HTP UFT 80 set point?

[DR-DEATH]

hi guys I had a HTP UFT 80 installed last November. All is well so far but I do have a question. I noticed my basement zone 3 was the only zone calling for heat and after watching the boiler it was reaching set point of 179f. The outdoor sensor was showing 37 degrees and according to the stock curve the set point should have been around 130-140 degrees at 37f.

The Set point was 180 and the return temp was 165 according to the information menu.

I’m confused why the set point was showing 180. Is it because that one zone has 13 ft of baseboard and the boiler was reaching temp to quick so it set the set point higher? The burner was on the whole time and didn’t turn off and then turn back on a bunch of times either.

Any insight would be great

 

[Dana]

Yours would be a good guess, but the answer may be buried in the manual, which I haven't really delved into in depth.

But note, 180F out, 165F is an average water temp of 172.5F. At an AWT of 172.5F the 13' of baseboard would be emitting about 6600 BTU/hr, which is almost exactly the minimum fire output of the UFT-080 at non-condensing temperatures. It may be "learning" the system, or has an inherent algorithm for ramping up the temp to avoid short-cycling when the temperatures are slewing rapidly even at minimum fire, automatically adjusting up the temperature until the return water temp stops rising quickly, ignoring the reset curve under those conditions.

Such a control algorithm would be the salvation of MANY boilers installed on systems with pipsqueak radiation zones. Don't know if that's what it's doing, but it's a reasonable conjecture.

 

[Sponsor]

 

[DR-DEATH]

Yours would be a good guess, but the answer may be buried in the manual, which I haven't really delved into in depth.

But note, 180F out, 165F is an average water temp of 172.5F. At an AWT of 172.5F the 13' of baseboard would be emitting about 6600 BTU/hr, which is almost exactly the minimum fire output of the UFT-080 at non-condensing temperatures. It may be "learning" the system, or has an inherent algorithm for ramping up the temp to avoid short-cycling when the temperatures are slewing rapidly even at minimum fire, automatically adjusting up the temperature until the return water temp stops rising quickly, ignoring the reset curve under those conditions.

Such a control algorithm would be the salvation of MANY boilers installed on systems with pipsqueak radiation zones. Don't know if that's what it's doing, but it's a reasonable conjecture.

Gotcha. I’ll comb though the manual to see if there’s anything about ignoring the curve. I did call HTP and the tech said it could have been a incorrect odr reading or from the short baseboard zone. I’m going to be doing a minimal remodel in the basement so I’ll have another 10ft of baseboard installed. That sounds like it will help with this issue and also heat the basement up faster.

 

[Dana]

As a short experiment you can turn up the basement thermostat for an extended call for heat, turn the others way down to suppress calls, then wait for it to get into the high-temperature setpoint condition.

Then, turn your biggest zone thermostat way up for an extended call, and see if it re-adjusts to ODR setpoint. If it does, GREAT! That means it automatically suppresses short cycling by raising the temperature if it needs to, but still tracks the ODR curve when it can. Even though it's not a hard algorithm to implement, most boilers just stick with the ODR curve, short cycling be damned.

If it doesn't drop back to the ODR setpoint you have a bit more sleuthing to do.

 

[DR-DEATH]

As a short experiment you can turn up the basement thermostat for an extended call for heat, turn the others way down to suppress calls, then wait for it to get into the high-temperature setpoint condition.

Then, turn your biggest zone thermostat way up for an extended call, and see if it re-adjusts to ODR setpoint. If it does, GREAT! That means it automatically suppresses short cycling by raising the temperature if it needs to, but still tracks the ODR curve when it can. Even though it's not a hard algorithm to implement, most boilers just stick with the ODR curve, short cycling be damned.

If it doesn't drop back to the ODR setpoint you have a bit more sleuthing to do.

I just tried that test. It took an hour or so to get the basement zone running at 179-181f and set point there too. I turned the main floor on which is about 45 ft of baseboard and once the zone valve opened the water temp dropped from 180 to 120 or so. Set point still stayed 180. I sat there for about 7-10 mins watching the water temp with both zones open raise to around 160 before I stopped watching. The set point still stayed 180 but with return water temp st about 120. I do feel that the boiler is ignoring the outdoor sensor to prohibit short cycling but maybe it just doesn’t drop the set point back down until the next flame ignition but idk.

 

[DR-DEATH]

Update: this morning both second floor and first floor zones were on and I went down to check the set point. The boiler was running for about an hour at that point and the water temp was 167 with a set point of 180. The outdoor temp sensor was reading 29f.

Reading the manual states that you cannot manually change the setpoint while an outdoor sensor is installed unless you change the actual curve. I haven’t changed the curve since install.

Max outdoor temp: 68
Min outdoor temp: 5

Max supply temp: 180
Min supply temp: 86

Could using nightly setbacks cause this? We turn first and second floor down to 64 at night and then back up to 69 during the day. I can watch the set point temp raise the longer the boiler runs. (Boost feature is turned off as well so I know it’s not that)

I know if we kept it at 68-69 all day and night that no matter the temp outside the boiler wouldn’t reach 180 f water temps as it would satisify the the thermostat before that happened. It almost sounds like the htps boost feature is on but it isn’t.

The only other difference from last year is I installed an ecobee (no room sensors for it though) for our first floor. I don’t think that would impact anything though

based on the curve I feel like it’s setting the setpoint wrong :/

 

[Dana]

It does indeed behave as if the boost feature is enabled. This is one to sort out with HTP.

You also might try to dial in the reset curve to the ultimate minimums and stop setting back, if you can still sleep comfortably at 69F. Anything that causes it to go above 125F for the return water temp is taking it out of the condensing zone, and eating up any potential energy use savings that you might have gotten out of the setback. (That's how most modulating condensing boilers deliver the best fuel economy.)

 

[DR-DEATH]

It does indeed behave as if the boost feature is enabled. This is one to sort out with HTP.

You also might try to dial in the reset curve to the ultimate minimums and stop setting back, if you can still sleep comfortably at 69F. Anything that causes it to go above 125F for the return water temp is taking it out of the condensing zone, and eating up any potential energy use savings that you might have gotten out of the setback. (That's how most modulating condensing boilers deliver the best fuel economy.)

HTP thought it was the outdoor sensor reading the correct temp but telling the boiler the wrong data. Tested the sensor with a multi meter and it’s functioning correctly per the manual. I did find another thread that had two other people with my issue and it was due to old firmware on the machine forcing a boost feature even though the controls said it was off.

It honestly only jumps set point if it’s running for a long time ie morning so I’ll get away from the set back and it shouldn’t do it anymore. Problem is now if I dial in my curve to where it never/barely satisfies the thermostat... I’ll have the issue continuously most likely.