Stupid heat pumps
May 7th 2009 08:35 pm
So our boat is in refit right now, and even though the workload seems to be reduced in theory, it’s been more stressful than ever. I can at least be thankful that I’m no longer in Engineering Department, since it still seems like Engineering division officers are forced to spend long hours at work all the time due to some new and exciting broken part.
One thing I’ve noticed though is that pretty much every job I’ve had that’s supposed to be “easy” (especially being the Tactical Systems Officer) is a lot harder in practice, since I actually attempt to perform all the duties/responsibilities instead of just leaving things to rot. It’s fine, as I know I’m accomplishing a lot but then I worry about what the guy who relieves me is going to do. :)
Anyways, as you may have inferred from the subject the heat pump in our house seems to have broken. The refrigerant line on the outdoor coil was completely iced up (which is unfortunate given that this is only supposed to ever happen in wintertime, and it’s quickly approaching summer here).
I’ve looked it up a bit online and it seems the scenario is either dirty coils (although the ones I can see look fine), clogged coils, low refrigerant (which implies a leak), or something other semi-minor issue. It’s times like this when I really value the Navy-style fashion of having gauges and pressure switches everywhere, at least I’d have a chance at figuring out what is going on. This system has no user-visible status of the refrigeration cycle other than when the lines freeze up. :-(
Although my time has been sharply reduced between Emma, Ian, and refit I’m still working on my programs. I’ve recently committed the purge log feature I recently blogged about. It doesn’t run by default however. I’ll try to make a release tonight but I also want to make a kdemultimedia introspective for JuK so we’ll see.
mandarin on 
Kerry on 
Hmmm. It might be very geeky, but reading your blog often reminds me of the beginning of most startrek episodes: “Tactical Officer’s Log stardate ….”
I’m just waiting for the blog where you talk about observing some wheird interstellar fenomenon…
Keep on blogging please ;-)
Is it in cooling mode? and the large pipe between the indoor and outdoor is covered with ice?
If that is the case, then shut the outdoor unit off, turn the indoor unit fan on until it clears the ice on the coil. How long depends how thick it is.
The dirty coil would be the indoor one. You may have a bit of trouble seeing it, since you may have to pull the indoor coil out of the cabinet. Sometimes it can swing out on the refrigerant lines. How old is the installation? Check the filters.
Or the fan may be at too low of speed. Or just plain broken. Sometimes a fan motor cycles on internal overload, of course running perfectly fine until you step away from it. I’m sure there is some scientific explanation for that.
What is happening is the compressor is fixed volume (sorta, but for this discussion…). The refrigerant boils in the indoor coil at the rate at which it can absorb heat. The system should be matched so that if all is working ok, the temperature/pressure of the indoor coil is above freezing. But if for some reason there is restricted airflow, the heat transfer rate drops, the refrigerant pressure/temperature goes down, and it freezes the moisture from the air. And gets worse and worse until the line to the compressor shows ice.
Low refrigerant can also cause low pressure/temperature, but typically if there is ice back to the outdoor unit, you have enough refrigerant. So I would suspect an air flow problem on the indoor unit.
And yes, I do this for a living.
Derek Kite
cool, heat pumps, I wish my house had heat pumps they are much cooler that standard heating…. you know what I mean. Actually I wish my house had any kind of heating at all.
As your second reply.
Switch it off until all the ice melts – the ice can act as a bit of an insulator: reducing/breaking the feedback to the thermometer – the ice can also block the air flow. The condensate can get jelly like (from bacteria?) and not leave the cooling part during defrost.
Oil from the compressor can leak into the refrigerant and wax up in the evaporator. There is usually a small inspection window (under a dust cap) to see if the refrigerant is contaminated.