Windhager People: Boiler Temp Question

[velvetfoot]

For you Windhager pellet boiler people, have you fooled around much with the boiler set and external temperatures? I currently have the set temperature maxed at 176 and external temperature at 161. The idea is to increase the run time by increasing the time run at modulated output (<100%). I'm thinking of decreasing external temp below 161, though not sure how low.

Opinions/Experience?

 

[Sparky978]

external temperature at 161.

Velvet
Is the 161 when your Ranco turns off your PB?

 

[velvetfoot]

external temperature at 161.

Velvet
Is the 161 when your Ranco turns off your PB?

No. There are two temperature parameters you can set on my BioWin: set and external. Set is the boiler setpoint, which I don't believe is exceded (by much anyway). The max set on mine is 176. External is the temperature that the boiler shoots for. What seems to happen though, is that the boiler continues to run even if the external temperature is met, although modulating itself down until it gets to the setpoint plus. Mine actually shut off yesterday when it was at 181 and 30% for a few minutes. I got to thinking about this again after reading nofossil's post about controlling a Froling's output (modulation) by modulating its return temperature. My idea is to run the boiler longer at lower average output since I have overcapacity, especially now.

I'm averaging around 2 hours, which isn't bad, but I'd like to increase it, without decreasing comfort too much.

I might try to map the relation of % modulation, boiler temp, and exhaust temp. I guess it'd be 3D. Sounds like too much work. Awww.. fuggedaboudit.

 

[bdud]

I have my Biowin set at 167F for Max Value Offset Temp, 158F for Set Temp Ext Heating Requirement, the Johnson Controls A419 which controls my boiler on - off with the probe in the storage tank, is set for 170F.
With these settings the boiler goes into modulation mode 30% for quite a while. I kept the storage tank set temp high so if any one zone is calling for heat or water, the boiler keeps in modulation mode until that zones thermostat is happy. My highest average boiler run time last year was 3.56 hrs, ~ 2.5hrs average with 1.5hrs in the fall and spring.
I kept the Max Value Offset Temp at 167F thinking slightly more efficient boiler output - storage efficiency rather than using 176F.
I have never changed the Set Temp Ext Heating Requirement value, not sure if the boiler uses it in my scenario.

 

[Tennman]

Proud to be a "Windhager people", but not sure what I'm doing is relevant to you. With extremely mild temps not expected to stay long I don't want to have to completely recharge sitorage so keeping boiler on. But I know that the larger the temp difference between stored and ambient, the larger the wasted energy leak rate. So lowered external temp to 125F to reduce pellet use. I'll be controlling the external set point to track weather extreme changes to minimize storage energy waste. I've presently set the boiler temp to 178. That big thermal battery gives us many options.

 

[Sparky978]

the boiler continues to run even if the external temperature is met,

It seems to me that the ext. heating set point doesn't control burner on/off. The on/off is only controlled by the Ranco on my storage tank. The boiler only goes into burnout when my Ranco reaches it set point of 180. So would lowering the ext. set point cause the boiler to go into a lower modulation sooner? Which I guess would give longer burn times. I increased my differential on the Ranco to get a little longer burn times.

 

[velvetfoot]

Hey Tennman, bdud and I have tiny storage tanks compared to you! But, and you want to make sure if I'm right, I believe with the external temp set at 125 and the boiler temp set at 178 (mine can't go above 176), with a continuing heat call, the temp of the tank will eventually reach 178. The settings I'm talking about are on the boiler control panel.

bdud, unlike you, I'm still using a wood insert most of the time, but my pellet boiler, while not big at 15kW, is still too big when the insert is running. It took about 2 hours to charge the tank with no zones calling (I believe) before I started my recent fiddling. I want to retain the potential to heat with pellets only when the weather is cold, or recovering from setback: that's why I went with the 15 vs. 10 kW setting.

I have it set a `156 for external temp requirement right now.

I'm also fiddling with the setpoint of the tank sensor to start the pellet boiler. The bugaboo is not only getting a head start on heating the zones with whatever heat's left in the tank, but also to supply dhw.

 

[velvetfoot]

So would lowering the ext. set point cause the boiler to go into a lower modulation sooner?

