Ducting a MrCool Olympus Mini-Split Slim Duct System on our Off-the-Grid Home Build DIY Barndominium
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- čas přidán 22. 10. 2021
- Still learning how this all works. I originally thought four ducts per unit would be ok but was told by my HVAC guy that the unit might need more air flow to insure the refrigerant would turn from a liquid to a gas after passing through the blower coil. If there isn't enough cfm (cubic feet per minute) across the coil then not all the liquid would evaporate sending fluid down the gas line to the condenser where it is turned back into a liquid. This could lower the life of the condenser which we don't want to do. So to get around this issue I'm building a larger plenum off the front of the MrCool Olympus Ducted Mini-Split System 6" which will allow me to add several more ducts.
A 1 Ton unit needs around 400 cfm to ensure that the liquid gets evaporated. Each 4" flex duct can carry around 40 cfm so with only four ducts that is 160 cfm, a bit short of what I need. The longer the run the less cfm that same 4" duct can push. This means that I would need to add at least double the amount of ducts I currently have. Luckily after some more research I was told that a Mini-Spilt actually only needs around 250 cfm per ton and that they like to be a little restricted. Because of this I should be able to safely add only a few more ducts per unit to reach the required air flow across the coil.
Looks good good for you for getting a pro to help so you get the most out of you system. I see a lot of homeowner installs that are insanely bad and they end up paying a pro redo it. Inverter heat pumps like yours are great they don't have the inrush of current like other type of a/c or heat pump systems. They can run on most inverters and generators. I'm sure your already know this and that's why you have them.
Awesome video subscribed to follow your journey
0:55 Who told you liquid ever makes it to that air handler? If you have a mini split heat pump, the refrigerant metering device as at the outdoor unit on the little line. A solid liquid filled tube coming off of the outdoor coil (condenser in the summertime) meters through an electronic expansion valve, then through the little tube to the indoor coil. That is the reason both refrigerant lines must be insulated. In the winter, the refrigerant flows the opposite direction. Your indoor coil is the condenser and the little line is full of liquid, which then goes to the outdoor unit through the electronic expansion valve inside the outdoor unit.
Thanks for the video great content I know it's hard to do this when your trying to work.
Work has really slowed is down recently and we often feel like things are standing still but that's part of the deal when you build your own house as things tend to get put on the back burner often.
We're glad people are watching and hope they arw getting something out of it.
What is the seer rating of those Mr cools? All three running at same time was only 3000 watts?
@@denniswallace4868 advertised at 22-23 SEER. We have 4 units and it is only around 3kW. most of that is the condenser.
Dang! there is so much work that goes into building a home, especially one that size.
@@sinbads.4189 Sometimes it seems like it will never end.....
Hey man I love the video be carefull to cause to much airflow can cause the superheat to be to high and you also don't want that. Unless it's got like a txv or somthing. I like how it's a heat pump thats pretty cool
I heard that mini-splits like more constricted air. Seems like things are working as intended so far but I'll keep an eye on it. Thanks
You are all over the place. The manual should tell you what the min an maximum static restriction can be. Remember the return filter size type will effect that too. And a 4" duct can handle way more than 40cfm. Are you saying without restriction? Noise ? Pressure and leak possibility? Because length of run and turns will effect that as well.
Go off the manufacturer specifications. But really you want 5-6 " ducts and then you can adjust with a damper the flow as desired for each room based on actual performance. And each unit would represwnt a zone. these systems have a variable cfm blower that adjust based on load. Some even calculate airflow restrictions and adjust.
A larger duct gives Lower air speed, lower pressure with the same volume and is definitely quieter. Pressure on the supply side is bad will blow all your tape off your joints. Get some mastic and use panduit straps. Tape will NOT be good enough
Thanks for the tips. The unit has been running for a while now and seems to work as it should. The air coming out of the registers isn't blowing, it's more of a nice breeze. House has stayed cool all summer and warm in winter. Not planning to change any of the ducting but do need to strap the flex onto the units. The tape has held but I can see it being an issue before to long.
