New Boiler Installed - Tweaking Reset Curve

David_16

Thanks again so much for all of the help in my previous posts. I'm happy with my boiler decision and the install.

Last week, I had installed a Weil-McLain ECO Tec 110-H boiler and 45 Gallon Aqua Plus Series 2 indirect water heater, replacing my CI oil boiler and indirect.

I have fintube hot water baseboards and 2 zones.

I posted a few pics. It seems like they did a decent job to me, but would value any comments about the install.

First of all, the amount of hot water I have now is night and day. Before, we'd be running low with less than a 10 minute shower and the bath took multiple stop and gos to fill up. Now doesn't seem like hot water runs out and the large tub fills hot with 1 shot. Indirect is set to 140 with mixing value at 120.

Next up is trying to lock in an ideal reset curve. Design temp here is 9 degrees. Outdoor reset temperature seems a bit off so I did a -5 degrees hardcode and seems pretty close now.

Installer didn't help to much with this part. They left me at settings where no one would ever call them about not enough heat. They left the curve at 160 @ 70 and 180 @ 25.
Weil-McLain defaults seem to be 130 @ 70 and 180 @ 0. It seems like it works on a simple linear curve.

I changed it almost right away to 130 @ 70 and 180 @ 15. Watching the boiler, it seems like boiler in is only about 10 degrees less than boiler out, so it's going to take 50 degrees outside to get me to a sub 140 return temp (if I'm understanding the numbers correctly) where I can condense. That's not going to happen much between December and February here. I guess that's ok because I watch the modulation rate and it could run in the 20% range for good periods of time so that should be providing some savings.

I also have a boost settings where I can say after X minutes, increase the water temp by 10 degrees if the call has not been satisfied. I'm thinking I might be able to use that along with a more aggressive curve.

I also have a max rate setting which, I think, will limit the boiler modulation rate. There's also a max voltage rate which seems like it does the same, but seems like I shouldn't touch that one.

So far, it's been almost a week and the house seems to be heating up just fine, but it hasn't dipped much below 30 at night.

I guess my question then is how do I determine if my reset curve numbers are "ideal"? I would assume that I've got to be saving gas over the installer default numbers. Do I measure the time it takes for the boiler to kick in and then go off? But I am not even sure what times I'd be looking for. Also, wouldn't my thermostat swing setting (which I can't change in my old thermostat) have a large effect on that? Do I just get more aggressive with curve until it's not properly heating the house? Like try 120 @ 70 and 180 @ 10? I know fintube starts to get bad under 130 or so. The system was programmed so that the 2 heating zones share a reset curve. Zone 1 is used all of the time and Zone 2 sits at 63-64 degrees and doesn't kick in too much. Zone 2 has always heated up very quickly so I'm not too worried about that zone if Zone 1 is heating up fine.

I'm a little hesitant to make too many changes because I don't quite understand if any of these changes could maybe affect the lifespan of the unit or something else like that.

There's no where that I could/should stick in a surge suppressor or UPS, right?

Would really appreciate thoughts on this.

Thanks again!

Hot_water_fan

Congrats on the install! 

There’s no harm in lowering the curve. Try 120 at the low end and see how it goes. If it’s 50F outside and 120F is keeping the house at setpoint, you can try lower. It’ll be some trial and error. 

Are you using any kind of setbacks? 

David_16

Hot_water_fan said:

Congrats on the install! 

There’s no harm in lowering the curve. Try 120 at the low end and see how it goes. If it’s 50F outside and 120F is keeping the house at setpoint, you can try lower. It’ll be some trial and error. 

Are you using any kind of setbacks? 

Lowering the bottom number to 120 isn't going to push me into the condense range much more, but if the house still gets warm quickly enough, I guess that's still an improvement. What's the balance that I'm trying to go for? It's good to have the boiler working to just barely get me to the setpoint but not too quickly? It's bad to get to the setpoint fast? I'm not really understanding the logic. If my boiler runs 80% modulation to do 180 degree water and satisfies a call in 10 minutes, that's worse for the system than running 20% modulation to do 150 degree water and satisfy the call in 50 minutes? The numbers are just made up, but isn't 20% for 50 minutes using more gas than 80% for 10 minutes?

