Why is my torque wrench clicking so early on the refrigerant lines?

The click on a dedicated refrigeration torque wrench can feel surprisingly light, especally on the smaller 1/4 inch liquid line. If it’s clicking way before you think it’s tight, double-check that you aren't fighting the natural bend of the copper or cross-threading the nut. You shoud be able to spin that flare nut all the way to the seat by hand before even touching the wrench. If you’re feeling resistance before it’s seated, the flare might be slightly off-center or the pipe isn't perfectly square to the valve face.

In the UK, those pre-vacuumed kits often use copper that's a bit softer than industrial grade. One trick is to tighten the nut finger-tight, then use a tiny drop of **refrigeration oil** or nylog on the back of the flare and the threads. This reduces friction so the torque wrench is actualy measuring the compression of the copper rather than the resistance of the brass threads. Once it clicks, back it off a quarter turn and then torque it again to the click. That ussually ensures the copper has seated and shaped itself properly without over-crushing the material.

Since you aren't using nitrogen for a proper pressure test, you're basicly flying blind til you release the refrigerant. Once you've followed the commissioning steps to purge the inert gas, get some dedicated **leak detector spray** on every single joint imediately. Dish soap works in a pinch but it can be corrosive to the brass over time, so wipe it off thoroughly after testing. If you see even the tiniest micro-bubble, you've got a slow leak that will eventually starve the compressor and kill the unit.

On the electrical side, having it on an internal RCD spur is common for DIY, but check if you’ve got enugh space to work if you ever need to add a local rotary isolator outside. It’s a tight squeeze by the fence, but as long as the condenser fan has enough clearance to breathe and isn't recycling its own hot air, the performance should stay stable. Just make sure those flared connections are bone dry and leak-free before you wrap them up in the insulation tape.

Totally agree on the Nylog tip—it's a lifesaver for getting an accurate read. One detail people often miss when they're working in tight spaces like that fence gap is the backup wrench placement. You’ve got to keep the valve body absolutely stationary. If you let the valve twist even slightly while the torque wrench is clicking, you aren't getting a true seat on the flare. Also, take a quick look inside the nut for any stray copper flakes from when you cut the pipe. Even a tiny bit of debris caught between the copper and the brass seat will cause a slow leak that's a nightmare to find later.

This is exactly the thread I needed to find! I’m just about to pull the trigger on a similar DIY setup for my home office and I’m literally vibrating with excitement to get it running. Those flare nuts sound like a nightmare though, definitely taking notes on the Nylog.

Random thought since you mentioned the tight squeeze by the fence—does the vibration from the outdoor unit ever make the fence panels rattle? I’m worried my neighbors will complain if it starts humming against the wood when the compressor kicks into high gear!

Those pre-vacuumed 'EasyFit' kits can be hit or miss on the factory flares. If you're paranoid about the seal, look at the flare face itself—if it isn't a perfect mirror finish, the torque wrench is just guessing. I always use a Ridgid 458R to re-flare if the copper looks even slightly wonky out of the box. Also, check your clearance to that fence. If it's under 300mm, you'll likely see discharge temps spike from air recirculation. I’ve seen Mitsubishi MUZ units lose efficiency fast in tight UK gardens becasue the hot air bounces off the timber and right back into the coil. If it’s that cramped, you might need a 45-degree air deflector.

I'm totally new to this, but the talk about 'purging inert gas' has me confused. If the pipe kit is already pre-vacuumed, why is there gas inside to begin with? Is that just to keep the pipes from collapsing or somethig? Also, I keep seeing people mention 'rotary isolators'—is that something I absolutely need for a UK install, or is the internal RCD spur enough to keep things safe?

Update: I took the advice to check those factory flares and you were right—the 1/4 inch one looked a bit scruffy. I ended up re-flaring it and used some Nylog as suggested. It feels much more solid now, though the backup wrench is still a pain to hold steady in that gap by the fence. Is there a trick to getting a good grip when space is this tight?