Is this right? Return split between SWCG and heater

[MassNerd]

So I returned home to my pool install. Fully plumbed and wired now. However the plumbing isn't quite what I expected.

Let me describe the setup:
Skimmer and main drain comes into the pump.
Pump goes out and into the filter
Here's where I was surprised: Out of the filter goes to another valve, one way goes to the heater (heat pump) and then to the returns on the shallow end stairs. The other way goes through the SWCG cell and to a different return in the deep end.

Is it normal to split the flow between SWCG and heater like that? And go to different returns? I suppose it shouldn't matter as neither requires a high flow. Just not what I expected... I figured they'd be plumbed in series: pump -> filter -> heater -> SWCG -> returns

 

[JasonLion]

No, that isn't normal. On high speed that plumbing should be just fine. It does present some challenges when running on low speed however. It is unlikely you will be able to use both the SWG and the heater at the same while on low speed (and we normally recommend running only on low speed if at all possible). While normal plumbing would not have an issue with this. Of course there is some change it will work even on low speed, but that seems unlikely.

Your expectations are exactly what I would expect, with the addition of the valve to choose between the returns placed after the SWG.

 

[4knights]

I would think it defeats the purpose of the heater, if you are only heating 1/3 of the water going back to the pool it will take a lot longer to heat the whole pool.
The SWCG is supposed to be plumbed after the heater but depending on brand there is a distance requirement after the heater as well.
I would call the builder and have them explain their rationale for doing it that way and the concern about not heating all the water returning to the pool.
(it's kind of like filtering only part of your water)

 

[MassNerd]

The only thing I can think is that the pump is a tristar wet end and even at the low speed its good for 80gpm. I will ask my PB what is up in the morning because it doesn't seem right.

@4knights - I would think the same amount of heat should go back into the pool whether is split or combined. I would just have "hot" water coming out of 1 return, rather than "warm" water coming out of all returns. My only concern would be affect of water flow rate on efficiency of the heater and SWCG.

 

[JasonLion]

4knights, the heater has a certain minimum flow rate. Below that flow rate it simply won't work at all, and above that flow rate it will work just fine. There is no issue there as long as the heater is getting the flow rate it wants, even with the plumbing the way it is now.

MassNerd, You will not be getting 80 GPM on low speed with that pump. Figuring out flow rates exactly depends on some many factors that it is not usually worth the trouble, but I am guessing you might get 40 or 50 GPM, maybe a little more if the plumbing is well designed (and evidence at the moment is that it is not).

 

[toofast]

However keep in mind that heat pumps also don't like a big differential between incoming and outgoing water...so if you are splitting the flow on low and even if your HP still runs, your flow might be so slow that your water is too hot. The aquacal service rep said 8 degrees difference is about the max.

I agree, I do not have mine setup like yours...something does not make sense.

 

[MassNerd]

I spoke with my pool builder and he is confident there will be enough flow through, at low pump speed, through both the SWCG and heater. He claimed before titanium heating elements, keeping the flow closer to the minimum extended the life of the heaters and might still improve the life with the titanium heater I have. He's done over 100 installations like this with no problems. He's been installing pools for over 25 years and has one of the best reputations in our area, so I'm satisfied to trust him for now. I'll report back after we have everything up and running.

 

[JasonLion]

I look forward to hearing how it works out.

 

[MassNerd]

Well, everything is hooked up and running. So I go out and set the pump to low speed and the heater gives me the low flow warning. I start turning the valve towards the heater path and I pretty much have to turn it all the way to heater to get the low flow warning to go away and for the heater to turn on. Guess I'll be talking to the PB tonight.... A little upset, but the pool build has gone well otherwise. I expect he'll make it right.

 

[toofast]

Remember though, HP have a PRESSURE switch vs. a true flow switch. The pressure switch can be reduced, HOWEVER it is absolutely CRITICAL that you don't turn the pressure all the way down. You gotta keep your flow above whatever you HP low flow threshold is. HONESTLY I have NO IDEA how that is going to work with your setup...I say it won't - without diverting 100% of the flow to your HP on LOW.

Good luck!

 

[MassNerd]

An update on my install:
The PB came back and adjusted the flow detector in the heater. Now I can run both the heater and the SWCG with the pump on low speed and the returns split 60%/40% heater/SWCG. I'm wondering if its possible to adjust the heater's flow rate detector below the recommended level for the pump, but the PB says its ok...
It does work though!