Is there value in using the boost setting too or restricting the max modulation rate?

We've got Zone 1 set to 68 most of the day, which is comfortable enough. Sometimes we might bump it up to 69 or 70 manually and then have it setback to 66 at night. I've seen that setback doesn't save much energy, but we prefer sleeping with it set to 66 vs 68 so I guess it's still ok to do that? If we are going to be out of the house for a few hours or more, should we lower the thermostat a couple of degrees or is that not helping any?

I presume with the water heater, I just want the boiler sending it 180 degree water with no restriction on modulation rate? I'm not even sure that can be changed with that zone set up as a domestic hot water zone.

Hot_water_fan

What's the balance that I'm trying to go for? It's good to have the boiler working to just barely get me to the setpoint but not too quickly? It's bad to get to the setpoint fast? I'm not really understanding the logic. If my boiler runs 80% modulation to do 180 degree water and satisfies a call in 10 minutes, that's worse for the system than running 20% modulation to do 150 degree water and satisfy the call in 50 minutes? The numbers are just made up, but isn't 20% for 50 minutes using more gas than 80% for 10 minutes?

Broadly, you want to use the lowest temperature water you can while keeping comfortable. Running at a lower modulation rate is more efficient, even when the return temp is the same. Running at 10% for an hour vs. 100% for 6 minutes is more efficient.

David_16

Hot_water_fan said:

What's the balance that I'm trying to go for? It's good to have the boiler working to just barely get me to the setpoint but not too quickly? It's bad to get to the setpoint fast? I'm not really understanding the logic. If my boiler runs 80% modulation to do 180 degree water and satisfies a call in 10 minutes, that's worse for the system than running 20% modulation to do 150 degree water and satisfy the call in 50 minutes? The numbers are just made up, but isn't 20% for 50 minutes using more gas than 80% for 10 minutes?

Broadly, you want to use the lowest temperature water you can while keeping comfortable. Running at a lower modulation rate is more efficient, even when the return temp is the same. Running at 10% for an hour vs. 100% for 6 minutes is more efficient.

So really I want the boiler running as long as I can at as low a rate as I can?

Is there value then in not lowing the water temps so much, but setting a max modulation rate that's lower? Or some combination of lower water temps and lower max modulation? Or just let the boiler modulate itself as long as I'm seeing low modulation rates when I'm watching? I'd have no idea what number to pick for that. If you recall the old threads, I'm probably needing 50K-60K BTU on a design day and I have a 110K BTU input boiler. Not sure if that means I could max the modulation at 60% and be ok. I definitely see times where it's over 60% though. That setting would only be on the heating zones, so it will still go to 100% for DHW.

KC_Jones

David_16 said:

Hot_water_fan said:

What's the balance that I'm trying to go for? It's good to have the boiler working to just barely get me to the setpoint but not too quickly? It's bad to get to the setpoint fast? I'm not really understanding the logic. If my boiler runs 80% modulation to do 180 degree water and satisfies a call in 10 minutes, that's worse for the system than running 20% modulation to do 150 degree water and satisfy the call in 50 minutes? The numbers are just made up, but isn't 20% for 50 minutes using more gas than 80% for 10 minutes?

Broadly, you want to use the lowest temperature water you can while keeping comfortable. Running at a lower modulation rate is more efficient, even when the return temp is the same. Running at 10% for an hour vs. 100% for 6 minutes is more efficient.

So really I want the boiler running as long as I can at as low a rate as I can?

Is there value then in not lowing the water temps so much, but setting a max modulation rate that's lower? Or some combination of lower water temps and lower max modulation? Or just let the boiler modulate itself as long as I'm seeing low modulation rates when I'm watching? I'd have no idea what number to pick for that. If you recall the old threads, I'm probably needing 50K-60K BTU on a design day and I have a 110K BTU input boiler. Not sure if that means I could max the modulation at 60% and be ok. I definitely see times where it's over 60% though. That setting would only be on the heating zones, so it will still go to 100% for DHW.

Continuously all winter long without stopping if you can manage it, but thats relatively rare. But, that gives you the idea of what you are shooting for.

