Uphill loop question

[riny]

As posted elsewhere, I'm planning to add an actuated heating loop and I have a pretty basic plumbing question. Assuming it looks like this:



Note that to the right is up an incline. The FPH is about 6' higher than the pad. The heating loop will be controlled by the green actuated valve. From reading about solar loops, I understand that the actuated valve should have a small hole in it to allow water to drain out of the loop when not in use, and a vacuum breaker should be included at the top. This means you also need a second positive-seal valve, plus a bypass valve, so the loop can be isolated for service.

Two questions then:

1. Does this all look good? Anything I'm missing?

2. What should go at the orange question mark, at the return side of the loop? I was thinking I could just put a check valve here. Are check valves considered positive-seal, enough that the loop can be fully isolated for service? Or do I need both a check valve and another service valve?

 

[JamesW]

I would not do a drain down.

Just use a three-way valve to select the bypass or the fph loop.

You can put a Jandy check valve on the return line from the fph.

 

[riny]

I would not do a drain down.

I trust you but out of curiosity, can you tell me why? I thought it was good practice to always do a drain down to avoid water stagnating in the loop. The distance is about 75' each way.

Also I'm going to tack on another question, because head loss calculations make my head hurt. All of my plumbing is 1.5", and the FPH is 1.5". But for the 75' loop runs (uphill and downhill), should I go up to 2" due to friction loss? Or is the friction not that big a deal over this distance?

 

[JamesW]

I thought it was good practice to always do a drain down to avoid water stagnating in the loop.

Do you expect that there will be long periods of time when the loop will not get flow?

If you want, you can just use a valve on the bypass to open or close the bypass.

When the fph is on, the bypass will be closed and all water is forced to go to the fph.

When the fph is off, the bypass will be open and "most" of the flow will go through the bypass but a tiny amount of flow will go through the fph.

Install a Jandy two way valve on each line going to the fph so that you can close them for service as needed.

 

[JamesW]

But for the 75' loop runs (uphill and downhill), should I go up to 2" due to friction loss?

Use 2" for best efficiency.

 

[riny]

Well you're right that my first picture was totally wrong because there's no actuated valve which closes the bypass. It needs to be a 3-way. So trying again; I've got three options, including your last suggestion:

Option 1, WITH drain-down:



Option 2, WITHOUT drain-down:



Option 3, bypass only:



Does that about cover it? I'm least confident in option #3 TBH because when the bypass is open (no heating), I'm not sure how the water in the loop will behave. The FPH is above the level of the jets so the water won't make the full loop but I'm not clear on what will be happening at the two tees.

 

[JamesW]

I would probably just do #3.

There's no reason for a drain down.

It really doesn't make much difference what's happening in the loop while the bypass is open.

Maybe a little bit of water will go through and maybe it won't but it should not matter either way.

 

[JamesW]

Option 2 might be a better choice. You don't want the fph to run with no water in the lines. I definitely would not do a drain down feature. Water sitting in the line for a day or so should not be an issue.

If the system will be off for a long time, you can close the valves and drain the lines.

You can install some sort of drain plugs on the lines for when you want the system down for an extended period of time.