Thanks for watching and posting.
Hi, excellent video and very informative.around 2 minute mark there are two white controllers above the plenum- what are those. I have those in my kit but don't know what they are used for.
I'm glad you upsized these. With ducted mini splits you also have to be concerned about inches of water column. I looked at the mrsplit manual and i think it says at 45 pa you get 400 m3h. 45 pa is .18 iwc and 400 m3h is 235 cfm. You can get more if you lower the static pressure. Below .18
So. 6x 4 inch units has an area of 75 sq inches which through 100 ft of flex duct at .1 iwc is 264 cfm and 507 fpm, which is darn near perfect for that unit if I'm reading the manual correctly.
Here is link to a previous video where I talk about those controllers.
czcams.com/video/50JM8V1zhDU/video.html
So far it all seems to be working just fine, just with the thermostat was better or there was an aftermarket option available but the only ones they make do not work with ducted units like this. If you find a programable thermostat that works, please let me know.
@@Off-Grid thanks for that info. That's helpful.
Mine is a midea and it came with a basic 7 day programmable thermostat
If you find out who makes the mrcool units(I think I heard gree?) you can look through their thermostat selection as they may work
@@jl9678 I bought a Cielo Breez Eco Smart AC Controller and mounted it in the attic space. Works most of the time but because I have two run by the same ap they sometimes get messed up. To solve this I have them turning on/off at different times. Here is an Amazon link to what I bought. amzn.to/3SMu0yC
10:40 Can you fill any airflow on that supply that you brought all the way down to the floor through a 4 inch flex? I doubt you’re getting 30 CFM. If you’ll notice when you have a pro HVAC guy size your ductwork using Man D, those longer ducts are usually one size larger and R-8 insulation.
I am looking to install the Mr Cool DUCT on my house and I am concerned about the amount of pressure drop through the ducting. What square footage is your house and what are you using yours mainly for(cooling/heating or both)? My load on my house is 1.5 but my required CFM is around the high range of the 2 ton unit so I am not sure if I want to split into a multi system like you at (2) 1 tons. Are you getting enough air through your ducting? It appears small and will have a great deal of pressure drop. How many more ducts did you add? I will have a MERV 8 filter on mine so that will add a bit of pressure drop also. I would love to pic your brain of line.
Keep in mind that our house is very tight and requires less tonnage to heat and cool all 3400 sqft. I've always been told by our hvac guy that air should flow through the ducts and not blow through them meaning you shouldn't feel blow dryer at each vent. You can feel air coming out of each vent but it isn't "blowing" out like most conventional systems do. The system we have is a 4-5 ton depending on how it is set up. Right now we're on the 4 ton setting but are planning a small addition and will add another unit changing the system to a 5 ton.
I do not have anything other than the washable screen filter on the units. I had originally bought MERV filters but know that they restrict the air flow greatly and didn't want to put any undo stress on the units. Plus our HVAC guy said they really aren't needed unless you have allergy issues and if you open your windows often, like we do, then it is pointless.
We use the units for cooling but also have ceiling fans in each room. We use the units for heating on sunny winter days but typically have a pellet stove going and the radiant heat on the lower level. The house stays plenty cool during the summer but the living room get a little warmer because of the large windows we have in there. The house stays plenty warm but I had to work up some extra ducting from the pellet stove to the back bedroom. I did this by ducting it through the McCool unit so all I have to do is turn the fan on and not the whole unit. If we weren't off-grid then I'm sure we'd just run the system the whole time.
Hi, love the video. I am installing a 18k BTU concealed duct mini split by a different manufacturer, but the rules for the ducting are the same as yours. Here's my problem, because the unit is a 18k, the CFM is rated at 450. The opening on the air unit is 6" X 28". I need to feed 6 total rooms (total is 800 sqft). I have calculated the CFM for each room but I am not sure sure I can feed 6 rooms when the opening is only 6" by 28". Do I make the duct connecting to the air unit bigger so I can connect 6 openings to it?