If you want the highest efficiency, take speed out of your vocabulary.

David_16

KC_Jones said:

Continuously all winter long without stopping if you can manage it, but thats relatively rare. But, that gives you the idea of what you are shooting for.

If you want the highest efficiency, take speed out of your vocabulary.

I'm getting it now, but still don't quite understanding the math of how boiler running constantly uses less gas.

Anyhow, I guess it comes down to how do I accomplish this while still keeping the house comfortable. My goal is not to squeak out ever penny of savings.

I guess I just adjust the reset curve towards cooler water until it takes uncomfortably long for the house to heat up or remain at the target temp?

How does the max rate setting play into this too? Should I max rate the boiler at 60% (or even 50%) modulation and see how that goes? I just don't want to take a chance and do anything that could have negative ramifications to the life of my boiler.

Seems like I shouldn't be using the boost setting then too.

hot_rod

Does that boiler have a boost function? Basically it watches the boiler set temperature and if it doesn’t rise after a period of time it boosts the swt, regardless of what the odr is telling it to run

David_16

hot_rod said:

Does that boiler have a boost function? Basically it watches the boiler set temperature and if it doesn’t rise after a period of time it boosts the swt, regardless of what the odr is telling it to run

Yes, from what I've read in the manual, the number of minutes is adjustable and then after that many minutes, if the call is not satisfied, it increases the boiler temp by 10 degrees and does that again and again after each x minutes until the call is satisfied.  Is that worth using and what's a good number of minutes to start with?  I also would need to dig in and make sure the maximum water temp doesn't go over 180.  I'm not sure if it uses the maximum for my reset curve or if there's another boiler max setting somewhere. Looks like there might be. I don't think I ever would want it cranked up to 200 degrees, right?

So would it make sense to lower my curve temps and then set the boost to like 30 minutes?

And still not sure how max modulation rate might play into this.

So many different ways to play with this.  Very interesting stuff.

hot_rod

Yeah, you need to keep tweaking to your need or liking. It’s nice to have all that adjustability

I have my boost at 15 minutes, as I recall. It can take a whole season of adjustments to get it ideal, as you need some design days along with mild days.

U less you have plenty of fin tube, you may not be able to get into condensing mode as often as you would like. Getting as close as possible to constant circulation will help maximize the lowest SWT at any point.

PeteA

My head is spinning with this outdoor reset stuff. There’s got to be an easier way to understand/explain this feature.

hot_rod

The heat loss of a building is fairly linear with outdoor temperature rise or fall
So basically the boiler tries to adjust its supply temperature to match that changing load. Its that simple.

Think of it as a cruise control that  you have on a vehicle. The accelerator moves up and down as you go up and down hills, trying to match engine output to the vehicle “load”

If you want to quickly pass another car, stomp the accelerator. That is what boiler boost does it speeds up the  time to reach  the desired speed or heat load

Hot_water_fan

I'm getting it now, but still don't quite understanding the math of how boiler running constantly uses less gas.

Just do the math: 

8,000btu/h x 24 hours = 80,000btu/h  x 2.4 hours. 

The heat output is the same. However! A modcon is slightly more efficient at a lower fire (there’s more surface area to exhaust), so although the output is the exact same, the input turns out to be slightly less. 

Similar to the car analogy above, driving at 55mph is more efficient then 110mph, even if it takes twice as long. 

David_16

Hot_water_fan said:

>Just do the math: 

8,000btu/h x 24 hours = 80,000btu/h  x 2.4 hours. 

The heat output is the same. However! A modcon is slightly more efficient at a lower fire (there’s more surface area to exhaust), so although the output is the exact same, the input turns out to be slightly less. 

Similar to the car analogy above, driving at 55mph is more efficient then 110mph, even if it takes twice as long. 

I wasn't sure that the math definitely worked that way. I haven't seen the modulation rate under 20% so I guess 20% for 1 hour = 80% for 15 minutes then.

Seems like running at 20% for 24 hours straight would be using a lot of gas. If I set the boiler to always run at 180, I don't think it would be running at say 80% for more than 6 hours throughout the day. I guess it could be, but doesn't seem like it would be.

