Case Study: Bertram 42 HVAC Replacement

Yacht-HQ recently completed the total replacement of a failed 16,000 BTU HVAC “split” system on a 1981 Bertram 42 convertible. Anyone familiar with the 42 Bertram (or convertibles in general) can appreciate that this was not a simple and straight-forward job, so we decided that we would publish this article as a representative “Case Study”.

Fast Facts:

  • Initial Estimate: $5,975.95 (includes FL Sales Tax)
    • $3,480 Parts (Condensing Unit & Evaporator Unit)
    • $1,520 Labor (Removal, Installation, and Testing)
    • $300 HVAC & Electrical Supplies
    • $285 Contingency Budget
    • $390.95 (State & Local Sales Tax @ 7%)
  • Deposit Required: $4,540
    • 100% of Parts & Materials ($3,780)
    • 50% of Estimated Yacht-HQ Labor ($760)
  • Balance Paid on Completion: $1,803.66
    • Balance of Initial Estimate: $1,425.45
    • Balance of Extras: $367.71
  • Total Actual Project Cost: $6,343.66
    • Initial Estimate: $5,975.95
    • Actual vs. Estimate: $367.71 (6.15% over budget)

As you will see below… Completing this project on-time and within 10% of our initial estimate is especially noteworthy considering the quality (and amount) of work performed.

Project Details

Most convertibles, and specifically the 42 Bertram, have split system air conditioning units. This means that the condensing unit (with the compressor) is installed in the engine room while the evaporator unit (with the blower) is located in the area to be climate-controlled. In the case of the Saloon HVAC system, the evaporator/blower is typically installed ABOVE the Saloon under the Flybridge dashboard or seating area.

Let’s start by taking a look at the evaporator/blower unit which is only accessible below the forward-facing bench seating on the Flybridge. The blower pulls air from the Saloon up into this “duct” through the green (square) air filter. This area probably hasn’t seen the light of day in several years. You can see the accumulation of dirt and the fiberglass insulation is falling apart. The duct tape is so old that it has turned into tissue paper.

Mental Note: Clean and/or replace your air filters and keep your HVAC ducts clean. Your nose and lungs will thank you.

Above: This old evaporator/blower is definitely an antique – probably original equipment from 1981.

Now the evaporator/blower has been removed, the refrigerant lines have been flushed-out and capped, and we’ve cleaned-up after ourselves.

Above: Cleaning-up only takes a few minutes… but it makes a big difference.

Here’s a better look at the prehistoric fiberglass insulation and duct tape. The plywood could also use some fresh paint.

Above: The old insulation clearly needs a little help.

We custom-fabricated a brand new evaporator/blower unit to be the EXACT SAME SIZE as the original unit. There was no “off-the-shelf” evaporator/blower that would fit properly, so we made our own.

Above: The new evaporator/blower was custom-fabricated to be an EXACT fit.

Yacht-HQ is very picky about wiring. All these wires should really have adhesive heat shrink terminals. We also don’t like to see wires leading “down” to a bus bar or terminal strip because water can run down the wire to the exact place where it can do the most damage. Wires should always lead UP (or at least have a “drip loop”).

Above: We’re very picky about wiring. This will not do.

This is what we like to see… tidy wiring, adhesive heat shrink terminals, and no wires leading drips of water to the terminal strip. We’ll put a plastic cover over this terminal strip to prevent accidental contact later.

Above: Ahh yes… Much better now.

As long as we’re here… we might as well sand the plywood and apply two coats of white two-part epoxy primer. The black insulation is 3/4″ ArmaFlex SA (self-adhesive neoprene with mold/mildew growth inhibitor).

Why ArmaFlex? We like ArmaFlex. Try it, you’ll see.

We also use ArmaFlex 1/8″ insulation on all of our refrigerant lines. We’ve even used ArmaFlex up to 3″ thick to insulate the aluminum and fiberglass hulls of motor and sailing yachts. There will be another post (or two) about ArmaFlex later on.

Above: Plywood was sanded & painted. New ArmaFlex insulation replaced “dead” fiberglass.

The evaporator/blower is nicely tucked-in to its new home. Our fabrication shop did such a good job that the pre-drilled screw holes in the new evaporator lined-up perfectly with the old screw holes in the transverse duct. Everything fit perfectly (like a glove) and installation was a snap.

We used white vinyl hull tape to re-attach the fiberglass insulation and then added some more ArmaFlex SA.

This is the part where you scroll back up to the first picture and admire the difference that quality workmanship/materials, good planning, and attention to detail can make. We’re Yacht-HQ and this is how we roll.

Above: Quality workmanship/materials and good planning make all the difference.

Now for the Condensing Unit… we’re squeezing into the engine room just forward of the STBD engine.

This is the “dead” condensing unit. Note that there is no condensation drip pan and the plywood under the unit is black and white from mold, mildew, and rot. We can only imagine what surprises are lurking below.

Above: This is the “dead” condensing unit. The plywood under the unit is badly deteriorated.

If you have read Yacht-HQ’s other posts about Air Conditioning, then you know that “condensation” is a theme that we discuss frequently. You might be wondering why condensation is such a big deal to us.

Good question. We’re glad you asked.

Condensation is a problem that MUST be carefully managed because the failure to do so can turn a very nice yacht into a stinking pile of rot in an alarmingly short period of time. Think “years” not “decades”.

