Importance of outdoor temp sensor for reset on Viessmann Vitodens B1KE-120 ?

GGross

What is the supply temperature that the boiler is making during a call for heat?

ThinkpadUser7

GGross said:

What is the supply temperature that the boiler is making during a call for heat?

Not sure. I assume I'll need to look through the menus on the boiler to find that? I'm guessing it was around 111F based on the 0.8 curve, +25F level adjustment, and approximately 50F exterior temp earlier this morning. Currently the heat is off because interior temp is 66 and thermostat is set to 64, but I could raise the desired temp to 67 to get it to come on. Or I could wait until the next time the heat comes on naturally...

GGross

If it gets cold again check then, you should be able to tap the up/down arrows to see various bits of info while the unit is running. They kind of maxed out the "shift" parameter, this just moves the whole graph you were referencing for the heat curve up drastically which can increase the setpoint temperature above what you want. Just want to make sure it is not too high

ThinkpadUser7

GGross said:

If it gets cold again check then, you should be able to tap the up/down arrows to see various bits of info while the unit is running. They kind of maxed out the "shift" parameter, this just moves the whole graph you were referencing for the heat curve up drastically which can increase the setpoint temperature above what you want. Just want to make sure it is not too high

I'd really like to get the heating curve as optimized as possible to reduce energy costs and not overshoot temps. Currently the system will turn on for about 8 hours to increase the temp one degree and then the house temp will keep raising 2 or 3 more degrees beyond that over the next few hours (due to outside temps raising while slab is releasing heat?). Over the next 24+ hours the temps will slowly drop again (mostly over the night) and the cycle will continue. At the current settings the system seems to use .5 therms per hour when on.

Would it be more efficient to have it running closer to continuously? I can only see that being possible if the therm usage drops significantly, like to 1/10 therm per hour or something. But maybe adjusting curve down and reducing the "shift" will do that? Wishful thinking, but perhaps it would cut down on the noise too?

GGross

In floor heating can be a bit tricky during mild weather. It's the flywheel effect, once the mass of the slab is warmed up if the temperature goes up a bit you can overshoot the thermostat. I imagine that shift setting is making the supply temperature quite a bit warmer than it needs to be as it bases the heating on +25 the base setting, so the curve is based on a 93 f indoor temperature. I really think that shift needs to come down to either zero, or +2-4 (target indoor temp of 68-72 degrees)

ThinkpadUser7

GGross said:

In floor heating can be a bit tricky during mild weather. It's the flywheel effect, once the mass of the slab is warmed up if the temperature goes up a bit you can overshoot the thermostat. I imagine that shift setting is making the supply temperature quite a bit warmer than it needs to be as it bases the heating on +25 the base setting, so the curve is based on a 93 f indoor temperature. I really think that shift needs to come down to either zero, or +2-4 (target indoor temp of 68-72 degrees)

Makes sense. FYI, I just lowered the slope to 0.7 and the "shift" (aka "level") to +2. I'll give that a try over the next few days.

exqheat

With more accurate slab temps in the winter, it would see spring coming. This is Technology?

GGross

exqheat said:

With more accurate slab temps in the winter, it would see spring coming. This is Technology?

If you have a bone to pick take it to private messages, this is a forum for helping people. You showing up and just telling everyone they are dumb, liars, wrong, etc is not helpful to anyone, it is unprofessional when you are acting as a representative of your company, and most importantly it is disrespectful of this forum. If your only sales tactic is "you are all wrong and I am right" when you clearly lack understanding of the subject at hand you should do better and just keep it to yourself. You also don't seem to understand that your target customer base is here on this forum, I make purchasing decisions for an independent wholesaler, I specify controls for hundreds of residential new construction projects every year, and I am glad I have seen how you conduct yourself in public prior to getting involved with your company.

I am not going to respond to your antics publicly any more after this, if you have a continued interest in acting like a fool take it to private messages

exqheat

"

" If your only sales tactic is "you are all wrong and I am right" when you clearly lack understanding of the subject at hand you should do better and just keep it to yourself.'

Could you find that quote for me? My apologies for any insult. As a consultant you should be resourceful enough to investigate technologies when they come to your attention. I don't recall your inquiries. Is it good to consult with a tool box half full.

I answer this publicly as you have defamed me publicly.

inquiries invited. www.exqheat.com

ThinkpadUser7

GGross said:

What is the supply temperature that the boiler is making during a call for heat?

Ok, heat has been running for the past 3-4 hours with the settings i mentioned earlier (slope 0.7, level +2). The heating water temp is 82F, the outside temp is 61F, interior temp is 63F and thermostat is set to 65F.

ThinkpadUser7

I assume this is showing the water pressure before it's reduced, not after?


There's also this gauge on the top of the boiler:


It's angled such that the only way to see it is to take a photo. Was there no easy way to orient it such that it faced towards the front of the boiler?

GGross

That sounds more normal to me. If the system has issues getting up to or maintaining set point then you may want to adjust the slope value up/down accordingly ( I dont think you want to go lower than you are at now). Just remember that high mass radiant slabs are slow to respond, so they don't do well with setbacks, and by the same token if the slab is too warm and then it gets up closer to warm weather shutdown temperatures the slab will cause the space to overheat. The goal is to get the curve to maintain the proper temperature with longer runtimes, generally this is better for efficiency, and better allows the slab to adapt to changing weather conditions as it is never overheated.

GGross

@ThinkpadUser7
I think when I see them they are generally installed forward facing on the boiler. It could have been an oversight by the installer.

ThinkpadUser7

GGross said:

That sounds more normal to me. If the system has issues getting up to or maintaining set point then you may want to adjust the slope value up/down accordingly ( I dont think you want to go lower than you are at now). Just remember that high mass radiant slabs are slow to respond, so they don't do well with setbacks, and by the same token if the slab is too warm and then it gets up closer to warm weather shutdown temperatures the slab will cause the space to overheat. The goal is to get the curve to maintain the proper temperature with longer runtimes, generally this is better for efficiency, and better allows the slab to adapt to changing weather conditions as it is never overheated.

Results of first experiment with slope 0.7 and level of +2:

The thermostat was set 65 and has remained at that setting for the past 24 hours. Yesterday afternoon the interior temp of the house held steady at 65 and the boiler was firing in the morning/early afternoon. The boiler wasn't running in the late afternoon and evening. The interior temp was still at 65 when I went to bed around midnight. When I got up this morning the boiler was firing and the interior temp was at 63. I think it got down to around 43 (outside) last night.

So I'm guessing I need to increase something... maybe bump the level a bit? Let me know what you'd suggest as the next setting to test.

GGross

I would bump slope to 0.8-0.9 You like it pretty cool in the house! What kind of thermostat do you use for the house?

ThinkpadUser7

GGross said:

I would bump slope to 0.8-0.9 You like it pretty cool in the house! What kind of thermostat do you use for the house?

Thanks, I bumped the slope to 0.9

I generally like daytime temp to be around 66, but prefer sleeping temps closer to 64, so it's a bit of a compromise.

This is the thermostat:
https://www.honeywellhome.com/us/en/products/air/thermostats/programmable-thermostats/t6-pro-programmable-thermostat-up-to-3-heat-2-cool-th6320u2008-u/

I disabled the schedule so it's now manually driven. I also changed the "heating cycle rate" from the original value of 3 to 1. I think the value of 3 was causing the heat to cycle on/off three times per hour.

Also, I finally got the ViCare app working and it looks like slope and level can be changed from within the app.

ThinkpadUser7

@GGross One thing I've noticed that I want to ask about. I'm not sure if it does it every time, but I've noticed that if the heat is running and I turn on the DHW I'll hear a pretty loud single occurrence groan noise that seems to emanate from the region of the boiler closet. Expected?

Alan (California Radiant) Forbes

@ThinkpadUser7 My Viessmann B1HE (heating only) with an indirect tank sits directly under my office and - I believe - makes the same groaning sound.

GGross

It may be the diverter valve switching position. Generally you can't hear this sound but I think it may be resonating through the wall it is on.

ThinkpadUser7

It's been a bit too warm recently to do any further fine tuning of the heating curve, so that will probably need to wait till next winter. But I do have one question remaining I'd really like to get an answer to.

How can I confirm that the radiant loop is running at a reasonable pressure and not something inappropriately high?

For reference, the full install photos are in the second part of this post: https://forum.heatinghelp.com/discussion/comment/1793859/#Comment_1793859

and a couple important additional photos here (2nd one is safety valve on top of boiler): https://forum.heatinghelp.com/discussion/comment/1794838/#Comment_1794838

In the last photo of the first link (and first photo of second link) you can see what looks a nk300s-100up, which is described as a "filling combination valve that contains an integrated pressure reducing valve, strainer, double check backflow preventer with air vent (to protect potable water supply against back flow of heating water into supply pipe), two shut-off ball valves, pressure gauge, and conveniently located test ports for easy inspections and check out. All the needed devices for refilling a heating system are contained."

The gauge on top of it is showing 75 psi. In the documentation it doesn't specify whether the reading is pre or post the pressure reduction. I just want to make sure my radiant loops aren't under 75 psi!

In the second link there's also a photo of the safety valve on the top of the boiler that reads around 17 psi. Does that indicate the pressure of the radiant loops?

GGross

The pressure gauge attached to the boiler will be the pressure in your radiant loops, or at least very close to it as they are attached to the same piping. 17 PSI is fine generally speaking

ThinkpadUser7

GGross said:

The pressure gauge attached to the boiler will be the pressure in your radiant loops, or at least very close to it as they are attached to the same piping. 17 PSI is fine generally speaking

Thanks for confirming. So does that mean that the gauge on the nk300s-100up is showing the pressure prior to the reducing valve?

GGross

Yes

ThinkpadUser7

GGross said:

Yes

I'm mainly asking because the product page ( https://customer.resideo.com/en-US/Pages/Product.aspx?cat=HonECC%20Catalog&pid=NK300S-100UP&category=NK300S&catpath=1.2.2.6.3 ) says:

"Outlet pressure adjustable and directly visible on the pressure gauge "

Maybe I'm misunderstanding what that means?

GGross

They installed the pressure gauge on the inlet side instead of the outlet for some reason

ThinkpadUser7

GGross said:

They installed the pressure gauge on the inlet side instead of the outlet for some reason

Ah, got it. Thanks for the explanation.

Hot_water_fan

Late to the discussion, but how much gas can a smaller house in Palo Alto possibly use? Are we chasing our tail here? 

ThinkpadUser7

Hot_water_fan said:

Late to the discussion, but how much gas can a smaller house in Palo Alto possibly use? Are we chasing our tail here? 

I'm not sure what you mean here... are you referring to the attempt to optimize the heating curve?
With the settings the installer had initially set the system was using about .5 therms per hour while on, which seemed to overshoot the desired temp. My old system would have probably used ~100 therms per month or more if I had just left the thermostat set to 65.

My goal is to have the heat generated match the heat loss as closely as possible for reasons of comfort, system longevity, and savings.

Hot_water_fan

100 therms including domestic hot water for the highest usage month with a low efficiency tank? So savings of maybe 10% for the most expensive month for central heating, then decreasing throughout the year as it warms? 

Comfort makes sense to some degree, the other reasons seem like you are chasing diminishing returns. 

In dollars, I think you’re chasing maybe $10-20 a year by continuing to change the settings. If the return temp is 120F or lower, you’ve done what you can do. 

ThinkpadUser7

Hot_water_fan said:

100 therms including domestic hot water for the highest usage month with a low efficiency tank? So savings of maybe 10% for the most expensive month for central heating, then decreasing throughout the year as it warms? 

Comfort makes sense to some degree, the other reasons seem like you are chasing diminishing returns. 

In dollars, I think you’re chasing maybe $10-20 a year by continuing to change the settings. If the return temp is 120F or lower, you’ve done what you can do. 

It's hard to know for sure. With my old system I had safety concerns that made me reluctant to have it running while away or sleeping. As a result we ran it for a few hours here and there but mainly used space heaters. I did one experiment shortly before getting the new system where I let it run for a full 24 hours. Over that time it used 12 therms according to the gas meter. There was a period last winter where gas prices increased and it was ~$5/therm. Assuming it used 12 therms every other day that's still 12*5*15 = $900 in gas for the month.

The new system also used .5 therms per hour with the initial settings, so forgive me for thinking I'd have the potential to save a lot more than $10-$20 a year by getting it running as efficiently as possible.

Hot_water_fan

If it’s condensing (return water at 120F or so), then any further gains are minimal. $5/therm? Are you sure? 

