Help! - Narcissistic Compressor Driven Fridge Thinks it's the Boss!

[Kick Ass 49]

1 hour ago, funlovincriminal said:

Don't fret - I'm not about to start undoing any pipes or anything - not a refrigeration technician by a long shot but also not an idiot!

Just wanting to learn as much as possible about what is in the boat and hopefully make a more accurate diagnosis of what is causing the issue.

If tapping or adjusting the txv (in and out but finishing back at same point as it started at) and checking location of bulb plus maybe exercising it a bit (plunging it alternately between cups of ice and hot water) doesn't cure it I'll get it replaced and regassed.

Expect a minium of a 1 boat dollar bill.....

[CarpeDiem 510]

4 hours ago, funlovincriminal said:

Don't fret - I'm not about to start undoing any pipes or anything - not a refrigeration technician by a long shot but also not an idiot!

Just wanting to learn as much as possible about what is in the boat and hopefully make a more accurate diagnosis of what is causing the issue.

If tapping or adjusting the txv (in and out but finishing back at same point as it started at) and checking location of bulb plus maybe exercising it a bit (plunging it alternately between cups of ice and hot water) doesn't cure it I'll get it replaced and regassed.

I highly recommend Nigel Calders Refrigeration on Boats book. 

It has a strong focus on engine compressor driven refrigeration and cold plates.  I found it very helpful. 

https://boatbooks.co.nz/electrics2.html#4209

[Jon 395]

Nigel Darren Kennedy is up your way and a very good fridge tech

PM me if you need his number

j

[Oldlog 11]

Hey Nigel I’ll second on Darren K. He is great to deal with…went through similar pain recently but mine was a few leaks that needed chasing down. Pain in the ass

in the end though a commercial fridge guy who was a boat owner too helped me sort it.

we put a industrial cool room temp control on the system. Probe in the fridge side set point to above freezing. So now it gets switched on and forget it. Has a manual override so you can really blast it down if you need. In the past I have destroyed a compressor by forgetting to shut it off and running at hi revs for ages

if not already I’d recommend having rubber hoses connected to the compressor before the copper starts to isolate the vibrations shaking ya copper about - I had to spend a few boat bucks to learn that lesson

personally it is worth the effort I’n my view unless your set up with solar and battery capacity that fits a freezers needs

The guy who helped me stared his apprenticeship in the 1970’s building and maintaining ice cream trolleys - those bikes that sell ice creams- they used the same system with brine etc freeze ‘‘em down and the ride town selling ice creams when sorted are super robust and will run for years and years

Nigel get a fridge guy to fix and enjoy summer of ice creams and cold beer -18 on the freezer is common on my boat

 

[Psyche 739]

From the archives, here's Matts articles on refrigeration;

https://www.crew.org.nz/forum/ccs_files/Refrigeration_For_Boats.pdf

https://www.crew.org.nz/forum/ccs_files/Engine_Driven_Fridge_Flush_and_oil_change.pdf

[funlovincriminal 194]

Thanks Psyche, yes had a read of those earlier. As always, well written and easy to follow.

Have a couple of questions, re: sight glass being full - does this mean solid liquid right up to the inside of the glass itself when running, or full to the orifice inside the unit?  I ask because mine has a conical dish above the orifice to refrigerant pipe with the word 'Full' on the tapered face. When running the liquid in the line rushes past only occasionally wetting the very bottom of this dish, never getting up to wet the bottom of the glass itself.

Second question, in Matts article he describes controlling the distance of frosting from compressor on the return line by opening and closing the adjuster on the TXV. Closing the valve moves the frost further away  or 'back up the line' from compressor. This 'closing of the valve' would mean winding the adjuster screw "in" or clockwise yes?

I ask as for some reason I have in my head that making the gap in the TXV smaller would mean that the refrigerant would compress 'harder' to get through the gap and therefore come out the other side with more energy, thereby cooling more. I guess like squeezing the end of a garden hose to spray your car down.

Interesting stuff, not quite as frightening as it first appears!

[Island Time 1,286]

TX valves are not simple (except mechanically!), as they adjust superheat. Superheat is a concept many struggle with. Here is a good article on the subject https://www.achrnews.com/articles/96890-understanding-superheat

So, in this case, what I was talking about is that the TX valve also regulates how much refrigerant can pass, and effectively slow down or speed up the flow rate in the system.  The frosting on the return line is where the liquid refrigerant is getting to before reverting to gas.

If the flow rate is too fast, liquid can get back to the compressor - cant compress liquid = compressor failure.

What you want is for the liquid refrigerant to loose most of it's cold energy in the eutectic tanks - which it can't do if it travels thru too quickly. So, you can slow the flow rate by closing (clockwise) the TX valve a bit (1/4 turn at a time) and this will move the the frosting back up the line some...

This is why refrigeration is a dark art to many!

 

[funlovincriminal 194]

So after a week of fiddling, testing and measuring it would appear I have excorised the demons from my freezer.

Wound txv in a couple of turns and back out to original position half a turn per day.

Been keeping a bunch of bottles of frozen water and hello fresh freezer packs in there and running motor freezer every day at random times, and happy to report its worked every day.

Not an easy task when not on a marina!

My jubilation at possibly saving $1000 or so was short lived this morning when I found that the knead-it repair I did on the exhaust elbow last year was indeed temporary, the raw water pump has developed a drip and the hot water cylinder has a puddle of bright red yanmar engine coolant under it.

Amazing what you pick up when sitting around waiting to measure freezer Temps every day!

 

[Island Time 1,286]

22 minutes ago, funlovincriminal said:

So after a week of fiddling, testing and measuring it would appear I have excorised the demons from my freezer.

Wound txv in a couple of turns and back out to original position half a turn per day.

Been keeping a bunch of bottles of frozen water and hello fresh freezer packs in there and running motor freezer every day at random times, and happy to report its worked every day.

Not an easy task when not on a marina!

My jubilation at possibly saving $1000 or so was short lived this morning when I found that the knead-it repair I did on the exhaust elbow last year was indeed temporary, the raw water pump has developed a drip and the hot water cylinder has a puddle of bright red yanmar engine coolant under it.

Amazing what you pick up when sitting around waiting to measure freezer Temps every day!

 

Ha ha, yep, its the time it takes that gives the poor reputation these systems have. If your prepared to learn and do it yourself, they are great and reliable once sorted, but if you pay for this, it takes time and is therefore expensive!