Return of the low-power server: a 10W, 6.5 terabyte, commodity x86 Linux box

5 years ago, I wrote about the build of the server hosting, which ran using only 18W of power.  After 5 years, it was time for an upgrade, and I’m pleased to say that I put together a much more capable system which now runs at only 10W!  This system handles external email and webserving, as well as handling media serving, energy datalogging, and backup storage for household purposes.  It’s the server which dished up this blog for you today. wattage, as measured by a Kill-a-Watt meter [amzn]

Continue reading

How is the Taco SmartPlus recirc pump working in my house?

The Taco SmartPlus hot water recirculation pump is designed to push domestic hot water around a recirculation loop, so that hot water is at the taps when you want it, saving time as well as water down the drain while you wait.  It’s designed to learn your schedule, to avoid energy losses associated with pumps that run 24 hours a day, due to both the electrical energy used, and the lost heat in the loop when there is no hot water demand.

The SmartPlus pump is supposed to be “smart” in the sense that it uses a temperature sensor on the output of your water heater to learn when you use hot water, and adjust its run schedule accordingly.

So I had to find out, “is our smart pump learning?”  And so far, I have to say it’s not. (edit: I think power loss to the pump is the reason, read on) Continue reading

Could wifi thermostats coordinate zone firings?

nest_smallerAs we approach the end of the renovation project on our house, we now find ourselves with three heating zones, vs. the two we had before.  (The 3rd zone is kind of ridiculous; that’s a different story.)

Having 3 zones pretty well dashes my hopes of outfitting the house with Nest thermostats; yes, we could have the main zone on a Nest, and the others not, but that offends my sense of order.  And three thermostats for $750?  Sorry, no.

But this got me thinking.  Wouldn’t it be cool if thermostats on multiple zones could communicate in order to coordinate boiler/furnace firings, to reduce short-cycling and firing losses?  If the zones have a swing of, say, two degrees, one could opportunistically turn on even  if it’s within one degree of its setpoint if another zone is firing, thereby maximizing the current boiler firing cycle.

Or conversely, if one zone has low mass fin tube radiators, and another zone has high mass cast iron, perhaps it would make more sense to try to fire those zones separately, and coordinate that with thermostat communication as well.

I had thought about trying to flesh these ideas out into a patent, but realized I don’t have the money or the lawyers to do so.  There’s probably already a patent out there, anyway.  But if not, here’s prior art & public disclosure.  :)

Nest finally has developed an API, as the Radio Thermostat (RTCA) folks did long ago [pdf].  But I’m not sure those are flexible enough to do this kind of coordination very well; it’d work better if it were in the firmware, I think.

Hey Nest?  If you like this idea, and you implement it, feel free to send me a thermostat.  Or three.  :)

Getting into hot water, fast!

We’ve been doing a really big renovation on our house since around July; for an energy geek like me you’d think I’d be blogging madly, but quite frankly the project leaves me with little free time!

But here’s what I was looking at this week – how to get hot water to taps fast, without wasting water or energy.

We built another 12 feet off the back of the house, and as designed, most of the hot water outlets are in the back half of the house – kitchen sink on the very back wall, and all bathrooms clustered on the “old” back wall – now 2/3 of the way towards the back.  Unfortunately, the only feasible / cost effective location for the water heater is on the very front of the house – up to 40 feet away.   This wastes water, energy, and time, because 40 feet of three-quarter-inch pipe can hold a gallon (about 4 liters) of water, and running a gallon through a 2.0gpm faucet or shower takes 30 seconds.  When you’re done, a nice hot gallon of water sits there cooling off.  So depending on the time since the last draw, you’ve wasted up to a gallon of water, the energy used to heat it, and 30 seconds of your time when you bring hot water to the tap.  (With a low flow fixture, water & energy are the same, but it takes even more time for the hot water to arrive).

How to solve this?  Well, just go read presentations from Gary Klein, like this one.  Or hear what I did, which at least gets close to Gary’s goal of no more than a cup of water wasted per draw.

The standard way to deliver hot water faster is to have a hot water recirculation loop, so that hot water is closer to fixtures when you need it.  The downside, though, is that it takes electricity to pump the water around (if you use a pump), and now you have a big radiative loop, causing the water heater to cycle more often.

