Cavitation when my heater starts

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T

thunderkyss

0
Jul 24, 2010
172
Pt. Arthur, TX
Hey guys,

I've had my pool for a couple of months now, only been using it for a couple of weeks. The first weekend, everything worked fine, the heater heated & controlled the temp just fine. Last weekend, it would heat up, but after several minutes there would be a violent cavitation noise, and the heater would shut off on high temp, even though it was no where close to control temp.

Today, the heater only runs for a few seconds, before it shuts itself down on high temp, even though the water doesn't have time to heat up at all.

I figured the noise and violent cavitation meant there was something in the pipes, even though the flow through the return jets do not show any signs that there is a restriction. I disassembled the pipes, going to and from the heater, and found nothing. I even pulled out the check valve and found it to be intact & operational.

Does anyone have any other ideas that I could check?
 
Sorry, as far as the heater goes, it's a Hayward 400. I don't know the make or model of the filter, but it is a large 4 filter type. I have it apart right now, and all 4 filters look fine & intact. The pump is a two speed tri star.

The pump and filter can be in service all day, without the noise and cavitation. As soon as the heater comes on though, it starts with the noise, then shuts itself down. Sometimees the fault goes away on it's own. Other times I have to cycle through the modes to get it to clear.
 
JamesW said:
It's not cavitation; the noise is caused by low flow to the heater.
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I can believe that.

The pressure gauge on my filter is still below 15 lbs, but while I had it off, I decided to clean the filters. They looked rough, but not bad. I sprayed down all 4 pretty good. I figured if I turn everything back on, and it took longer for the noise to start, then I was on the right track & should probably give the filters a more thorough cleaning.

I admit I could have cleaned them better, but they are worlds cleaner than they were when I took them out. Yet there is no difference. I put everything together, filter pressure is still below 15, but it is still only a matter of seconds before the pipes going to the heater starts making noise & it shuts down on high temp.

Like I said, without the heater on, I can run the filter & pump all day, no noise or shaking pipes whatsoever. Turn the heater on & there's a loud ruckus and the heater shuts down. Normal operation is restored a few seconds after the heater shuts down.

Which leads me to believe I am not supplying enough water to the heater & what I am supplying is getting boiled off creating air in the lines, and cavitation.
 
After disassembling the filter & cleaning it, I removed the pipe between the heater & the filter again. The heater is downstream of the filter.

I found nothing. & while the filters may have been a little dirty, everything was intact & I find it hard to believe anything solid passed through them to the heater.

One more thing. I have a puck type chlorinator downstream of the heater. After using up the pucks the builder left me, I had been using the BBB method. Is it possible, that the empty chlorinator downstream may somehow be causing this?

I won't be able to test this until Monday or so when I can buy some pucks to stick in there & see.
 
JamesW said:
Is there an external bypass? If yes, is it open, closed or partly closed?

Is the heater giving any error codes?

Is the pump on high speed or low speed?

It could be the Bypass Service Cartridge allowing too much water to bypass the heater.

The heat exchanger could be scaled, which would prevent sufficient water to flow through the heater. What is your CSI?

http://www.hayward-pool.com/pdf/manuals/Manual225.pdf
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The heater is giving me the HS code. I can't measure the gpm, but the pump apears to be working fine. the return jets appear to be working as well as they always have, & I see no air bubbles in the pump basket, or the flow indicator on the pool return.

The Pump is running on high speed.

There really isn't a way to check the bypass service cartridge while the machine is running. However, I mentioned earlier I pulled it out & it seemed to be intact and functional. Another thing, it doesn't start acting up, until the heater turns on. the water runs through the heater at all times, there is no external bypass.

I guess it could be possible that the heater is scaled. It's only been in service for 2 months, so I doubt it. but stranger things have happened.

Tomorrow I'll check the reading on the screen. I normally never see it as I let the remote unit control the temperature. I'm thinking maybe there is a faulty temperature sensore, we'll see.

Thanks for the manual. My pool builder already supplied it in both hard copy & pdf. But I appreciate your effort.
 
What temperature is the remote set for?

Have you verified that the pool water temperature that the heater is displaying is the correct temperature?

I really don't think that it is a sensor issue. If it were just a sensor, then there would not be any noise. The banging along with the error code indicates a lack of flow through the heater.

If you're sure that there is adequate flow, then I think that the heater is scaled (or otherwise blocked by debris), or the bypass is malfunctioning.

If you have an in-line chlorinator after the heater, it might be restricting the flow enough to cause a problem. However, if that were the case, your pressure would be over 15 psi unless you had a small pump.

What is the horsepower of your pump?

What are all of your chemical readings?
 

