Micro heaters cut 87% off my electric heat bill • Hacker News Board

Re: Micro heaters cut 87% off my electric heat bill

#231

Post by Rapzid » Thu, Jul 31, 2014, 12:27 PM UTC

roel_v wrote: post #115

dredmorbius wrote: post #67

OK, Paul Wheaton simply doesn't know what he's talking about: "I think that this does produce some savings, but not as much as you might think. If you set your thermostat to a constant 70, the heater works a little at a time throughout the day. If you drop it to 50 at night or in the middle of the day, the heater stops working, but then when the time comes to warm the house again, the heater has to work at full power…

Sure, if you have shitty insulation. The proper strategy is to have good insulation, and then to have the heat on constantly using a CV system at low temperatures, because heating constantly with water of 30 degrees (C, that is) is much more energy efficient than heating in peaks with much warmer water (60, 70, 90 even 20 years ago). So yes, in houses with crap insulation warming constantly is less efficient. However…

Yeah, you'd probably need to spend over 1 million on a home here to get one with good insulation(if). Housing costs/quality is my biggest complaint for NZ.

Re: Micro heaters cut 87% off my electric heat bill

#232

Post by dirkf » Thu, Jul 31, 2014, 12:36 PM UTC

dredmorbius wrote: post #219

dirkf wrote: post #197

Earlier quoted context omitted.

I'm currently living in a passive house (in Belgium, Europe). We've only moved in two months ago so we haven't experienced a winter yet but even in the current summer climate it has already been an order of magnitude more comfortable than any of the other places I've lived in. When the temperature hit 30 degrees Celsius for a couple of days last week the house was at a comfortable 23 degrees. Everywhere. Key design p…

Chlupp's design borrows very, very heavily on passive house concepts. And he uses massive amounts of insulation. He creates a large (big enough to walk in) wall cavity, and fills that with blown cellulose. I think it's on the order of twenty tons of cellulose. Not only does it insulate, but it forms a thermal mass. Similarly for his foundation: a large sand base as I recall, then a slab, which create yet more thermal…

In our case it's something like five tons of cellulose. It's supposedly a good buffer against summer heat getting into the house but it doesn't really store heat to release it slowly when the temperature goes down again. I can imagine it works well high up north but here I think it would make it more difficult to control the temperature. It's one of the reasons why we have chosen a wood-based construction using I-joints. We do have a concrete foundation slab, screed everywhere and ceramic tiles on the ground floor.

The big stratified water tank is a well known concept but you need to have room for such a big tank. Here in Belgium space is at a premium so houses tend to be on the small side. Solar thermal panels are often connected to a tank of 500 litres or less, simply because of space constraints...

There are several possible construction models; it's a matter of selecting one that fits your local climate and your habits. Not everybody likes a stove for example.

The last couple of years we've seen a shift happening from applying the passive house concepts on new houses (pretty much a solved problem) to renovating existing ones. Here in Belgium there's a massive amount of old houses constructed before the seventies/eighties which is when they finally started putting in insulation. Now that all new houses are energy efficient it's time to tackle the massive waste in those old houses. Most people buy such an old house and start renovating so there's a lot to be gained.

Re: Micro heaters cut 87% off my electric heat bill

#233

Post by jccalhoun » Thu, Jul 31, 2014, 12:49 PM UTC

byuu wrote: post #111

dredmorbius wrote: post #67

OK, Paul Wheaton simply doesn't know what he's talking about: "I think that this does produce some savings, but not as much as you might think. If you set your thermostat to a constant 70, the heater works a little at a time throughout the day. If you drop it to 50 at night or in the middle of the day, the heater stops working, but then when the time comes to warm the house again, the heater has to work at full power…

His article on CFLs ( http://www.richsoil.com/CFL-fluorescent-light-bulbs.jsp ) is very cringe-worthy as well. As part of his argument, he references a report he heard of claiming that kids gained 20 IQ points by switching back to incandescent bulbs. Seriously.

as soon as i read "greenwashing" I knew we were getting into dumb territory...

