Mod CON? Or Power vent 85%?

NY_Rob

Try to limit setback to 2F or so, anything above that will take hrs to overcome. After a lifetime of using deep setback, it takes a bit of time to get used to small or no nighttime setback... but you will.

Mine (same boiler, close to same size house) took a little over an hour to climb 2 deg this morning. Cold start from deeper setback will take longer to recover too.

What are your ODR curve settings Rich, they may need tweaking?
Min outdoor temp:
Max CH water temp:
Max outdoor temp:
Min CH water temp:

Once you get the ODR and setback settings dialed in, you won't need Boost.

Here's our outside temps for last night (you live within 10mi of me so your temps will be similar) so you know what your boiler ODR sensor was dealing with..

Suzook

Min outdoor temp: 0
Max CH water temp: 165
Max outdoor temp: 50
Min CH water temp: 120

If it only took you an hr to climb 2 degrees, something is wrong, as i am climbing maybe a half degree per hour, and its not that cold out. I am concerned about the winter. Only thing I have different is most on my fin baseboard is in a slab on my 1st floor. Wondering if I should increase the Min CH, as I am probably "losing" temp in the slab.

BTW, boiler is condensing very nice. My drain was temporary put into a bucket, and i have ALOT of water.

NY_Rob

Here's your current curve then...


Looking at last night's temps at 4am it was about 45F outside which gives you 125F SWT and 115F AWT. Standard fintube only puts out 185BTU/Ft at 115F AWT... that's not much and it will take a long time to recover from 63F to 68F indoors with 115F AWT.

Shoulder seasons are tough to dial in the ODR values because it may be 35F at 5am then 65F at 8am but your house is still cold inside even though the boiler is close to max outdoor temp shutdown.

Boost may be helpful during shoulder seasons, but try to remember to disable it during the winter.
Maybe try +10deg after 30min?

Suzook

^Thanks. Yes, will use boost in early, late season. Along with readjusting my setbacks a bit. We prefer it cool at night, so boost should help us recover quickly in the morning.

NY_Rob

Don't worry about being cold during the winter.. you have plenty of output for your house. Probably 2x what you'll probably ever need.
It takes a while to get the ODR "just right" to prevent short cycling but still keep warm and overcome some setback. My mod-con was up and running by July of last year, I was still tweaking the ODR curve in Jan due our strange weather last fall/early winter.

Jean-David Beyer

I have a mod-con and my boiler has a boost feature. My main heating is radiant in a slab at grade. Consequently, setbacks are completely useless with a mod-con because my reset curves are set to supply the minimum heat to the slab depending on outside temperature. If a setback is attempted, it takes four to eight hours to notice a temperature of a degree or two, and 24 to 48 hours to drop to 62 and stabilize. And for ending setback, it does not put enough heat into the slab to restore from setback for a couple of days. It recovers from setback faster with the boost feature enabled, but not enough to matter.
When storm Sandy turned off all power for 6 1/2 days, my house dropped about 10 degrees (It was cold outside, but not below freezing). When power came back on, I forgot and just let it run. A day later, it had recovered little. I just disabled the reset and let it go, and it took about two days to get up to temperature and another day for the system to stabilize.
And upstairs, where there is baseboard heat (but way more baseboard than usual) it is just as bad raising the temperature after a setback, even though the boost raises the water temperature 10F after 4 hours and another 10F after another four hours. Just too slow. So for what I consider a well set reset curve on each zone, I think setbacks do not make sense with a mod-con.

NY_Rob

^ for radiant slab Boost is useless, as is setback where it could take days to recover.

For regular fin-tube baseboard it can be useful if the homeowner still likes to use a couple deg of nighttime setback vs. none at all.

Suzook

Here I am, back at this thread....LOL. The boost function works, but not as good as I would like. I am wondering if I should just skip the setbacks, and set my house to 70, and be done with it. It just seems wasteful to have my house at 70 for 8 to 12 hours while I am at work, along with having my circ pump running continuesly. Am I saving $ with the setbacks? Or wasting $???

gschallert

Suzook said:

Here I am, back at this thread....LOL. The boost function works, but not as good as I would like. I am wondering if I should just skip the setbacks, and set my house to 70, and be done with it. It just seems wasteful to have my house at 70 for 8 to 12 hours while I am at work, along with having my circ pump running continuesly. Am I saving $ with the setbacks? Or wasting $???