Sounds like next thing to try after evaluating further might be to drop to 120 @ 70 outside and maybe turn on the boost function.

Still not sure if I should try setting the max rate to 50% or 60%. Would be interesting to see what effect that has, but I need to be sure that's not damaging in any way.

Mosherd1

Another thing to consider is, do you need 180* water for heating? You can try lowering your max set point as well.  Try lowering it to 170* and see if you can maintain temperature when it’s at design temp. If you can, lower it another 10*, do this until you can’t maintain temperature, then raise it back up slightly. 

David_16

Mosherd1 said:

Another thing to consider is, do you need 180* water for heating? You can try lowering your max set point as well.  Try lowering it to 170* and see if you can maintain temperature when it’s at design temp. If you can, lower it another 10*, do this until you can’t maintain temperature, then raise it back up slightly. 

Don't really know if I need 180 degree water on a design day. Unfortunately (or may not) there are not too many design days around here anymore to test on. It looks like we won't be below high 20s for the next 10 days at least. It's going to be tough to really evaluate things without a really cold day.

I definitely could try changing the reset curve to 120 @ 70 and 170 @ 15 instead of 130 @ 70 and 180 @ 15 like I have now.

Hot_water_fan

Seems like running at 20% for 24 hours straight would be using a lot of gas. If I set the boiler to always run at 180, I don't think it would be running at say 80% for more than 6 hours throughout the day. I guess it could be, but doesn't seem like it would be.

The boiler doesn’t run for kicks. It runs to satisfy a thermostat. It can do that for a long time at a low rate or a short time at a high rate. The energy supplied is the same. 

Lock it out at 60% and see how it performs. It will not hurt the boiler. 

hot_rod

The less a boiler cycles, the more efficiently it is running. So all day at 20% fire would be more efficient than banging on and off every 10 minutes at full fire. To cover the same heat load.

Think of stop and go city driving in 35 mph zones, driving compared to a consistent 35 mph to cover the same distance.

David_16

Hot_water_fan said:

Lock it out at 60% and see how it performs. It will not hurt the boiler. 

Not quite ready to max rate yet or add boost setting yet, let me see how things settle out a bit first.
I did change the reset curve to 120/70,180/10. That will make it a little harder to get to 180. So far seems like everything is still comfortable in the house, but it's not been very cold.

I did take a tour of readily available settings and have a few questions:
First of all, there's a timer menu where I can see how many hours each zone has run and how many cycles the boiler has gone through. I just reset the timers now. That probably can provide some helpful info. Like the zone I barely use has been on for 11 hours vs 77 for the main zone. Surprised it was that high. I lowered that thermostat to 63, but I don't want to make that section of the house too cold, so that's fine.

Are there any boiler high and low temps that I should be concerned with? I've caught it down under 110 when idle and then it takes a long time to get back up to target. Not sure where those settings might be. Would I use different summer/winter high/low temp settings, like when I'm just using it for DHW, do I change the limits? I don't see anything specific to boiler limits, but if that's something I should adjust, I can look.

Hot_water_fan

Are there any boiler high and low temps that I should be concerned with? I've caught it down under 110 when idle and then it takes a long time to get back up to target. Not sure where those settings might be. Would I use different summer/winter high/low temp settings, like when I'm just using it for DHW, do I change the limits? I don't see anything specific to boiler limits, but if that's something I should adjust, I can look.

No, you're fine and you can always change them back. You can run a radiant floor with much lower temps than you're using, so the boiler is built for low return temps. 180F is a fine place to start for the high end.

DHW isn't that important here, whatever is default is probably fine. If it has a warm weather shut off enabled it should only run for DHW calls.

David_16

Hot_water_fan said:

No, you're fine and you can always change them back. You can run a radiant floor with much lower temps than you're using, so the boiler is built for low return temps. 180F is a fine place to start for the high end.

DHW isn't that important here, whatever is default is probably fine. If it has a warm weather shut off enabled it should only run for DHW calls.

Yes, I have a warm weather shut down option which is set at 70 and does not affect DHW.

