Boiler Indoor design temp setting

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Old 01-10-14, 03:05 AM
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Boiler Indoor design temp setting

Hi everybody , It has been awhile since I posted on the forum.

Last week when it was really cold the heat system did not have any problems keeping all the zones warm. Last Thursday we noticed that 2 bay windows in the living room were leaky, so we sealed them using plastic. After sealing the windows the heat system was not keeping the living room zone warm. The circulator was on and the water in pipe was warm. I've been using a tekmar 260 for few years and did not have any problems. The setting were:

No indoor sensor
Room occ 70
Room unocc 64
Outdoor dsgn 4
Terminal unit 4
Boil indr 70
Boil dsgn 170
Boil max 180
Boil min 110
Fire delay 10 sec
Boil diff 25

I changed the the Outdoor dsgn to 0 and let the system run for a day, did not make a difference. This was driving me nuts, I did not have any problems before. I woke up yesterday morning thinking the only thing that changed in the zone was sealing the windows, which did not make sense to me, sealing the windows should help keep the heat in. So I changed the Boil indr to 60. The first thing I noticed is that the target temp went up by about 15 degrees, and the system now is keeping the zone warm. I thought I understood how the tekmar worked but this situation confused me. How does the Boil indr setting effect the demand?
 
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Old 01-10-14, 06:32 AM
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The boiler indoor setting determines where the target temperature is set based on the outdoor temperature , as does room occ. and terminal unit . If you had the indoor sensor it would select the heating curve that would give the lowest target temperature to keep you comfortable and thus the lowest fuel bill.Remember for every 3 degrees F the system water temperature is lowered there is a 1% fuel savings .
 
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Old 01-10-14, 09:19 AM
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So with the indoor sensor not connected then that setting should have no effect on operation of the control? Is that what you are saying?
 

Last edited by NJT; 01-10-14 at 10:06 AM.
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Old 01-10-14, 09:34 AM
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According to Tekmar "The BOIL INDR is the room temperature used in the original heat loss calculations for the building. This setting establishes the beginning of the Characterized Heating Curve for the boiler zones."

I did not know that it will change the slope of the curve. When I changed the setting to 60 I noticed that the target temp went up by 12-15 degrees.

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I tried an indoor sensor before, I did not get good results. The heat system is split into 6 zones and the boiler is over sized. The first challenge was to find a spot to install the sensor that will measure the average temp in the house. We ended up with cold spots in the wrong places.
The second challenge was preventing the boiler from short cycling, the controller assumes that the boiler is properly sized. Auto diff was causing the boiler to short cycle. I had to set the differential to 25 to minimize the short cycling.
 
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Old 01-10-14, 09:37 AM
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It is good to hear from you Trooper, it's been a while. This is what is confusing me. What is the boiler indoor setting doing?
 
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Old 01-10-14, 10:26 AM
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Good to see you too!

I think I misunderstood what 'saves' was trying to explain...

Boiler Indoor should be the same temp that is used for indoor temp when doing the heat loss estimate and is typically 70F.

Looking at the 'CHC' chart you posted, you see that the origin of the curve is at the intersection of the Boil Indr and the ROOM OCC setting, so changing that to 60 I would think that the target temperature would have DECREASED because you have changed the slope of the curve with the origin lower.
 
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Old 01-12-14, 01:47 PM
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esalman
Boiler Indoor design temp setting
No indoor sensor
Room occ 70 ( The day time target Temperature - User setting )
Room unocc 64 ( The night time target Temperature - User setting )
Outdoor dsgn 4 (Reset slope)
Terminal unit 4
Boil indr 70 (Reset slope)
Boil dsgn 170 (Reset slope)
Boil max 180 (Target limit)
Boil min 110 (Target limit)
Fire delay 10 sec
Boil diff 25


(Boil Design - Boil indoor)/(Boil indoor - Outdoor Design) = slope of the reset curve

ex1) (170-70)/(70-4)=(100/75) = 1.33
ex2) (180-70)/((70-(-40)) = (110/110) = 1.0

Each time you change the heat loss of the building you change the slope of the reset curve.
See Fig 6 Page 2 Tekmar Essay E002 http://tekmarcontrols.com/images/_li...e/e0002_06.pdf

Note: Room occ/unocc uses the indoor sensor when connected.
 
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Old 01-12-14, 05:16 PM
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Thank you for all the responses, trying something new.

Installed indoor sensor, different location from last year's experiment
Installed a timer to prevent DHW calls while we are sleeping (using cheap stat)
Room occ 70
Room unocc 70 (I'm not setting the temperature back)
Outdoor dsgn 0
Terminal unit 4
Boil indr 70
Boil dsgn 170
Boil max 180
Boil min 110
Fire delay 10 sec (basically all criculators running, to help reduce short cycling)
Boil diff Auto




Read more: http://www.doityourself.com/forum/ne...#ixzz2qEj3qyv2
 
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