If you've got a modcon tuned for best efficiency (lowest SWT & good ODR curve) it's best to leave it be and forget about thermostat setbacks. You're wasting money trying to recover from the setbacks and sacrificing comfort. Set it and forget it. ;-)

NY_Rob

I used to use daytime setback w/the old CI boiler, but I abandoned it when I went w/the mod-con.... and I still saw greater than 20% savings on my heating bill last winter (adjusted for temp). I just keep the house set at 69F during the day.

I still use -2F nighttime setback to 67F, but I start the recovery back to 69F at 5am.

I think you'll be surprised how little gas the UFT uses putting along 8K BTU's output which is probably where it will be set most of the daylight hours only making up 1 deg temp drop.

You have the Alpha for your CH pump right?
I have mine set to "Auto" and it only burns 11 watts w/one zone running and 16 watts with two zones running. Electricity costs will be minimal w/this pump.

Suzook

^Yup, I have the alpha on auto. I was concerned with the usage, but thats minimal. Guess I will try 70, and see how we like it.

GW

Boiler conversation is boring, i just want to know if the Op has a Suzuki, and if what what is it? RMX450??

Suzook

^Had 3! 2 gsxr 750's, and a gsxr1100.

Suzook

NY_Rob said:

I used to use daytime setback w/the old CI boiler, but I abandoned it when I went w/the mod-con.... and I still saw greater than 20% savings on my heating bill last winter (adjusted for temp). I just keep the house set at 69F during the day.

I still use -2F nighttime setback to 67F, but I start the recovery back to 69F at 5am.

I think you'll be surprised how little gas the UFT uses putting along 8K BTU's output which is probably where it will be set most of the daylight hours only making up 1 deg temp drop.

You have the Alpha for your CH pump right?
I have mine set to "Auto" and it only burns 11 watts w/one zone running and 16 watts with two zones running. Electricity costs will be minimal w/this pump.

BTW, set my tsat to 69. Last night boiler ran for 30 mins, shut for 20, and cycled like this pretty much all night. This sound OK? Or should I do some more tinkering to try to get it to run as much as possible?
EDIT, I forgot to turn off boost, maybe thats the issue? Will turn it off.

GW

Suzook said:

^Had 3! 2 gsxr 750's, and a gsxr1100.

Cool I had a gsxr750 back in the late 80s, had to get rid of it b4 i killed myself. And i meant RMZ, not RMX,,,,geeesh, I'm a dirt bike guy

Leon82

> @Suzook said:
> I used to use daytime setback w/the old CI boiler, but I abandoned it when I went w/the mod-con.... and I still saw greater than 20% savings on my heating bill last winter (adjusted for temp). I just keep the house set at 69F during the day.
>
> I still use -2F nighttime setback to 67F, but I start the recovery back to 69F at 5am.
>
> I think you'll be surprised how little gas the UFT uses putting along 8K BTU's output which is probably where it will be set most of the daylight hours only making up 1 deg temp drop.
>
> You have the Alpha for your CH pump right?
> I have mine set to "Auto" and it only burns 11 watts w/one zone running and 16 watts with two zones running. Electricity costs will be minimal w/this pump.
>
>
>
>
>
> BTW, set my tsat to 69. Last night boiler ran for 30 mins, shut for 20, and cycled like this pretty much all night. This sound OK? Or should I do some more tinkering to try to get it to run as much as possible?
> EDIT, I forgot to turn off boost, maybe thats the issue? Will turn it off.

I would drop your odr curve by 5 degrees and see what it does for cycle times.

When you say shut down. It met the set point or the boiler and pumps shut off

Suzook

^ It met the setpoint. Not 100% sure it turned off. I am looking at my ecobee report. I believe if I am reading it right, it shuts off.

flat_twin

Suzook, I'd try for longer burn times especially with a low fire rate of 8k. This method helped me get the ODR dialed in. Set your thermostat to 80, think of it as a high limit. Now let the ODR settings go where they may. Adjust as needed for long continuous burns that will hold your desired temperature. I like to see my indoor temps sag a little on cloudy windy days. It tells me I'm right on the edge of making enough heat. A sunny calm day, using the stove or oven, laundry, showers, or almost any human activity is enough to raise the indoor temp a bit.
We leave the thermostat at 72, no setback at all. Our upstairs bedrooms have no emitters and are cooler which is fine for sleeping so a lucky coincidence there as well.

NY_Rob

It looks like a lot of your cycling occurred when the outdoor temps were in the mid/high 20's last night.
Here's the ODR curve you were using last time you posted:


Notice your SWT is 141F@26deg outside. I plotted a couple of trial curves that will lower your SWT a bit. Give one a try without BOOST enabled.

