So You Want to Order a Heat Pump

What equipment should you order? What consumables should you order?

Okay, first of all, this is meant to be a guide for my internal team, but I’m going to publish it here in case anyone was curious.

Sometimes it’s easy, sometimes is actually QUITE hard, like in this case here

Generally speaking, there are 5 categories of items you need for every installation:

1. OEM Equipment. This is your Mitsubishi or Daikin-branded outdoor unit (aka condenser), or the indoor unit mini-splits or air handler. Aka the actual “heat pump”. These are manufactured by the major OEMs and have their logo/labels on them, and you can find submittals¹ that look like this which lists out their technical specs.

2. Refrigerant Lineset/Line Set². This connects the outdoor unit to the indoor units, and carries the heat that’s exchanged between inside & outside via. refrigerant. (If you are confused, watch these videos.) They come in different sizes, are made in copper, and you need to get the right line set that corresponds to the specific outdoor unit & indoor unit pairing. You can find that information on the submittal.

3. Line Cover. This covers the line set on the outside of the house, and protects it from UV radiation & the elements, which can degrade the insulation & copper line sets over time.

4. Communication Wiring. This also connects the outdoor & indoor units like the refrigerant line set, but it carries communication & power so when you press the on button for an indoor unit, it tells the outdoor unit to start working. In some cases (i.e. multifamily) in certain jurisdictions, you need special communication wiring that is extra robust (e.g. metal clad for ducted).

5. Pad & Stand. The outdoor unit heat pump isn’t just going to hover there. You need an 18 inch stand to elevate the outdoor unit so it doesn’t get buried in snow during the winter, a pad to place the stand on, and maybe some rocks/gravel to level the pad & stand because you don’t want the outdoor unit to tip over.

NOTE: this doesn’t include the electrical disconnect, which for us is out of our scope. We let our amazing electrical team take care of that.

Beyond those standard categories, you have additional materials you’ll need depending on the type of installation you’re pursuing: ductless vs. ducted swap vs. ducted (new ductwork).

Ductless

1. Condensation Drain Hose. The mini-splits will dehumidify during the summer, and the water has to go somewhere. You need a condensation drain hose (usually a clear or corrugated plastic tube) to route that water out to a safe place to drain.

Ducted Swap

1. Thermostat. You’ll need a thermostat for the air handler.

2. Sheet Metal. You need to fabricate a return plenum that fits the new air handler. You can either create it yourself with sheet metal, or you can get a pre-fabricated plenum box. Beware: the prefab ones in the dimensions you want may not be available at all supply houses, and may take a few days to get.

3. Mastic Tape + Aluminum Tape. You’ll want to tape the finished air handler setup very well so you don’t have air leaking out of it.

4. Condensate pump. You’ll need this for most basement air handlers.

New Ductwork

In general, new ductwork takes more consumables and I write all about that over here. I’ll list out the 3 main things I think about when it comes to new ductwork, but please be aware that the list (and how much these items can vary) is quite large.

1. Thermostat. You’ll need a thermostat for the air handler.

2. Sheet Metal. Everything I mentioned in the ducted swap scenario above, but you’ll need a lot more to fabricate the supply trunk, which carries freshly conditioned air to the branches (and eventually the rooms).

3. Flexible Ductwork. These are the branches that takes air out from the trunk to individual rooms (like a tree - branches come off of the trunk).

4. Takeoffs & Boots. These connect the trunk to branches, and branches to ceiling registers.

5. Condensate pump. You’ll need this for most basement air handlers.

This is the part where I tell you that this is a NON-EXHAUSTIVE list. Your specific installation tech may request more of this, or special items that aren’t on this list. This is just a good place to start that covers the main set of items you’ll need on every install.

Alright, okay. We’ve covered the main categories. Let’s move onto each of the main categories and cover more details about specific details.

OEM Equipment

The most important thing for you to know is how to find the submittals, those technical specification docs.