Re: Micro heaters cut 87% off my electric heat bill

#234

Post by raverbashing » Thu, Jul 31, 2014, 12:56 PM UTC

jay-saint wrote: post #223

jwmerrill wrote: post #114

Earlier quoted context omitted.

Your theoretical analysis misses an important physical fact: houses are able to exchange air with the outside world, not just heat. As you heat a normal room, it will expel air in order to maintain constant pressure, and similarly, as you allow a room to cool, outside air will enter again to keep the pressure constant. There was an article about this in the American Journal of Physics [1, 2] a couple years back, and…

I have been told by multiple HVAC professionals recently that one should keep their fan on their system always running. They have in fact adopted this practice at our offices and it greatly help with keeping temperatures in consistent from room to room. The arguments they provided for this were: [1] Constant air flow creates more consistent temperatures (less highs and lows from interior to exterior or floor to floor…

About 3, the idea is right, but they're probably overstating the difference between starting power and running power.

Starting a motor is not something you do lightly for bigger motors (but big like a subway or a car) but I doubt they're that heavy for it to be a big concern.

My bet is that it'll spend the starting power in around 5s of running, tops.

Re: Micro heaters cut 87% off my electric heat bill

#235

Post by japhyr » Thu, Jul 31, 2014, 1:11 PM UTC

micro_cam wrote: post #142

japhyr wrote: post #95

Earlier quoted context omitted.

I live in southeast Alaska, where heating issues can make or break your ability to pay rent or afford a mortgage. Most homes are heated using fuel oil. We moved into an awesome old house last summer, and we were worried about heating costs. The landlord had a heat pump installed last fall. I'm sure we would have had some $300-$500 heating bills (per month) last winter if we were using oil, but the heat pump never cos…

Ground Loop or air to air heatpump? What brand and model? (I ask because we just bought a house in montana and are thinking about a heatpump before winter...we have propane radiant heat now. We'd want one that would work with cold temps though it rarely gets bellow -10 F here.)

The model number is ASU15RLS2.

Re: Micro heaters cut 87% off my electric heat bill

#236

Post by Shivetya » Thu, Jul 31, 2014, 1:19 PM UTC

yxhuvud wrote: post #221

Good grief. If you live in a country that gets cold, learn to insulate your houses better. Seriously, it is that simple. /lives in a country where triple windows are standard for all new buildings intended for people.

I live in a larger house, being single any house is overkill but I went a bit beyond because of pricing and location. As such I have three bedrooms and two baths where the vents are kept closed. This does mean they seal completely so in winter the rooms can hit the 50s (F) on a below freezing week.

You don't need to live in a cold climate to want good insulation, it can save a bundle in hot climates too if your a fan of extreme AC; think 72F that some I know live by. I do the ceiling fan method, 78F and a nice big ceiling fan in every room.

Re: Micro heaters cut 87% off my electric heat bill

#237

Post by dredmorbius » Thu, Jul 31, 2014, 1:21 PM UTC

jay-saint wrote: post #223

jwmerrill wrote: post #114

Earlier quoted context omitted.

Your theoretical analysis misses an important physical fact: houses are able to exchange air with the outside world, not just heat. As you heat a normal room, it will expel air in order to maintain constant pressure, and similarly, as you allow a room to cool, outside air will enter again to keep the pressure constant. There was an article about this in the American Journal of Physics [1, 2] a couple years back, and…

I have been told by multiple HVAC professionals recently that one should keep their fan on their system always running. They have in fact adopted this practice at our offices and it greatly help with keeping temperatures in consistent from room to room. The arguments they provided for this were: [1] Constant air flow creates more consistent temperatures (less highs and lows from interior to exterior or floor to floor…

For offices, it's likely more a matter of keeping pockets of hot/cold air (or other quality issues not related to temperature) from forming. Even just with lighting and office equipment, there's a fairly considerable energy flux into many office spaces, and without mixing you'll tend to get uncomfortable pockets forming.

Your #3 point strikes be as fairly valid: large electric motors do impose a very high load, and the current draw could be harmful to the motor (and switching / control circuits), while the imposed load might also be hard on other equipment. I doubt the energy usage argument (for cycling the motors off) really carries much weight, and it should be possible to idle such systems at low power. For most commercial buildings, you've got systems for heating, chilling, and air handling which are pretty much all operating simultaneously: you have a need for hot and cold air in different places, there are mixers which will deliver what's needed where it's needed (at least in theory), and the fans blow all the time.