David_16

Here's some data since I reset my counters:
17 hours - It's been between 28 and 45 degrees
Boiler running 11 hours
Zone 1 - 0 hours (this zone is set to 63)
Zone 2 - 10 hours (this zone is set to 66-68)
DHW - 1 hour
30 ignitions

It looks like I've used about 4 therms in about the same time period as well. I think that's what I would have expected.

My curve is 120 @ 70/180 @ 10 now.
I also turned on max rate = 60%

Not sure how I might cut down on the number of ignitions?

Seems like boiler mostly goes to max rate when it's been off for a while and the temp is low and then there's a call for heat so it uses max rate to get up to the target temp faster. Usually if it's maintaining, I see it around 30%.

hot_rod

30 ignition cycles in 11 hours is not so bad, what are you hoping to see?

You could turn the firing limit down. Does it have step firing. That function allows you to lock the boiler at 10, 20, 30, 40% firing for a specific time. If it has a boost function that would overide the limiting if the boiler temperature doesn't rise within a specific time period, also adjustable.

It might take a call to tech support to see if or how you could enable functions like that.

You are trying to get the boiler to modulate exactly to any given heat load at any given time. It takes some trial and error to dial it in exactly.

Lots to read about in that control section of the manual.

David_16

hot_rod said:

30 ignition cycles in 11 hours is not so bad, what are you hoping to see?

You could turn the firing limit down. Does it have step firing. That function allows you to lock the boiler at 10, 20, 30, 40% firing for a specific time. If it has a boost function that would overide the limiting if the boiler temperature doesn't rise within a specific time period, also adjustable.

It might take a call to tech support to see if or how you could enable functions like that.

You are trying to get the boiler to modulate exactly to any given heat load at any given time. It takes some trial and error to dial it in exactly.

Lots to read about in that control section of the manual.

I'm not really sure what I was hoping to see. Glad to hear that 30 cycles in 11 hours is not bad.

It's nice to have these kinds of stats. And good that I can read my meter as well to get an idea of the gas usage.

Yes, the advanced manual is great. I'm definitely not going to be playing with too many settings though. Just the reset curve temps, max rate and maybe boost.

Still trying to figure out max rate. I have it set to 60%, but I'm seeing the boiler modulation percentage go above that a bit. Seems to start out at 64% and then drops down to 60%. Not certain how that setting is working exactly yet. Maybe it takes a bit to "find" the 60% maximum.

And still not sure what to do with boost. I don't see lowering my curve temps any from where they are now as it's probably about as low as one would go with fintube. It doesn't seem to be taking too long to heat up so I don't think I'd need boost. I guess that might help if I ever did a large enough fallback and wanted to get back up to temp faster. I guess turning on boost set at 30 minutes couldn't really hurt much though as it'll never be used unless it's ever taking that long to get to temp.

Hot_water_fan

You can always lower the max temp to flatten the curve. If it’s not enough, change it. 

David_16

Hot_water_fan said:

You can always lower the max temp to flatten the curve. If it’s not enough, change it. 

I'll need a cold enough day to test that and there might not be one coming yet this season. If I were to lower the max temp, that would probably make it more likely that I'd need boost, but can't really tell until there are some cold days.

Hot_water_fan

Lowering the max lowers the temps at all other temps too. So if 160F at 5F outside isn’t enough, you’ll probably know when 140F isn’t enough at 35F. 

David_16

That makes sense. So far no issues heating up the house properly .
I'll try 120@70/170@10, max rate 60%, no boost.

With the variable water temps should the house be heating up more comfortably? I would say previously with 180 water from my oil boiler, if I was in a smaller room or in bed at night, I felt the heat to be uncomfortably warm at times when it kicked in. I supposed this would be better as I'm not always getting blasted with heat from 180 degree water. Does that make sense?

Hot_water_fan

It'll be more consistent heat: the boiler will run longer and temperature changes will be more gradual.

Daveinscranton

As I understand it, if your heat loss at design day is 60,000 btu/hour, then setting max boiler rate at 60,000 btu an hour makes a lot of sense.

ODR will do a lot to help.  In an ideal world (doesn’t exist), you can about throw away the indoor thermostat.  (Not possible).  Still an intriguing thought.

