A Heated Conversation
We occasionally get asked whether it is possible to run a reverse-cycle marine air conditioner (heat-pump) when the water surrounding the boat is at freezing temperatures. The answer to that is “yes, it is indeed possible”, but is it a sensible, safe, and reliable way to heat a boat in those conditions?
Most of these inquiries come from live-aboards up north, although we may well be hearing from some in Florida and other southern states in the days to come once this arctic blast hits down there also. We hear that many marinas are now stipulating that plug-in heaters are prohibited, citing insurance issues, including even the ceramic and oil-filled radiator types, which seems a little overly precautious to my mind.
For a really cozy cabin you could install a diesel-fired forced air or circulating water system, but these are expensive and complex installations that require strict adherence to the manufacturer’s instructions in order to prevent potential ventilation, exhaust, and noise issues. Then, they sit idle for half the year.
So, your vessel is sitting in freezing/frozen water and you want to use your reverse-cycle air conditioner to heat the boat. You won’t get that much heat out of it, but once it’s up and running and you have a warmish cabin, you should get around 30F higher air temperature at the air outlet than at the inlet. Just don’t stop it once it has started, as it will take forever for the system to start producing any useable heat again. A cold compressor will suck up all the heat being produced by the system for the first 15 to 30 minutes until that heavy hunk of metal has had a chance to heat up.
Under the Cover of Darkness
By necessity, this will be a truncated blog this week as my trusty laptop is going in for a hard drive transplant tomorrow so I’ll be on edge all day hoping the surgery was successful. My current C drive is 98% full, and it’s amazing how much storage solid state hard drives have these days. This little upgrade will obviate the need to replace the whole darn machine just to gain some breathing room.
I asked my IT guy for advice on the laptop issue and he came back with some options and a recommendation, which I duly followed. We at Coastal Climate Control endeavor to advise our customers on the best way to plan, install, and troubleshoot the equipment we offer and represent, but there’s always some folk that want to ignore good advice and go their own way. Why is that?
Here’s a good example, with a less-than-good outcome. My neighbor has a beautiful and probably very expensive Porsche, a real sporty beast all shiny and jet black. His house is at the corner of an intersection in our sleepy neighborhood, and he keeps it parked on the street and nearly always covers it in a matching black cover.
One night a year or so ago I came home driving our company Sprinter van, and as I turned the corner I almost clobbered the Porsche, hiding there in the dark under its black cover, having seen it only at the very last second. I mentioned this to the neighbor and suggested he put some reflective tape on the cover to hopefully prevent any future carnage, but my suggestion was shrugged off. No reflective tape materialized.
Dead Cool Battery Banks
We received an inquiry recently from a customer who is contemplating installing a large 12v (volt) AGM (Absorbed Glass Mat) battery bank, and he asked a pertinent question: Which would be better; several 12v batteries wired in parallel to multiply capacity, or large capacity 2v, 4v, or 6v cell groups wired in series to produce a high capacity 12v bank? Good question.
This customer estimates he needs around an 800 A/hr (Amp/hours at the 20 hour rate) 12v battery bank to achieve the holy grail of running his air conditioning overnight from batteries through an inverter in addition to supplying the regular daily house loads. This is a popular dream of boat owners these days, and highly achievable with the equipment we have available, and there are several battery configurations to consider. Typically it will all come down to what will fit where, so first let’s look at space constraints and then focus on the technicalities. Cost will not be considered in this article as you can’t put a price on creature comforts, now can you?