NY_Rob

^ oh yeah, you can set the "anti-cycling" feature on that boiler for up to 20min so that will prevent cycling too.

Suzook

^So to do this just change my Max ch temp. Correct?

Leon82

> @Suzook said:
> ^So to do this just change my Max ch temp. Correct?

I would drop the odr temp evenly.

NY_Rob

You have to be careful on the low end that you don't drop the SWT below the boiler's minimum BTU output based on your shortest zone.

Example 1:
You have a 8K BTU minimum fire rate boiler and 40ft of fin-tube in your shortest zone.
130F SWT gives you 120F AWT at 210BTU's/ft of fin-tube for 8,400BTU's output... no short cycling.

Example 2:
If you have a 8K BTU minimum fire rate boiler and 40ft of fin-tube.
120F SWT gives you 110F AWT at 160BTU's/ft of fin-tube for 6,400BTU's output... with a boiler that can't supply less than 8,000 BTU's.... short cycling will occur.

To calculate the low SWT end of the curve, you have to look at your shortest zone and boiler minimum firing rate.
Cast iron radiators and cast iron baseboard is a little more forgiving because it takes so long to heat up and cool down, short cycling might not be an issue like it is with no mass fin-tube at low temps even in short zones.

Suzook

^ I have 50 ft of fintube on 2nd floor. The run feeding it though goes into the attic and is about 75 ft before it gets to the first heating section. The pipe is insulated, but i!m sure there is some loss. I do expect some short cycling on the 2nd zone. I'm not gonna worry about it. I'm just trying to dial in the 1st floor the best I can. Last night with the warmer temps, I only had 3 off cycles, at 10 mins each. Think I will wait for some colder weather,before any more changes.

NY_Rob

^ Now you see why so many posters here have found their installer has left the ODR curve set at factory default.
There's just no way an installer can camp out or make multiple return visits during changing weather conditions to tweak the ODR and still turn a profit.

Leon82

If you know the heat loss and how much radiation you have you can get somewhat close

Suzook

Ok, so the wife hates the house at 69 in the morning when she is getting ready for work. She's says it's too warm. But likes it at 70 in the evening/night while watching TV. I didn't realize I would have issues with setbacks. Any suggestions?

NY_Rob

^ that scenario shouldn't really present a problem.

Set it for whatever she likes in the morning, then have it climb up slowly at some point later on in the day so it hits 70 when she wants. This is one case where you may want to enable BOOST to help overcome the morning setback if it takes too long to get to 70.

Suzook

^ OK, will give 66 at night, and 69 during day a try. Wondering If I should keep boost off for now, and see where i am at by 3 pm when someone is getting home. What do you think??

NY_Rob

It will be trial and error especially considering using a ODR curve makes it a moving target.

With Boost enabled, there's no doubt you'll hit 69F with a couple hours to get there, I'd try it without boost first and see what happens.

The nice thing with your boiler is that Boost has three different adjustable parameters; Boost Function (0-120min), Boost Degree (5-15F) and Boost Interval (0-120min) which make it easy to customize for your needs.

It doesn't help that it's supposed to be 55F here tomorrow afternoon... not ideal conditions for setback recovery testing.

Suzook

So I am back yet again!! Still having an issue with the upstairs reaching the setpoint of 69, when the downstairs zone is calling for heat too. This have anything to do with not having pri/sec piping? Any suggestions?? I am concerned how cold it will be upstairs when we get real cold. I know I have enough boiler, but why is the 2nd floor suffering when 1st floor calls?

SeymourCates

NY_Rob said:

You have to be careful on the low end that you don't drop the SWT below the boiler's minimum BTU output based on your shortest zone.

Example 1:
You have a 8K BTU minimum fire rate boiler and 40ft of fin-tube in your shortest zone.
130F SWT gives you 120F AWT at 210BTU's/ft of fin-tube for 8,400BTU's output... no short cycling.

Example 2:
If you have a 8K BTU minimum fire rate boiler and 40ft of fin-tube.
120F SWT gives you 110F AWT at 160BTU's/ft of fin-tube for 6,400BTU's output... with a boiler that can't supply less than 8,000 BTU's.... short cycling will occur.

To calculate the low SWT end of the curve, you have to look at your shortest zone and boiler minimum firing rate.
Cast iron radiators and cast iron baseboard is a little more forgiving because it takes so long to heat up and cool down, short cycling might not be an issue like it is with no mass fin-tube at low temps even in short zones.