Mold and mildew (collectively, “rot”) need only three things to thrive and multiply: fresh water (not salt water); warm/humid air; and some sort of “food” like wood, paper, cardboard, etc. If you have an environment where ALL THREE of those things are constantly available then you have a perfect recipe for a “science project” (aka “disaster”).

It’s interesting to note that salt water does not contribute to “rot” – at least not like fresh water does. Rain, condensation, and fresh water plumbing leaks are the three main causes of “rot” that we see. Most molds and bacteria can’t survive in salt water…at least not terrestrial, cellulase-producing varieties that cause “rot”.

That is why any place where warm, moist air might condense on a cold surface MUST have the means to collect and route condensation to an appropriate bilge or sump area. Air conditioners are major sources of condensation because (in Florida) they tend to run non-stop about 300 days per year. This is how the condensation from your air conditioner provides a nice, consistent supply of fresh water to all the little critters that are trying to eat your boat.

The “ivory” discoloration of what used to be “white” paint on the compressor strongly suggests that the compressor has been repeatedly overheated. Perhaps it wasn’t such a good idea for the previous HVAC installer/technician to mount the electrical control box DIRECTLY on top of the compressor? (see above). It’s amazing what we see when “residential/commercial” HVAC companies/technicians step outside their areas of expertise and start playing around (where they don’t belong) on yachts.

Above: The “ivory” discoloration indicates that the compressor has been repeatedly overheated.

Yep – there is definitely a “rot fest” happening under that condensing unit. Condensation strikes again. This will not do… time for a little unexpected surgery. There isn’t enough “wood” left here for us to simply paint over the rotten plywood.

Above: Removing the condensing unit reveals badly rotted plywood underneath.

Rotten wood is like cancer… you can cry about it all day long but in the end the only real solution is to cut it out with extreme prejudice and use a bunch of nasty chemicals to try to keep it from coming back. Oh yeah, and you also have to stop doing the thing(s) that caused the problem in the first place.

Above: Check out all the rotten wood “fiber” that came from the plywood section that we removed. Note the use of wooden dowels and hose clamps to plug the sea water hoses.

We made a new piece of MARINE plywood to replace the rotten section. Then we installed cleat strips and stainless steel screws to secure the repair panel. Two coats of white epoxy primer protect the plywood from moisture and make the repair look better than the rest of the engine room.

You can’t see it – but we brushed epoxy EVERYWHERE paying special attention to the “cut” edges where the new plywood meets the original plywood.

Above: We made (and painted) a new piece of plywood to replace the rotten section.

We custom-made the new condensing unit with the exact same footprint and dimensions as the original unit.

Note: Yes, the new unit has a condensation drip pan.

Above: We built the new condensing unit to the same dimensions as the original unit.

The new condensing unit was installed and secured using Starboard mounting pads to prevent moisture from accumulating below the unit. Adding this 3/4″ of height allows us to route the condensate pan drain line to the bilge without “kinking”.

We tag all of our installations with our business card so the owner knows who to call for service. The blue paper towels tied around the sea water lines help us spot leaks (if there are any). This unit was designed for (and charged with) R-407C which is our preferred alternative for (obsolete) R-22. Finally, we mounted the electrical control box on the forward bulkhead AWAY from the compressor.

Above: The new condensing unit is installed and working properly.

Now, there are a TON of other details about this installation that we haven’t covered – so I’ll summarize them (briefly, if possible) here.

  1. We flushed-out the refrigerant lines with a special chemical product that removes dirt, oil, and other contaminants from the lines. We don’t want any foreign “garbage” in our nice, new, clean refrigerant loop.
  2. We also flushed-out the brand-new evaporator just in case there happened to be any particles lurking in there. We didn’t need to flush the condensing unit because it had already been flushed and pressurized with a nitrogen holding charge.
  3. Once we re-assembled the system and tightened all the fittings we pressure-tested the system with 200 PSI nitrogen and left it sitting for 24 hours. No loss of pressure (not even 1 PSI) means that we have a tight system and no leaks.
  4. We triple-evacuated the system using dry nitrogen and then pulled a vacuum to well below 500 microns with (practically) zero vacuum decay.
    • 500 microns (0.5 Torr, 0.0007 Bar) is roughly equivalent to the atmospheric pressure at an altitude of ~32 MILES (or so) above sea level. That’s just beyond the edge of the Stratosphere and a few miles into the Mesosphere. For comparison, the jet stream is at about 6-8 miles altitude and the ozone layer is at about 12-18 miles altitude. Most meteors burn-up in the mesosphere.
  5. We charged the system with R-407C and fine-tuned the charge (over the course of a comple hours) until we achieved a steady-state of operation with a 25F delta-T and an “actual superheat” value that was within a degree (or so) of our calculated “target superheat”.
  6. We checked-out all the settings on the digital control panel (and made a few changes) so that everything was configured properly.
  7. We wrapped-up this job with our customary “finishing touches” which included: making sure that the refrigerant lines were properly insulated; replacing hose clamps and checking for proper torque; cleaning-up our work area; and removing all our tools, supplies, and equipment from the boat.

If you appreciate the quality, value, and attention to detail that you see in this Case Study then you should put Yacht-HQ on your “short list” of marine service providers. We do a lot more than HVAC work – including electrical, electronics, engine/mechanical, hydraulic, and systems engineering.

We’re the High Quality yacht specialists. Please contact us today so that we can get started on your next project.

Share this story