Thursday, February 6, 2014


Uh oh...
We've been going thru a cold spell here in Seattle...  several days where it never got much above freezing, and nites in the low 20's.

Tuesday morning when I got out of bed, it was 49° here in the cabin.  That's pretty cold - a few more degrees and we'd be talking about the temperature inside your refrigerator.  I lit the Dickenson and thought about it.  The heat pump was running its little heart out, but it was delivering cold air.  On the other hand, heat pumps are not known for their great temperature rise, so it could have been that the air was so cold going into the heat pump that it wouldn't be much warmer coming out.

But I had a really bad feeling about this.

I stuck a thermometer in the heat pump's air discharge - it was actually colder than the cabin!  Whoa.

Now, I need to note an event that happened in the middle of November.  It was very windy out, and the wind had a lot of easting in it.  That had Eolian shoved against the dock, hard.  And she was surging back and forth, rolling the fenders.  And as it turns out, the outlet for the water which is the heat source for the heat pump is right there by the fenders.  On that morning too, we had awoken to a cold cabin.  I surmised (correctly, it turned out) that the boat's motion had rolled a fender over the water outlet and held it there long enough for the evaporator in the heat pump to freeze up.  I waited a couple of hours and tried the heat pump again, and it worked normally.  At the time, it seemed that that was the end of it.

Thinking that the same thing might have happened on Tuesday, I shut down the heat pump and waited a couple of hours before trying it again.

But when I turned it on, it pegged the ammeter and tripped the breaker.   

<engage engineer's grey cells>

I surmised that the early December freeze-up had cracked the inner tube in the tube-in-tube heat exchanger where the freon is heated by the circulating seawater.  And that it took this long for the freon to slowly leak out.  And that when it was finally all gone, seawater got into the freon tube, made its way to the compressor and hydrostated it.

This morning (Thursday), after having had enough time to get used to the inevitability of things, I pulled the heat pump.  At the moment of truth, I cut the small copper freon line going from the evaporator to the compressor, and was rewarded with a stream of seawater.  Nailed it.

Crap.  It's junk.  But I should be able to sell that copper heat exchanger for maybe $25 as scrap.  That'll at least cover the beer that this incident has required.

So now we are heating with the diesel Dickenson and a couple of space heaters, in what is turning out to be the coldest part of this winter.  But they're keeping up; it's 70° in here.

And I've ordered a new heat pump (ℬ1.565).  This one comes with safeties for:
  • Overheating protection
  • Freeze protection
  • Insufficient water flow protection
  • Abnormal operation protection
  • Low pressure protection
  • High pressure protection
Our previous unit had safeties for:
  • High pressure protection
That's it.

The lack of low pressure protection, freeze protection, and/or insufficient water flow protection was the reason the unit started the slow-motion self-destruct sequence when the water flow outlet was blocked.

Once bitten, twice shy.  It should be here next week.


No comments:

Related Posts Plugin for WordPress, Blogger...