Thursday, January 26, 2017

High Temperature Thermostat

One of my side jobs is doing facility support for my local yoga studio. They have some unique HVAC requirements - specifically thermostats that have higher than normal set-points.

Most commercial thermostats go up to 90°F or 94°F maximum. I was able to find one thermostat - the Jackson Systems Model T-32-P which can be programmed up to 122°F heating set-point.

It actually seems to be a very versatile device, with a ton of flexibility for many different systems:
  • Up to 3H/2C conventional and heat pump systems
  • 7 day programmable
  • Large backlit display
  • Auto or manual changeover
  • Keypad and/or setpoint lockout
  • Smart fan logic for commercial control
  • Adaptive recovery
  • Optional indoor sensor (T-32-S1 or TS-32-S2) or outdoor sensor (T-32-OTS)
  • Outdoor temperature display with optional outdoor sensor (T-32-OTS)
  • Available with integrated Modbus communications (Version 2.20)
We've got three of these installed right now - two in a large studio (forced air and baseboards, both heat only, and programmed for automatic warm up and night settings) and one in a small studio (heat / cool / forced air, no programming) and all are working great. 

Thursday, June 25, 2015

Summer Peak Savings

EnergizeCT, the energy saving arm of Eversource, has an interesting web page devoted to reducing peak demand: CT Power Update: Demand / Air Quality - with a tool that maps forecasted and actual demand.


My suspicion is that, as smart metering rolls out, utilities such as Eversource will begin to pro-rate energy based on time of use (peak / off-peak) and perhaps even ding consumers for peak demand and/or low power factor, as they do commercial and industrial clients.

On the same page, they are also promoting a "Wait Until 8" program to encourage consumers from running major appliances during peak demand hours (12 noon - 8 pm). Things like dishwashers, clothes dryers, swimming pool pumps, etc. that could be run more consciously.  

Friday, May 1, 2015

Tesla Energy: Powerwall Home Battery

The internet (and public radio, for that matter) is abuzz with the launch of the Powerwall Home Battery, by Tesla Energy. 

Link through to read the details, but here are some highlights:
  • Applications include load shifting, decreasing need to sell solar power back to utility, and back-up power. 
  • Two primary capacity ratings, 7 kWh (daily use applications, $3000) and 10 kWh (back-up applications, $3500)
  • Does not include inverter. 
  • Ten year warranty.
Sorry, Elon Musk, but I need to rain on your parade. As the owner of a small condo (1200 square feet, including the basement, which is finished as my office) that has electric everything (heat, hot water, dryer, stove and oven), and as an electrical engineer concerned with energy efficiency, I happen to monitor my home energy use. I'm not a spendthrift - I've converted all the thermostats to digital / timer, all my lights are CF or LED, I keep the heat at 65F when I'm around and 58F overnight or when I'm out.

In February this year (admittedly brutally cold), I used an average of 175 kW-Hr per day.


 April (not quite warmed up, but more typical of a regular month), it fell to 60 kW-Hr per day.


So tell me just how useful your 7 or 10 kW-Hr worth of battery is going to be for me?

Yes, if one is burning fossil fuel for heat, cooking, clothes drying, hot water, has a modern energy efficient home, then I imagine 10kW-Hr could give you close to a days worth of power, if you don't dry your hair, turn on the A/C, or switch on a space heater. And it seems to be that if the bulk of home energy use is still coming from fossil fuels (to run a home for 12 hours on 10 kW-Hr, that seems to be a prerequisite) we're not really that revolutionary.

Edit: And because this has been sticking in my craw for a day or so, I did some additional digging.  According to the US Energy Information Administration:

In 2013, the average annual electricity consumption for a U.S. residential utility customer was 10,908 kilowatthours (kWh), an average of 909 kWh per month. Louisiana had the highest annual consumption at 15,270 kWh, and Hawaii had the lowest at 6,176 kWh.
909 kW / month = 30 kWh / day. And with most of the USA averaging 4-5 hours of peak solar production, (let's call it 8 hours of solar power), our "back-up" is going to need to supply at least 16 hours, or 20 kWh of demand. Twice the Tesla device capacity.