 I have been amazed at how low I can cut my max (allowed) rate.  House comfort for me has not suffered, but I have a different application (radiant floor).   My stack temperatures are pretty low and my supply temperature is quite low.

Less cycling means more economy it seems.  Less wear and tear on all the stuff that has to start/stop.  Less wasted gas in the start cycle etc.

The myriad of choices in the menu is intriguing.  It seems to take a bit of experimenting to sort out the best solution.   Or near best solution.  Which is ok too.  

It seems that the default settings will keep you warm but may not be ideal.  It is also the type of thing that is unfair to expect out of the installer.  Can take quite awhile to maximize efficiency.  I doubt many homeowners want to pay for many hours of the pro to tweak over days, weeks, months.  I doubt that many homeowners will be happy if they get a cold/cool house as part of the tweaking experiment.

David_16

Hot_water_fan said:

It'll be more consistent heat: the boiler will run longer and temperature changes will be more gradual.

Definitely seems as if it's a more comfortable heat so far.

Daveinscranton said:

As I understand it, if your heat loss at design day is 60,000 btu/hour, then setting max boiler rate at 60,000 btu an hour makes a lot of sense.

ODR will do a lot to help.  In an ideal world (doesn’t exist), you can about throw away the indoor thermostat.  (Not possible).  Still an intriguing thought.

 I have been amazed at how low I can cut my max (allowed) rate.  House comfort for me has not suffered, but I have a different application (radiant floor).   My stack temperatures are pretty low and my supply temperature is quite low.

Less cycling means more economy it seems.  Less wear and tear on all the stuff that has to start/stop.  Less wasted gas in the start cycle etc.

The myriad of choices in the menu is intriguing.  It seems to take a bit of experimenting to sort out the best solution.   Or near best solution.  Which is ok too.  

It seems that the default settings will keep you warm but may not be ideal.  It is also the type of thing that is unfair to expect out of the installer.  Can take quite awhile to maximize efficiency.  I doubt many homeowners want to pay for many hours of the pro to tweak over days, weeks, months.  I doubt that many homeowners will be happy if they get a cold/cool house as part of the tweaking experiment.

I find the whole process of how this works very interesting.

Last night had setback from 68 to 66, woke up and it was 65 (I think my thermostat has a pretty large swing value). 8am it's back to 68 and sometimes we'll put it on 69 so now it's got 4 degrees to make up. It's using about 142 degree water and it's taken over an hour to bump up 2 degrees. I think here's exactly where boost might help some. My goal is not to save every penny, I want to be comfortable too. So I turned boost on for 30 minutes.

Seems like 140 degree water requires some higher modulation to get to target and then it settles in at around 22% and keeps running at that. I just happened to turn on the zone 2. I wasn't sure how it works, but my 2 heat zones were programmed as 1 priority so it's got both circulators running simultaneously now. Boiler temp immediately dropped when I turned on the second zone, it took a few minutes to get back to target and now it's running at around 33% with both zones calling for heat. Zone 2 has heated up 2 degrees in probably 15 minutes. That zone has always heated up very quickly.

I wonder what the modulation settles in at if I ran 2 zones at 180 degree water on a 10 degree day. I'm thinking that percentage times my boiler size is my design day need. Not sure if that makes sense or not?

hot_rod

Or change the setback amount or the time when it comes off of setback. If the temperature is too cold at 8 am?

David_16

hot_rod said:

Or change the setback amount or the time when it comes off of setback. If the temperature is too cold at 8 am?

I turned off boost for now and will monitor. Earlier return to temp is definitely an option.

I think I've got decent settings at the moment that I'll run with for a bit and monitor. This has all been very helpful.

David_16

I think I'm about done here. Here's a recap of where I'm at.
I reset the counters on 2/12 at 9am and noted the gas meter reading
I've been set to 120@70, 170@10, max rate 60%, boost off
Temperature has been right around seasonal norms (30s)
House has been comfortable with the time it takes to satisfy calls acceptable

So after 96 hours:
Run Time 53 hours
Heat Zone 1 2 hours
Heat Zone 2 51 hours
DSW 4 hours
Boiler Ignitions 108

Therms used 17


I'm not really sure there's much more I can do. Fintube gets real bad at 120-130 or so so I don't really think I would go lower than 120 @ 70 on that end.