Though I've only a pretty glancing familiarity with HVAC in general, not particularly my area of expertise.

Re: Micro heaters cut 87% off my electric heat bill

#238

Post by dredmorbius » Thu, Jul 31, 2014, 1:24 PM UTC

dirkf wrote: post #232

dredmorbius wrote: post #219

Earlier quoted context omitted.

Chlupp's design borrows very, very heavily on passive house concepts. And he uses massive amounts of insulation. He creates a large (big enough to walk in) wall cavity, and fills that with blown cellulose. I think it's on the order of twenty tons of cellulose. Not only does it insulate, but it forms a thermal mass. Similarly for his foundation: a large sand base as I recall, then a slab, which create yet more thermal…

In our case it's something like five tons of cellulose. It's supposedly a good buffer against summer heat getting into the house but it doesn't really store heat to release it slowly when the temperature goes down again. I can imagine it works well high up north but here I think it would make it more difficult to control the temperature. It's one of the reasons why we have chosen a wood-based construction using I-joi…

In Chlupp's case, he pretty much designs his structure around the tank, it's integrated to the building core.

An alternative he points to in Europe is a community / neighborhood storage, where a thermal storage tank serves a number of homes. Another option is seasonal thermal storage using ground-base storage, where you've got suitable geology (no moving water table to whisk your heat away helps a lot), used in at least one instance in Canada. Heat is pumped in during the summer and extracted in the winter, as part of a ground-loop heat pump.

Re: Micro heaters cut 87% off my electric heat bill

#239

Post by happyscrappy » Thu, Jul 31, 2014, 1:24 PM UTC

ams6110 wrote: post #85

dredmorbius wrote: post #67

OK, Paul Wheaton simply doesn't know what he's talking about: "I think that this does produce some savings, but not as much as you might think. If you set your thermostat to a constant 70, the heater works a little at a time throughout the day. If you drop it to 50 at night or in the middle of the day, the heater stops working, but then when the time comes to warm the house again, the heater has to work at full power…

I agree with all your theory. I thought the same thing. Then I went out and bought a programable thermostat, set it quite low overnight and during the day, and warmer from 5-8 AM and 5-8 PM. My heating bill was higher than just maintaining 68-70 all the time. And that's not even counting the $100 I spent on the thermostat (now on a shelf in the garage, I put the old manual one back in its place).

You are heating the walls and floors which take a long time to come up to temp. I liken it to the difference between keeping large truck at 65mph compared to getting it up to speed.

Re: Micro heaters cut 87% off my electric heat bill

#240

Post by pbhjpbhj » Thu, Jul 31, 2014, 1:30 PM UTC

mikeash wrote: post #158

ams6110 wrote: post #85

Earlier quoted context omitted.

I agree with all your theory. I thought the same thing. Then I went out and bought a programable thermostat, set it quite low overnight and during the day, and warmer from 5-8 AM and 5-8 PM. My heating bill was higher than just maintaining 68-70 all the time. And that's not even counting the $100 I spent on the thermostat (now on a shelf in the garage, I put the old manual one back in its place).

Either the laws of physics are different than well established theory says they are... or your thermostat didn't do a very good job. I vote for the second one.

Putting in heat over a short time, to recover from low temperatures, is different to putting in heat over an extended period. If your heater has very low efficiency at high heat output then it seems highly possible that extended low output could be better. It's a financial efficiency we're talking about primarily when people are looking to more efficiently heat their house.

If you're heating with electric for example you can sometimes buy electricity far cheaper at night (demand is low and traditional production can be easily spun-down). Thus buying electricity all night and keeping the house warm, whilst using more electricity, could be cheaper than paying for peak rate electric.

Physics alone could explain it in very rare circumstances - board construction that expands in warm air closing gaps, cool air opens gaps and causes more cooling. Heat exchange rate from in- to outside is then possibly greater at lower temperatures. Houses aren't simple to model.