For us, we have the submittals attached to the scope of work generator we have in our internal Manatee platform. So, for every customer & their system design, it’s easy for us to find the technical details.

If you’re looking for them on your own, typically I like to do the following:

Mitsubishi

Mitsubishi has a great documentation website: https://www.mitsubishipro.com/catalog

You can find and easily search for every submittal. No notes, 10/10.

Daikin

Daikin’s submittals are kinda impossible to find on their own website, so I keep all their submittals in a folder on my laptop. But besides that, my favorite way to find Daikin submittals is via. Got Ductless:

LG

LG makes it easy, but you’ll need to go on the LG HVAC website (NOT the consumer-facing website) to find the submittals.

Okay, once you’re done finding the submittals³, you’ll be ready to use them to order line set. Let’s dive into that.

Refrigerant Lineset

Streamline Duraguard Lineset. This is the gold standard.

Okay, so you’ve downloaded the equipment submittal. In the submittal, there should be a section that points out, very specifically, the size of 2 line set that you need to get (gas connection & liquid connection).

So, looking at the submittal above, this particular unit needs a 3/8” gas line and a 1/4” liquid line. Those fractions refer to the outer diameter of the copper pipe — gas lines are always larger than liquid lines because gas takes up more space than liquid.

Here’s the step-by-step:

1. Estimate the total run from where the outdoor unit will sit to where the indoor unit will be. Add maybe 15% to 30% additional for slack, bends, leftover short pieces, etc. So if your total line set length is 275 ft, order maybe 350 ft worth of line set.

   1. Keep in mind this is 350 ft of paired lineset; just like how order 350 socks would give you 350 right socks + 350 left socks, you’d get 350 ft of both gas and liquid lines.

2. Round up to the next standard length. Line sets come in 50’, 100’, and 164’. Always pick the next size up rather than ordering two shorter sets; cutting 1 long line run is better than brazing/pressing 2 shorter ones together, b/c each is a potential leak point. If you’re order for 350 ft, I’d just get 2x 165 ft if available and maybe an additional 50 or 100 just in case.

3. Specify the brand and type. Ask for black Streamline Duraguard with UV protection, pre-insulated. Only fall back to other brands if Streamline isn’t available — and even then, make sure it’s pre-insulated and UV-rated.

4. Specify the pairing. Tell the supply house you want the 3/8” gas connection & 1/4” liquid connection line set pairing (sub in your actual sizes). Some supply houses sell them as paired boxes; if not, you’ll order each size separately.

5. Add line set insulation tape (optional but preferred) — a roll or two for wrapping exposed insulation around flare connections.

Contractor Language

Ordering line set for the first time is always a bit nerve wracking, since it’s so unintuitive, so here’s an example of what an installation team might ask for:

Lineset:

5x 100’ lineset 3/8, 1/4

What this means is:

Order 5x 100 ft of paired lineset, for 500 ft total. So that’s 500 ft of 3/8 lineset, and 500 ft of 1/4 lineset.

Again, the supply houses will have boxes that pair the 3/8 & 1/4 lineset together already. If you want, you can specify to the supply house that you’re looking for the 3/8 gas connection & 1/4 gas connection lineset pairing, and they should know what you’re talking about if they’re competent⁴.

Related Stuff the Install Crew Already Has

You don’t order these per job, but worth knowing they exist:

• Flare nuts & fittings — for connecting the line set on each end.

• Nitrogen — for pressure-testing the line set after install.

• Refrigerant — units come pre-charged for a standard length (see Refrigerant Pre-Charged Pipe Length on the submittal). If your run is longer, the crew tops it off on-site.

Line Cover

We typically go with 4.5” Fortress line cover. It looks like this one the outside:

Here’s another, highlighting a few parts aside from the lengths that you may need:

Long story short, you can expect a different part for every possible turn that you do. If you’re turning flat at a right angle, like the above, you’ll need a “flat 90”. If you’re turning around a corner on the side of the house, you’ll need an “outside 90” (I think).