I'm still not sure what to do with the max rate setting. Before I had it set, it seemed to really go above 60% if the boiler was cold and got a call and I guess wanted to get to temp fast. It also goes above that for DHW, but the max rate setting isn't limited for that zone, so that's fine. Otherwise, it seems to be humming along at 20-35% so the max rate setting probably is having no effect. Maybe if it's real cold and has to do 170 water for 2 zones at the same time it would go higher? And if that happens, maybe I want it to go higher? Or on the other hand, maybe I could limit it to 35% even and that would likely have some effect that would lengthen the run times, but that seems like way too low a number. A 60% it's probably pointless so maybe just better turning it off and letting it do its thing?

Hot_water_fan

It needs 60% at design day if I recall correctly, so don’t lower it. 

David_16

Hot_water_fan said:

It needs 60% at design day if I recall correctly, so don’t lower it. 

We don't really know that other than in my older thread, we figured, based on my oil usage, I probably need around 60K BTU on a design day and this boiler is 110K input so around 60% makes sense.

I definitely wasn't really going to lower it. I'm not sure the point of keeping it in place at all. Seems to hit 60% very little when it was off so why even bother. If the boiler needs 80% for a couple of minutes to get itself from 100 to 150 faster than it would if I had it limited to 60%, maybe that's not bad anyhow. I'm not really getting any heat until the boiler gets to near target temp.

I guess I'll leave it for now. If anything, 60% is probably close to the correct number.

flat_twin

One method of dialing in the ODR is to raise the thermostat to 80 or higher and allow the ODR settings to dictate the indoor temperature. When you find the point where the boiler is just able to maintain your desired indoor temperature, bump up the supply water temp a couple degrees at both ends to cover extremely windy conditions. Our modcon is a Weil Mclain Eco 110 btu (previous model to yours) and like yours it ramps up after firing and then slowly settles at whatever point the ODR tells it. Don't worry much about the firing percentages. I actually limited ours to 70% to imitate a 70k btu max firing rate.

David_16

flat_twin said:

One method of dialing in the ODR is to raise the thermostat to 80 or higher and allow the ODR settings to dictate the indoor temperature. When you find the point where the boiler is just able to maintain your desired indoor temperature, bump up the supply water temp a couple degrees at both ends to cover extremely windy conditions. Our modcon is a Weil Mclain Eco 110 btu (previous model to yours) and like yours it ramps up after firing and then slowly settles at whatever point the ODR tells it. Don't worry much about the firing percentages. I actually limited ours to 70% to imitate a 70k btu max firing rate.

Wow, great input, very similar situation!

Would be an interesting test, I guess, to see what water temp is needed to maintain the temp where I want it to be, but I'm not trying to necessarily squeeze every penny of savings. Frankly, I'm pretty surprised that 145 water temp keeps the house at target when it's 40 degrees out. There's probably not much lower than 120@70, 170@10 that I could realistically go.

Nice to see you confirm what I see as far as modulation rate. Based on my old oil calculations, 60K BTU is probably the max I'd need on a design day so I'll probably keep it limited to 60% for now then. If we get a really cold day, I'll turn up both zones and see if it gets close to 60% ever.

How reliable has your WM Eco been? How long have you had it for?

exqheat

Love long discussions. They eventuaklly make little or no sense to those that heat their homes with something no one knows how to operate.
1. Why strain to heat the outdoors.
2. Installers never take the tie to tweak them. They can't.
3. I prefer indoor technology.

flat_twin

The modcon boiler was installed Nov 2016. A year later I installed an indirect water heater. No problems at all with the boiler. It's the earlier version ECO boiler with just enough controls for space heating and to run an indirect WH. We have cast iron radiators one zone. Supply water ranges from 90 to 142 degrees for heating. ODR is set to cover from 60 to -20 outside temp.

David_16

First full month gas bill was $184 for Feb. There's no chance it would have been under $400 of oil and probably closer to $500. I was paying $4/gal this winter, even at $3, it would have been double my gas spend.

Still doing some weekly measuring of boiler run hours and ignitions, but I think I have it dialed in around where it should be at this point.