What Should The High Boiler Temp Be Set To For Heating DHW During Summer Months?
#1
05-06-11, 07:00 AM
What Should The High Boiler Temp Be Set To For Heating DHW During Summer Months?
Had a new Buderus G115/3 boiler and Buderus ST150 indirect DHW heater installed in February which has worked great.
Now that winter is finally over in Upstate NY and I don't need to heat the house only the DHW, I'm wondering what the High temperature setting on the boiler should be?
During the heating season, the installers set the boiler with a 125 degree low temp setting and a 185 high temp setting. They said I could turn the high temp setting down during the non heating months since I don't need 185 degree boiler water to heat the indirect DHW. They suggested a high temp boiler setting of 150, but is that high enough?
I have the aquastat on the indirect set at 125 degrees if that matters.
Thank you.
Now that winter is finally over in Upstate NY and I don't need to heat the house only the DHW, I'm wondering what the High temperature setting on the boiler should be?
During the heating season, the installers set the boiler with a 125 degree low temp setting and a 185 high temp setting. They said I could turn the high temp setting down during the non heating months since I don't need 185 degree boiler water to heat the indirect DHW. They suggested a high temp boiler setting of 150, but is that high enough?
I have the aquastat on the indirect set at 125 degrees if that matters.
Thank you.
#2
05-06-11, 01:41 PM
anything higher than your tank setpoint is fine. 150 is good. your incoming water will be warmer so it will balance itself out nicely. dont go any lower than about 140-145 on a cast iron boiler. 150 is perfect to play it safe.
#3
05-06-11, 02:45 PM
By running it lower you may notice that after heavy periods of HW use the tank won't recover as quickly. Two long steamy showers in a row might have the second person screaming when the cold water starts hitting them... so, you may have to adjust your habits a bit, but maybe not... I guess a trade-off in fuel savings might be worth it, but I'm not sure it will save a heckuva lot. After all is said, BTUs are still BTUs. It will take a certain amount of BTUs to heat the water up (1 BTU per pound of water per degree) so let's say you use 20 gallons of hot, that's 167 pounds of water (8.34 lb per gallon). Let's say the incoming water is 65°. You are heating to 125°... so, 60 X 167 = 10K BTU. Whether you transfer that 10K BTU from 150 or 180 water, won't make a difference in the amount of BTUs, you still are doing the transfer. At 180 it will just happen FASTER because of the driving force... you still need to burn the same amount of fuel to heat the water.
Where the savings comes in is the fact that you won't be leaving as many BTUs stranded in the boiler to radiate into the home, wasted, and putting more load on the A/C system. Your 'standby' losses will be less. If your boiler controls allow a 'post purge' into the DHW tank, you can recover even more of that wasted heat into the domestic tank.
So, even if it's only a percent or three, it's still a savings and it can't hurt to try!
Where the savings comes in is the fact that you won't be leaving as many BTUs stranded in the boiler to radiate into the home, wasted, and putting more load on the A/C system. Your 'standby' losses will be less. If your boiler controls allow a 'post purge' into the DHW tank, you can recover even more of that wasted heat into the domestic tank.
So, even if it's only a percent or three, it's still a savings and it can't hurt to try!
Last edited by NJT; 05-06-11 at 03:20 PM.
#4
05-06-11, 04:49 PM
My boiler controls do not allow a " post purge." I think I'll just try leaving the high temperature setting at 150 for now and see how it works during the summer.
As I've stated, this boiler/indirect set up is new to me so I'm trying to understand it's operating characteristics.
One question I do have is how often should the burner turn on during the summer to heat the indirect only?
What I've been observing is that during the day when there is virtually no hot water demands, the burner turns on at least once every 45 minutes which seems too frequent when you consider the published heat loss of the Buderus indirect is 1/4 degree an hour?
Does this sound right?
Is there a potential problem with the aquastat on the indirect that is calling for the water to heat up more often than it should?
Thank you.
As I've stated, this boiler/indirect set up is new to me so I'm trying to understand it's operating characteristics.
One question I do have is how often should the burner turn on during the summer to heat the indirect only?
What I've been observing is that during the day when there is virtually no hot water demands, the burner turns on at least once every 45 minutes which seems too frequent when you consider the published heat loss of the Buderus indirect is 1/4 degree an hour?
Does this sound right?
Is there a potential problem with the aquastat on the indirect that is calling for the water to heat up more often than it should?
Thank you.