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I can give you one thought that happens with my pool. I will lose flow if the water level is too low. When the pump comes on the power forms a whirlpool in the basket area of the inlet. This pulls air into the pump housing. I need to make sure the pool water level is a few inches above the bottom height of the inlet. Also, putting one of those nylon filters in the inlet basket helps prevent the possibility of a whirlpool forming. I'd say get all the air out and when you turn it on look at the inlet, just in case the problem is that simple. Good luck.
 
In the header of the heater with the flow ends of the pool plumbing attached, is an internal bypass. It sounds like it's broken open and not allowing water to enter the heat exchanger tubing. Repair the bypass and the problem should be gone.

Since this is a relatively new system, I sincerely doubt scaling is the issue. That takes quite a while to develop.

This sounds like a warranty issue.

Scott
 
PoolGuyNJ said:
In the header of the heater with the flow ends of the pool plumbing attached, is an internal bypass.

It sounds like it's broken open and not allowing water to enter the heat exchanger tubing. Repair the bypass and the problem should be gone.

This sounds like a warranty issue.

Scott
Click to expand...

This is where I am leaning. Either the internal bypass is broken, or the pump is discharging too much pressure, overriding the bypass.

I'm going to take everything apart again & try to pass something through the heater, like a hose or a wire or something.
 
thunderkyss said:
This is where I am leaning. Either the internal bypass is broken, or the pump is discharging too much pressure, overriding the bypass.

I'm going to take everything apart again & try to pass something through the heater, like a hose or a wire or something.
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Since the heater is only two months old, shouldn't it be covered under warranty?

You should not try pushing a wire, hose or anything else through the heater.
 
JamesW said:
thunderkyss said:
This is where I am leaning. Either the internal bypass is broken, or the pump is discharging too much pressure, overriding the bypass.

I'm going to take everything apart again & try to pass something through the heater, like a hose or a wire or something.
Click to expand...
Since the heater is only two months old, shouldn't it be covered under warranty?

You should not try pushing a wire, hose or anything else through the heater.
Click to expand...

Yes, it is still covered under warranty. I'm only trying to see if there is some sort of obstruction.

I didn't have anything small enough to fit through the holes. Although the plumbing mates to the heater via a 2" PVC line, the holes in the heat exchanger are much smaller. Instead, I held a water hose to each hole & noted the flow coming out the other end. After seeing how small the holes were, I pretty much ruled out an obstruction through the heater coils anyway.

I once again removed all my filters & thouroughly cleaned them. They look brand new. The pressure on my filter cartridge was 15lbs before & after the cleaning, so I'm rulling that out as well.

After cleaning the filters & checking for obstructions, the heater is acting exactly the same way as it was before. I'm thinking it is definitely a malfunction of the heater, & will call my builder tomorrow.

I believe I have done all I can do.
 
My pool builder sent out a repair man to check my heater. He says it's got calcium scale in it.

My most recent numbers are
FC: 3 ppm
CYA: 60 ppm
TA: 200
ph: 8+
ch: 270

The heater was in service for about 4 weeks, I don't understand how it can already be scaling.
 
What are you using to test the water? If the results are accurate, the TA and pH need to come down. If this is a plaster pool then your CH is on the low end of the acceptable range. I do not know if a high TA and pH cause scale in a small environment like the heat exchanger even if the CH is as low as 270.
 
Your numbers definitely indicate a scaling risk. If this is new plaster, then the calcium hydroxide given off by the curing cement will raise the pH and can become calcium carbonate, especially if you have vacuumed the plaster dust through the system. Running the heater increases the risk.

DO NOT turn on pool heater until there is no plaster dust in the pool.
http://www.npconline.net/StartUp.pdf
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You need to get the pH and TA down ASAP.
 
JamesW said:
You need to get the pH and TA down ASAP.
Click to expand...

That's what my builder said after the service rep told him my heater was scaled. I wish he would have put more importance on it before, like told me when he turned it over to me.

JamesW said:
Your numbers definitely indicate a scaling risk. If this is new plaster, then the calcium hydroxide given off by the curing cement will raise the pH and can become calcium carbonate, especially if you have vacuumed the plaster dust through the system. Running the heater increases the risk.

DO NOT turn on pool heater until there is no plaster dust in the pool.
http://www.npconline.net/StartUp.pdf
Click to expand...
Click to expand...

Good info.... If I knew then what I know now. I asked my builder about the dust I saw when I brushed the pool, he said it was sand. I have a lot of sand around my pool, when they dug up my yard, they didn't replace the grass, they filled everything back in with sand.

He said it was nothing to worry about, only that I need to clean my filter more frequently until I finish landscaping.

I didn't budget to relandscape.
 

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