Yes. I'm curious to see how pronounced it is.
Now, I'm not sure if it's less efficient when modulated down.
I figure the fewer starts the better, and if it just kinda of hanging out at 40 percent or whatever, there could be a chance that another zone would come on and take more of the boiler heat.
The Ranco on my tank controls the start but I let the boiler run until it shuts itself down.
Bear in mind our tank are probably similar to my 119 gallons, where Tennman has 1000 gallons to think about!

 

[Sparky978]

The Ranco on my tank controls the start but I let the boiler run until it shuts itself down.

How does the boiler shut itself down without the Ranco opening up the call for heat circuit? Maybe your model is different than mine?

there could be a chance that another zone would come on and take more of the boiler heat.

At that time wouldn't the Max set boiler temp start dropping and increase the output %?
Yes I have the 120 gal. TurboMax tank.

 

[velvetfoot]

How does the boiler shut itself down without the Ranco opening up the call for heat circuit? Maybe your model is different than mine?

The boiler shuts itself down depending on the "set" temperature on the boiler control panel. Mine is set at 176, the max, but the temp on mine actually gets to 181.

At that time wouldn't the Max set boiler temp start dropping and increase the output %?

The max set boiler temp doesn't change-it is set in the parameters section in the service part of the control panel screen. Yes, the boiler temp would drop and the percent goes up.

 

[Sparky978]

The boiler shuts itself down depending on the "set" temperature on the boiler control panel.

So at what temp on your Ranco does the start contact re-open to get ready for the temp drop in your tank to call for boiler start?

 

[Tennman]

VF, to clarify, on our system the A419 turns the boiler on and off based on mid storage temp of 125-145F. 178F is being supplied to storage which when it warms mid tank water to 145F the PB shuts down.

 

[velvetfoot]

So at what temp on your Ranco does the start contact re-open to get ready for the temp drop in your tank to call for boiler start?

It's not a matter of re-opening. I have it arranged so that after the Ranco closes, which I have now at 120, a relay closes and keeps the demand for heat on until the boiler turns itself off. There is a differential of 1, but it doesn't come into play at all.

VF, to clarify, on our system the A419 turns the boiler on and off based on mid storage temp of 125-145F. 178F is being supplied to storage which when it warms mid tank water to 145F the PB shuts down.

You have totally the opposite problem that I have. You have too much storage and I have too little. I'm trying to squeeze as much as I can into/out of my tank, and your trying to make do with the minimum, which is a lot compared to mine.

 

[Sparky978]

It's not a matter of re-opening. I have it arranged so that after the Ranco closes, which I have now at 120, a relay closes and keeps the demand for heat on until the boiler turns itself off. There is a differential of 1, but it doesn't come into play at all.

Ok, So you power a latching relay to keep the demand circuit closed which keeps the boiler running. After the boiler shuts down on its own how does the relay reset?

 

[velvetfoot]

What keeps the relay latched is voltage sensed from the induced fan running, which is the best I come up with to check if the pellet boiler is running. It also keeps the pellet boiler pump running until the fan shuts off, which I recall is 11 or 13 minutes.



























































































































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[Sparky978]

The boiler shuts itself down depending on the "set" temperature on the boiler control panel. Mine is set at 176, the max, but the temp on mine actually gets to 181.

Velvet
I've been watching my system closely the last few weeks now that temps outside are colder. I notice that with the colder temps my zones are calling more and I'm getting much longer run times. I have never seen my boiler go into burnout until my storage tank sensor tells it to, which is set for 180. My "set" temp is set for 176 also and its has gone up to as much as 189 on the Biowin display but has never shut itself off. Is there something else that you do to make the PB shut itself down.

 

[velvetfoot]

its has gone up to as much as 189 on the Biowin display

Mine shuts itself off at 181. I currently have the external temperature at 156 which leads to more modulation and longer runs. I have a wood stove going but also do a couple of setbacks, so it's not running as hard most times, but the setbacks are a strain and need some oomph especially if we've been out of the house and not running the stove..

I've never seen 189 for sure. You can lower the set temperature (not the external temperature)-maybe that'd do it.

