[Guite]

Originally Posted by tush

The question still remains unanswered, is it safe to get the beam drilled with a 2-3 inch hole? The only relevant answers this installers give is, Sir "the core cutting machine is specifically for this purpose". It doesnt cause any vibrations vis a vis the previous methods when installers use to do it the manual way with the hammer which affects the entire beam.

Please see my previous post: it is not safe to cut a floor beam whether by hammering or core cut. A floor beam is always attached to the floor slab and can be anywhere between 8 to 12" from bottom of slab, depending on span (length) of beam. This is for a typical apartment / house. It can even be more depth if span is large.

As a thumb rule take 1/10th of span (column to column), deduct slab thickness (typically 4 to 5"): this will give you depth of beam below slab. Avoid any cut whatsoever in this zone.

You are obsolutely right in your observation, the beam is the most probable choice left and I have seen major installations on the beam.

Almost major interior designers also say there is nothing to worry.

Interior design courses are not as regulated as architecture and civil engineering. No offence to interior designers in general: there are lots of highly qualified and good interior designers.

Came across one such person who says bottom floor apartments its not done as that is where the entire buildings load is mostly managed.

Critically of beams is same on all floors. It is columns which are more critical at lower floors, most critical at ground and basement (if there is).

Mounting the indoor unit on a beam is okay so long as the cut for pipes is below beam. While drilling for screws to fix the mounting plate, care should be taken not to cut reinforcement bars of floor beams. If a bar is encountered at one location, shift to another screw position. There are multiple provision for screw holes in the back plate, missing one or two position is not going to compromise the rigidity of the indoor unit installation. Risk to the building is far greater.

Cutting a stirrup (ring bar) is not as risky as cutting main horizontal bars of a beam. There are x-ray machines available to look at the bars inside concrete, but obviously the AC installation guys do not have it. Without it, there in no way of knowing which bar you are likely to cut. So why risk?

[Aroy]

Cutting beams is dangerous especially if it cuts reinforcement.

What we do while building is to insert a 2" pipe in the beam after consulting the structural engineer.

The preferred method of installing split AC in a room is
. Position the IDU on a brick wall
. Route the piping so that no concrete is cut
. Avoid sharp bends
. Position the ODU where direct sunlight will not fall on the heat exchanger. If unavoidable install an FRP sheet to shade the ODU.

The problems start where the builders have created large Windows/French doors, so that the edges are concrete with no wall between the window and the structure. In such case we route the AC pipes through the window frame. It may look ugly but you are safe structurally.

NOTE. In no case allow any one to cut/core the vertical columns. It is a recipe for disaster.

[tush]

Originally Posted by Guite

Please see my previous post: it is not safe to cut a floor beam whether by hammering or core cut. A floor beam is always attached to the floor slab and can be anywhere between 8 to 12" from bottom of slab, depending on span (length) of beam. This is for a typical apartment / house. It can even be more depth if span is large.

As a thumb rule take 1/10th of span (column to column), deduct slab thickness (typically 4 to 5"): this will give you depth of beam below slab. Avoid any cut whatsoever in this zone.


Interior design courses are not as regulated as architecture and civil engineering. No offence to interior designers in general: there are lots of highly qualified and good interior designers.



Critically of beams is same on all floors. It is columns which are more critical at lower floors, most critical at ground and basement (if there is).

Mounting the indoor unit on a beam is okay so long as the cut for pipes is below beam. While drilling for screws to fix the mounting plate, care should be taken not to cut reinforcement bars of floor beams. If a bar is encountered at one location, shift to another screw position. There are multiple provision for screw holes in the back plate, missing one or two position is not going to compromise the rigidity of the indoor unit installation. Risk to the building is far greater.

Cutting a stirrup (ring bar) is not as risky as cutting main horizontal bars of a beam. There are x-ray machines available to look at the bars inside concrete, but obviously the AC installation guys do not have it. Without it, there in no way of knowing which bar you are likely to cut. So why risk?

Originally Posted by Aroy

Cutting beams is dangerous especially if it cuts reinforcement.

What we do while building is to insert a 2" pipe in the beam after consulting the structural engineer.

The preferred method of installing split AC in a room is
. Position the IDU on a brick wall
. Route the piping so that no concrete is cut
. Avoid sharp bends
. Position the ODU where direct sunlight will not fall on the heat exchanger. If unavoidable install an FRP sheet to shade the ODU.

The problems start where the builders have created large Windows/French doors, so that the edges are concrete with no wall between the window and the structure. In such case we route the AC pipes through the window frame. It may look ugly but you are safe structurally.

NOTE. In no case allow any one to cut/core the vertical columns. It is a recipe for disaster.

