The Refrigeration Saga

The electrical control panel for the Grunert refrigeration

Halfway through the visit with David and Anna from Alberta, with seven people staying on board, the refrigeration refused to start after coming back from a day sail. The boat refrigeration is nothing like a home fridge; it's not a monolithic device that sits in your galley (kitchen). It's broken into components, and the components can be hiding anyplace. The cold storage units themselves are installed in the galley cabinets with access through the counter top and through the cabinet sides below. The boat was chock full of seven peoples' belongings and luggage, and this was not the time to start tearing the boat apart and locating systems. We just filled part of the fridge with ice from the marina and moved on. The ice cream, of course, had to be quickly consumed.

The first chance I had to look at the fridge system was the end of August. I thought it was under the bunk in the owner's cabin, but when I looked there it was just part of the fresh water storage and the exhaust lines for the engine and the generator. Next place to check was the aft lazarette (a storage space), port side, since the fridge and freezer are on the port side, accessing it through a deck hatch. Just sticking my head in I spotted the copper lines that carry the coolant to the fridge and freezer, and they connected to a cylinder that was attached to an electric motor by a fan belt. I couldn't get a great view sticking my head down, but I could stick my arm in and take a bunch of pictures with my phone. Looking at the pictures, the hardware was definitely the compressor, and next it it, attached by a few wires, was a white metal control box. The cover was attached by screws. No doubt about it, I would have to go down and investigate.

The hatch opening is plenty long, but only a little over 8 inches wide. The lazarette is about four feet deep, so one needs to be careful not to get wedged into the opening before the feet get to the bottom of the lazarette and could help push back out. I stepped in and my feet got to the bottom, so far, so good. Then wiggling through the hatch opening, I could get in as far as my behind, but that was it. I couldn't get into the lazarette. This was about all I could see of the probable control panel:

I checked in the boat documentation, and indeed, the refrigeration system was Grunert. The interior of the panel would remain a mystery until I could get someone else to get into the lazarrette open it.

Helga came down with me on Labor Day Weekend, she is small enough to get through the port lazarette hatch, and she was able to take off the panel cover and take the photo that leads off this article. Inside the cover is the wiring diagram:

Because there is both DC power and AC 100v power going into the panel, I didn't want Helga to be going in with a voltmeter into a completely hot panel, so I was looking for someone more familiar with electrical for that task. In the meantime, I thought about getting a spare relay and solenoid, the only two interesting parts in the box. Even if they weren't bad right now, they could be sometime down the road. Helga and I checked the fuse and the power switch already.

I hunted around online for the parts but was having difficulty because they are so old; this system was installed in 1997. I called my sort of friend Anders at Swedish Marine to see if he could help me with parts that would be currently available that might replace the parts I had. He was less interested in that than helping me just fix my system. He explained that my system was a pure DC system, except that for power to be supplied, either there had to be AC current available on board (presumably to charge the batteries) or the engine had to be creating oil pressure (presumably meaning it's running and it is charging the batteries). He told me to check voltages between terminals 10 and 1 (basic power available), 9 and 1 (either AC power or oil pressure), and 8 and 1. He said that if all those were good, check voltage between 2 and 4; if that was good the issue was bad brushes in the compressor motor.

So I had marching orders, I just needed to find someone who could handle a voltmeter on a live panel AND could fit into the lazarette through the hatch.

I contacted my friend Kevin who is also the former owner and maintainer of Green Rosetta. He told me he didn't know much about the refrigeration system, but that the starboard lazarette hatch was just a little bit wider than the port hatch, and he could fit through it if he really worked at it. The challenge then is to get from one side of the lazarette to the other, past the steering and autopilot hardware, and the lines for the deck and cockpit drains. He also told me that whenever possible, he had his spouse, a petite woman, do the work in the lazarette.

Armed with a little bit more information, I gave the starboard lazarette hatch opening a try. Stepped down into the lazarette. Check. Got my behind through the opening. Check. Got my belly through the opening. Check. Get my chest through the opening. No, sort of stuck. OK, exhale fully and try again. I got further in but then got semi stuck again, only I couldn't inhale. Panic. Pushing on the deck with my elbows too come back up. Nope. More panic. Push with the legs, carefully. Nope. Push with the legs pretty hard. Maybe. Stomp with the legs in bursts. Yes, bit by bit. I came back up, pretty bruised and scraped. I'm not trying that again. I think I may be just a hair bigger than Kevin, in the chest.

My sailing buddy Frank subsequently volunteered for the refrigeration investigation and lazarette duty. Frank is older than I am and slightly less spry, but he is at least my equal in troubleshooting and surpasses me in system knowledge and in being careful. Most importantly, he is more slender.

Frank checked voltages; good at ten, good at nine, no voltage at eight. So it was the "HP" switch, or maybe there was actually HP, which we took to mean "high pressure".

I took a trip to Swedish Marine and caught Anders as he was walking out the door. I walked with him toward his car, and let him know who I was. It had been a few weeks, but he still remembered our exchange. I told him no voltage at eight. He turned around and we both walked back into his shop. He handed me the replacement high pressure switch that mounts on the compressor. I said that since this involved sensing coolant pressure, I wouldn't be able to do it, not consumer replaceable. He continued walking out but said there is a valve that closes the sensing port, so it is consumer replaceable. I asked him about paying for the part, he said he was on his way to Sweden, and we would settle up when he got back in a few weeks. Wow, one thing actually went right. I caught Anders before he disappeared for the better part of a month, he had the part, and it was consumer replaceable.

The next day Frank successfully installed the replacement high pressure switch, with a little bit of trial and error on how the valve that closed the pressure sensing port worked. Success, we have refrigeration! Reflecting on that high pressure switch, I think it is the basic on/off switch for the system. Downstream from the compressor are two coolant valves controlled by thermostats from the fridge and freezer. If either of the valves opens because the temp is high enough in the cooled compartment to trigger it, pressure drops as the coolant is pushed to the cooled compartment and the compressor turns on if all the other requirements are met. The compressor runs while the cooled compartment thermostat closes the coolant valve. Pressure builds up and the compressor turns off. Elegant.

Collateral damage: In my trip into the starboard hatch opening of the aft lazarette, I stepped through the 3 inch hose that is the drain hose for one of the cockpit drains. The hose used for this is exhaust hose and is supposed to be very solid, including a spiral steel wire for extra strength. Completely decomposed. Part of the main exhaust line is in almost the same shape.

A three inch diameter opening directly from the outside of the hull to the inside, barely above waterline.

Yes, I stepped on it, but this hose has seen better days.

This was actually a bit of luck. If I had taken Green Rosetta into following seas that were breaking on the stern eight inches up from the waterline, water could have gone directly from the drain hole into the hull. Even if the bilge pump could keep up and it wouldn't be a sinking hazard, salt water would be spraying all over the steering system, the refrigeration system, the HVAC system, and getting into the nav/comm electronic network connections. The next big task is to replace the cockpit drain line, and the section of the main exhaust from the anti-siphon loop to the exhaust port.

Thanks to everyone who helped or offered advice in this project, including Sheldon, who didn't make it into the details of the narrative but offered good suggestions and also didn't fit through the port lazarette hatch opening, and to Dan who wasn't wrong about it NOT being an issue with the relay or the solenoid.

< Previous Article   Next Article >