We did the recirc loop, with code-mandated insulation throughout, to minimize heat loss.  Rather than using thermosiphoning, a constant pump, a timer, a temp-controlled system, or a demand switch, I decided to try Taco’s “smart” recirc pump, which in theory learns when hot water draws occur, via a temperature sensor on the outbound pipe.  It then cycles the pump for 1hr either side of that “learned” event.  If it’s done well, it’ll be great.  If it turns out my pump firmware has bugs (which would be shocking, I’m sure!) it might not be great.  I plan to instrument & measure to find out once we get back to living in the house.  Taco does say that it ignores short draws, and only “learns” from draws of (unspecified) longer duration.

One thing that went wrong on the initial install is that the plumber didn’t put in a proper check valve  to prevent thermosiphoning.  So when the pump wasn’t even plugged in, water was circulating around the loop on its own, wasting heat energy.  Argh!  The plumber did put in a swing check valve which will stop reverse flow and draws from the bottom of the DHW tank, but a spring check valve is needed to prevent forward flow via thermosiphoning.  I’ve brought the issue up, and presume it’ll get fixed.

The other thing that didn’t go too badly, but could have been better – I don’t think we got the shortest possible runs from the recirc loop to the fixtures.  On one shower it’s still 12 feet to the valve, due to a strangely chosen circuitous path.  And the kitchen is 13 feet off the main loop simply due to the house layout; this could be solved by adding another return line and circulating past that fixture as well.

Here’s how it looks overall:

Seconds wait @ GPM:
Distance, ft Gal Waste Cups Waste 1.5 1.6 1.8 2 2.2
Kitchen Sink 13 0.123 1.962 4.9 4.6 4.1 3.7 3.3
½ Bath Sink 2 0.019 0.302 0.8 0.7 0.6 0.6 0.5
Master Sink 2.5 0.024 0.377 0.9 0.9 0.8 0.7 0.6
Master Shower 2 0.019 0.302 0.8 0.7 0.6 0.6 0.5
Hall Sink 7.5 0.071 1.132 2.8 2.7 2.4 2.1 1.9
Hall Shower 12 0.113 1.811 4.5 4.2 3.8 3.4 3.1

(Yellow cells are the waits for the most likely flow rates for these fixtures).

So we didn’t make the one-cup goal everywhere, but we’re under 2 (if you don’t count valve-to-outlet distances).  It’ll be very interesting to see how well this works – in particular, how well the pump learns, and what its thresholds are.  Unfortunately, I don’t think it’s field upgradeable.  :)  But you can turn off the “smarts” and put it in manual mode; then I’m just a temp sensor, a relay, and an arduino sketch away from doing it myself, if necessary.

Advice I’d have for anyone having this kind of work done:  State your goals clearly to the people doing the work.  “I want a recirculation loop” isn’t really going to suffice, even if all you care about is convenience and wait time.  Long branches off a recirc loop defeats the whole purpose.

If I had it to do over again, I’d have said something like “My wish is to have no more than 5 feet of pipe between any fixture and the recirc loop.”  Stating that goal clearly would have probably stuck in the plumber’s mind a bit better, and avoided the oddities like the 12-foot run to the shower.

Making it easy


(Image link goes to Amazon)

Read any collection of energy tips, and you’ll get pretty much the same thing.  Turn off lights behind you, unplug your cell phone charger, put your AV center on a power strip, etc.  The problem with these ideas, IMHO, is that you have to remember to do them, everyone in your family has to do them, and you have to keep doing them indefinitely to keep getting any benefit.  And face it, it’s hard to change behavior. Continue reading

Spinning down a WD20EARS “Green” drive

Ok, this is a pretty utilitarian post.  I did finally get my 18W Server up and running; in fact, it’s serving this post!  But I can’t really get to 18W unless the 2x 2T WD20EARS [amzn] drives I have in it for media storage spin down when not in use.

And I had a heck of a time making that work.  hdparm -y would quickly spin them down, but using hdparm -S to set an idle timeout seemed to have no effect; I had been trying to use hdparm -S 241 to set a 30 minute spindown time, and I had no luck whatsoever.  With the drives spinning, the server used more like 30W.

Mostly through trial and error, I found out that if you set a lower spindown timeout, i.e. hdparm -S 3, the drive will spin down in 10 minutes. Continue reading

Opower goes social

I wrote about Opower almost 2 years ago, a company which is working to reduce energy use by simply making people more aware of what they use in comparison with others.  At the time of that post, they seemed mostly focused on working directly with utilities, and sending out reports to customers showing them how their energy use compared to similar homes in their area.  The idea seems to be that if you are at all conservation & efficiency minded, seeing where you are in relation to others may actually encourage you to do even better.  They track the results, and apparently, it works.  However, that method works only if the utility is on board to provide the data. Continue reading