How to calculate settings for taco xpb

tacampa

UPDATE: It seems it was a matter of changing temp settings and a possibly faulty outside temp sensor. For now, it's working fine at 0F° since I have changed the out dsgn temp.

Hi all,

I have radiant floor heating with a taco xpb1 pump. After much trouble as a first time homeowner in Alaska, i thought i had solved the problem with the heating not reaching setpoint when the temperature dropped. It was working fine but then we had yet another drop in temp (single digits F) and it's having trouble to reach setpoint again. I don't want to mess with the settings without having a reference of how high i should set up the water temperature. I'm also wondering if the system won't be able to heat up the place if we hit -30F. Anyway, is there a source to calculate the setting i should use in the taco xpb1? Last time I changed mix dsgn (145) and mix min (115) and that did the trick. I tried calling taco, but the agent said I needed to know which sensors I have installed to receive tech support (sadly I don't know because the previous owners didn't leave any instructions though im almost certain you can figure it out with their support).

Jamie Hall

With radiant particularly you really have to experiment — and give things time to stabilize. Is this unit connected up to outdoor reset, or do you have it targetting a particular setpoint? Either way, you have to raise the temperature of the water circulating — or get more water to circulate.

I too wonder if you will be able to heat the place with radiant floors at -30 F…

LRCCBJ

I have no personal knowledge of the XPB1 but it is clearly a very capable and costly control.

Here is the instruction manual.

https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1347302276781/79661_PROD_FILE.pdf

Pay careful attention to the "VIEW" menu. In this menu you can observe the temperature of the heating source and the temperature of the supply to the floor. These are your starting points. With a radiant floor, you are somewhat limited on the supply temperature to the floor before it becomes uncomfortable to walk on it.

Once you have documented the baseline of where it is currently operating (and it could be operating on outdoor reset where the supply to the floor is reduced at higher ambient temperatures), you can consider making further adjustments, incrementally, to achieve your goals.

The manual is well written but you will need to read it carefully.

I, too, have serious doubts that the floor can maintain 70F in the space with a -30F ambient.

EdTheHeaterMan

I wonder if you got to the right person at Taco. @SteveSan monitors this forum. Perhaps he has some insight on how to determine what sensors you have

tacampa

@Jamie Hall hmm… I thought people were calculating a heat curve to do the pump settings. I'm not sure if we have outdoor reset. I'd assume we do because there's an outside temperature sensor, but then I wouldn't need to change the settings by myself, right? Is there a way to see if it's on outdoor reset ?

I can definitely turn the boiler up to get a higher water temperature, but I don't know if I should. I'm thinking of increasing mix max, mix min, mix dsgn.

tacampa

@EdTheHeaterMan he did suggest contacting taco support on my previous post a couple of weeks back. Maybe I should reach out again and hope I don't get Debbie.

tacampa

@LRCCBJ thanks! I did read the manual, but my problem right now is that I don't know how high temperatures should be. And how much hotter will I have to set it up for an Alaskan cold snap if it's struggling in the ~10F. I assumed this unit would regulate itself.

LRCCBJ

https://forum.heatinghelp.com/discussion/comment/1816789#Comment_1816789

That is the proverbial question. You have a practical limit on a radiant floor if you intend to walk on it. I suspect that you really cannot operate it much above 130F. However, if this is your only source of heat, you may need to experiment with higher. I believe the manual limits you to 140F MAX mixed temperature so that is what you probably will need to do if the worst happens. Of course, you don't need to leave it there. Read the manual to understand how to program the outdoor reset curve to reduce the floor temperature as the outdoor temperature rises.

tacampa

@LRCCBJ thanks again. I was trying to avoid that whole section because I was under the impression that my system was not on outdoor reset setting. However, now I'm extra confused because the "Outdoor reset settings" section references the design supply setting, which is not available to me (unless it's mix dsgn), but OUT DSGN is set to -30F, so I think that would mean my system is actually currently in outdoor reset mode.

Either way, I don't know how high mix dsgn should go, but I'll turn it up some degrees and maybe try to call taco again so I don't burn my house down.

LRCCBJ

Yes, it appears that outdoor reset is functional and that the outdoor design temperature is -30F. The system will most likely increase the mix temp to 140F. However, we don't know at what temperature this will happen. It will certainly happen at -30F but I believe you will need it to happen somewhere around -5F. You can change the outdoor design to -5F and the system will reach 140F at -5F and stay there all the way to -30F. It won't mix above 140F.

You can't burn you house down……………😉

Dave H_2

Some of the most common issues in programming a controller with outdoor reset is changing the OUT DESIGN to a temperature that is colder than it actually reaches in that area to make the system work "faster" or "better" when in reality it is better to go the other way to achieve a higher supply water temperature for the radiant floor at colder temps.

For example, you say outside design is -30 and water temp design is set for 140. The radiant system will only "see" 140 degrees when it reaches -30. The rest of the entire winter, the water temperature will be less warm.

So in essence, if you are not heating the house today, change the outside design temp to something warmer to get a target temp of 140 earlier.

Now, the designed water temperature is a function of the heat loss and the installation method of the radiant system as well as insulation values and finished floor coverings. There are limitations to max water temperatures, installation methods and floor coverings.

tacampa

@LRCCBJ you should have written the manual, the way you phrased that made the out dsgn setting finally make sense!

tacampa

@Dave H_2 thanks! Yeah, that makes total sense now. I definitely didn't get that from the manual. From the manual I understood I should use the average coldest temperature in the area. Anyway, thank you so much. I will change that setting and see what happens.