Central Heating Efficientcy Plumbing Question

is this the latest trend in outsourcing? get some sucker to do the design work??

You can buy a calculator and a pencil at the local stationary store the rest is just math

a) Hire a mechanical engineer

b) pay him or her for the answer you require

There is not a simple answer. The type of boiler being used is the biggest source of heat loss (out the flue). If you have a condensing boiler, running at 100 degrees vs 200 degrees could give you about a 15% improvement in boiler efficiency. If you don't have a condensing boiler, you will have to maintain your boiler at a minimum 140 to 160 degrees to keep out of the condensing range. Operating at say 150 degrees vs 200 degrees might give you a 2% to 3% improvement in efficiency. The 150 degree water would be blended with return to maintain 100 degrees in the heating loop.

At 200 degrees the amount of heat loss in the distribution system could be greater than the amount of heat the house needs at 50 degrees ambient and windows would have to be cracked open to maintain comfort. However if the pipe is well insulated, maybe not. Some heat will be lost in the distribution system. If the pipe chases can vent to the attic or if the pipe runs are in spaces that would otherwise be kept cool (crawl space i.e.) then some of the heat loss through the insulation would be wasted.

Running the water temperature lower will require greater flow as the delta T between supply and return will probably be much less. Consequently the central pump will have to be bigger and the bigger pump will use more energy in the course of the year. It will also require bigger radiators (or fin-tube).

Downsizing the piping by your example, 75%, will increase the pumping head required. You will need a bigger pump. For the same flow, reducing the pipe cross-sectional area by 4 will increase required pumping power by 16. Heat loss through the piping might be slightly less for smaller diameter pipe, but not by much.

I recall in the three day working week in UK period that Ed Heath suggested turning central heating down in industrial sites by 2 deg F from the national standard of 67F to 65F - such was the knock on effect that 2,000 tanker drivers were put out of work. (UK side - that is)

Seems to me that in these days when CE's are important that if there was a method of having a central heating system follow a straight line that would ensure maximum efficiency in relation to ambient temperature and the heat of the hot water for either central heating and or ablusions etc adjusted automatically to mix efficiently with ambient cold water to make it comfortable to use - such CE savings may have real impact and be releated to a real first world contribution

I dont know where to start but my guess is a couple of sensors - n'est pas

Hi Howe

Thanks for your studied reply

If there was just one easy-to-do thing you could recommend to tweek up efficeincy on all domestic central heating systems - what does your instinct tell you it would be? Its got to be practical for all to do and mustn't cost much - with quick payback - maybe its too general a question - however it is based on my observation with regards to turning down the industrial environmental heating thermostats by 2 deg resulted in 2000 tanker drivers being made redundant - (1960's)

Best wishes

Ben

Lowering the thermostat is the easiest way to achieve savings. I like it cool in the house in winter. My sinuses seem to do a lot better. It also gives me a reason to wear those hand knit Irish sweaters the wife likes to buy.

Condensing furnaces offer about a 20% reduction in energy costs vs a conventional new furnace. Compared to an old worn out furnace, they might cut energy usage in half. Expect to have a more troublesome furnace than an equivalent conventional furnace.

If memory serves correct, I think Honeywell did construct 2 identical houses side by side in the same Minneapolis Minnesota suburb in the 1970s, to experiment with system differences, heating efficiencies, etc. I think there was some DOE funding involved. See if they still have records on this experiment.

I recall in the three day working week in UK period that Ed Heath suggested turning central heating down in industrial sites by 2 deg F from the national standard of 67F to 65F - such was the knock on effect that 2,000 tanker drivers were put out of work. (UK side - that is)

Seems to me that in these days when CE's are important that if there was a method of having a central heating system follow a straight line that would ensure maximum efficiency in relation to ambient temperature and the heat of the hot water for either central heating and or ablusions etc adjusted automatically to mix efficiently with ambient cold water to make it comfortable to use - such CE savings may have real impact and be releated to a real first world contribution

I dont know where to start but my guess is a couple of sensors - n'est pas