Here’s a visual diagram:

And here’s the 5 categories:

1. Lengths. Straight sections, sold in something like 6’6” sticks. You can typically say something like “I need 100 ft of straights” and the supply house people will order it for you.

2. Elbows. For changes in direction. Three types: inside (turning into a corner), outside (wrapping around a corner), and flat (90° turn on a flat wall). Walk the run and count each type before ordering.

3. Wall Inlets. Cover the hole where the line set enters the house. One per wall penetration.

4. End Fittings. Caps for the open ends of the run. Keeps bugs and water out.

5. Couplers. Join two straight lengths together. One per joint.

You’ll want to order a bunch of extra items here, because if the crew is missing just one item, then they need to make a supply house run, which is time consuming.

Sometimes, you’ll need special ductwork for cases where you need to jump a soffit or wrap around a corner. In these cases, you’ll use corrugated line hide, aka flexible line hide:

Remember those couplers? You actually need a special type of coupler to connect flex line hide & straight line hide:

Due to this complexity, I’d say that you can probably guess about 75% of the line cover you need for a typical job, but the last 25% the crew probably has to pick up on the first day. Not the end of the world, you’ll just have to bake that into the planning.

Communication Wiring

You’d typically use something known as tray cable in most cases.

That being said, there are 3 overall options + a bonus 4th for thermostats:

1. Tray Cable (default). 14/4, sunlight-resistant, direct-burial rated, and approved for in-wall installs without conduit (per 2017 NEC). Works for the vast majority of single-family residential jobs. (14/4 = 14 AWG wire gauge, 4 conductors. The smaller the AWG number, the thicker the wire.)

2. Duckt-Strip. Required in certain juristidctions for multifamily ductless. All-in-one mini-split cable that combines power, communication, and control wires in a single jacket. Has a Rip-N-Strip feature so the crew can separate the conductors without a blade. Works for both 4-conductor and 5-conductor installs. It’s 3x the price of tray cable.

3. Metal Clad (MC) Wire. Required in certain jurisdictions for multifamily / commercial / ducted installs where code calls for extra-robust wiring.

4. Thermostat Wire. This is specifically for ducted installs with a thermostat, and 18/4 thermostat wire should work in most cases, preferably shielded & stranded⁵.

The interesting thing is that duckt strip is like, apparently manufactured by only one dude (company?) in New Hampshire, and all the electricians here know about this duckt strip monopoly. (It’s also 3x the price of tray cable!!) It’s actually kinda hard to source duckt strip; the HVAC supply houses typically won’t have it, so you’ll need to go to a place like Northeast Electrical. And even then, they may not have it close by unless you order ahead of time.

So, order ahead of time!!

If you’d like a guide on how to actually wire the system, watch this video:

Pad & Stand

All I have to say is: please make sure it’s big enough for the condenser. Daikin condensers require 1802 QuickSling stands (extra-wide), not 1801. And make sure your pad is large enough: if not, the stand won’t fit!

A 36 x 48 is probably good, though you may want to double check on that on the QuickSling website.

Okay, that’s all I’ve got! Good luck out there. If you’re a typical LC reader, I hope this at least gives you a sense of the complexity that you’re paying for when you’re getting a heat pump installed. It’s actually really hard to get it right every time, particularly if you’re juggling like 5 upcoming installations on the docket. It’s a slightly different flavor of the CFS-styled industrial procurement (set items, very long lead times) but nonetheless in the same family of supply chain/logistics/coordination expertise.

I appreciate the people who do it.

1. Submittal = technical documentation summary, typically shorter than the engineering manual but still a few pages

2. No technical difference, just spelling

3. What brand should you choose? From a performance & installation difficulty standpoint, here’s what we think:

Honest Review of LG, Mitsu, Daikin, Midea+

4. Which, annoyingly, is maybe not always the case.

5. I actually don’t have a solid perspective on this - you should ask the HVAC people; it seems like these people think you’ll run into problems if you don’t do shielded.