The 6 rooms will have the following duct size to get the correct CFM: 3 registers with 5" duct and each will supply CFM (150 total), 2 registers with 7" duct and each will supply 110 CFM (220 total), 1 register with a 6" register to supply 75 CFM. So the total CFM I am splitting is 435 CFM which works well since my 18k unit is rated for 450 CFM. I just don't know how to make it work with the size of the opening on the unit
@@IADHDD I have another video that was posted soon after this one where I had to add more ducts and built out a plenum ti accomplish it. I just used the same duct board.
Here is the video
czcams.com/video/6DRN-JNgYTU/video.html
7:09 So where did you hear that ducted mini splits like to have restricted ductwork? I need to read up on that. What is the ESP or external static pressure of that unit? I’d be surprised if it’s more than 0.3 inches of water column.
Just the opposite, restrictions are never good
Also, what type of air filter do you open to use on the return?
After talking to my HVAC guy he said to just use the washable filter it came with as it is the least restrictive. Meaning the unit doesn't have to work as hard. Unless you have issues with allergens he said the MERV Filters are not needed.
If I had used a MERV Filter I would have used an 8x24 filter that I could attached directly to the return air on the unit in place of the washable one.
When you use the screen that the unit came with the coil and blower Gets very dirty over time. Not having just a basic merv 8 filter to capture some fine dust and dirt will only cause that thing load up with dust and dirt. Then the coil ends up getting mold on them in time. I've seen it many of times. When you can hold up a factory screen filter and see right through it how much dust of dirt will it stop ?
No a standard merv 8 filter won't restrict the air flow too much. It will if you only change them once a year .....
@@pineychristian Sorry I missed your reply. My AC guy told me that he has seen the same issue with these types of units. Funny though that he is also the one who told me not to use the Merv Filter. I'll be opening the units up to inspect the coils soon. The screens have never really gotten to the point they need cleaned but I'll probably do it anyway. Thanks for the advise, be it that my response is a bit late.
@@Off-Grid yea I have over 40 that I maintain in 3 of my buildings. The brand really does matter they operate the same for the most part. I've switched all my ceiling cassette on basic Merv 8 filters years ago. Saves me a lot of time on cleaning.
@@pineychristian I have the filters I initially bought. Can't remember what merv number they but will give them a shot, thanks again.
What is the yello foam insulation you are using called I need that for a project please
Duct Board. Should be able to get it at any box store. I bought it at an HVAC Supply company.
Hello friend, I wanted to know if you can help me connect mine, I already connected the ducts, I only need the electrical and the drainage
Hello, here is the playlist for the full install. I go over wiring and the condensate drains.
czcams.com/play/PLkmO_DrGWs-Kkk8YFGC-oHVSennYYOgiH.html
Please how can I get the flexible aluminum dotting hose? Can you supply that to me?
It is just 4" flex duct purchased off the shelve at home depo
@@Off-Grid ok I need it give the contact am in Nigeria
How did you know how to size your system?
Rule of thumb is 1 Ton per 500 sqft (400-600 or 500 on average). Mini Splits are a little more efficient so you could go 600 sqft per ton. Because our house is well insulated (spray foam) I went 700 sqft per ton.
One ton is 12,000 BTUs if you are sizing it that way.
So we have a 3400 finished sqft meaning I needed a 5 ton unit. We've gone through several seasons and it has been working fine. Hope this helps.
Those tapes wouldn’t last long especially on the positive pressure side.
I have had to touch up the insulation layer once already but the inside, plastic to metal, hold really well. I'm sure I'll need to zip tie them soon.
Your HVAC guy should’ve bought you a one gallon bucket of mastic and a 3 inch brush. He should know better than to give you only plain foil tape to attach takeoff and assemble a non-shiplap box for your supply plenum. You tape the inner plastic liner with the helical spring wire with foil tape, then use mastic. Then you pull the insulation and outer Mylar foil over top of it, and tape it to the return plenum, then use mastic again. Did I mention using mastic? For 30 bucks I can guarantee you it will never come apart the rest of these unit’s 10-12 year life.
