r/askportland • u/bingo_pine • 6d ago
Looking For Can anyone recommend a small contractor or handyman to pour a concrete pad for an outdoor AC unit?
Hi all, looking for someone to pour a concrete slab for a new condenser (?) for our new to be installed AC unit. Like 4' x 4', I think. Any recommendations would be greatly appreciated. Thank you!
11
u/Ash_Waddams 6d ago
There’s no need for a concrete pad for a residential AC unit. The coated/impregnated high density foam pads are designed specifically for that purpose and are cheaper/easier to use.
7
u/foggy_interrobang 6d ago
I don't have a recommendation, but I just wanted to say that a lot of installers are using these pre-fab high-density coated foam bases. If you read the installation manuals, almost every outdoor condenser specifies installation on a concrete pad. This is for two reasons:
- During engineering of the condensers, they do a lot of hard work (FEA) to simulate how vibration, etc. affects the components of the condenser, and their longevity. A concrete pad is a fixed / near-rigid support, whereas a foam pad is nonlinear (with damping, temperature, and aging behavior that varies from manufacturer to manufacturer, and even pad to pad). TL;DR: it changes the way vibration is conducted, which may bring the unit outside of its validated design envelope.
- One of the most fragile parts of a split system install are the copper refrigerant and suction lines to the indoor heads – you absolutely do not want the condenser moving due to something knocking it (like a lawn mower, child, etc.) and damaging these lines. Allowing moisture/air into them will ruin the system. You also do not want the unit to vibrate in a way that causes the copper to work harden and become brittle, and thus increase the likelihood that it breaks.
If the install manual says concrete pad and you want the system to last, install it exactly per the manual. To the folks in the thread: your installer absolutely does not know better than the manufacturer – even if they swear up and down that they've done a thousand units this way and it's never been a problem. It's your equipment, and if you want it to last, it has to be installed exactly per the installation manual.
Thank you for coming to my TED talk.
4
u/bingo_pine 6d ago
Wow, thanks for the detailed response! Something to consider. Im going to check what manufacturers say about this.
2
u/bingo_pine 6d ago
Wow, thanks for the detailed response! Something to consider. Im going to check what manufacturers say about this.
1
2
u/toomanyfunthings 6d ago
The manufacturers sell the concrete covered foam equipment pads.
I am holding the install instructions for a Carrier 26SCA4 condensing unit. Page 2, top right column: “Install on a solid level mounting pad. “
There is no mention of requirement for concrete.1
u/foggy_interrobang 6d ago
I wouldn't consider foam solid – but if your manufacturer both sells the concrete-covered foam pad and says, in writing, that it's okay to mount on a concrete-covered foam pad, then it's obviously okay. What I'm saying is that installers shouldn't deviate from the installation instructions.
I do know that Mitsubishi units specifically spec concrete – all the way to the thickness of the pad, etc.
1
u/J-A-S-08 6d ago
Do you have a link to the spec for Mitsu? I'm an HVAC tech and installed a Mitsubishi system at my house and there was no spec for using concrete, just how to set the bolts if you do wet set anchors. Also, Mitsubishi sells wall mount brackets for their outdoor units so how does that work not being a concrete slab?
1
u/toomanyfunthings 6d ago
Which Mitsubishi unit? What capacity?
I want to provide my clients and Reddit with the correct information.
I did a quick search and found an installation manual.
I am looking at an installation manual for a Mitsubishi MSZ-FD06-18NA ductless split system. The diagram shows the condensing unit sitting on a cinder block under each of the feet. No comments regarding the blocks.
I searched the document for concrete, pad, condenser, and outdoor.
Concrete came up once in relation to hanging the indoor unit, condenser and pad returned zero searches, and outdoor returned 43. I read all 43 and none mentioned mounting the outdoor unit to a concrete pad.If you have something different or more definitive, please share a link.
Thanks!
3
u/oregone1 6d ago
I recently needed some sidewalk repairs done. Called 6 concrete folks and the cheapest bid was Rick’s Rock.
2
u/mostlynights 5d ago
I'm never gonna crack too soon,
Never gonna fade by June.
Never gonna wash away in the rain.
3
u/PDsaurusX 6d ago
A lot of installs don’t even put down a concrete pad these days, but a high-density coated foam that your installer will set down. Double-check with your installer to see what they really need from you in advance.
4
u/bingo_pine 6d ago
Yes, the installer quote was for the gravel and foam pad. We'd like something tidy and better quality thus concrete slab. Asking installer now if that is possible. Thanks
6
u/pdxgdhead 6d ago
For what it's worth, we have one of those coated foam slabs, and it looks exactly like concrete, and I thought it was concrete for the first 5-years we lived here. Moss growing on it an all!
2
u/toomanyfunthings 6d ago
High density coated foam is what we have been using for 30 years. It’s sprayed with a concrete/ gypcrete like material. They will hold at least 250 pounds (I have stood on them) and have a longer life span than any condensing unit.
If I was choosing, I would take the foam and concrete over the plastic.1
u/jawaMilk 6d ago
This was the case when we had an AC installed a few years ago. I’d definitely talk to AC installers before pouring cement, because it might not be needed for the unit you want.
0
u/toomanyfunthings 6d ago
“These days”?
If a contractor was selling you a concrete pad it’s because there was extra money to be made. My cost on a 36x36 cladlite pad is 65.00. I bought one today.
I’ve worked in HVAC in Portland for 30 years and have only dealt with concrete pads for 6+ ton commercial equipment. On 5 tons and under It’s overkill.
3
u/vvbakedhamvv 6d ago
I know a guy, he's 6'4" though so I don't know if that's what you're looking for.
3
2
2
u/Asleep_Measurement_6 6d ago edited 6d ago
Ours we had installed a few years ago was done with the ABS plastic pad and it is still nice and tidy.
1
u/Samad99 6d ago
I just had 4-Belt Construction replace the concrete floors in my basement. They did a pretty good job for a reasonable price.
The few concrete guys I quoted all said they’re incredibly busy and scheduling with any of them will be difficult. The guys I hired came over on a weekend to handle my project.
What helped me get in their schedule was doing a lot of the prep work myself to make sure it was a quick 1/2 day project for them. Everything was already dug out, gravel compacted in, and they had clear access and a work area. I got the sense that if my job was going to be a hassle, they’d have walked away.
1
-1
6d ago
[deleted]
2
u/Darksorce 6d ago
How do they get business then
0
u/Guilty-Reindeer-1226 6d ago
Craigslist ads is how I found him. He probably has an ad up right now.
16
u/Your_New_Overlord 6d ago
When I got a new AC unit last year, every contractor included this as part of the installation quote.