In the second example, you have an excess of 1600 BTUH for the entire system. Figure the boiler and the zone have 15 gallons total fluid volume. The extra 1600 BTU would raise the SWT by only 12 degrees in one hour. The boiler currently has a margin of 12 degrees above HL before shutdown.

So, I would not characterize a one hour continuous run (discounting the warmup period to achieve SWT) as "short cycling".

This mod-con can easily accept "cycling" once every 30 minutes, if absolutely necessary before any concern arises. The installer menu provides the capability to limit the number of cycles per hour to two or less by utilizing parameter 16:FT and setting the parameter to 20 minutes. If this is done, the boiler cannot "short cycle". It will operate for 10 minutes (unless the zone is ridiculously small) and shutdown for 20 minutes while the zone pump continues to operate and distribute BTU's.

It should be additionally noted that it is beneficial to chop the curve at the bottom end so the boiler does not end up in a situation where the emitters only have 4K capability to distribute. Far better to lift the bottom end of the curve and "suffer" the zone satisfying the 'stat and waiting (probably one hour minimum) for the next call.

NY_Rob

Suzook said:

Still having an issue with the upstairs reaching the setpoint of 69, when the downstairs zone is calling for heat too. ... why is the 2nd floor suffering when 1st floor calls?

If your two zones have different head values, more CH water will flow through the zone with the least resistance.

You may need to put a globe valve on the 1st floor zone to restrict flow slightly to match the two zones.

If you want to test it, set your alpha to CP speed 1, place your boiler in installer mode and activate the CH pump run mode (34:AP). Manually open 1st floor zone valve only, record pump wattage and GPM values. Repeat test for CP speed 2 and CP speed 3, record wattage and GPM for both speeds. You should have three sets of watts/GPM figures.
Now repeat the same procedure with only the 2nd floor zone valve opened... go through all three pump CP speeds- record the watts and GPM values for all three speeds.
Compare the 1st and second floor test results.
I bet you'll find the 2nd floor zone takes more wattage to push the same amount of water or it simply has lower flow than the 1st floor zone.

Suzook

^^ The 2nd upstairs zone definitely has a higher head(lower flow?) That zone is very long, probably 60 feet before it gets to the emitter. The 1st floor that goes into the slab leaves on 2 pipes, then splits to front and back of house, then returns on one pipe. What if I just turn the ball valve that's in place already a little on the 1st zone? That should create a restriction, no?

Suzook

SeymourCates said:

NY_Rob said:

You have to be careful on the low end that you don't drop the SWT below the boiler's minimum BTU output based on your shortest zone.

Example 1:
You have a 8K BTU minimum fire rate boiler and 40ft of fin-tube in your shortest zone.
130F SWT gives you 120F AWT at 210BTU's/ft of fin-tube for 8,400BTU's output... no short cycling.

Example 2:
If you have a 8K BTU minimum fire rate boiler and 40ft of fin-tube.
120F SWT gives you 110F AWT at 160BTU's/ft of fin-tube for 6,400BTU's output... with a boiler that can't supply less than 8,000 BTU's.... short cycling will occur.

To calculate the low SWT end of the curve, you have to look at your shortest zone and boiler minimum firing rate.
Cast iron radiators and cast iron baseboard is a little more forgiving because it takes so long to heat up and cool down, short cycling might not be an issue like it is with no mass fin-tube at low temps even in short zones.

In the second example, you have an excess of 1600 BTUH for the entire system. Figure the boiler and the zone have 15 gallons total fluid volume. The extra 1600 BTU would raise the SWT by only 12 degrees in one hour. The boiler currently has a margin of 12 degrees above HL before shutdown.

So, I would not characterize a one hour continuous run (discounting the warmup period to achieve SWT) as "short cycling".

This mod-con can easily accept "cycling" once every 30 minutes, if absolutely necessary before any concern arises. The installer menu provides the capability to limit the number of cycles per hour to two or less by utilizing parameter 16:FT and setting the parameter to 20 minutes. If this is done, the boiler cannot "short cycle". It will operate for 10 minutes (unless the zone is ridiculously small) and shutdown for 20 minutes while the zone pump continues to operate and distribute BTU's.

It should be additionally noted that it is beneficial to chop the curve at the bottom end so the boiler does not end up in a situation where the emitters only have 4K capability to distribute. Far better to lift the bottom end of the curve and "suffer" the zone satisfying the 'stat and waiting (probably one hour minimum) for the next call.

