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This is winter-design temps & wind chills in the upper Midwest- check Btuh usage

This is winter-design temps & wind chills in the upper Midwest- check Btuh usage

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  #1  
Old 01-05-15, 08:03 AM
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This is winter-design temps & wind chills in the upper Midwest- check Btuh usage

This is winter-design temps & wind chills in the upper Midwest with which to check the heating Btuh performance of your Oil or Gas furnace.

With a notebook; list the temp & wind velocity; list Burner-Run-Time; then list time of next Burner start; divide the Total-Cycle-Time (TCT) into the burner run-time, X's the listed burner OUTPUT listed on furnace tag.

Then do a heat-loss heat-gain calc & see how the results of each compare. Burner runs 15-mins it's 60-mins to next start-time; 15-BRT / 60-TCT is .25% * OUTPUT of furnace is 57,000-Btuh = 14,250-Btu/hr. Burner Runs 30-mins TCT to next start 60-mins; .50% * 57000 is 28,500-Btuh.

Do the same during hottest summer weather with around 15-mph winds... This will help to correctly size your next A/C or heating system replacement; also illustrate where you can reduce energy usage..
 
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Old 01-05-15, 02:42 PM
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This is pretty cool, thanks. How could it be applied to a heat pump? I am specially interested in the heat-loss calculations. No that I am back stateside and can witness things daily, I suspect my heat pump cycles too much and want to see if it is because the house is losing energy too quickly or the unit is oversized. With 50*F OD, the Delta T register/return is about 25* (no electric heat on). It was running about 10 minutes on, then 10 -12 minutes off. Stat set at 67*
 
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Old 01-05-15, 06:33 PM
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You could use a Temp-SWING type RM-TH with an adjustable on-off temp-differential.

I take it the thermostat is not located where supply air heat would affect it too much. Could cold air be getting to the back of the thermostat?
 
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Old 01-06-15, 09:35 AM
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There is a register about 6 - 7 feet from the t-stat, which is on an inside wall (so I do not think it is getting cold air) just above the return. I have tested the t-stat against air temp right around it and it is reading good.

Our house is two story ,about a 1000 ft/sq on each floor. The bottom floor has ten-foot ceilings and 305 ft/sq of windows and French glass doors, open floor plan, 8 registers. R-19 in the walls, foam under the first floor over a somewhat sealed garage (garage doors are not insulated) that keeps about 50* during winter, foam under the roof, 6-year old house, 2-ton Trane for each floor.

There is good insulation between floors. We keep the upstairs a little cooler and at times I think this may contribute to the problem. But I am also trying to see if the unit is oversized or I have heat loos problems.

We have a basic Trane t-stat with no swing adjustment. Recommendations on a t-stat?

Regards
 
  #5  
Old 01-11-15, 07:53 PM
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This only applies if the existing equipment is working correctly and outputting what is should.

--------------
swing is obsolete as far as I know - the better t-stats are algorithm based and you adjust cycles per hour, not swing.
 
  #6  
Old 01-12-15, 05:17 AM
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I really like the swing thermostats; would rather have them than the cycles per hour type.

The cycles-per-hour (cph) are okay too; you need to be able to adjust the temp on/off differential.

The Swing-types are available & gaining popularity, as I know.
I like them...do a search for them. I would never want a TH that had a half or one degrees on/off differential.

You can check airflow CFM then check temp-rise over return air temps to finally get Btuh output. Newer furnaces should be close to their rated output; techs can check output for you...
 
  #7  
Old 01-12-15, 03:10 PM
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I am pretty happy with the heat pump as it is producing about 25* delta between return (and coil intake, easy to drop a thermometer through the filter hatch and it was actually only 1* different than at the return grill) and register (did not want to take apart the AH to put a thermometer on the output side of the coil, so I used the register).

I just want less cycling and rather to do it through swing than cycle restriction.
 
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Old 01-20-15, 03:08 PM
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Adjusting the cycles per hour setting directly affects swing - try it before replacing the t-stat. The swing isn't fixed on more advanced stats (it varies based on load, cph setting, length of previous cycles, etc) nor should it be.
 
  #9  
Old 02-04-15, 01:23 PM
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Here in SW WI tonight -8F below zero; wind-chill to be -15 to -20F below zero

Here in SW WI low tonight -8F below zero; wind-chill tonight Wed. 02/04/15 to be -15 to -20F below zero.

Not nearly the coldest but worth checking Btuh to hold TH setpoint; but close to the winter design in a lot of climate areas.

Would be a decent time to check some burner runtimes & cycle times start-times.

Write down burner start-time to off time; then write down next start-time; divide burner runtime by total from first start-time to next start-time; times * furnace OUTPUT Btuh listed on furnace Tag.

Not on tag; INPUT *X's furnace Efficiency Rating for OUTPUT.
 
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