How do I explain this...

Tom_133

So I am doing a job for a 30 year plumber, this job includes snowmelt. Here is the design for the snowmelt when done properly.



The problem is he decided to go 12" centers and only put 2 loops in!!! Yes, its poured.

Here is the numbers I am getting trying to fudge it as much as possible.






Manifold 1 is the ramp and Manifold 2 is the connector, also keep in mind the ramp hasn't been poured yet so thats going to be right.

Seriously, how do can I explain to a 30 year plumber that we need to break up the concrete and start again on his dime because it wont work?
Most of all I am curious how you guys illustrate/explain less tubes means greater head??

EBEBRATT-Ed

You can explain it to him will he listen? Depends if he is a know it all or not.

With the same flow rater smaller pipe=less tubes=greater head

hot_rod

Maybe try to explain it as BTU/ sq ft. Or the different ASHRAE classes of snow melt.

Is it just the 500' that you are concerned about design calling for 5- 300" loops, 93,000 load? If so 186 BTU/ sq. ft. that is a fairly hefty system. Is it a critical application, b building entry? Hospital pad? Insulated below and edges?

2 loops of 5/8, 300'? You could work it backwards and show how many BTU that system is capable of. less than 1/2 of what is expected, possibly.

Was there a design criteria based on the class 1,2 or 3?

Tom_133

Its the connector for 2 parking areas in a senior center. I havent seen if it will somewhat covered, or completely open to the weather. As for the class, I am not sure of that either. I will look into it. I was hoping for a good illustration that explains more tube less head. Thats what he is missing.

ratio

Maybe a cross section of the pipes, visually showing the flow area?

hot_rod

changes to head is related to tube diameter, circuit or loop length, flow rate, type of fluid, etc.
SIM like radiant output is based on the amount of heat BTUs per square foot, regardless of how you get it there.

The wide spacing will be a challenge, typically 6- 8". And inadequate loops will make it hard to get the output of 186 btu/ sq ft. if that is the expectation.?

That being said, it will work to some degree, slowly and with some striping. It comes down to expectation for the customer. And amount of snow or ice expected

A neighbor in the mountains has 12 PB in his drive with a 40 gallon gas water heater! Slow but steady and inexpensive to install

Idronics 12 explains how energy moves in a liquid and all the relationships of heat transfer.

https://www.caleffi.com/sites/default/files/file/idronics_12_na_2019.pdf

Jamie Hall

For some reason, explaining the relationship between head loss, pipe (or pipes!) diameter (and fittings), and flow has always seemed to be difficult for many people to grasp. Confounding the problem is that for almost all the work we do around here, we rarely have a truly constant head source to play with -- and throwing a pump and pump curve into the puzzle doesn't help any.

I've sometimes noted faint glimmers of understanding when it comes to multiple pipes in parallel, though, with comparing it to a superhighway with one, two, three or fours lanes and how many cars can go by...

The Steam Whisperer

Maybe this is another application for a timed 3 way valve that can reverse flow in the loop to even out the heat delivery.

Zman

I like the original design better and the plumber should have followed the design.
That being said, I see a ton of poorly designed snowmelt systems and would give the original design a, "A" and what the plumber did a "B-". It will melt snow pretty well. You will see a bit more striping on startup but it will get the job done.

Tom_133

So, just an update. It turns out the GC shrunk the pad almost in half. Its now 290sqft with 2 loops of 5/8" tube 300' long. So I didnt have to explain anything to him. The best part of this is I learned a lot about snowmelt design. Thanks all

hot_rod

Tom_133 said:

So, just an update. It turns out the GC shrunk the pad almost in half. Its now 290sqft with 2 loops of 5/8" tube 300' long. So I didnt have to explain anything to him. The best part of this is I learned a lot about snowmelt design. Thanks all

That's workable