Heater Problems

[Dean Roberts]

Can anybody with experience tell me how much on/off cycling I should expect to see from a Hayward 1000 natural gas heater heating a 12 foot diameter (18,000 liter) above ground pool.

Since day one this heater has been able to keep water warm ... but I believe it is not working correctly. I've had it serviced many times each year since its installation and usually give up since the water is warm ... but ....

Here is what the heater does.

If I crank the thermostat to full, the heater comes on and stays on and can get the pool very toasty. I've never bothered to see just how toasty it can get.

However, if I dial back the thermostat to a more natural position, when the pool "reaches temperature" the heater will begin on / off cycling at, what I believe, is an pathological rate. I've timed it and it will come on for about 90 seconds. Shut off for a about two minutes, then back on for 90 seconds etc.

Depending on which service guy (from the same company) comes out I'm told that this is normal, or that this is for sure a problem. They've replaced the thermostat twice, the board once and even changed the heat exchanger.

So essentially each year I just give up since, the water is warm. But I the constant on/off annoys me and I can't believe it is very efficient.

This spring things are even worse. Again, with the thermostat all the way up the heater can stay running for hours at a time. But set an an appropriate level, now the unit is cycling on for 30 seconds, off for a minute ... continuous.

I've spoken with a couple of different service companies this spring. One of the guys hates Hayward 1000 heaters and has had several reports of these things being just tenacious and generally not working well. He suggested that since I can get the heater to stay on I should just use it to heat the pool when I know I'll be using it. He claimed this was how most people heated small above ground pools.

He did say he liked the Jandy Lrze (sp) and Raypak 125k btu units a lot better than the Hayward 1000.

At this point I'm almost ready to just spend the $1500 for heater plus install if I can be certain that a correctly functioning small pool heater can, in fact, maintain a consistant temperature with a more reasonable on/off cycle. And was wondering if people could share their experiences as to what a reasonable duty cycle would be.

Thanks for any advice you can give.

[txpoolguy]

Based on your description, I don't think the heater itself is the problem. Once the heater reaches the temp set on the thermostat, it should cycle off, then back on when the water temperature drops @2 degrees. Cycling this rapidly does not sound normal, but the heater has to be responding to a change in the water temp. If your return/s are located near your skimmer, it could cause symptom like this because the skimmer could be pulling in water that has just come from the return, giving the heater a "false" actual temperature. Try pointing your return jets towards the bottom of the pool, or away from the skimmer and see if it improves. When the thermostat is set to maximum, it will take approximately 104 degree water to turn the heater off, so when you dial it down, it looks for a lower temp.

[Dean Roberts]

Thanks for the reply.

I did try this last season since the return and skimmer are close to each other. To be really sure I stuck my vacuum hose over the return to exhaust the return on the other side of the pool, far from the skimmer. No change. I also used a sensitive digital thermometer in the skimmer itself and did not see any temperature changes while the heater was cycling.

[Pool Clown]

Almost sounds like a mixing problem. Have you checked the flow control thermostat? (not the thermostat on the front of the heater) Or the internal bypass, for an obstruction or failure?

[Dean Roberts]

Ya all of these things have been checked and or replaced over the course of troubleshooting.

I decided to build an Arduino project to solve my problems. I'm a software guy, and have not done hardware since high school so this was a lot of fun. It is finished and been working like a charm for a few weeks now.

Here are some pictures for anybody that might be interested.

http://www.flickr.com/photos/drobertsca/sets/72157624251075916/detail/

The project uses an Arduino board (an Atmega micro controller built up on a board with a C compiller) to receive wireless pool temperature data from an Oregon Scientific pool thermometer. The controller uses a relay to control power to the pool heater as required. As an added bonus I threw on a WiShield so the controller can attach to my wifi network and wrote a little web server that runs on the Arduino so I can monitor and control pool temperature from any web browser.

Now I'm just working on making the web UI a little prettier and adding basic scheduling support. I've set my temperature delta at +/- 1 degree F. Typically the heater will come on for 30 minutes or so and then turn off for an hour or two. I have to say I was actually surprised at how slowly the pool looses heat.