I've been running the oil boiler a lot lately.

 

[heaterman]

For you Windhager pellet boiler people, have you fooled around much with the boiler set and external temperatures? I currently have the set temperature maxed at 176 and external temperature at 161. The idea is to increase the run time by increasing the time run at modulated output (<100%). I'm thinking of decreasing external temp below 161, though not sure how low.

Opinions/Experience?

If you have the boiler temp set a little lower than external demand, you'll get the result you're trying to achieve.
Ex. Boiler at 170 and external storage demand @ 175.

The boiler "sees" 2 inputs and will stay running until bothare met in this scenario.

 

[Sparky978]

If you have the boiler temp set a little lower than external demand, you'll get the result you're trying to achieve.
Ex. Boiler at 170 and external storage demand @ 175.

The boiler "sees" 2 inputs and will stay running until bothare met in this scenario.

Is there a reason why when my Biowin gets a call for heat it doesn't kick in until the temp on the Biowin screen comes down to 165*? Is there a setting that causes this to happen? My call for heat kicks in at 160* with a 20* diff.

 

[velvetfoot]

I'm no expert but the highest boiler temp I can set is 176. So, maybe after it went over 176 on the heat up, it won't let itself restart until it's cooled off 10 degrees.

 

[Sparky978]

I'm no expert but the highest boiler temp I can set is 176. So, maybe after it went over 176 on the heat up, it won't let itself restart until it's cooled off 10 degrees.

I've got my boiler temp set at 176 also. Maybe it's a preset differential. Would the "hysteresis" setting have anything to do with it? Doesn't Hysteresis usually deal with differential?

 

[velvetfoot]

Yes, preset, I would say. Not sure what the hysteresis does exactly-kind of like an anticipator, I imagine.
You don't let your tank cool off too much. Where is your tank sensor located on the tank?

 

[Sparky978]

Yes, preset, I would say. Not sure what the hysteresis does exactly-kind of like an anticipator, I imagine.
You don't let your tank cool off too much. Where is your tank sensor located on the tank?

My sensor is at the bottom of the tank. I have 5 heating zones and a DHW zone pulling off my tank so when they kick in especially lately with the colder weather i've noticed my tank temp has dropped into the 130's so I try to kick in on sooner to get it going. When it was milder out I had it kicking in at 150. I've noticed these past few weeks sometimes that the water temp going up to my baseboards can be as low as 150's. You mentioned that you want yours to modulate for a longer period and thats what mine does and I like that but when I get that big demand I wish that it would stay at 100%. Am I missing something on the settings?

 

[velvetfoot]

160 water going into the boiler is pretty warm, I think. It wouldn't take long for the boiler to start modulating. Although it does take some time for the boiler to get up to temp, and the zones could be draining the tank in the meanwhile.

If the system is plumbed so that the zones get first crack at boiler heat (before the tank), and multiple zones are pulling, then I can see most of the interaction being between the boiler and the zones, with the tank being left out of the mix. I can see the zones being cool as the boiler warms up. Also maybe the slugs of cool water in the zones have to work themselves out after the zones activate. You have a boiler protection valve set for 140? I can see that giving 150's while the boiler is warming up.

Perhaps you could set priority to on for the dhw zone, so that the heating zones are off when it's on. Maybe stagger setback recoveries via thermostat so they don't all happen at the same time. Then you could use a lower tank temp?

 

[Sparky978]

If the system is plumbed so that the zones get first crack at boiler heat (before the tank), and multiple zones are pulling, then I can see most of the interaction being between the boiler and the zones, with the tank being left out of the mix.

When I run in "pellet boiler only mode" the zones can only get their heat from the storage tank.The PB charges the storage through the isolated coils then the zones draw off the storage. I've attached a rough sketch (nothing fancy) to show how my system is piped. By turning valves 1-5 I can run PB only, oil only or both.

QUOTE="velvet foot, post: 2048137, member: 208"]You have a boiler protection valve set for 140?

My boiler protection is set at 115* which fully closes the bypass at 133* so I can heat up my storage quicker.

Perhaps you could set priority to on for the dhw zone,

I do keep the priority switch in the on position so that DHW gets first crack at hot water.