Speaking of Pool Heaters

[Stormin Mormon]

Just drain the pool about 1/3, and top it off with non toxic RV antifreeze.

Or, you could valve off the pool heater, and blow the water out with compressed air.

[Stormin Mormon]

Sounds right, to me. Almost not worth the bother. And a lot of money in natural gas, too.

[trader4]

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I don't see how a pool heater with any reasonable and safe design could have a control panel that gets ruined if the pool heater is not shut down via its own control panel prior to the pool pump being shut off. What happens if the breaker trips or power goes out in while the heater is on? Even if it has that limitation, are you saying you can't get a seperate timer for the pool heater and have it energized after the pump timer goes on and before it shuts off?

Definitely best to only fire it up long enough to heat it up before using it. You have a relatively large heater for a 10,000 galloon pool. The one here is 400K BTU for 48,000 gallons. The heater may be cheap, but I'd keep an eye on the gas meter. Even with that size pool, I think you'll be surprised how much heat in can use. Compare that 265K BTU to a typical home furnace and it's 3X the capacity. Using the cover will cut the heat loss substantially.

[gfretwell]

Pool heaters are interlocked 3 ways. The A/C power to the heater control circuit is on the pool pump circuit (gas valve), there is a flow switch and you have an over temperature cut off. If any of these drop out the heater turns off. There is also a fireman's switch that acts as an emergency power off.

[JimT]

I don't see how a pool heater with any reasonable and safe design could have a control panel that gets ruined if the pool heater is not shut down via its own control panel prior to the pool pump being shut off. What happens if the breaker trips or power goes out in while the heater is on? Even if it has that limitation, are you saying you can't get a seperate timer for the pool heater and have it energized after the pump timer goes on and before it shuts off?

Definitely best to only fire it up long enough to heat it up before using it. You have a relatively large heater for a 10,000 galloon pool. The one here is 400K BTU for 48,000 gallons. The heater may be cheap, but I'd keep an eye on the gas meter. Even with that size pool, I think you'll be surprised how much heat in can use. Compare that 265K BTU to a typical home furnace and it's 3X the capacity. Using the cover will cut the heat loss substantially.

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The heater works pretty effeciently so far. I had a 30k BTU (?) before and it tooks days to heat the pool but it was really only intented for the spa.

The new heater has a story behind it. Like I said it's a Raypak:

I got it, installed, like new, for $1000, with a replaced control panel. It was used, and the previous owner had returned it to the store because she had it on a timer that would just shut the heater off. The people who sold it to me said that was why her control panel fried. So I took my timer "off-switches" off and now I manually turn the pool off and on.

As far as keeping the pool running, we had a cold front move in and I've decided to stop heating the pool. It looks like November 1 is about the cut off date. Plans to keep it going to December are dropped but I'll continue to use the spa.

I think my house furnace BTUs are higher than the pools but I could be wrong. My gas bill goes up dramatically when the furnace kicks in. That reminds me I need to get my fireplace up and running.

Jim

[trader4]

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nyurl.com/23jud2x

It's typical to have help in a pool store on par with, or maybe even less informed than what you find at HD. Find the installation manual for the heater and read it. I'll take bets that it doesn't say that if you don;t manually shut off the heater before you shut off the pool pump it's going to fry the heater controller. If it worked that way, they;d be out of business with warranty returns.

I agree competely with gfretw's reply. The pool heaters I've seen have had a flow sensor that turns off the heater when water flow stops and they also have an over temp cut-off. They are usually also wired so that they are on the same circuit as the pool pump and hence turn off when the pump stops.

[JimT]

It's typical to have help in a pool store on par with, or maybe even less informed than what you find at HD. Find the installation manual for the heater and read it. I'll take bets that it doesn't say that if you don;t manually shut off the heater before you shut off the pool pump it's going to fry the heater controller. If it worked that way, they;d be out of business with warranty returns.

I agree competely with gfretw's reply. The pool heaters I've seen have had a flow sensor that turns off the heater when water flow stops and they also have an over temp cut-off. They are usually also wired so that they are on the same circuit as the pool pump and hence turn off when the pump stops.

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Oh yeah and no doubt. The fact is, a pool heater that is heating should not be just "shut down". Those sensors are for problems like power interruptions and pump failures. I don't think the mfg of Raypak want their heaters to fry circuit boards on shut down but you should let your pool heater run for awhile anyway, after it's been heating, to let the pool water cool down the heater. I don't have a problem "going manual."

