Installing new mini split- need advice

Reply

  #1  
Old 04-19-18, 02:15 PM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
Installing new mini split- need advice

Hey gang! Finally going to install a mini split a/c system in this old house. I had a contractor come out and quoted a 24k btu unit with 12k & 15k indoor units... Obviously that was way out of budget and planning to buy and install myself. I am an electrician with experience in most things mechanical. I have my gas certificate but don't do AC work very often (got certified at work in order to recharge our buildings AC units. )

I'm looking at blue ridge or LG, and going to go with ceiling cassettes vs wall units.
First questions center around start up. I understand the compressor comes pre-charged with 410a. Specs say enough for 170' of line set, I should be at about 100' total for both units.
I'm going to buy an inexpensive vacuum pump to evacuate the system.

Does anyone with more experience have any tips or guidance for me? Let's say I've connected all my lines and such... Where/how is the vac pump then attached? Do I also need to pressure test using nitrogen? After I do all that I assume I will open a valve on the compressor to release the 410a. Will I need to add or remove any 410a?
I have an older recovery machine and possibly gauges (if I can find them)... Can that be used to pull a vacuum? Can it be used at all with a 410a system?
Sorry if I sound ignorant, in just trying to get my ducks in a row before pulling the trigger.
Thank you!
 
Sponsored Links
  #2  
Old 04-19-18, 02:38 PM
Member
Join Date: Oct 2016
Posts: 1,294
Received 32 Votes on 29 Posts
Nitrogen and nitrogen regulator to pressurize to 500-600 PSI. Vacuum pump and micron gauge. Flair block and tubing cutter. The fitting on the unit will likely be 5/16” so an adaptor as well.
 
  #3  
Old 04-19-18, 02:43 PM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
The micron gauge checks for vacuum leaks right? I have not looked yet, but that may be the thing I won't be able to easily (inexpensively) obtain...
 
  #4  
Old 04-19-18, 02:48 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,524
Received 327 Votes on 306 Posts
Although I would consider installing a split unit a DIY project..... be sure to check out the warranty if the unit is self installed.

Since charging a home air conditioner must be performed by an HVAC technician with a refrigerant license.... the DIY administration does not allow discussions on charging in the open forums.

Sorry....

doityourself/air-conditioning-cooling-systems-charging-your-A/C
 
  #5  
Old 04-19-18, 03:21 PM
Member
Join Date: Oct 2016
Posts: 1,294
Received 32 Votes on 29 Posts
You’ll likely have $500 or so tied up in tools for the project.
And I wouldn’t use some old leaky gauge manifold either.
 
  #6  
Old 04-19-18, 06:12 PM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
Sure no problem, I understand the forum bring a diy place. How much would you expect to pay a competent contractor to do the start up for me, assuming I did the physical install myself?
 
  #7  
Old 04-19-18, 06:46 PM
Member
Join Date: Oct 2016
Posts: 1,294
Received 32 Votes on 29 Posts
Depends on who you get.
There’s plenty of guys on Craigslist that would probably hack through it for $100 cash. And you’d never hear from them again even if you had a problem and attempted to contact them.
With nitro pressure test, evacuation, possible refrigerant if needed, I’d say you’ll be out $400-$600 for startup and checkout.
 
  #8  
Old 04-19-18, 07:00 PM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
That's a little more than I'd want to spend.. but illcall around a few places and see what they say. Most likely ill end up having someone do it because as was mentioned ill spend that much in equipment anyway.

The next questions have more to do with system design. The pro came and recommended 24k btu mitMitsubi unit paired with a 12 and a 15k indoor wall units. My house is roughly 900 SQ feet, basically devided in two halves. Kitchen, bathroom bed room in one half.... Living / dining room and two bedrooms in the other half.

I'd rather use ceiling cassettes because they will 'fit' better in the rooms, and because the lines will run thru the attic and come down outside in a hidden area vs wall unit lines coming down the outside walls like you see on other houses/ buildings.

Best guess.... Is 24k (20-21 seer) the right size? Paired with 12&18 k ceiling cassettes (not available in 15k). BTW, I'm in a Chicago area suburb, so figure Midwest summers.
 
  #9  
Old 04-19-18, 08:00 PM
Member
Join Date: Oct 2016
Posts: 1,294
Received 32 Votes on 29 Posts
Need a load calculation to determine proper size. Can’t suggest proper equipment sizing based solely on square footage.
 
  #10  
Old 04-20-18, 03:14 AM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
The guy that came out from one of the biggest outfits around just did it by sq'. I know a few websites I've visited looking at equipment have had calculators that asked about insulation, windows, exposed walls, etc in order to help determine proper size.

What exactly is involved in a proper load calculation?
 
