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

exqheat

"But the chart just shows supply temp vs outside temp, so I don't understand how target room temp is involved with these curves."

How about that? They haven't thought about it very much.

ThinkpadUser7

@GGross Ok, here are photos of the before and after:

Old system, likely installed around 75 years ago:






New system:

GGross

Can you make sure one of the 3" rubber plugs on top of the unit is removed (there are 2, one on either side)? Not the small rubber plugs that are facing forward! I would rather see a separate connection for intake air, expansion tank is currently located on the supply and should be on the return, and generally these are meant to be piped primary/secondary. If the flow rates are acceptable for the boiler they can be direct piped, but generally not a great idea.

ThinkpadUser7

GGross said:

Can you make sure one of the 3" rubber plugs on top of the unit is removed (there are 2, one on either side)? Not the small rubber plugs that are facing forward! I would rather see a separate connection for intake air, expansion tank is currently located on the supply and should be on the return, and generally these are meant to be piped primary/secondary. If the flow rates are acceptable for the boiler they can be direct piped, but generally not a great idea.

How important is the expansion tank location for this situation? Enough to ask for justification? Enough to ask them to fix? How would work would it involve? Does Visesmann specify where it should be located in the installation instructions?



I did ask about intake air and was told that the upper and lower door vents to the outside where fine, and this option seemed to be shared by the other installers that gave me bids:

GGross

I'm sure it's ok like it is, maybe not 100% ideal but things rarely are lol. were you able to locate the correct QR code on the unit to connect to the app? this part is sort of confusing as there are multiple, the correct one has a wifi symbol on the top, sometimes located on the front or side of the unit. If its not there I can guide you toward it, as they hide one inside the front control

ThinkpadUser7

@GGross Yeah, I think I identified the correct one. I've gotten part way through the process, but wasn't able to get past the Wifi connection part where it's trying to pair. It gives me the password to the Viessmann network, I pick the Viessmann SSID on my phone's Wifi list, enter the password ... but then there's an error on the ViCare app (can't remember the exact wording...). The app then instructs me to cancel the pairing and try again. I did this process 3 times but got the same error every time. My phone was about 2 feet from the boiler while attempting.

ThinkpadUser7

Will ViCare let me view the heating curve slope and level? Can I modify them too from within the app?

GGross

I've used the installer version of the app, I am fairly certain the owner version allows you to change the curve and DHW temp

ThinkpadUser7

Can you guide me through viewing the slope and level on the boiler itself?
I don't want to mess anything up accidentally, but I'm curious what the current values are

mattmia2

exqheat said:

"The heat loss varies with solar gain and wind so there are settings for modifiers to the reset curve on most boilers that will do things like increase the setpoint if the heat call lasts over a certain time."

Why not just control the heat from the thermostat information?

Because it has no idea if the loss is at design conditions or 1/8 that so it has to assume it is design conditions and heat the water to the temp that will produce enough output for design conditions. That reduces the efficiency of a mod con and reduces the length of the cycle and increases overshoot so the temp is less even. ODR sets the water temp based on the outdoor temp so it matches the output of the system to the loss of the house, at least something close to it.

ThinkpadUser7

@GGross Ok, I figured how to use the controls on the boiler to view settings...

Currently the heating curve has:
Slope: 0.8
Level: 25 K

The "temperature setpoint" is "Normal 126 degrees"
Scald protection is on

DHW temp is listed as 131.5 F

Thermostat function says it's "OFF"
Heating circuit pump says it's "OFF"
(FYI, boiler was not running at the time)

Do these values look Ok? Any suggested changes?
Why is the DHW temp higher than the "Temperature setpoint"?

ThinkpadUser7

I've tried about 10 times but can't get my phone to connect to the boiler. This is the error I get every time after selecting the Viessmann boiler SSD and then going back to the ViCare app (as instructed):
"Unfortunately, we could not establish a connection to your device. Please hold the MENU button for 3 seconds until setup is closed. After this please proceed to repeat the commissioning process."

I even tried deleting the app's local storage and redoing the full process, but it always returns that error.

mattmia2

exqheat said:

"But the chart just shows supply temp vs outside temp, so I don't understand how target room temp is involved with these curves."

How about that? They haven't thought about it very much.

The additional complexity and cost doesn't warrant it. A change in delta t of 10 degrees doesn't change the load that much. It only makes sense in large buildings to spend the money on measuring the 10 other less influential factors on load. Increasing the setpoint in increments if the call doesn't end in a certain time frame is a great proxy and inexpensive.

hot_rod

If there is no insulation under that 40 year old slab, the initial ramp up will take some time. You are heting the concrete and earth below. Give it a day.

With a large high mass uninsulated slab, you really want to dial in the ODR. If not you over-heat the slab and it radiates heat beyond the thermostat setting. Warming it slowly via ODR is the way to go with as slab like that.

ThinkpadUser7

hot_rod said:

If there is no insulation under that 40 year old slab, the initial ramp up will take some time. You are heting the concrete and earth below. Give it a day.

With a large high mass uninsulated slab, you really want to dial in the ODR. If not you over-heat the slab and it radiates heat beyond the thermostat setting. Warming it slowly via ODR is the way to go with as slab like that.

78 year old slab! Thanks for the advice. I'm definitely interested in optimizing it as much as possible. I'm kind of surprised how little documentation there is on this feature for the specific boiler. I looked through all of the pdfs on the Viessmann Vitodens B1KE page and I haven't seen the heating curve "level" defined in any precise way. It apparently moves the whole curve up, similar to increasing the target temps, but the amounts are mysterious. I wonder if the app makes it more clear with a visual representation. Too bad I haven't been able to get the app working yet.

One thing I don't understand about ODR:
If the optimal setting is to exactly match the heat loss of the house based on exterior temp, then how would you ever be able to increase the temperature of the house? If you adjust it so you can put more energy in than is being lost then it will inevitably shut off when it reaches the target temp. I guess maybe it's just a goal to strive for but impossible to 100% meet.

mattmia2

matching the swt to the heat loss of the house and the step boost functions are sort of competing goals too. you want it to run constantly but you also don't want it to not keep up so you gradually add to the curve setpoint until the t-stat is satisfied.

Alan (California Radiant) Forbes

ThinkpadUser7

Should there be elbow pieces on the intakes to prevent dust/debris from falling in?

Alan (California Radiant) Forbes

If the optimal setting is to exactly match the heat loss of the house based on exterior temp, then how would you ever be able to increase the temperature of the house? If you adjust it so you can put more energy in than is being lost then it will inevitably shut off when it reaches the target temp. I guess maybe it's just a goal to strive for but impossible to 100% meet.

Imagine your house without a thermostat. With ODR and the correct reset curve, your house would maintain your desired room temperature.

Alan (California Radiant) Forbes

Currently the heating curve has:
Slope: 0.8
Level: 25 K

Interesting that the installer set the parallel shift at 25 which increases the starting water temperature to 93F. You can play with this number, too. 

Viessmann used to have documentation about when to change the shift and when to change the curve. 

ThinkpadUser7

Alan (California Radiant) Forbes said:

Currently the heating curve has:
Slope: 0.8
Level: 25 K

Interesting that the installer set the parallel shift at 25 which increases the starting water temperature to 93F. You can play with this number, too. 

Viessmann used to have documentation about when to change the shift and when to change the curve. 

My old system had been running with the aquastat set to 150F all the time, so that might have had something to do with it. I assume I should try lowering it?

Alan (California Radiant) Forbes

Yeah, that might be why. I would live with it for awhile as it might be the correct setting. 

hot_rod

It really takes a homeowner willing to play around with the control to get it to the most efficient and comfortable setting. There is no one correct answer and you cannot expect the contractor to make a bunch or trips back without getting paid.

I would study the manual, maybe see if Viessmann has online control trainings. I’ll bet you can find plenty of You Tube videos on set up for that boiler.

exqheat

"It really takes a homeowner willing to play around with the control to get it to the most efficient and comfortable setting. There is no one correct answer and you cannot expect the contractor to make a bunch or trips back without getting paid."

Absolute nonsense. It needs to be automatic for most consumers who don't know the difference between a boiler switch and a light switch.

Panheadsforever

Souns like an outdoor reset or not. Outdoor reset will save $$$ and you can change the curve

hot_rod

exqheat said:

"It really takes a homeowner willing to play around with the control to get it to the most efficient and comfortable setting. There is no one correct answer and you cannot expect the contractor to make a bunch or trips back without getting paid." Absolute nonsense. It needs to be automatic for most consumers who don't know the difference between a boiler switch and a light switch.

From his many past posts it sounds like the OP is asking  and willing to learn the fine tuning of his system. Good for him.

More consumers should embrace the heating system. 

Studies show the majority of homeowner's are unhappy with their heating systems.

hot_rod

Tekmar, now a Watts company pioneered outdoor reset controls, sold thousands. Now most boilers have this option built in

Their essays are still some of the best at explaining reset functions 

ThinkpadUser7

GGross said:

... generally these are meant to be piped primary/secondary. If the flow rates are acceptable for the boiler they can be direct piped, but generally not a great idea.

Can you elaborate on flow rates being acceptable? I'm fairly certain that I'm never going to exceed the max flow rate, but I have faucets that don't often support much flow. What will happen if i regularly use a faucet below the minimum flow rate? I see the B1KE-120 lists 0.5 gpm as the minimum flow through the heat exchanger for boiler start. Does that mean that 0.5 gpm is the minimal flow? If I use less then 0.5 gpm will it just never produce hot water? And if I'm using 0.6 gpm and it gets reduced to 0.4 gpm the hot water will cease to come out?

My main concern would be that I was doing damage to the boiler so hopefully that's not the case. Maybe it cycles a few additional times leading to a bit more energy use and wear?

edit: I just checked my bathroom faucet and it's only about .3 gpm currently
It clearly needs a new aerator, despite the current one being less than a year old. Mineral deposits tend to build up over time. I cleaned it a bit and got the flow above 0.5 gpm.

I found this quote:
"A low-loss header must be used when the system flow rate exceeds the maximum (or minimum) flow rate of the Vitodens 100-W boiler"

I'm guessing I don't have a "low-loss header"...

Alan (California Radiant) Forbes

Going back a bit, I don't like the way the new boiler was piped; direct instead of Primary-Secondary, especially on a high output boiler with a small load even though the boiler can throttle down to 12,000 BTU.

And a pet peeve of mine is to be able to service the expansion tank without draining the system, so a ball valve, drain and union would have been a nice feature. It tells me the installer hasn't done a lot of service.

As far as the expansion tank location, it seems more pumping towards than pumping away.

Unions on the PVC condensate pipe would have been nice and the dielectric union on the domestic pipe at the ceiling will corrode; a brass nipple is always better.

Other than that, the installer did a nice, neat job in a very cramped space and used quality components. I don't think there's anything you can call him back on, just some details that come with experience.

neilc

ThinkpadUser7 said:

GGross said:

... generally these are meant to be piped primary/secondary. If the flow rates are acceptable for the boiler they can be direct piped, but generally not a great idea.

Can you elaborate on flow rates being acceptable? I'm fairly certain that I'm never going to exceed the max flow rate, but I have faucets that don't often support much flow. What will happen if i regularly use a faucet below the minimum flow rate? I see the B1KE-120 lists 0.5 gpm as the minimum flow through the heat exchanger for boiler start. Does that mean that 0.5 gpm is the minimal flow? If I use less then 0.5 gpm will it just never produce hot water? And if I'm using 0.6 gpm and it gets reduced to 0.4 gpm the hot water will cease to come out?

My main concern would be that I was doing damage to the boiler so hopefully that's not the case. Maybe it cycles a few additional times leading to a bit more energy use and wear?

edit: I just checked my bathroom faucet and it's only about .3 gpm currently
It clearly needs a new aerator, despite the current one being less than a year old. Mineral deposits tend to build up over time. I cleaned it a bit and got the flow above 0.5 gpm.

I found this quote:
"A low-loss header must be used when the system flow rate exceeds the maximum (or minimum) flow rate of the Vitodens 100-W boiler"

I'm guessing I don't have a "low-loss header"...

I think you're mixing up your min flow rate for your domestic hot, 0.5 gpm, and the low loss header that you likely should have for the heating flow,

the domestic, and the aerator you just cleaned,
if the 0.3 was you only hot domestic call, the boiler heater would not have turned on, or stayed on if it did turn on, now with the clean aerator flow at or above0.5, the boiler will send hot water.

the low loss header, or primary secondary piping, allows for required heating flow thru the boiler, if and when a too small flow rate zone is calling for heat.

2 different issues wrapped up inside you wall heater.

ThinkpadUser7

@neilc Ah yes, I see how confused my post sounded! Thanks for explaining. My post was really about DHW, but I was also wondering how it would affect heating as well.

Given that I only have one zone (with three loops), I assume that the flow needs never change for the heating flow? The heat works currently, so whether I have a low loss header or not doesn't really matter for my particular application? I can see how a system with a bunch of different zones might have flow variance based on how many zones are being used at the time, but I'm guessing flow rates don't typically change if the zone or zones used does not change.

ThinkpadUser7

Somewhat related question:
At the times when my heat is off and I use the DHW, even if it's just for a few seconds, and I'll hear the boiler come on and then it will continue to make noise for another minute or so after the flow has stopped. What is happening that is causing the noise to continue?

ThinkpadUser7

@hot_rod Thanks for pointing me to the Tekmar essays. I plan to read through some of that and might make a new thread for help specific to dialing in my heating curve to be as efficient as possible.

neilc

ThinkpadUser7 said:

Somewhat related question:
At the times when my heat is off and I use the DHW, even if it's just for a few seconds, and I'll hear the boiler come on and then it will continue to make noise for another minute or so after the flow has stopped. What is happening that is causing the noise to continue?

that's usual, they keep the burner fan running incase you're doing just as you say, little shots of hot water, like washing the dishes, or whatever, less wear and tear on the burner relay and motor. starts and stops are murder

Alan (California Radiant) Forbes

Or just a post-purge.

ThinkpadUser7

neilc said:

ThinkpadUser7 said:

Somewhat related question:
At the times when my heat is off and I use the DHW, even if it's just for a few seconds, and I'll hear the boiler come on and then it will continue to make noise for another minute or so after the flow has stopped. What is happening that is causing the noise to continue?

that's usual, they keep the burner fan running incase you're doing just as you say, little shots of hot water, like washing the dishes, or whatever, less wear and tear on the burner relay and motor. starts and stops are murder

Hopefully little shots aren't that bad. It's kind of unavoidable with DHW. Washing hands, pretty much any activity in the kitchen, etc. Lots of little bursts of hot water.

GGross

try this to connect via wifi

ThinkpadUser7

GGross said:

try this to connect via wifi

Thanks. That is what I had repeatedly tried. Holding OK for 4 seconds puts the boiler in "pairing" mode. I then follow the instructions in the app to connect to the boiler's wifi network. I then return to the app (as previously instructed by the app), and the app eventually shows the error text I mentioned earlier. There is no error on the boiler, which still says "pairing". The app tells me to try again by getting the boiler out of pairing mode as a first step.

ThinkpadUser7

I'm currently observing what I believe is called "short cycling":

Honeywell T6 Pro thermostat has been set to 64 for the past 24+ hours. All of yesterday the interior temp remained at 64F and I never saw/heard the boiler come on. Exterior temps dropped last night, and when I got up the boiler was on (Honeywell showed current interior temp as 64). Since getting up I've heard the boiler go through multiple on/off cycles, despite the interior temp not deviating from 64F.

Should I make an adjustment to the heating curve based on this? It's currently at slope of 0.8 and level of 25K.

A few days ago, this was my other boiler experience: Thermostat had been set to 65F. Interior temps were 64F. The boiler ran for about 6 hours continuously, at which point the thermostat showed 65F and the boiler turned off. A few hours later interior temps had risen to 67F and the boiler remained off for the next couple days (it took a couple days for interior temps to drop down, despite exterior temps being in the low 50s at times)

ThinkpadUser7

I looked at the "advanced setup options (ISU)" for my Honeywell T6 Pro and it looks like the "heating cycle rate" is set to 3, which I think means it will cycle on/off three times per hour. Also, it looks like "Adaptive Intelligent Recovery" is turned on, though I'm not using a schedule so perhaps this setting has no effect currently.

Perhaps I should lower the cycle rate to 1 and turn off adaptive intelligent recovery?

Is it normal for a boiler to keep running after the desired room temp is reached?