ThinkpadUser7

Hot_water_fan said:

If it’s condensing (return water at 120F or so), then any further gains are minimal. $5/therm? Are you sure? 

yes, the tier 2 rates (over 60 therms) in Jan 2023 were $5.74/therm: https://www.cityofpaloalto.org/files/assets/public/v/15/utilities/rates-schedules-for-utilities/residential-utility-rates/monthly-gas-volumetric-and-service-charges-residential.pdf

I'm not sure what you mean about the return water temp. The curve I'm currently using has the loop running much lower than 120F and using one fifth the gas that it did originally: I'm at about 1/10 therm per hour now. Granted outside temps aren't getting very low anymore so I'll need to test more next winter.

Hot_water_fan

That’s great! You want low return temps. The lower the supply temp, naturally that helps you achieve a low return temp. If you’re much lower than 120F already, then you’re done. No more juice left. 

FYI: therms per hour isn’t the best way to measure this, so might be leading to confusion. For example: .5therms/hour for 4 hours/day costs the same as .1therms/hour for 20. The measure that is more useful is therms/heating degree day (google that if you haven’t), it adjusts for temperature, which is what drives heating needs, not hours or anything else. If you can, you can now compare a month or so of the old boiler’s therms/HDD vs. the new boiler’s therms/HDD. This will show you the true savings. 

yes, the tier 2 rates (over 60 therms) in Jan 2023 were $5.74/therm

Ah yes, the extreme outlier. 

ThinkpadUser7

Hot_water_fan said:

That’s great! You want low return temps. The lower the supply temp, naturally that helps you achieve a low return temp. If you’re much lower than 120F already, then you’re done. No more juice left. 

FYI: therms per hour isn’t the best way to measure this, so might be leading to confusion. For example: .5therms/hour for 4 hours/day costs the same as .1therms/hour for 20. The measure that is more useful is therms/heating degree day (google that if you haven’t), it adjusts for temperature, which is what drives heating needs, not hours or anything else. If you can, you can now compare a month or so of the old boiler’s therms/HDD vs. the new boiler’s therms/HDD. This will show you the true savings. 

yes, the tier 2 rates (over 60 therms) in Jan 2023 were $5.74/therm

Ah yes, the extreme outlier. 

Yeah, I feel like the system is pretty well tuned for the 65F day, 45-50F night temps. I have a feeling I'll need to adjust things when day and night temps drop lower, but that probably won't be for another 9 months.

I'll look up therms/HDD. Thanks for the tip!

Fortunately it was an outlier, but with only a few months each winter it didn't feel like that much of an outlier. But even at $2.50/therm we're still talking $450/month in my example.

Hot_water_fan

Historically, are you using more than 200 therms in any 1 month in Palo Alto? That’s a whole lot for somewhere that warm and with a house that size. 

ThinkpadUser7

Hot_water_fan said:

Historically, are you using more than 200 therms in any 1 month in Palo Alto? That’s a whole lot for somewhere that warm and with a house that size. 

We have been averaging around 50-60 therms a month in the winter (including gas for 40 gallon DHW tank and gas stove) but this was without really using the old heating system due to safety concerns. The system was turned on maybe 20 hours a month at most. We mainly left the thermostat set to 50F and we used space heaters.

The safety concerns were due to specific incidents in the past: the pump being stuck resulting in the entire boiler violently shaking, pilot going out but still getting gas flow because thermocouple only shuts off main gas supply, excessive pressure spewing water all over the closet

The system seemed very unsafe so we never wanted it on while away or sleeping.

Simply Rad

ODR is the logic providing comfort and efficiency of the boiler.   One way to see if you have the curve set correctly is to pick the heating zone with the highest heatloss….generally the great room.  But your heatloss calcs will tell you that, highest btus/sqft.  Do this on a cloudy day, to take solar gain out of the equation.  Turn the thermostat up in that room to 80F and let the system run for a day.  If the tstat achieves a higher setting than your desired set point(68F).  You can turn down the slope and shift.  I would start at 0 for shift. As said earlier in this thread you can run your house off a perfectly set reset curve without a tstat.  At that point you are heating your home with the lowest possible supply water temp which in return provides a constant inside temp.  The idea is call constant circulation which is the ultimate in comfort and efficiency. 

Jeffrey 

exqheat

How many folks can accually do that. All New boilers have that capability. I have yet to see that they are set up with outdoor reset properly adjusted.