Overall piping length in swh systems

[bernard]

Originally Posted by stevehull

You need a supply pipe to the collector and then a return pipe from it. Thus, I doubled the point to point length.

I did not understand you this, I apologize.

When you said:

Originally Posted by stevehull

then each story only adds ~ 5 meters or so for each run (10 meters for the input and output; two pipes)

the way I have understood you is:
for each story add 5 meters of piping in one direction (from collector to the storage tank), 5 meters in the other (from storage tank to collector) = which is 10 meters overall per story.
Did I understand that correctly?

Then how come you get approximately 60 meters in your case?
You have 6 stories in straight shot, or two stories of complicated piping schedule (not a straight shot)?

[stevehull]

Let me start again.

Assume it is 10 meters from the lowest level (where the storage tank is perhaps in the basement of the home) all the way up to the roof. This might be two stories total. This is the one way distance. Add a couple meters of pipe to get to the tank and to the collectors.

The total one way distance is about 10 meters. This is for just one pipe. The total pipe length (supply and return) would be double this - or about 20 meters (at most for a two story building).

It could be a lot less. If the storage tank is in the attic, then the distance from there to the roof might be only a couple meters (one way).

Steve

[bernard]

Thank you Steve.

I seem to undestood you correctly previously:

Add 5 meters of pipe length per story (for supply) + 5 meters of pipe length per story (for return) = 10 meters total per story.
And add 2 to 3 meters for the pipe length on roof (let's say 3meters).

So for a two story building with basement (basement, ground floor, first floor, roof), if storage is in the basement, and collectors on the roof, one would have:

3stories (basement counted as a story) * 10 meters + 3 meters (on the roof) = 33 meters.

I am wondering, why do you have 60 meters (200 feet), which is almost double than 33 meters?

[bernard]

Hi Steve,
I do not mean any disrespect, and I am very grateful on the help you have given me so far.

Could you please just answer on my last reply:

Originally Posted by bernard

Thank you Steve.

I seem to undestood you correctly previously:

Add 5 meters of pipe length per story (for supply) + 5 meters of pipe length per story (for return) = 10 meters total per story.
And add 2 to 3 meters for the pipe length on roof (let's say 3meters).

So for a two story building with basement (basement, ground floor, first floor, roof), if storage is in the basement, and collectors on the roof, one would have:

3stories (basement counted as a story) * 10 meters + 3 meters (on the roof) = 33 meters.

I am wondering, why do you have 60 meters (200 feet), which is almost double than 33 meters?

Thank you, and apologies for disturbance.

[stevehull]

It is better to overestimate length than to underestimate it. Perhaps you could get by with a very straight point to point run and go the entire length with only 30 meters. But if you have any right hand 90 degree bends or other restrictions than the pump may not have enough capacity. Generally, I estimate cautiously.

Without seeing the actual site it is impossible to say exactly how much length is needed. But here is a way to do it. Identify the exact route the pipe must take and then measure from there. That said, there may be obstacles in the way, concrete partitions, concrete floors, that are very difficult to drill through, so allowances must be made.


I am sorry if this sounds like a very wide guess, but I am not aware of any specific formula. I did get a private message about story height and it varies from country to country and even within cities. For example, in many new constructions there is a false ceiling where all ducts and infrastructure goes - often taking up 6-7 feet (2 meters). And this is on top of each living unit of 3 meters or so in height (9 feet)!

The key is to know the total flow, then the height issue (gravity), that allows you to know the pump requirements. Then size the pipe diameter to not introduce turbulence (keep it wide).

Hope this helps . . .

Steve

[bernard]

Thank you Steve.

How many stories do you have for your total pipe run length of 200 feet?
3 stories with basement included (basement - where the storage tank is, ground floor, first floor, and then goes the roof)?

[bernard]

Thank you shagarg.

Can you tell me what is the total pipe length run in your solar loop?
And how many stories do you have?
Thank you.

[jeff5may]

Originally Posted by shagarg48

Assume the system shuts off for some reason in the daytime (power outage). The collector heats up to several hundred degrees (doesn't matter if C or F) in the hot sun. When the power is restored, the water in the drain-back supply is pumped up, goes into the collectors and immediately flashes into super heated stem - and it melts plastic pipe in the return.

Use a thick walled copper for the first dozen meters right off the solar panel on the return to storage if you are using a drain back. The copper has sufficient thermal mass to absorb the flash heat in the above situation.

What you are describing here is a steamback system. There are a few differences with steamback design systems, mainly a pressurized collector loop and an expansion tank that can handle the volume of steam contained in the collector when it is hot and stagnant. These steamback designs are used like boilers in Europe way more than in America.

Check out this article for more information:
Fundamentals in Steamback Design 11/08/2010 - Solar Thermal Manufacturer | Solar Hot Water & Heating Manufacturer

[Daox]

Bernard, did you ever start on your solar hot water project?

[bernard]

Originally Posted by Daox

Bernard, did you ever start on your solar hot water project?

Hi Daox,
Please take my apology for taking me too long to reply.
I did start.

@jeff5may:
Thank you for the reply, and link. That is really useful information.