I just officially claimed pool season is over. I can turn the heater off and put my pump "off timers" back on. I'm thinking I'll cycle the pool for about

4 hours a day.

Jim

[gfretwell]

The instructions for your pool heater will say you should be using a 2 stage timer that lets the pump run a few minutes after the heater goes off.

[JimT]

Of course you're right but the installer didn't say anything about it. I'll have to look into getting that done sometime in the future. There is a lot of new wiring that will need to be done. I think my pool was installed in

1983 and needs some updating as far as wiring goes.

As a side note: I tried to replace the pool light fixture but it was impossible to pull the light wiring through the conduit. Old pools can be money holes but I love mine anyway.

Jim

[trader4]

No such instuctions for the Jandy here. As soon as the pump cuts off, the heater goes off. Nor does it have any capability of doing that even if I wanted to. The water flowing through it keeps the thing cool while it's fired up. The water leaving this 400K BTU heater is only 7 deg F warmer than it comes in. Any residual heat that results when the pump and heater shut off at the same time may warm the water a bit, but not anywhere near hot enough to be concerned about.

[gfretwell]

This is from page 20 of the Sta-rite gas heater installation book.

"The filter pump should run continuously when the heater is on, and for at least 15 minutes after the heater is off."

[JimT]

The instructions on my Raypak talks about the dual timer:

"To operate the heater with a time clock, connect the timer to the fireman's switch connection in the heater's wiring. The time clock should be of the dual switch type and set to shut off the call for heat to the pool heater 15 to 20 minutes prior to shutting down the pool pump."

Jim

[trader4]

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OK, I stand corrected on what Jandy has to say.

Here's what Jandy has to say on the subject from the installation manual for one of their similar heaters:

"If you install a time clock to control the filter pump operation, it's recommended that the time clock have it's own low voltage (fireman's) switch to turn off the heater before turning off the pump. The switch should shut off the heater about 15 minutes before the filter pump shuts off. This will allow for a more efficient operation by removing any residual heat contained in the heat exchanger back to the pool."

I think the important thing here is the REASON for the recommendation. Jandy is not saying shutting off the pump and heater at the same time is going to destroy the control panel or destroy the heater. Only that it allows for more efficient operation by allowing the remaining heat from the heater to make it to the pool instead of being wasted. Similar to a forced air heating system where the blower continues to run after the burner shuts off so as to not waste the remaining heat. In the grand scheme of pool heating, I'd say this little bit of heat is insignificant.

The pool here with a Jandy was installed by one of the largest installers in the area and it has a single switch timer. The pump and heater turn off at the same time. It's been running for 5 years with no problems. When it shuts off, there is no evidence of the heater, pipes, etc getting hotter than they do during normal operation. If that's all it took to ruin the heater, what would happen when a breaker tripped or you had a power outage? When it shuts off, the heater is full of water at 85 deg. IMO, and apparently Jandy's too, there isn't enough heat left in the heat exchanger metal to raise that water temp high enough to cause any problems.

If I was doing a new install though, I would agree that I'd use a two switch timer, as all it requires is a timer with that capability and it does capture a tiny bit of extra heat.

[gfretwell]

You can still feel heat coming out of the pipe for about a minute after the heater shuts off with my Sta-rite. I agree 15 minutes is overkill. I do bet you will boil the water in the pipe if you shut them both off at the same time. That will typically be the high spot in the system so the hot water will not migrate away by convection. My pump runs about 10 minutes after the heater goes off. The pump is on a solid state relay and there is a fat capacitor across the LED gate that holds it up.

[trader4]

If that happens, don;t you think I'd be hearing gurgling, ie sounds of boiling? Also, if you could heat the water that hot, I would not expect Jandy to say they recommend having the pump run longer to aid in efficiency. I'd expect them to say that it's mandatory. A heat exchanger is there to do transfer as much heat as possible. Meaning, the heat from the combustion gasses passes through it to the water on the other side. You then have a temp gradient across the metal, combustion gas temp on one side, ~85F on the other. I just don't see that metal having enough thermal energy in it after the flame goes out to heat the 85F water that's inside to 212F. I'd guess that it might get to 125 or so tops.

But now I'm curious. Next Spring I'm going to do a simple test. Let the heater run to get it to normal temp. Then shut it off for 10 mins and turn it back on. I'll put a temp probe at one of the returns and see how hot that first burst of water is when it comes out.

[JimT]

If that happens, don;t you think I'd be hearing gurgling, ie sounds of boiling?

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I have. You might call or e-mail them.

Jim