I guess that's at least 3 of us posting here that have an FPH from Hotspot running. I still love mine, very efficient, green and all that. But I wanted to post an update about it, in part to point out what may be obvious, that somewhat complex systems like this can be - well - complicated.
A couple weeks ago I came home to a house that was way too warm. The A/C thermostat was calling for cooling, and the air handler was running. I walked out to the condenser unit and it was not running - no compressor or fan running. Hmmm. Just to round out the info gathering, I decided to see if the FPH was calling for pool heat - and it was. But I noticed my variable speed pool pump was not running. I remembered we had installed a high pressure cut-out for the compressor contactor in case of running in pool heat mode without adequate water flow - so my guess was that the condensor/compressor overheated (over-pressure) and cut out due to the pump not running. I checked the variable speed pump control panel and indeed it had faulted. I reset the controller, the pump started, and when the pressure subsided in the condenser things seemed to be back to normal. I knew I would have to figure out why the pump faulted, but I also hear that this is common for variable speed pumps - for example if flow is restricted (clogging filter, etc) or they lose prime. So I cleaned the filter, checked for flow, all good, still was unsure why this happened. (As an aside - it's not great to over-pressure your compressor, but that cut-out switch saves the compressor earlier than the internal compressor heat overload protection would).
An hour later I happened to hear rapid clicking of relays in the condenser unit. I then looked at the FPH PID control screen, and I could also hear the PID internal relay clicking in and out. The PID display showed rapid and wild swings in displayed temperature, which accounted for the relay clicking in and out. This rapid switching back and forth between water cooled mode and air cooled mode in my condenser was preventing the compressor from ever doing anything useful, and it kept turning on and off the pool pump, forcing it to again fault. After a fair amount of troubleshooting I determined the PID was defective and replaced it.
So this is all fine when I'm around to debug things, but what happens when you're away and you're the only one who understands the system? I guess if I was on the phone with my wife I would have asked her to shut off the FPH (simple switch on the controller) and power cycle the pump controller, then debug when next I could. But if you call the average A/C repair folks, I doubt they will find it quickly, if at all, and it might get expensive in the process. Most pool services would be in further distress in my experience. This all might be an argument to find some professional to oversee the entire installation, so that would be the initial point of contact. Perhaps a home automation company, not sure. In my case, as others have indicated, I had to do a lot just to train my A/C folks on how to set up the refrigeration side - then I did the pool control integration and plumbing. Maybe this is just the same peril we all face when in DIY mode, especially on more complex systems
..........
On a semi-related matter, especially for anyone building their own system like this, I identified at least three different controllers that can work with this system, as follows:
- The original TET612 PID (about $37), and there are dozens of very similar products. I have this one in my FPH control enclosure outside. One example at:
Dual Digital F C PID Temperature Control Controller | eBay
- The smaller XMT7100 ($22) - I use this one inside the house on a wall plate I customized (pictured), one example at:
XMT7100 Digital Intelligent PID Temperature Controller Red Screen | eBay
(PIDs can be confusing to set up, even when used in a very simple use case like this. In order to use the XMt7100 which only offers normally open relay contacts, you have to set it to "Control mode 3" ("One Line Relay Output"), set also to "heat mode" and then set "AH" to lower temp limit and "AL" to upper temp limit (yes reverse of what you would think). There may be other setting combos that work, I tried many, this took me forever to figure out)
- A simpler and more user friendly one called a "Fahrenheit 110V Temperature F Controller Temp Sensor incubation thermostat Relay" ($14). This one I bench tested but have not yet installed. Upside is that it has tenths of a degree readout and far simpler to set up and change, downside is it's a little wider and would require enclosure mods to mount in the FPH controller enclosure. Example at:
Fahrenheit 110V Temperature F Controller Temp Sensor Incubation Thermostat Relay | eBay
About the water temperature sensors fyi.... The first aforementioned PID controllers generally come with PT100 sensors - thin cylinders encased in a sealed plastic tube. The PID's also offer support of at least ten other types of thermocouples / sensors, but I never got it to work with any "standard / sold pool pipe-mounted sensors" - mostly I think because the sensors are sold to be matched with their controllers and they don't state the technology used in the actual sensor (eg K type thermocouple, T type, PT-100 thermo resistor, etc). So I tried all or nearly all PID option settings against a couple standard sensors to no avail - I only got it to work with a PT100. Write to me if you want advice on how to mount a PT100 to a pipe for reliable sensing. It can be tricky especially if you use a variable speed pump that does not fill the pipe with water. And I learned the hard way (oh my, the hours spent) that the sensor must be all the way in the pipe, in full contact with water, versus having just the tip or even the first half of it in the water. I'll try to post about that with pictures.
Have fun - I need to spend more time IN the water - LOL. ... Joe
