Heat pump for swimming pool. How to control chlorinator

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sfrasernz

227 posts

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#306815 23-Aug-2023 18:45

We have PV solar and a swimming pool and now the sun is shining are sending 20 kWh back to the grid some days for a return of 8 cents per kWh. Not worth it so looking at heat pump options for the swimming pool.

I’m thinking I’ll use Home Assistant to switch on the pool pump when we have excess solar generation. Today that would have meant 5 hours of extra running.

But if I suddenly start running the pool pump and salt water chrlorinator for 5 hours a few days a week then my chlorine levels will begin to rise.

Is there a solution to this? The pool controller allows me to dial up and down the chlorine levels (from 0-100%) but only at the controller.

mentalinc

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#3119524 23-Aug-2023 19:26

Are you intending to use the pool, i.e. it takes many hours/days running to get to 28 degrees for example.

You'd then be putting the cover back on, and treating the pool as open so full TLC etc...

You're also looking at many thousands of dollars to purchase and install..

Our you'd also need to looking into a smart salt chlorinator

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sfrasernz

227 posts

Master Geek

#3119528 23-Aug-2023 19:37

Yes if we decide to make the investment then we would heat to about 28. Point taken on how long it’ll take but if we days like today then we should be able to slowly raise the temp. We have the three hours free power each night as well.

Just need to figure out if we can do something to manage the chlorine if the pump is running a lot more than usual (or less).

mentalinc

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#3119530 23-Aug-2023 19:50

How do you control the chlorinator?
Does it have a dial?
If so you could try to find something that will turn it for you?

Or you'll need to change the chlorinator to be smart controlled.
You'd also need to test daily at a guess to check chlorine is within bounds

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elpenguino

3419 posts

Uber Geek

#3119619 24-Aug-2023 00:07

Ahh, control theory.

Assuming the chlorinator is 'dumb' and can't be altered, you have an option to add an external controller. For this discussion, I assume the chlorinator works by adding chemical when water flows through it.

You could add a solenoid valve to open and close the water input to the chlorinator, under the control of your smart controller.

You then have the choice of making your control system open or closed, meaning with or without feedback. If there are chlorine sensors then one can be used to feed back into the smart controller and you have a regulated system, tuning for system parameters notwithstanding.

If you have an open system without feedback, the chlorination system can be tuned to some degree (with timers etc.) but you may find that whenever there's a big change in conditions such as the sun, usage, what have you, the system wont stay in the desired range using the automatic settings.

Sounds like you already have already a smart-ish controller, see if it can be made into a closed type of system by adding a sensor to provide feedback.

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SirHumphreyAppleby

2844 posts

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#3119632 24-Aug-2023 07:18

Anything with a compressor, including a heat pump, will need to be intelligently controlled. You can't simply switch it on and off as you can with a pump - slowly raising the temperature on an overcast day isn't an option, it's all or nothing.

We heat our pool the traditional way, by pumping water through rubber on the roof. The great thing about this setup is it's largely self-regulating. The pump only comes on when the roof is hot, the roof is hot when the sun's out, and when the sun's out, we're generating the most solar power. The disadvantage is that temperature control isn't as precise as a heat pump.

If your primary motivation is to use the excess electricity, I would suggest looking to see if there are heating elements available. This isn't something I have looked into, but while it would be less efficient than a heat pump, it would be a simple on/off device with almost zero maintenance.

Finally, your chlorine use will increase significantly with heating. Using more of the power you generate may end up costing you a lot more than you think.

muppet

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#3119661 24-Aug-2023 09:35

I can control our pool pump and our heatpump seperately (so I can have the pool pump running but not have the heatpump running, or have both) but I can't currently control our chorinator remotely.

I just manually adjust it though, I find in Winter it's easier just to crank the Chorine generatoion up until there's a high level in the pool, then keep the chorinator off until testing shows it's getting low again. Given we have a cover and there's no one swimming, it stays pretty high for a few weeks and slowly drops down.

I could go and buy a second smart plug and plug the pump into one plug and the chorinator into the other, but you need to always be testing chorine levels anyway so I don't see the point of bothering.

mentalinc

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#3119666 24-Aug-2023 09:45

The problem is needing to run the heatpump and pool pump, but not the chlorinator.

I wouldn't recommend the approach of cranking the chlorinator up then turning it off for a period.

You could see if the chlorinator is powered separately, and use a smart plug to turn off the chlorinator but have the heat pump and pool pump running - but suggest you check with the manufacturer if you can just turn it on and off like this.

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MikeAqua

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#3119684 24-Aug-2023 10:36

I'm not sure how your chlorinator works. Ours is simply a tube that a stack of big chlorine tablets are inserted into. Water flows through the tablets and the chlorine slowly dissolves. To adjust the chlorination rate, the number of tablets in the stack are adjusted. Works.

We have a heat pump, and cover. The cover floats on the water when closed. The heat pump gets switched on at the start of NZDT, and we run it about 10 hours per day. We're in Marlborough, so lots of sunshine and the cover heats up like a tyre in the sun, conducting some of that heat into the water. The first two weeks the pump is running, but the pool is still winterised. I fit extension pipes to the water inlet to divert the incoming warm water to the bottom of the pool. This breaks up any thermal stratification.

By mid-November, our afternoon pool temp is over 25*C.

Mike

Jase2985

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#3119875 24-Aug-2023 19:05

our heatpump runs off water flow as as long as the pump is running it will turn on and heat if needed, so you would only need to automate the pool pump in this instance. it does have about a 5 minute cool down after being switched off before it will turn back on.

so you could automate a regular power point (im assuming its a 240v socket powered pump) then just have the chlorinator run as normal on tis own power/schedule.

Be aware about running a pool heatpump at night that the noise doesnt annoy the neighbours. ours is near the neighbours bedroom so it runs to 9pm at the latest which is hardly ever.

muppet

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#3120016 25-Aug-2023 10:07

mentalinc:

I wouldn't recommend the approach of cranking the chlorinator up then turning it off for a period.

Why not?

In my mind it's the same as our old pool where I used to monitor the chorine levels and chuck in in approriate amount of Chorine when it got on the low side.

Is there some reason it's a bad idea - we a salt chorinator.

mentalinc

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#3120103 25-Aug-2023 13:44

You should be maintaining your chlorine levels particularly during summer when it's being used lots.

Having low chlorine may lead to algae outbreaks, and high chlorine is bad for the person in the pool.

You should be able to find the right output level on your chlorinator to maintain the chlorine at the right level for your pool considering CYA levels etc.

Particularly with a salt chlorinator, there is no effort of having to add or remove the chlorine tablets or whatever you use.

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MikeAqua

7773 posts

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#3121881 30-Aug-2023 13:34

mentalinc:

Particularly with a salt chlorinator, there is no effort of having to add or remove the chlorine tablets or whatever you use.

For fine tuning, you can also adjust the through-flow rate on the chlorinator. At least on ours you can. I haven't seen anyone else's.

Mike