Burger 80 - Work in Progress

And I thought it was my eyes.

This is off-topic, but about the holes in the dock: those look like floats made of concrete pods joined with wood waler boards, similar to the docks at a couple of marinas I'm familiar with. If they are similar, then the pods have little diagonal cut-outs on the corners that end up making a small "hole" but it's not big enough to get a foot into. You can sort of see them in this picture:

I'm 68 feet, and I have 6 air handlers on the main deck. Two in the aft salon, two in main salon, one in the galley, and one in the wheel house. The sum of the 6 units is close to 9 tons of BTU. Having used her both in the NE as well as the Bahamas, I wouldn't subtract a single ton if I had to do it over again.

I have five staterooms below, each with their own air handler. There is also one in the ER. Total of 12 air handlers, some of which share the same control board and thermostat in the salons.

Agreed. Im running 2 x 5, but mostly just one. I only energize #2 if the need is recognized. The chiller tonnage can be outmatched by the air handler tonnage, the beauty of chillers.

My experience, best outcome is heat pump setup for most conditions. Especially for a glass boat. I'm relying on a twin 12kw heat strip setup in the loop when I need to get a boost of heat, especially in the aluminum hull. If I found I needed the extra heat more often I might be tempted to set up a heat exchange system with a diesel furnace.

Key on heat is to set the temp low. The water doesn't need to be scalding. 20 degrees is the temp delta that encourages the heat exchange to be meaningful. So that's 20 degrees above your desired temp. 70 degrees? You need 90. That isn't going to hurt anything...no, you don't need to be at the precipice of steam here...

you’d set the water heaters to maintain a specific loop temperature. The chillers would be turned off. The air handlers would do the work supplied by the glycol loop. Loop pump would keep running. KISS.

I went to 2 Force 10 stainless 20 gal water heaters. They’re more effective than a household 40 and need less power. Plus they have the internal heat loop that can share heating with your genny. Nice setup perhaps.

I think the heater volume might do the trick. Worth a shot for sure. It consumes some space but could be the trick.

My experience aboard with my electric heat cylinders for the loop, I set the water temp for the loop to run around 90 degrees. In fact I think one of the two 12KW devices turns off at 90, and the second works to keep the loop between 90 and perhaps 100. Most often only one engages once I reach operating temp in the loop. So the water is typically 85 to 95 during heat requirements. But if the room is 50 0r 60 degrees, that 90 degree transaction brings the room to 68-70 very quickly and takes the edge off the chill. Obviously all of this is personal preference. I introduced my comment solely based on the concept of "being too hot for the chillers". I don't think the chillers would be upset by seeing the loop heated to, say, 120.

I like diesel systems, especially on the aluminum boat where they can really warm the engine iron. If I went diesel I'd certainly introduce a heat exchange manifold to manage the hot water as well as the overall ER environment. I'd certainly interact the furnace with the loop to obtain radiant heat in the living areas. Nothing drives me sideways (weather-wise) like dry heat from an electric heat strip or flame.