Ductless Mini Split Heat Pumps

Darren Wright

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We're getting ready to have some structural issues fixed on our home. Basically we have a loft area where the main beam across our lower level sags about 1 1/2" in the center of a 15' span. The contractor is installing a steel beam in place of the original wood beam, then also closing off the loft area to add additional square footage upstairs.

In installing the beam, it will be cutting off part of the duct work for our sunroom on the back of the house. I've got a couple of options for re-ducting that area, but the bids came back about $2000 (about $300 materials/$1700 labor).

I spoke to the HVAC guy about other options. He originally suggested doing a PTAC unit, which is much like the ones you see in hotel rooms sticking out through the outside wall. This would require framing and electrical run to the location we install it at, coming in at about $2000 also. My first thought about this type of system is that I've never, ever slept well in a hotel room, mostly due to hearing one of those units run all night, let alone watching TV over the noise.

I asked about the newer style of ductless mini splits where there was still an outside unit and only a hole to drill through the wall to run the freon tubes and electrical to. He came back with an estimate of $4000 - $5000 for one of those setups.

I think after a little research, he simply isn't going to make money on those, so doesn't bother pushing them. However, I'm finding that there are several companies selling DIY setups for the mini split systems and even the borgs sell them. They come pre-charged and the lines have special fittings on some where they've already pulled vacuums on each unit to make installation go quickly. I do have vacuum gauges and a pump, so I'll probably vacuum the system anyway and let it hold overnight to check for any leaks.

https://www.youtube.com/watch?v=G2CfLLRKi68

I think I'm actually looking at about $1200 - $1500 for one of these, and the installation should be pretty easy. Only have to run electrical to the outside unit, which back feeds to the wall unit. It's mostly supplemental to our downstairs to help with cooling and heating in addition to the main HVAC and the pellet stove.

Just curious if anyone has done one yet or not?
 
My sister and BIL have a couple of those types of units on their house. They had them installed at the same time they replaced their furnace with a combo heating/cooling unit. (They abandoned their evaporative cooler.) Don't know anything about the installation, but they've been happy with the units.
 
Ya probably know I was a HVAC contractor for 20 years by now. :p

The ductless splits are great, I'd highly recommend a pro installation with field installed lineset.

If you do decide to go DIY, the linesets would not only be pre-evacutaed, they would also be precharged. I notice you said you'd probably evacuate anyway - that won't work. If you do that you'll just dump all the refrigerant that's in the unit and either have to recharge it yourself or have someone do that. You have to be very careful with precharged linesets for 2 reasons: length and kinking. The kink goes without explanation, you kink it off and don't notice and it's toast. As for length, assuming it's not too short - it's probably going to be too long. You can't have vertical coils or they will trap oil and the compressor will be short for this world. You'd have to have any extra coiled up horizontally (picture an old moonshine still) so that oil can return to the compressor. If the lines are left the way they are in that video all coiled up vertically behind the unit they'll be selling a lot of replacement compressors!

If none of that scares you, it will certainly work and looks like a great option!
 
Ya probably know I was a HVAC contractor for 20 years by now. :p

The ductless splits are great, I'd highly recommend a pro installation with field installed lineset.

If you do decide to go DIY, the linesets would not only be pre-evacutaed, they would also be precharged. I notice you said you'd probably evacuate anyway - that won't work. If you do that you'll just dump all the refrigerant that's in the unit and either have to recharge it yourself or have someone do that. You have to be very careful with precharged linesets for 2 reasons: length and kinking. The kink goes without explanation, you kink it off and don't notice and it's toast. As for length, assuming it's not too short - it's probably going to be too long. You can't have vertical coils or they will trap oil and the compressor will be short for this world. You'd have to have any extra coiled up horizontally (picture an old moonshine still) so that oil can return to the compressor. If the lines are left the way they are in that video all coiled up vertically behind the unit they'll be selling a lot of replacement compressors!

If none of that scares you, it will certainly work and looks like a great option!
Thanks Robert. What's your opinion of the ptac units in regards to noise?

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Thanks Robert. What's your opinion of the ptac units in regards to noise?

Sent from my SM-G920P using Tapatalk

The newer PTAC units are quieter than the old ones but you still have a compressor in a metal sleeve attached to your room so they will always be a 'well-built' window unit. You can usually find decibel ratings on manufacturer websites and that makes comparison easier. The ductless splits are very quiet as there is only a fan inside.

If you didn't have optimal conditioning of the space prior to making this change then I'd certainly consider adding new equipment as that will improve the zoning control and better meet the heat loads of that area. If the comfort was great before the duct change, it is worth considering investing in the duct-work modification; adding equipment increases future energy and maintenance costs.
 
The newer PTAC units are quieter than the old ones but you still have a compressor in a metal sleeve attached to your room so they will always be a 'well-built' window unit. You can usually find decibel ratings on manufacturer websites and that makes comparison easier. The ductless splits are very quiet as there is only a fan inside.

If you didn't have optimal conditioning of the space prior to making this change then I'd certainly consider adding new equipment as that will improve the zoning control and better meet the heat loads of that area. If the comfort was great before the duct change, it is worth considering investing in the duct-work modification; adding equipment increases future energy and maintenance costs.

Thanks Robert, Heating is mostly the issue, seems all the cold air in the house goes down there anyway, but we have the pellet stove for that. If/When we move forward with our plans to add an addition, the space will probably be used less anyway. It may be a MIL suite in the next few years, so may address it then. Thanks again! :wave:
 
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