  #11  
Old 04-20-18, 04:02 AM
Member
Join Date: Oct 2016
Posts: 1,294
Received 32 Votes on 29 Posts
  #12  
Old 04-20-18, 06:54 AM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,767
Received 4 Votes on 4 Posts
Never heard of Blue ridge and Id never recommend LG anything to anyone. We have way to many issues. Fujitsu, Mitsubishi would be my go to. Are you looking at these to heat? because you will freeze with you are wanting any LG to heat your home in a Chicago winter.
 
  #13  
Old 04-20-18, 09:49 AM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
Blue ridge seems to be a company based in Chicago that rebrands other companies over run equipment, so you don't know which you'll get. That's my take...
What problems have you encountered with LG equipment? I'm not counting on this setup providing primary heat as the house has hot water heat. But I am looking forward to taking advantage of the heating feature during the spring and fall.

The HVAC contractor that recently installed a Fujitsu unit in a new addition at work is here today doing startup. I talked to him about sizing and asked if he could come and do start up. His estimate is 200-250.

He said there will be no need to remove any 410a. Unit pre-charged for 170', only going to use about 100'. Does that sound correct?
 
  #14  
Old 04-21-18, 04:38 AM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
Moving forward... I am glad to have the start up hurdle covered.

Back to equipment selection. I want to use ceiling cassettes, but the HVAC guy told me those are intended more so for drop ceiling grids in commercial spaces like a conference room or store front. The install guide says they are hung from threaded rod and although it does not specifically mention a drop ceiling it does seem like that would be the ideal situation.

Has anyone used a ceiling cassette in a regular frame ceiling (open attic above)? Any insight or thoughts?
One concern of mine would be ceiling thickness. For example the kitchen area is about 3"+ thick what with a couple layers, ceiling tiles, etc. I think this may pose a mounting and/or maintenance problem.
So, if cassettes are out we are looking at wall units. Ideal locations in each space has 'challenges'.
The kitchen area above the window is tight. Ill have to trim back the window casing some and the unit will be only 2" from the ceiling. Will this be too close for proper operation? (This is the locating quoted by the pro company).
The living room area has a good spot, but it's a boxed in space... Meaning that when I punch thru with my drain etc I will be in a blind area and need to turn and run a couple feet before emerging outside. No big deal with the line set and power cord... But the drain is concerning.
In order to get it right, I may have to open up that box area... Uggg.. more drywall work.

Ok, nuff rambling for now.... Wife says I'm over thinking this (I think she's under thinking it, lol)
 
  #15  
Old 04-21-18, 05:50 AM
Member
Join Date: Oct 2016
Posts: 1,294
Received 32 Votes on 29 Posts
The cassette units aren’t intended for a really thick ceiling. And you’ll have to put access doors all the way around the unit for maintenance purposes.
I have seen them in a drywall ceiling.
 
  #16  
Old 04-21-18, 07:56 AM
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 672
Received 19 Votes on 15 Posts
Ill have to trim back the window casing some and the unit will be only 2" from the ceiling.
Two inches may be a little too tight but may work. I had a similar situation above a closet door in the family room and was able to get 3 inch clearance by reducing the door trim.

Running the line set and drain piping through the closet was no big deal. You should be able to run your drain through the dead space without having to rip out drywall. Just drill holes on each end and stick the pipe through (pitched, of course.)
 
Attached Images  
  #17  
Old 04-21-18, 12:13 PM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
Another contractor came by today. Both companies were sent by Mitsubishi after I did an online request. This one is also a big company, also Mitsubishi diamond dealer. He sized down a bit, which I feel is correct, and spent more time talking to us about the system. He gave me a quote for the same 24k condenser, but smaller 9 & 12 k indoor units (vs 12&15). $6100 installed including condensate pumps required to put them in my desired locations and run piping up thru attic (other guy was going to squeeze them in on outside walls for easier install.). Mitsubishi has $500 instant rebate and utility company(comed) has $400 rebate, so should end up at $5200 said and done.

We will most likely go this route. So much for doin' it myself!
 
  #18  
Old 04-21-18, 12:17 PM
Member
Thread Starter
Join Date: Jan 2008
Location: West of Chicago
Posts: 314
Received 0 Votes on 0 Posts
BTW- anybody know offhand how much space is required to the side of the units? One of my desired locations has a wall on either side... If it can't fit here, ill have to use a secondary location.
 
  #19  
Old 04-21-18, 01:56 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,524
Received 327 Votes on 306 Posts
Room to the sides is not usually required for the operation of the unit but it may be a little tougher to service.
 
  #20  
Old 04-22-18, 07:12 AM
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 672
Received 19 Votes on 15 Posts
so should end up at $5200 said and done.
That price looks to be reasonable, especially if condensate pumps are included.

I would be concerned about possible noise if the pumps are to be located in or near the occupied space. The mini units are extremely quiet and having a pump come on intermittently may be disturbing.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: