Structural integrity of a welded steel stand for two condenser units 8

[Parker87]

I've recently bought two mini split heat pumps and want to build a stand to hold the outdoor units. I would like to obtain an E-shaped cantilever structure but am unable to determine whether the beams will hold the units safely in place without adding some form of additional support (e.g. diagonal braces).

I plan to use 50mm x 50mm x 2mm (2" x 2" x 14ga) square steel tubes which are going to be welded together as shown in the drawing above. The small cylindrical shapes are rubber-metal mounts that will go underneath the condenser units to prevent vibrations from being transferred to the steel frame. I might also use some larger rubber-metal buffers to decouple the stand from the concrete foundation on which it will be mounted, so any unmitigated vibrations don't find their way into the nearby walls of the house.

The weight of the outdoor units is 43kg (95lb) each, and the way this weight is distributed on each corner is shown on page 11 of LG's product data book (i.e. page 13 of the PDF) linked below.

https://www.lgbusiness.es/wp-content/uploads/2019/11/PDB-Dec.06.2018-10.pdf  

Since this stand is only going to be secured to the ground (and not to a wall), my main concern is stability, i.e., supporting the weight and stress from the two condensers without bending, breaking, or tipping over, while enduring the fluctuating weather conditions.

Any thoughts or advice would be greatly appreciated. 

 

[r13]

The design looks good. Get plastic table/chair leg floor pad from store, they are cheap, replace as often as required.

 

[BAretired]

BART... have you actually run the moments?

Yes, but the geometry may change. (see 9 Aug 20 02:35 post by OP).



BA

 

[Parker87]

Get plastic table/chair leg floor pad from store, they are cheap, replace as often as required.

Is this supposed to be some kind of a funny joke?

In case you misunderstood what I was saying, I was referring to the ones I want to put between the stand and the concrete which, just like the smaller ones for the condenser units, are specifically designed to kill vibrations. The stand needs to be bolted down to them (or vice versa if I use the threaded variety) and they need to be bolted down to the concrete, as shown in one of my earlier posts (which has the 7 Aug 20 23:24 timestamp).

 

[radiocontrolhead]

95 lbs each? We are structural engineers. Not furniture designers.

At 95 lbs a piece... the structure itself will probably weigh And cost (fabricating in time and materials) more than both units combined.

 

[r13]

Parker87,

You shall find a way to fasten the unit on a wall, the connection shall be high (top shelf level) to make the unit stable in any situation (wind/earthquake), without the need to bolt to the concrete floor. So a cheap chair leg pad, or rubber pad, can dampen the vibration.

 

[LittleInch]

I really think you're worrying excessively about the vibration thing.

Too much compliance and the stand will wobble.

The feet of these things and the motors inside them are usually already on compliant mountings.

Bolt the frame to the concrete flat and as hard as you can to stop the thing falling over and just get on with it!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[r13]

I think this is all you need. Note, you have find a way to fasten the upper unit for lateral stability. Otherwise, you might kill a cat, dog, or even a small kid. This is no joking when you stack weights vertically.