#5
05-06-11, 05:14 PM
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That is way too often. After showers in the morning mine runs maybe 1 time during the evening or night with no use. I am guessing you do not have a cold start aquastat or something is wrong
#6
05-06-11, 06:15 PM
What is this low setting on the boiler? Did you use the indirect to replace a tankless coil? If so, convert your boiler to cold start. It is coming on every 45 minutes to maintain your boiler at 125 degrees all the time.
#7
05-07-11, 04:53 AM
The low boiler setting is 125 degrees.
I did not install the indirect to replace a tankless coil. I previously had a stand alone Bock oil fired DHW heater that hardly ever ran. I installed the indirect along with a new Buderus G115/3 based on suggestions from almost everyone I talked to that it would provide more than adequate hot water and save fuel compared with operating two separate burners.
How do you convert the boiler to a cold start?
Is there a downside to converting to a cold start?
I did not install the indirect to replace a tankless coil. I previously had a stand alone Bock oil fired DHW heater that hardly ever ran. I installed the indirect along with a new Buderus G115/3 based on suggestions from almost everyone I talked to that it would provide more than adequate hot water and save fuel compared with operating two separate burners.
How do you convert the boiler to a cold start?
Is there a downside to converting to a cold start?
#8
05-07-11, 07:51 AM
I completely missed the fact that you said in your first post that there was a 'LOW' setting on your system... and as others have said that is exactly why your boiler is firing up every hour or so. I'm sure there is nothing wrong with the aquastat on the indirect.
Can you tell us what aquastat is installed on the boiler?
Depending on what you have, it could be as easy as pushing a few buttons, or as difficult as swapping out the aquastat for an appropriate model.
I can never understand why installers specify a 'triple aquastat' (which means one with both a low and a high setting, rather than a 'single' with just the high setting) when installing systems with indirect water heaters. Just doesn't make any sense and more or less defeats the savings that you should or would be getting by going with the indirect water heater.
Can you tell us what aquastat is installed on the boiler?
Depending on what you have, it could be as easy as pushing a few buttons, or as difficult as swapping out the aquastat for an appropriate model.
I can never understand why installers specify a 'triple aquastat' (which means one with both a low and a high setting, rather than a 'single' with just the high setting) when installing systems with indirect water heaters. Just doesn't make any sense and more or less defeats the savings that you should or would be getting by going with the indirect water heater.
#9
05-07-11, 02:29 PM
The aquastat on the boiler is a Honeywell L 7224U.
It's digital and based on what the installers showed me its easy to adjust. They suggested changing the high temperature limit from 185 to 150 once the heating season is over which is now. But said nothing about adjusting the low temperature limit from 125.
When I went down to the basement to get the brand and number off the aquastat, for the heck of it, I adjusted the low temperature limit downward to see how far it would go and found that it went to 110 than the next setting was OFF.
Can I assume that OFF is where the low temperature setting should be during the non heating months?
Or do I need to change to a different aquastat? If so, which one?
Thanks again
It's digital and based on what the installers showed me its easy to adjust. They suggested changing the high temperature limit from 185 to 150 once the heating season is over which is now. But said nothing about adjusting the low temperature limit from 125.
When I went down to the basement to get the brand and number off the aquastat, for the heck of it, I adjusted the low temperature limit downward to see how far it would go and found that it went to 110 than the next setting was OFF.
Can I assume that OFF is where the low temperature setting should be during the non heating months?
Or do I need to change to a different aquastat? If so, which one?
Thanks again
#11
05-07-11, 04:07 PM
Like I said, going cold start could be as easy as pushing a few buttons, and it is.
Turn the Low limit OFF and leave it OFF, heating season or no heating season, you don't need it. The Low limit should only be used for boilers that make domestic hot water with a 'tankless coil' in the boiler. You don't have one. So turn it OFF.
The boiler now will not attempt to stay warm and waste fuel. It will only fire up on demand, which is what you want it to do.
Turn the Low limit OFF and leave it OFF, heating season or no heating season, you don't need it. The Low limit should only be used for boilers that make domestic hot water with a 'tankless coil' in the boiler. You don't have one. So turn it OFF.
The boiler now will not attempt to stay warm and waste fuel. It will only fire up on demand, which is what you want it to do.
#12
05-07-11, 04:12 PM
Droo asked:
No, because there is no cool water returning from the system to chill the boiler and cause condensation. The return in this case is coming from the DHW and that will already always be pretty warm. Not a problem.
Is maintaining the boiler at 125 going to be a condensation issue?