What with the initial plaster removed during interior work of a home for implementing concealed wiring. These interior designers allow removing atleast one inch of plaster of a beam/column if it comes in between to pass on the concealed piping for the wires of home lighting, AC wiring requirement. If core cutting for out door unit is avoided, then what with this 1-1.5 inch plaster on the face of beam/column removed to house the concealed wiring pipes? Is that safe?, although its not through and through. They say its just the plaster, we aint touching the core concrete, although a bit of concrete gets brushed while removing that amount of plaster(but by first using cutter with round blade so removing later with so called channi & hatoda becomes easier). Have seen it everywhere, not sure whats up with all this.

Reading all your helpful comments, it is kind of leading to believe to stay away from split AC and instead go for tower AC, which are like cooler as far as their build is concerned, and have wheels so could be taken into any room.

I believe all forum members and in general everybody while buying an AC should consider all the important points discussed so far in our few posts.

No regulations, or lack of implementation of regulations, lack of knowledge and no awareness is leading a majority of Split AC installations in a wrong manner.

Moderator should create an anonymous poll to find out atleast in our forum the percentage of Split AC install via core cutting of beam vs brick wall.

[Guite]

Quoting my own post to add more clarity.

As a thumb rule take 1/10th of span (column to column), deduct slab thickness (typically 4 to 5"): this will give you depth of beam below slab. Avoid any cut whatsoever in this zone.

There may be non typical beam depths. So best bet is to clear the wall plaster in the zone where core cut is intended, and visually analyse the underlying material. In case of brick wall, you will immediately know whether you are in brick zone or concrete beam zone. In case of hollow concrete or AAC block wall visually it may be difficult to judge but not impossible. Mild chipping may be required to judge the material.

Critically of beams is same on all floors. It is columns which are more critical at lower floors, most critical at ground and basement (if there is).

This is not to say that columns at upper floors are not critical. Collapse of column at upper floors can bring down entire tower, refer WTC 9/11.

Cutting a stirrup (ring bar) is not as risky as cutting main horizontal bars of a beam.

This is strictly with respect to drilling a hole for a single screw.

Originally Posted by Aroy

What we do while building is to insert a 2" pipe in the beam after consulting the structural engineer.

They mostly allow only in middle third of depth. I have been allowed 4" sleeve in 20" deep beam.

[sgiitk]

Mostly, they do not bother to check, since Civil Construction works on a safety factor of 10x or even higher.

[Aroy]

Originally Posted by sgiitk

Mostly, they do not bother to check, since Civil Construction works on a safety factor of 10x or even higher.

That would be carrying too far, I would settle for 2-3x. That is assuming that the materials and workmanship is as per original design. Sadly in most of the cases the materials are of lower standard and workmanship leaves a lot to be desired, hence the safety factor drops drastically from 3 to much lower. This is evident when some thing goes wrong during or after construction - foundation subsides or a mild earthquake and then some multistory buildings come tumbling down.

In this scenario, unless I am sure of the builder/contractor, I would desist from tampering with and weakening the structure.

[dkaile]

Originally Posted by sgiitk

Mostly, they do not bother to check, since Civil Construction works on a safety factor of 10x or even higher.

That is quite true but mostly for personal constructions. I remember, few years back when I was constructing one my factories, the architect who had been doing my work for the last 20 years gave me a structural drawing. Just to cross check I gave it to a friend who was just fresh out of a civil engineering course to make his version of the structural drawing. Lo and behold, his drawing saved me exactly 50% on steel costs which my architect had overdone.

[Guite]

Originally Posted by sgiitk

Mostly, they do not bother to check, since Civil Construction works on a safety factor of 10x or even higher.

That would be very expensive construction indeed, whether it is built by a builder / promoter or own house. IS Code requires 1.5 times over design and engineers add about another 0.5 times margin for fluctuation on quality of material and construction.

[sgiitk]

Originally Posted by Guite

That would be very expensive construction indeed, whether it is built by a builder / promoter or own house. IS Code requires 1.5 times over design and engineers add about another 0.5 times margin for fluctuation on quality of material and construction.

This is for multi-stories or group housing where individual design calculations are done. In one-off jobs it is mostly rule of thumb, as attested by dkaile! Even the basic design computations work on sume (pretty high) safety factor.

[diyguy]

I am planning to buy a 2 Star Samsung 1T Split for my kids room. They rarely venture there and typical usage should be day time - 2-3 hours maybe 3-4 times a week. They are not fearless enough to sleep alone as this is on the first floor while the rest of us are on the GF. The room has curved windows fronting the house and on both sides, there are small closed balconies. I am in a dilemma on choosing a split because if I put it on any of the side walls, it will need maybe 6m of copper atleast to reach the ODU and maybe more if we want the ODU to be low enough to service easily.
There is a provision of a window and I have a hitachi 1.5T already, but I have had very bad experience with window units, especially this Hitachi. I have spent about 11K so far in repairs on it, it is only about 6 years old. It has conked again now.
1.) Will the 1T be ok, if it is connected with a 6-7M copper coil from the ODU?
2.) Since low usage, I am going for a 1T split. Should I still consider a window ac as there is a ready provision and it will be a plug and play for me.
Thanks for your opinions!

