How Are Your Temps?

Ron Gillen

Mike, am I missing something? Meter clocking formula is capacity of test dial in cubic feet times 3600, divided by number of seconds for one revolution, times calorific value of the gas (Natural-1000 btu's/cubic foot. I get 2x3600/95 sec.x 1000= 75789 btu/h, no?

Mike T., Swampeast MO

4:30 p.m.

18°F out (24° hi, 17° lo, 10-15 mph N wind & gusty)

65°F in

Flue: 91.7°F

Supply: 93.7°F

Return: 82.4°F

Reported Boiler Temp (Vitodens 200 6-24): 103°F

Clocked gas input (measured 3x in 30 min; less than 5 second variance of 2-foot dial): 31,000 btu/hr

Manual J Loss @ 18°F: 84,000 btu/hr

Original gravity system with standing iron radiator and TRVs. Directly driven by boiler--single circulator for entire system.

Home: 1903. Reasonably insulated. 3,500 sq.ft. on 2 full floors plus basement/attic.

Wayco Wayne_2

Sounds nice

You are doing your part for conserving our nat gas resources. Everyone should have such a system. I personally am conserving by using a high eff. heat pump split system, with a hot water coil reheat driven by a Taco variable speed circ dialed in to keep the supply duct temps at 120 degrees. (For the parts of the house that don't have radiant floor yet.) The hot water comes from a Munchkin set at 135 wt 20 degree differential. My energy bills are very nice. WW

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jp_2

sounds off

less than 9 btu's/sqft sounds a little low for an old house/old windows?

with your 5 second error, whats the high and low readings?

I'm convinced now manual calcs are based on nighttime readings, no solar gains, cloudy days will introduce solar gain.

Mike T., Swampeast MO

Near the end of a sunny day with temp falling (16F by 5:00 p.m.) and expected to be below design (8F) tomorrow morning. I agree that the sun has a lot to do with it... South-side outside air temp maxed at about 40F.

Yes, LOTS of original, old windows and a wicked North exposure. 3 minutes 55 seconds, 3 minutes 52 seconds, 3 minutes 50 seconds for 2-foot dial. (pilot for water heater running and temp falling during 30 minutes or so for three clockings)

3 minutes 40 seconds at 5:00 p.m. @ 16F

Will clock later this evening. Doubt input will be above 45 mbh.

Mike T., Swampeast MO

7:30 PM

13.5°F out, 64.9° in.

Thrice clocked, 3 min; 3 min 5 sec; 3 min 5 sec

Input: 39 mbh

Flue: 93.3°F

Supply: 96.0°F --- Return: 82.4°F

Manual J loss: 78 mbh

Mike T., Swampeast MO

10:00 pm

11°F out; 64° in.

input: 39 mbh

94.1° flue; 96.8° supply; 83.3° return.

Reported boiler temp: 106°F

jp_2

why is?

1st DT at 47F, and 84mbh

2nd DT at 51.5F and 78mbh

your delta T increases and your heatload decreases????

JohnG_3

What is Clocked Gas Input?

I'm not sure what you mean by "clocked gas input." Are you reading your gas meter or measuring the gas input to your boiler some other way? I read my gas meter every day. This is fine but it includes baselines usage of domestic hot water and clothes drying, which I estimate at 100,000 btu/day.

I have steam heating for a 1650 square foot colonial built in 1929 in the Boston suburbs. Gas consumption for heating is about 8 btu per square foot per degree day. This is down from over 12 btu/sf/dd prior to blowing cellulose and replacing windows.

Mike T., Swampeast MO

Sorry about that. I forgot to adjust away from the standard 70F room air temp in the first Manual-J estimate.

Mike T., Swampeast MO

Am using one rotation of the "two cubic foot dial" to measure gas input. Only other thing consuming gas is the pilot light of a stand-alone water heater.