You need a big tub of mastic. Seal all that stuff up
Was so looking forward to watching but the loud music makes me change the channel
Yeah, sorry about that. Not sure what happened. There are several other videos on the channel about the system and the install. Here is the playlist
czcams.com/play/PLkmO_DrGWs-Kkk8YFGC-oHVSennYYOgiH.html
How is it working out?
No issues besides the thermostat that comes with the unit is junk. We ended up buying a Celeo controller which is better but still has it's issues. But the house is cool in the summer and warm in the winter.
I would have built a full 20" long supply and return plenum for more volume and not use mold making fiber board. Built it out of metal and insulated with R8. Those 4" ducts only flow 40cfm each when hard piped all the way not using flex duct. Flex kills the flow.
Yep, you are right. I will most likely be changing the plenum out at some point. The 4" ducts are sized properly for the units though. Wish I would have done rigid pipe but it would be difficult to switch that out now.
How about consulting with HVAC guy before you run ductwork. Or better yet do you research online. You could’ve put four 6” R-8 flex supplies.
Our hvac guy said 4" was ok and the online research showed the same thing. I just needed to add a couple additional runs. The system is working fine and heats/cools the house as it should. Thanks for watching and commenting.
Those little air handlers rarely put out more than .3 inches of water column external static pressure. You need to size your ductwork, larger than what you normally would with a .5 external static pressure blower. Besides, 6 ea 4”flex ducts lose more pressure and your heat loss/gain is higher than with 3 ea 6” flex ducts. Always use R-8 insulated flex.
Do you have a finished look video?
There are several other videos on our channel about the Mini-Split system. What questions do you have?
@@Off-Grid I looked through it and couldn't really find it very easily but was just trying to see how it looked when it was all finished but I just ran into your channel so I'm not really sure how far along you are on this project
@@claytonjames4779 it was around two years ago when I installed them.
@@claytonjames4779 here is the playlist
czcams.com/play/PLkmO_DrGWs-Kkk8YFGC-oHVSennYYOgiH.html&si=rtPtvqG4J8bw3kT1
Are you willing to share your HVAC company's name that you consulted with? I'm entering this realm now!
I'd want to ask him first but all the info was basic for any qualified HVAC technician who knows how to size duct work and charge a system.
@@Off-Grid you mentioned a required CFM for a minisplit. Is this parameter specified in the technical specs? If so what is that label called?
@@SolarDrew a typical one ton unit requires around 400cfm but I've been told that a Mini-Split needs to be constricted so it is around 250cfm if I remember correctly. This was not noted on the unit and MrCool was absolutely no help when I called to ask.
I am allergic to sheet metal every time I touch them I bleed 🥲
Good one....!
I was gonna say, you forgot your plenum , should be at least 18” on those I believe
why is the music SO LOUD and your talking so soft!
Really! I'll have to watch it again. Usually the music is to soft. If you have a question about the set-up please let me know.
Lol, Yep I agree. Sorry about that. Unfortunately I can't change it now. Thanks for watching.
@@Off-Grid LOL
How do you like the air flow with the flexible duct? I’m considering 3 outlets (6”, 6”, 4”) off a 1 ton head (48k Multi5 Olympus) with solid pipe and would like your thoughts.
@@Dave-tg1pu the cfm of the unit would be around 250cfm. That duct set up is around 210cfm. The units are supposed to be constricted some so that should be fine. Adding another 4" would make it spot on.
lose the loud music
I can't now unfortunately. It was an editing error on my part. Sorry.
With no proper plenum, and using flex you'll be lucky to get 10 CFM out of each duct.
You would money ahead to hire a professional installer to install your system properly. As is, you'll never get the full capacity out of your system.
It's been working fine for some time now. Even with the weeks of 100+ temps this summer the house was cool. I had a CFM gauge and took readings when I hooked the system up and was getting around 35 cfm. Thanks for the comment but it's all good.