#14
05-07-11, 04:50 PM
Originally Posted by NJ Trooper
No, because there is no cool water returning from the system to chill the boiler and cause condensation. The return in this case is coming from the DHW and that will already always be pretty warm. Not a problem.
#15
05-07-11, 05:40 PM
It's really the cool water coming back from the system that is the problem. That cool water coming back is keeping the surface temperature of the fire side of the boiler below the dewpoint of the flue gases. With the boiler maintaining 125 in the water, you can be pretty durn sure that the surfaces on the fire side are hotter than that. Remember that there's a temperature gradient throughout the cast iron. Don't forget also that there is NO circulation on a 'keep warm' cycle. The pump ain't running.
On the other hand, imagine a large water volume system dumping a huge amount of cool/cold water back into the return... for a long time... that volume of water dumping into the boiler is enough to keep the cast iron cool enough for condensation to occur.
I've seen varying temp numbers for the dewpoint of oil fired combustion, but it seems that 115 is pretty typical. For gas fired systems, 135 seems to be the number.
On the other hand, imagine a large water volume system dumping a huge amount of cool/cold water back into the return... for a long time... that volume of water dumping into the boiler is enough to keep the cast iron cool enough for condensation to occur.
I've seen varying temp numbers for the dewpoint of oil fired combustion, but it seems that 115 is pretty typical. For gas fired systems, 135 seems to be the number.
#16
05-08-11, 06:14 AM
I think I need more input and advice.
As indicated in my previous reply, I set the low temperature setting to OFF and also adjusted the temperature setting on the indirect from 125 to 120 because 120 degree hot water should be fine.
In any event, for some reason, the burner is still running pretty often when there is no demands for hot water. I haven't timed it but can tell because I checked the boiler temperature on both the boiler gauge as well as the digital display on the boiler aquastat after 3 or 4 hours before going to bed last night and the temperature was still 140 degrees in the boiler. Plus the piping from the boiler to and from the indirect was very hot to touch. I also checked it first thing this morning after no demands during the night for hot water and I still found the water temperature in the 140's and the pipes hot.
So I'm assuming there's a secondary ( or maybe primary) issue causing this. Could it be a bad aquastat on the indirect? Or is there something in the TACO SR503 Zone Relay that could be telling the burner to fire?
I plan to call the installers tomorrow but would like to have a pretty good idea what could be causing the problem so I'm in a position of knowledge when they get here.
1. Is there a way for me to test the aquastat on the indirect?
One thing I can tell you is that once the burner fires, as a result of whatever is triggering it, it runs a very long time before the aquastat on the indirect is satisfied and the burner/circulator shuts off. Last night, I observed it, with no demands for hot water anywhere in the house at the same time, running for 45-60 minutes before the burner/circulator shut down. Since this boiler/indirect set up is new to me I cannot draw on previous operating knowledge regarding how long it should take to heat the water in the indirect to the setting level (120) but my instincts tell me 45-60 minutes is way too long.
2. Could there be something in the TACO zone relay that is telling the burner to run even though the low temperature setting on the boiler aquastat is turned OFF?
Would appreciate any thoughts or ideas on what the remaining problem could be.
Thanks again.
As indicated in my previous reply, I set the low temperature setting to OFF and also adjusted the temperature setting on the indirect from 125 to 120 because 120 degree hot water should be fine.
In any event, for some reason, the burner is still running pretty often when there is no demands for hot water. I haven't timed it but can tell because I checked the boiler temperature on both the boiler gauge as well as the digital display on the boiler aquastat after 3 or 4 hours before going to bed last night and the temperature was still 140 degrees in the boiler. Plus the piping from the boiler to and from the indirect was very hot to touch. I also checked it first thing this morning after no demands during the night for hot water and I still found the water temperature in the 140's and the pipes hot.
So I'm assuming there's a secondary ( or maybe primary) issue causing this. Could it be a bad aquastat on the indirect? Or is there something in the TACO SR503 Zone Relay that could be telling the burner to fire?
I plan to call the installers tomorrow but would like to have a pretty good idea what could be causing the problem so I'm in a position of knowledge when they get here.
1. Is there a way for me to test the aquastat on the indirect?
One thing I can tell you is that once the burner fires, as a result of whatever is triggering it, it runs a very long time before the aquastat on the indirect is satisfied and the burner/circulator shuts off. Last night, I observed it, with no demands for hot water anywhere in the house at the same time, running for 45-60 minutes before the burner/circulator shut down. Since this boiler/indirect set up is new to me I cannot draw on previous operating knowledge regarding how long it should take to heat the water in the indirect to the setting level (120) but my instincts tell me 45-60 minutes is way too long.
