 producing excees water in cabinet that freezes.1

Where is the thing sited? Is it in a very warm environment like a kitchen or somthing?
I have work on these and have had them fail in simlar ways to you by genral over heating (not over three months though)

Cheers taz.

[steve-design]

head pressure is high, foster design there equipment so the head pressure is between 10c and 12c above the ambient so in a 25c ambient on R404A you should be around the 15 bar mark

do you have a E number for the cabinet?

[The MG Pony]

I'd retro fit it to a water cooled condenser. Currently a shop here has been having high failure rates do to top mounted plants and temp at ceiling hight is 30C on a cool day! :eek: So needles to say not too happy of a plant. The one dinosaur of a freezer there has a water cooled condenser and is doing peachy. So my solution was to fit them all liquid cooled clean out the oil cooler and use a needle valve to let a trickle of water flow through to cool compressor.

It may be a good solution to think if the sight warrants it, this is providing that it is a fault of the condenser and environment that it is working in.

[fowlie]

i to have had some problems with the hot gas defrost valves either passing or restricting the d
discharge and causing failures to compressors this maybe worth changing if fitted to your unit.
another problem i have came across is the capillary line getting blocked by copper fillings,it may be worth cutting it out where it is reduce from the 1/4 line
hope this can help

[Sledge]

:confused: Can anyone help me? i have a fosters freezer that every three months fails from eitther, 1- overheating compressor, 2- failing to reach setpoint, 3 producing excees water in cabinet that freezes.
i have replaced compressor with manufacturers part, installed clean up dryers new liquid drier blown out caps coils and pipe work, had new evap and condensor fans controls all as they should be. AM not amateur at this lark but thgis one unit is doin me in ! After repair unit runs great down to -21 but after 3 or 4 months the gas is degraded and unit pipe work driers and internals smell of burnt oil. I have replaced the oil with correct type. kitchen ambient is 25 c so holds no probs there. Are fosters kit that bad or i jus picked up someone elses cack job? runningh pressures 15 psi suction and 250 - 280 psi head help !!!!!!!!!!!1

Hi

Burnt oil, failed compressor means overheating. failing to reach setpoint, that could be tied to overheating.

Producing excess water in freezer, that freezes...sounds like drainage problem on defrost. Is the coil completely clear at end of defrost? What kind of defrost is being used? Is the fan shutting off during defrost?

Are these intermittent troubles, or does the unit consistently fail to reach setpoint?
Can you tell us the temperature at the discharge of the compressor?

Overheating;
77degrees ambient (sorry still working in F), assuming R404 and TD of 30F should mean head of 252. If as someone else has stated, the TD should be10-12C (always thought in terms of 30F 16C TD) That would mean an even lower head pressure. Your head pressure is too high.
Check your condensor fans, perhaps someone has put the wrong fan motor, or fan blade in the past. I have seen this a few times, when dealing with stingy customers, or places with maintenance electricians.

You mention condensor fan controls; does this unit have a head pressure control cycling the fans? This could be suspect. Try running with this bypassed and fans running whenever the compressor runs.

I know this is a bit basic, but check the fan blade housing. I have seen it a few times where the housing was damaged and installed incorrectly, allowing the air to bypass the condensor.

I have recently encountered a fridge made by True Mfg, using a condensor with a very small surface (81 square inches, but almost 4 inches thick, forget how many passes) They altered the design after one year and now go with a standard Tecumseh condensor with a surface area of 154 sq in. If you ask them for a part for this fridge they send parts for the new design and have no record of the old condensor. As you can imagine, the amount of air (face velocity) going across that tiny coil was huge, and the fan supplied for the new style condensor simply doesnt cut it. Getting replacement parts was difficult and confusing. I had to retrofit it completely. Perhaps you are facing something like this.

Does the customer shut off all ventilation to the kitchen at night? Supco makes a throw away chart recorder. I would stick one of them in there and see if the unit is facing high temperatures over night.

[Sledge]

Hi again

I have been talking about this with one of my techs. We have seen this before, I forgot. Our trouble was on a 4 door side by side fridge/freezer.

IFthe condensor is clean, the fan is correct, the fan motor is correct, the fan shroud is ok, no noncondensibles and the ambient is correct...

We figure that the problem is overcharge and cap tube is wrong sized.

The problem we took over had been going on for a long time. I don't like cap tubes, so our solution was to change the system to a tx. This required installation of a reciever.
I wasnt fully confident with this, so I also added a suction accumulator to protect against liquid slugging. Of course we installed a LL filterdrier, purged with Nitrogen, leak checked, and vacuumed below 400 microns.

I havent heard anything about this freezer since.

[lana]

I don't like cap tubes, so our solution was to change the system to a tx.

I am just like you. With cap tube the control is not in our hands (sort of speak):confused: .
Cap tube rules:mad: .

Cheers

[Sledge]

I agree, I have a lot of trouble getting a handle on what is actually happening, when a cap tube is involved.

I find that TX valves are so much easier. I try and retrofit when I can justify it.

[lana]

I agree, I have a lot of trouble getting a handle on what is actually happening, when a cap tube is involved.

I find that TX valves are so much easier. I try and retrofit when I can justify it.

Me too:D .

There are ice machines here which most of them use cap tubes. I built one with TEV and it works as I like.
Some are using cap tubes just for the cost, but I think it is not a good reason considering the benefit you get from TEV.
Cheers

[Sledge]

I understand that a new equipment manufacturer, with expensive precision equipment, can construct and charge a piece of equipment in controlled conditions, using a cap tube, that will function well and give years of service.

As a service tech, I always feel uncertainty when working on a cap tube system. In the field it is difficult to get perfect conditions, and the cap tube simply is not forgiving enough.

When I look at the cost involved to retrofit the freezer I was working on, tx=$100, LLreciver=$50, Suct acc=$35, it is a small price in an industry where there are many companies charging $100+/per hour. For the most part the time involved for the retrofit was not significantly more than to change the compressor and leave the original cap tube.

[philfridge]

Head pressure is too high causing compressor to overheat and cook thats what the burning smell in the gas is. Suspect unit overgassed slightly but more likely ambient getting too high. Ventilation in kitchen needed.