Thats very interesting. I have to sit back, and stop worrying about short cycling. I have OCD about it. So raise the temps of Min CH water temp?

Gordy

Yes, especially with zoning, and setback schedules.

Especially when zones, and their emitters were not initially designed to achieve that goal.

Your goal is to heat the space with the lowest avg water temp possible with out losing control of the systems ability to keep up to loads under most conditions. This takes advantage of condensing when ever possible.

SeymourCates

Determine the proper curve for your building as shown on page 58 in the manual. Notice that the default takes the boiler all the way down to an SWT of 86°F (7:cl) at an outdoor of 68° (4:Oh). We really don't want to run the boiler down to an SWT of 86°F and prefer the minimum to be somewhere between 105°F and 115°F depending on radiation and installer's preference. The higher values would typically allow the boiler to operate without any HL trip. The lower values would generate an HL trip under certain conditions (single zone calling). Use 16:Ft to delay restart under such conditions.

It is important to note that it is not desirable to simply raise 7:cl. Follow the curve upward and find the minimum SWT desired (installers choice). Now find the outside temperature that corresponds to that chosen SWT (at the bottom of the Y axis) and put that value into 4:Oh. You now have effectively "chopped" the bottom of the curve without affecting the slope.

Suzook

NY_Rob said:

Suzook said:

Still having an issue with the upstairs reaching the setpoint of 69, when the downstairs zone is calling for heat too. ... why is the 2nd floor suffering when 1st floor calls?

If your two zones have different head values, more CH water will flow through the zone with the least resistance.

You may need to put a globe valve on the 1st floor zone to restrict flow slightly to match the two zones.

If you want to test it, set your alpha to CP speed 1, place your boiler in installer mode and activate the CH pump run mode (34:AP). Manually open 1st floor zone valve only, record pump wattage and GPM values. Repeat test for CP speed 2 and CP speed 3, record wattage and GPM for both speeds. You should have three sets of watts/GPM figures.
Now repeat the same procedure with only the 2nd floor zone valve opened... go through all three pump CP speeds- record the watts and GPM values for all three speeds.
Compare the 1st and second floor test results.
I bet you'll find the 2nd floor zone takes more wattage to push the same amount of water or it simply has lower flow than the 1st floor zone.

SeymourCates said:

Determine the proper curve for your building as shown on page 58 in the manual. Notice that the default takes the boiler all the way down to an SWT of 86°F (7:cl) at an outdoor of 68° (4:Oh). We really don't want to run the boiler down to an SWT of 86°F and prefer the minimum to be somewhere between 105°F and 115°F depending on radiation and installer's preference. The higher values would typically allow the boiler to operate without any HL trip. The lower values would generate an HL trip under certain conditions (single zone calling). Use 16:Ft to delay restart under such conditions.

It is important to note that it is not desirable to simply raise 7:cl. Follow the curve upward and find the minimum SWT desired (installers choice). Now find the outside temperature that corresponds to that chosen SWT (at the bottom of the Y axis) and put that value into 4:Oh. You now have effectively "chopped" the bottom of the curve without affecting the slope.

Yikes, I actually just came back from raising 7cl...It was at 125, raised it to 130. What you just wrote is another language. This is getting tiring.

NY_Rob

Suzook said:

^^ The 2nd upstairs zone definitely has a higher head(lower flow?) That zone is very long, probably 60 feet before it gets to the emitter. The 1st floor that goes into the slab leaves on 2 pipes, then splits to front and back of house, then returns on one pipe. What if I just turn the ball valve that's in place already a little on the 1st zone? That should create a restriction, no?

You can temporarily try it with the ball valve, but that type of valve is not meant to adjust flow, it's an on or off valve. It creates too much turbulence and could lead to air in the lines. If throttling zone 1 does work, install a ball valve for a permanent fix. I have spare 3/4" threaded ball valves that I purchased when I was setting up my system. I found I didn't need them as my zones were really very close head wise. You're welcome to them if find throttling zone 1 works.

Suzook

Well, upstairs today is struggling. I am now 5 degrees below setpoint. Yes its cold!! But whats gonna happen when its 0 out? I am thinking I just dont have enough radiation to keep it warm enough with low supply temp. Only way for that is higher supply temp. Never had an issue with my old boiler running high temps.

EDIT....Could it be the the unit is not putting out enough BTU's when both zones are on? I have it lowered to 70% output.