2. Could there be something in the TACO zone relay that is telling the burner to run even though the low temperature setting on the boiler aquastat is turned OFF?
Would appreciate any thoughts or ideas on what the remaining problem could be.
Thanks again.
#17
05-08-11, 07:26 AM
Let's back up a bit...
Describe the system a bit more, you said you have an SR503, so we can presume that you are zoning with pumps, correct? In other words there is a separate pump for the indirect, and one for at least one heating zone. Is there anything else connected to the 503?
There are switch settings in the 503, one for DHW 'priority', what are these switches set to?
Are there any additional controls on the system? for example, an OutDoor Reset control?
Describe the system a bit more, you said you have an SR503, so we can presume that you are zoning with pumps, correct? In other words there is a separate pump for the indirect, and one for at least one heating zone. Is there anything else connected to the 503?
There are switch settings in the 503, one for DHW 'priority', what are these switches set to?
Are there any additional controls on the system? for example, an OutDoor Reset control?
#18
05-08-11, 07:30 AM
On the 7224 a'stat, do you know how to check the 'differential' settings?
If so, what are they set at? Since you have the LOW set to OFF, (verify this to be certain it really is OFF) just tell us the Hdf setting for now.
Is there any wiring on the ZR or ZC terminals of the a'stat?
If so, what are they set at? Since you have the LOW set to OFF, (verify this to be certain it really is OFF) just tell us the Hdf setting for now.
Is there any wiring on the ZR or ZC terminals of the a'stat?
#19
05-08-11, 07:34 AM
adjusted the temperature setting on the indirect from 125 to 120 because 120 degree hot water should be fine.
Are you on city water?
Did they install a 'mixing' or 'tempering' valve on the water heater? If not, they should have.
#20
05-08-11, 09:06 AM
NJ Trooper, I'm answering your questions in the order you raised them starting with the oldest.
1. There are 3 zones each with a separate pump(s).
-Zone 1 is for the indirect and is set up as the priority zone
-Zone two is for heat in the basement
-Zone three is for heating the main floor (actually has 2 pumps)
There is there no Outdoor Reset Control or anything else connected to the 503
There are no switches that I can see for "DHW" but there seems to be connection choices and instructions that allow for setting up zone 1 as the priority zone. For example, the jumper between Terminal "P" and Terminal "ZC" has been removed and the thermostat wires from the indirect aquastat go to Zone 1.
2. The "Hdf" setting is 10 and I verified the Low Temperature is set to "OFF"
There are wires going to the ZR and ZC terminals
A black wire (I presume its 120Volts) goes to the "ZC" terminal which has a jumper between it and the "H" terminal
There's a White thermostat wire going from terminal "ZR" in the 503 to the TT terminals in the boiler aquastat (L7224U)
3. We are on well water.
After googling "legionella" I changed the temperature setting on the indirect's aquastat to 130 degrees.
I do not see any separate valves on the indirect and assume a "mixing or tempering valve" was not installed. I don't recall the subject ever coming up during installation.
Hopefully my answers will be helpful in trying to sort this out and zero in on the problem.
Let me know if you need clarification on anything I said.
Thank you.
1. There are 3 zones each with a separate pump(s).
-Zone 1 is for the indirect and is set up as the priority zone
-Zone two is for heat in the basement
-Zone three is for heating the main floor (actually has 2 pumps)
There is there no Outdoor Reset Control or anything else connected to the 503
There are no switches that I can see for "DHW" but there seems to be connection choices and instructions that allow for setting up zone 1 as the priority zone. For example, the jumper between Terminal "P" and Terminal "ZC" has been removed and the thermostat wires from the indirect aquastat go to Zone 1.
2. The "Hdf" setting is 10 and I verified the Low Temperature is set to "OFF"
There are wires going to the ZR and ZC terminals
A black wire (I presume its 120Volts) goes to the "ZC" terminal which has a jumper between it and the "H" terminal
There's a White thermostat wire going from terminal "ZR" in the 503 to the TT terminals in the boiler aquastat (L7224U)
3. We are on well water.
After googling "legionella" I changed the temperature setting on the indirect's aquastat to 130 degrees.
I do not see any separate valves on the indirect and assume a "mixing or tempering valve" was not installed. I don't recall the subject ever coming up during installation.
Hopefully my answers will be helpful in trying to sort this out and zero in on the problem.
