Calling any Taco X-Pump Block experts

bhowden

I have a small radiant floor setup using an X-Pump Block and am just trying to understand how it is behaving. Watching the various values while it is running there is often a very big lag between what I think it should be doing and what it is actually doing. I am assuming the onboard microprocessor is running some sort of PID algorithm to keep the input and output balanced. Given that these devices span a wide range of applications am I correct in assuming that the algorithm is self learning and adjusts the P, I, and D rations over time? If so, how long should I be waiting for it to stabilize with new values when something changes. Is there any way to reset the box so it starts relearning? Am I overthinking what this is doing? As I said, it seems to be working but I would like to understand it all.

Brian

bhowden

Perhaps I spoke too soon about it all working correctly. An example of what I am not understanding seems to be going on right now. This morning everything was fine with a target mix of 93F and an actual supply mix moving between 92F and 94F with the supply pump running at about 2 bars. Right now the target is 90F and the supply mix is 76F with the supply pump not running at all. And worse, it is starting to get cold in the room! If I press the test button the supply pump spins up to full speed and the supply mix temp climbs up to about 82 before slowly falling back down. It all seems to be working mechanically but the controller seems to have decided not to run the supply pump for some reason.

Brian

bhowden

Update: So after 3 hours it suddenly woke up and is running normally now. Target temperature of 90F and a supply mix of 90F. When I checked the supply pump was running with one bar. I have not touched anything and all the parameters are the same. The thermostat has been calling for heat the whole time and the floor loop pump (the continuous one) has been running the whole time. It would be nice to understand what this thing is thinking and why it is doing what it is.

Brian

HomerJSmith

Check your wiring to the back of the control, check your sensors for good contact. If you have outdoor reset check that. Go over your installation instructions.

bhowden

I did check the wiring an it all looks fine. The sensors are all reading and displaying values (on the X-pump display using the item button) that match my temperature gun. This morning the thermostat called for heat at 7:30AM. The X-Pump came on and the circulation pump fired up but no supply pump. The target temp display read 90F. The supply mix stayed at 68 for an hour then over the next hour it crept up to 74F and then over the next 15 minutes it climbed up to 89 and sits there now working exactly as it should.

I am now wondering if perhaps it is designed to have the thermostat continuously calling for heat 24 X 7 and depending on the outside temperature sensor to regulate the room temperature. If the PID values adjusting the temperature take several hours to get it into the correct zone and that it has to start all over every time the thermostat goes off for a bit then it might explain what I am seeing. If so, I am in trouble. There is some solar gain in the room for part of the day and I am depending on the local thermostat to keep the room even temperatures. I also have a floor sensor that I need to kick in to protect the flooring from overheating. I could live with keeping the temperature even 24 hours per day but I would prefer to set it back a few degrees for the 12 hours a day we are not in the room.

Continuing to ponder and hoping for insight...... It would also help if this wasn't happening on Valentines day!

Brian

Joe Mattiello

hi Brian
for your convenience, I attached the XPB instruction sheet, and catalog data file too. sounds like the this unit has been installed for a while and may have been working fine, until recently? If so, it's likely a bad sensor not providing accurate temperature to respond appropriately. You can ohm out the sensors; instruction sheet covers it. there is a manual button behind the control you can use to validate the pumps too. if you put the switch in manual mode, both pumps should operate at full compliment; it basically circumvents the control.
Hopefully this helps, and if your require additional support, contact Taco technical support at 401-942-8000 and ask for tech support. Let us know the outcome

bhowden

Thanks for the reply. It has only been installed since December 2020 and I have made a couple of changes since then (added another floor zone) so it is still in the teething phase. When I first installed it the supply pump was barely running and the zone was too hot. Based on advice here I throttled the supply loop by partially closing the return valve which worked perfectly. The supply loop pump now runs more visibly and when it feels like working, the supply mix tracks the target within a degree or so. My current puzzle is that every now and then the temperature drops way below the target and supply pump doesn't run for a couple of hours. I have been watching more closely over the last few days and after a few hours it decides to come back to life and the temperature comes up to normal and tracks quite well. It was fine at 8:30 this morning but by 11:30 the supply mix is down to 71 and still falling with a target of 90 and the supply mix pump is still not running. Holding the up arrow down for 10 seconds does put it into test and both pumps spin up as the manual describes and the relays actuate as described. The manual override switch does actuate both pumps at full speed and the floor loop rapidly rises in temperature but I can't run it that way or the floor will overheat very quickly. My non contact thermometer agrees with all the sensors and the ohm meter shows values very close to the manual. I don't have any good way to track when the thermostat is calling for heat but from periodic checks, the problems seem to start when the thermostat has been off for a while and has just come back on. I would expect a period of time where things come back to equilibrium but several hours is very uncomfortable and seems excessive. Is it designed to not really want the room thermostat to be regulating the temperature and to use the outdoor temperature instead? As I mentioned earlier, that won't work for me because of solar gain.

Brian

bhowden

Update: So the supply mix temperature gradually fell until it got to 71F where is sat for 2 hours. At 1:20 this afternoon it suddenly woke up and was happily sitting at 91F 10 minutes later. Nothing changed in the mean time. The target has been at 90F and the thermostat has been calling for heat the whole time. The X-Pump shows (and has shown the whole time) DEM on the display which I am assuming indicates that the demand switch is being sensed properly.

Brian

bhowden

So yesterday the thermostat called for heat at 7:30 and the pump spun up and was up to temperature in about 15 minutes. This morning, the thermostat called for heat at 7:30 and by 9:30 the supply circulation pump was still not doing anything and the supply mix temperature was still 64 degrees. The floor loop circulation pump was running the whole time. By 10: it woke up and everything was fine with the supply mix temperature right at the target temperature. I phoned Taco support and the tech seemed to know his stuff. Knew the equipment and all the switches but basically had no suggestions. We went through the usual test modes and it all worked correctly. We reviewed all the settings and all were reasonable. His only suggestion was to play with the settings a bit to see if there was a combination that worked better. Apparently it should come up to temperature fairly quickly when the thermostat calls for heat. While I would prefer to use the Outdoor Reset mode I am considering trying the setpoint mode and letting the thermostat do all the regulation in the hopes of avoiding several hour stretches of no heat. Unfortunately Sanden recommends the Outdoor Reset mode because they want the water returning to the boiler to be as cold as possible.

Brian

bhowden

Well, I am not sure but I think I have solved the problem. It will take some more time to be sure but I think the thermostat on / off was a red herring. My current theory is that the boiler protection feature is overriding the call for heat and keeping the source circulation pump from running. It stays that way until the heat pump runs and warms the tank up enough to exceed the boiler minimum set point in the x-pump.

Does anybody know what conditions cause the X-Pump to turn on the boiler flame icon on the display? I did ask Taco tech support but I must not have explained what I was looking for very clearly as I did not get an answer.

Brian