I am reviewing a parking garage that is 5-stories in height fully equipped with an NFPA 13 sprinkler system.
The calculations provided for floors 4 and 5 indicate an elevation of 0 at the 3rd floor riser, with the elevations going in the negative values back to the hydrant.
Floor 3 calculations indicate an elevation of 0 at the Floor 2 riser. Floor 2 and 1 calculations show an elevation of 0 at the hydrant where the flow test was conducted.
Does the location of the "0" elevation affect the calculations demand, if the total change in elevation is still accounted for?
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8/25/2021 07:12:56 am
8/25/2021 08:17:28 am
This is common when using XREF's with AutoSPRINK (I can't speak to the other design programs). The designer draws each floor at an elevation as if you were standing on the floor without regard to if the floor is +16' or +2160' above the arbitrary (to us) 0 elevation of the project.
8/25/2021 08:24:26 am
AutoSPRINK works awesome with CAD when everything is finally modeled currently.... until then, URG! I can picture that monitor and sticky notes now.
Glenn S Berger
8/25/2021 08:31:44 am
"0" being at the midpoint is typically down when this is the main discharge point of the elevator/building.
8/25/2021 08:32:44 am
Alex is correct - the software will only look at changes in elevation, so you could potentially add or subtract any arbitrary amount from all of your elevations and still come up with the same answer.
8/25/2021 09:19:26 am
You just need to be careful with gridded systems where the entire piping network is being used during the calculations.
8/25/2021 08:38:05 am
Alex and Dan pretty much nailed it. I like to think there are three types of elevations in our calcs. The ones that have a critical outcome on the calc. The ones that have some bearing on the calc, but typically don't affect it too much. The last ones don't affect the calc at all. The critical elevations are the nodes for your water supply (source point) and then the driving (hydraulically most demanding) sprinkler. The second type of nodes are ones that do affect the calc, but not in a major way. Nodes that are in your actual calc area can have some minor affects on the calculation, but usually don't affect the calc in a major way. The elevation of the non-driving (but flowing) heads will affect how much delta flow you will see at those heads for example which can increase or decrease the total demand of the system. The last type of node are ones that don't matter at all when it comes to elevation, which are the rest of the nodes. For example, if your test node is at 0 feet and then your underground pipe coming into the building is -8', but then your driving head is at +10', you are still only going to net a 4.33 psi loss due to elevation. The fact that the underground pipe is -8' has no affect on the calc, other than the total footage of pipe. I always tell my new designers that you could have a supply main that goes up to the moon and back down to your building and it would not affect the calc as far as elevation goes. As a plan reviewer, the first thing I would look at is driving head elevation and source point elevation. That will have the biggest affect on the calc and can be a major screw up. 2nd is to check that pipe sizing on drawings matches calcs, and 3rd is to check and see if sprinkler head k factors match from drawings to calcs. If you don't look at anything else, at least check those three things. That is typically where the easiest mistakes are made AND the ones that have the most impact.
8/25/2021 09:20:57 am
Its all relative to the supply node.
8/25/2021 09:57:31 am
I m not getting something.
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