Let me know if you need clarification on anything I said.
Thank you.
#21
05-08-11, 11:12 AM
Yeah, the 503 is prioritized by jumpers, the 504 and above are the ones with the switch.
In item #2 above I want to clarify for others that Targa is talking about the wiring in the SR503.
In the 7224, are there any connections to ZC or ZR ?
It's actually a PAIR of wires, probably one white and one red, going from the X1 and X2/ZR terminals of the 503 to the TT terminals on the 7224, correct?
There are no pumps connected to the 7224 then, correct? All are running of the 503?
All being so, it sounds wired correctly.
What you can do is disconnect the wires from the indirect aquastat to the 503 and observe to see if the boiler still fires up. If not, it's a sure bet that the indirect is calling for heat.
I wonder if perhaps the installers did not install a 'heat trap' on the domestic piping coming out of the indirect? See:
http://www.comfort-calc.net/Indirect_Piping.html
In item #2 above I want to clarify for others that Targa is talking about the wiring in the SR503.
In the 7224, are there any connections to ZC or ZR ?
There's a White thermostat wire going from terminal "ZR" in the 503 to the TT terminals in the boiler aquastat (L7224U)
There are no pumps connected to the 7224 then, correct? All are running of the 503?
All being so, it sounds wired correctly.
What you can do is disconnect the wires from the indirect aquastat to the 503 and observe to see if the boiler still fires up. If not, it's a sure bet that the indirect is calling for heat.
I wonder if perhaps the installers did not install a 'heat trap' on the domestic piping coming out of the indirect? See:
http://www.comfort-calc.net/Indirect_Piping.html
#22
05-08-11, 01:02 PM
If the indirect aquastat was malfunctioning and calling for heat when it wasn't supposed to, wouldn't the temperature of the water in teh indirect be well above the set temperature?
Also, how many BTU's is your boiler and what size indirect do you have?
Also, how many BTU's is your boiler and what size indirect do you have?
#23
05-08-11, 03:51 PM
Here are responses to the most recent questions raised by NJ Trooper and drooplug.
Yes, correct
Yes, correct.
I do not believe there is a "heat trap" but can relate to what the link provided says about them. The pipes coming off the back of the indirect are always very warm/hot. Could this make a big difference?
Though I'm not sure of its relevance, my house has a recirculation loop for the hot water going to the bathrooms on the far side of the house. It's hooked up to the recirculation o/p connection on the back of the indirect.
My boiler is a Buderus G115WS/3 set up for 85,000 BTU output
My indirect is a Buderus ST-150 with a 40 gallon capacity
One other thing I discovered that may account for the frequency in which the indirect calls for heat is its aquastat. It's a Honeywell L4006A that has a differential adjustment wheel set to "5". I don't really understand exactly how it works at this point, but the adjustment range is 5-30.
The other thing I wonder about is the advice to set the high temperature limit to 150. It seems to me that with average boiler water temperature of 140-150 it will take a long time to heat the water in the indirect to 130 degrees.
Perhaps one reason the frequency of demand from the indirect and the length of time it's now running is due to during the winter when the high limit was 185 the boiler simply heated the indirects water that much faster. Does this makes any sense?
Could it be that the combination of the 5 degree differential (being too little) in the indirect's aquastat, coupled with the current 150 degree boiler high temperature limit is my problem?
Thank you.
It's actually a PAIR of wires, probably one white and one red, going from the X1 and X2/ZR terminals of the 503 to the TT terminals on the 7224, correct?
There are no pumps connected to the 7224 then, correct? All are running of the 503?
I wonder if perhaps the installers did not install a 'heat trap' on the domestic piping coming out of the indirect?
Though I'm not sure of its relevance, my house has a recirculation loop for the hot water going to the bathrooms on the far side of the house. It's hooked up to the recirculation o/p connection on the back of the indirect.
My boiler is a Buderus G115WS/3 set up for 85,000 BTU output
My indirect is a Buderus ST-150 with a 40 gallon capacity
One other thing I discovered that may account for the frequency in which the indirect calls for heat is its aquastat. It's a Honeywell L4006A that has a differential adjustment wheel set to "5". I don't really understand exactly how it works at this point, but the adjustment range is 5-30.
The other thing I wonder about is the advice to set the high temperature limit to 150. It seems to me that with average boiler water temperature of 140-150 it will take a long time to heat the water in the indirect to 130 degrees.
Perhaps one reason the frequency of demand from the indirect and the length of time it's now running is due to during the winter when the high limit was 185 the boiler simply heated the indirects water that much faster. Does this makes any sense?
Could it be that the combination of the 5 degree differential (being too little) in the indirect's aquastat, coupled with the current 150 degree boiler high temperature limit is my problem?
Thank you.
#24
05-08-11, 05:05 PM
I would stay with the 180F high limit on the boiler, personally. You will have a faster recovery the higher the boiler temp is. The differential on the indirect determines when it makes a call for heat from the boiler. With your setting of 130, the indirect will make a call for heat when the temperature hits 125. The setting of 5 degrees is really close. I think I have mine set at 10. You can try 15 or more and see what the performance is like when you are taking a shower. That constant circulation pump is another factor that will make your tank reheat more frequently. Having a heat trap installed with that thing will have no effect in savings. Is the piping for your recirc loop insulated?
#25
05-08-11, 05:20 PM
Though I'm not sure of its relevance, my house has a recirculation loop for the hot water going to the bathrooms on the far side of the house. It's hooked up to the recirculation o/p connection on the back of the indirect.
Maybe you can put a timer on the recirc pump to only run it when you are home and likely to be using hot water?
The pipes coming off the back of the indirect are always very warm/hot. Could this make a big difference?
Honeywell L4006A that has a differential adjustment wheel set to "5".
The other thing I wonder about is the advice to set the high temperature limit to 150. It seems to me that with average boiler water temperature of 140-150 it will take a long time to heat the water in the indirect to 130 degrees.
I would recommend a mixing valve set to 120° be installed on the indirect, set the a'stat on the indirect to at least 130 (140 is better for Legionella elimination), and an appropriate diff setting... more than 5°, but not so much that the cut-in temp is below about 130 or so or your mixing valve won't function well. There is another upside to the mixing valve. It effectively 'increases' the size of your water tank since you will be using less of the water IN the tank. The 140 water coming out will be mixed with some cold on it's way to the tap.
Thermostatic Mixing Valves - The Dangers of Hot Water and Scalding - Learn About - Watts
Think about the timer on the recirc pump, and INSULATE the hot water pipes!
#26
05-08-11, 06:01 PM
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I'm going to come out of the shadow and state that the constant recirculation is 90% of the problem with another 5% being the narrow differential. Instant hot water is a blessing but the cost is often so high as to negate the effect. This is especially true when you have low-cost municipal water and a flat-rate sewerage charge.
The pipes on the entire domestic hot water system, supply and recirc, need to be heavily insulated AND the pump should be timer controlled or have both a timer and an aquastat to keep it from running constantly. The cheapo foam insulation tubes sold at the homecenter for insulating pipes is only slightly better than useless for this insulation but it IS better than nothing. Ideally you should have nothing less than a 2-inch wall rigid fiberglass insulation and don't forget the elbows and tees. Any piping that runs inside walls should really be insulated but rarely is.
The pipes on the entire domestic hot water system, supply and recirc, need to be heavily insulated AND the pump should be timer controlled or have both a timer and an aquastat to keep it from running constantly. The cheapo foam insulation tubes sold at the homecenter for insulating pipes is only slightly better than useless for this insulation but it IS better than nothing. Ideally you should have nothing less than a 2-inch wall rigid fiberglass insulation and don't forget the elbows and tees. Any piping that runs inside walls should really be insulated but rarely is.
#27
05-08-11, 06:07 PM
With your help, it sounds like I might be making some progress with my problem.
I should have previously mentioned that my "recirculation loop" does not have a pump. It was in place with the Bock oil fired stand alone hot water heater so the people who installed my new Buderus equipment connected it to the recirculation return port on the indirect in order to duplicate the way it was originally piped. While the hot water in the bathrooms at the other end of the house isn't instant, warm water starts flowing within 10-15 seconds first thing in the morning. I figured that was good enough, and matched the previous performance with the Bock, so I decided not to install a pump.
None of my domestic hot water pipes flowing from the indirect are currently insulated so I need to do that as soon as I can.
I'll also look into installing a mixing valve as suggested.
One important question I have, because this equipment and set up is new to me, involves how often should the indirect call for a warm up when there is no hot water usage such as at night or during the day when no one is taking a shower, or running the washing machine or dishwasher? When its just sitting idle. Is it once every two hours or once every 8 hours? All I know is that my old Bock did not run very much and heated water quick and I had trouble giving it up for the indirect.
Also, once the settings on the aquastats are at the proper points, on average, approximately how long should it take the boiler to bring the indirect up to it's temperature set point? Assuming the high temperature limit for the boiler is 20 degrees above the indirect's setting? I realize there are a number of variables, but I'm asking because I don't know if it should take 15 minutes or 30 minutes.
Thank you for helping me sort this out...it has certainly been educational.
I should have previously mentioned that my "recirculation loop" does not have a pump. It was in place with the Bock oil fired stand alone hot water heater so the people who installed my new Buderus equipment connected it to the recirculation return port on the indirect in order to duplicate the way it was originally piped. While the hot water in the bathrooms at the other end of the house isn't instant, warm water starts flowing within 10-15 seconds first thing in the morning. I figured that was good enough, and matched the previous performance with the Bock, so I decided not to install a pump.
None of my domestic hot water pipes flowing from the indirect are currently insulated so I need to do that as soon as I can.
I'll also look into installing a mixing valve as suggested.
One important question I have, because this equipment and set up is new to me, involves how often should the indirect call for a warm up when there is no hot water usage such as at night or during the day when no one is taking a shower, or running the washing machine or dishwasher? When its just sitting idle. Is it once every two hours or once every 8 hours? All I know is that my old Bock did not run very much and heated water quick and I had trouble giving it up for the indirect.
Also, once the settings on the aquastats are at the proper points, on average, approximately how long should it take the boiler to bring the indirect up to it's temperature set point? Assuming the high temperature limit for the boiler is 20 degrees above the indirect's setting? I realize there are a number of variables, but I'm asking because I don't know if it should take 15 minutes or 30 minutes.
Thank you for helping me sort this out...it has certainly been educational.
#28
05-08-11, 06:25 PM
Super Moderator
It's hooked up to the recirculation o/p connection on the back of the indirect.
so the people who installed my new Buderus equipment connected it to the recirculation return port on the indirect
I may be wrong but something dont jive. The boiler in and out in the back? Along with cold domestic back bottom? . Hot domentic out the top?
Just wondering if you guys caught this.
Mike NJ
#29
05-08-11, 06:48 PM
The recirculation loop you have is sucking heat out of your indirect constantly. It's probably all ghost flow through that loop. So it's hard to say how often your indirect needs to be reheated during the day.
My boiler is 105,000 BTU with a 30 gallon indirect. It probably takes about 15 minutes to heat the tank up from 100% cold. It takes about 2 burn cycles of the boiler to heat it up after a shower has stopped. Because your boiler is smaller than mine, it would take a bit longer to reheat.
My boiler is 105,000 BTU with a 30 gallon indirect. It probably takes about 15 minutes to heat the tank up from 100% cold. It takes about 2 burn cycles of the boiler to heat it up after a shower has stopped. Because your boiler is smaller than mine, it would take a bit longer to reheat.
#30
05-08-11, 06:48 PM
lawrosa asked-
regarding the recirculation o/p connection on the back of the indirect.
Is there a stand alone port?
regarding the recirculation o/p connection on the back of the indirect.
Is there a stand alone port?
Yes, there's a separate port that Buderus calls "P&T/Recirculation Return"
#31
05-08-11, 06:55 PM
Super Moderator
Sorry I was looking at the sst.
This is what you have?
http://www.buderus.us/files/20100503...Manual0906.pdf
Mike NJ
This is what you have?
http://www.buderus.us/files/20100503...Manual0906.pdf
Mike NJ
#32
05-08-11, 06:57 PM
Yes, there's a dedicated port for the 'recirc return' on the tank, near the top, on the back, just below the hot outlet. All the ports are on the back.
http://www.buderus.us/files/20100503...Manual0906.pdf
I don't know why this manual doesn't have the 120 listed, but it's the same configuration.
Targa, did they leave you the manual? You know they recommend cleaning it out every two years, and checking the anode every year?
http://www.buderus.us/files/20100503...Manual0906.pdf
I don't know why this manual doesn't have the 120 listed, but it's the same configuration.
Targa, did they leave you the manual? You know they recommend cleaning it out every two years, and checking the anode every year?
#33
05-08-11, 11:40 PM
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If you didn't have the recirculation system and didn't use any hot water the indirect tank should hold temperature for at least a full day and possibly for several days. Try closing the valve on the recirculation piping returning to the heater for a few days and see what happens.
I don't know if you will be able to continue to use the "gravity" recirculation if you add the tempering valve. If not, then a small bronze or stainless steel pump will be necessary and then you can properly control the pump with a combination of timer and aquastat.
Definitely insulate all the accessible piping.
I don't know if you will be able to continue to use the "gravity" recirculation if you add the tempering valve. If not, then a small bronze or stainless steel pump will be necessary and then you can properly control the pump with a combination of timer and aquastat.
Definitely insulate all the accessible piping.
#34
05-09-11, 05:09 AM
Try closing the valve on the recirculation piping returning to the heater for a few days and see what happens
Definitely insulate all the accessible piping
Targa, did they leave you the manual?
My plan is to try a number of adjustments including changing the "temperature differential" setting on the indirect as well as the high temperature limit on the boiler to see what combination works the best.
I hope that ultimately the new indirect works as well as the old Bock stand alone did with no increase in fuel usage. At this point, I doubt I'm saving any fuel.
As I make changes and updates as have been recommended and discussed, I'll report back my experience and findings.
Thanks everyone for helping me with your expertise.
#35
05-09-11, 08:24 AM
Originally Posted by Furd
I'm going to come out of the shadow and state that the constant recirculation is 90% of the problem with another 5% being the narrow differential.
As for the high limit, I would just leave it at 180 degrees. Your boiler is small enough that the indirect should put a decent load on it and keep it from bumping the high limit.
#36
05-09-11, 09:06 AM
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I am with the others my boiler will cycle 1 time after a shower or 2 to heat to 130 and after showers in the morning with no or little HW use it may or may not turn on in the middle of the night before the next mornings showers.
#37
05-09-11, 12:20 PM
NJ Trooper,
Toward the beginning of this thread you said-
So I'm wondering whether there is a formula that I can use and plug into the appropriate variables to calculate how much it currently costs me each day (or each time the indirect calls for heat) to heat my hot water.
If you can answer this question for me without going through much work, I'd sure like to know my current cost as depressing as it may be.
Thank you
Toward the beginning of this thread you said-
By running it lower you may notice that after heavy periods of HW use the tank won't recover as quickly. Two long steamy showers in a row might have the second person screaming when the cold water starts hitting them... so, you may have to adjust your habits a bit, but maybe not... I guess a trade-off in fuel savings might be worth it, but I'm not sure it will save a heckuva lot. After all is said, BTUs are still BTUs. It will take a certain amount of BTUs to heat the water up (1 BTU per pound of water per degree) so let's say you use 20 gallons of hot, that's 167 pounds of water (8.34 lb per gallon). Let's say the incoming water is 65°. You are heating to 125°... so, 60 X 167 = 10K BTU. Whether you transfer that 10K BTU from 150 or 180 water, won't make a difference in the amount of BTUs, you still are doing the transfer. At 180 it will just happen FASTER because of the driving force... you still need to burn the same amount of fuel to heat the water.
If you can answer this question for me without going through much work, I'd sure like to know my current cost as depressing as it may be.
Thank you
#38
05-09-11, 03:41 PM
It's really not as easy as it might seem... too many variables!
One thing I have (and some others do also) is a clock or an elapsed time meter on the oil burner. The clock or meter is wired in to run only when the oil valve is open. Once it's hooked up, it's just a matter of multiplying the GPH rating on your oil nozzle to the elapsed time on the clock to determine the oil usage.
What burner and primary control are on your system?
One thing I have (and some others do also) is a clock or an elapsed time meter on the oil burner. The clock or meter is wired in to run only when the oil valve is open. Once it's hooked up, it's just a matter of multiplying the GPH rating on your oil nozzle to the elapsed time on the clock to determine the oil usage.
What burner and primary control are on your system?
#39
05-09-11, 04:42 PM
What burner and primary control are on your system?
The two primary concerns I have right now are:
1. Reducing the frequency of burner cycles to heat the indirect
2. Reducing the elapsed burner run time to satisfy the indirect when its aquastat calls for heat.
Based on input from you and others over the last two days I've increased the burner high temp limit from 150 to 170. And also increased the temperature differential on the indirect aquastat from 5 degrees to 15 and it has already made a very noticeable difference.
With no other changes yet, run frequency has gone from every 45 minutes to 2.5-3.0 hours. Plus, based on being near the burner when the indirect called for heat, actual cycle time is about 16-17 minutes with only 9 minutes of it burner run time.
So I think I'm heading in the right direction. Hopefully, once I insulate the hot water pipes, sort out the recirculation loop and the other suggestions I can get the efficiency of this indirect to where I'm comfortable with it. At this point, there is no question my old stand alone Bock was much more efficient.
Thanks again