[tush]

Originally Posted by sgiitk

This is for multi-stories or group housing where individual design calculations are done. In one-off jobs it is mostly rule of thumb, as attested by dkaile! Even the basic design computations work on sume (pretty high) safety factor.

Does multi-stories just includes very high rise residential buildings or its applicable to even moderate 7 to 12 floor buildings.

Originally Posted by Aroy

That would be carrying too far, I would settle for 2-3x. That is assuming that the materials and workmanship is as per original design. Sadly in most of the cases the materials are of lower standard and workmanship leaves a lot to be desired, hence the safety factor drops drastically from 3 to much lower. This is evident when some thing goes wrong during or after construction - foundation subsides or a mild earthquake and then some multistory buildings come tumbling down.

In this scenario, unless I am sure of the builder/contractor, I would desist from tampering with and weakening the structure.

Originally Posted by sgiitk

Mostly, they do not bother to check, since Civil Construction works on a safety factor of 10x or even higher.

Additional i just got to know that core cutting done by the very last floor flat occupant that is just below the terrace doesnt matter, as the slab at the top just has a terrace and nothing further so it doesnt harm. Not sure how technically correct this statement made by an electrician is, but there is a point.

[R2D2]

Originally Posted by R2D2

Thanks for these useful inputs. Your thoughts will most certainly help me with the decision. As mentioned earlier I'm already leaning in favour of Daikin Inverter 1.5 or a 1.8T split AC.

An update - I decided to go in for the Daikin 1.8T Inverter AC for my BR.

Paid the booking amount yesterday and the installation is expected within a week. This delays are due to an atrocious strike by traders against the proposed LBT (local body tax) in Pune.

[sgiitk]

Originally Posted by tush

1. Does multi-stories just includes very high rise residential buildings or its applicable to even moderate 7 to 12 floor buildings.

2.Additional i just got to know that core cutting done by the very last floor flat occupant that is just below the terrace doesnt matter, as the slab at the top just has a terrace and nothing further so it doesnt harm. Not sure how technically correct this statement made by an electrician is, but there is a point.

1. It is a simple matter of whether it is cost effective for the designer. Remember if you are building 200 identical houses, then even 0.5 ton per house, adds up to 100 tons of steel. Yes, you design, but for a one-ff house it is not worth it.

2. Depends on whether it is a structural element (beam) then what he says is correct, on the other hand if it is the roof, then hardly matters whether it is the first or the top floor. The loading is the same.

[khoj]

Brr, you had me worried, I will post shortly as to why.

Originally Posted by Guite

A cut of any size will compromise integrity of a structural floor beam. .... This is very very risky.

In most cases what is getting cut is the window lintel beam. Cutting this will not compromise the entire building, it may bear more load on the window frame. If you are 10" above and 12" away sideway from window you are safe..

The need here is not for reconciliation but for comprehension.

Originally Posted by khoj

provided your install deserves that level of attention.

Originally Posted by Inquisitive

Would you please reconcile your exact take on the quality of service provided by these companies?

[Guite]

Originally Posted by tush

Additional i just got to know that core cutting done by the very last floor flat occupant that is just below the terrace doesnt matter, as the slab at the top just has a terrace and nothing further so it doesnt harm. Not sure how technically correct this statement made by an electrician is, but there is a point.

It's just a terrace slab but a very heavy one at that. RCC structures are very heavy. Refer attached sketch, 10'x10' slab weights 3.6ton, the beam has to carry 0.9ton weight. You do not want that weight to fall on you, do you? It's not my intention to scare people. A beam failure may not suddenly bring down the structure like cards because there are filler walls, but the risk to life and property is too huge to be negligent.

Also refer schematic diagram on RHS which shows load on beam is same on each floor beam but load on column progressively increases as you go downward. So as far as core cutting on beam is concerned the risk to the beam is same irrespective of the floor on which that beam is located. However beam collapse on lower floors can be far more catastrophic because the columns will buckle.

Originally Posted by sgiitk

Depends on whether it is a structural element (beam) then what he says is correct, on the other hand if it is the roof, then hardly matters whether it is the first or the top floor. The loading is the same.

I am a little confused by this response. I think there possibility of misinterpretation. The electrician says its okay to core cut at terrace level and you say he is correct if it is a structural beam. With due respect, that's wrong.