This is not rocket science (oops, bad analogy, I'm a big fan of Space-X). Folks have been using battery back-up in UPS (Uninterruptible Power Supplies) for decades for critical applications (computers, networks, patient care, etc.) - in much higher power ratings. But truth be told, it's really not all that cost-effective, most applications switch to some other form of energy storage for extended outages. Perhaps there's a mechanical solution (magnetic bearing flywheel? compressed fluid?), a thermal one (some form of heat engine), a chemical one (fuel cell), or something else. 

I like what you are trying to do. But it's sad that in all the interviews I've heard and stories I've read today, nobody has really done the math. 10 kW-Hr is not nearly enough capacity to take a typical home off the grid, even on a sunny day.

Tuesday, February 24, 2015

Follow-up: Bait and Switch - Electric Supplier Edition

Lawmakers Seek To Ban Variable Rate Electricity Contracts

Lawmakers signaled Tuesday they would revisit the controversial third-party electricity supplier market and seek to ban variable rates in residential electricity contracts.

It will be the second consecutive year the legislature aims to address consumer complaints about third-party suppliers, who they say attract customers with deceptively low teaser rates that quickly expire and leave consumers open to paying variable rates well above the standard rate available from a utility company.

Hugh McQuaid | Feb 24, 2015 3:44pm

Thanks to CT News Junkie for keeping on top of this!

Tuesday, February 10, 2015

Space Heaters = Power Quality Headaches

It's the time of year when space heaters begin appearing under desks, in alcoves, and in cold corners of offices in homes and commercial spaces.

"Looking for the space heater" is often my first check during a power quality audit in the winter - because electric space heaters are often the culprits in many power problems. 
  • Fuse blowing or circuit breaker tripping
  • Voltage drop problems
  • Overheated connections or receptacles
  • Neutral-ground voltage issues
A typical space heater will draw 10 - 12 amps at highest setting, and sometimes higher. This is close to the maximum rated for a 120 VAC, 15 Amp receptacle or circuit - which often also feeds lighting, office equipment, computers, etc. So a circuit or receptacle that has been perfectly adequate all year long is suddenly a problem. Coupled with laser printers (another power quality culprit) and it's a wonder anything works in the office this time of year.

If you need a space heater, check to see if you can get a dedicated outlet or circuit to power it - so that its current draw (and resultant voltage drop) do not affect your sensitive equipment. Remember that receptacles are often daisy-chained, so the empty outlet you find to plug your heater in may still be on the same circuit. And that same "daisy chain" may also be the point of failure - connections or splices in an upstream box or receptacle may be the place where the space heater added load causes a failure.

Here at the PowerLines home office, we've installed a dedicated 15A circuit - to run the space heater in the winter, and the air conditioner in the summer.

Monday, January 5, 2015

Bait and Switch: Electric Supplier Edition

I received a letter this afternoon from Verde Energy, my electrical supplier.

The big news: 

  • Your current generation rate is 0.0999/kWh. You are currently under a fixed plan, which means your generation rate will remain fixed until 12/14/2014.
  • Your generation rate will be 0.2099/kWh in your next billing cycle. 
Yes, you are reading that right, my energy rate is going to more than DOUBLE next month. The letter is dated 12/31/14 and arrived 1/5/15.

Needless to say, I hopped right on this, and procured a different supplier with a much more reasonable rate (the CL&P standard rate is, at present, 0.12629/kWh) - but I'm still pissed off that, from 12/14 through whenever the new supplier kicks in,. I'll be paying 21 cents / kWh.

And for what it's worth CL&P is damn useless here. I visited the Electrical Supplier website at www.energizect.com and was directed to the CL&P phone line to return to standard generation rate. The "electrical supplier" option was a simple pre-recorded message, and when I punched through to get an operator, it was a 30 minute wait. I hung up, and went to sign up with a different supplier.

Imagine how many people would ignore this letter or not notice until the next billing cycle. I'm planning to put the expiration date of the next contract period into my phone to get a reminder next year BEFORE the rate expires.

Electrical deregulation is, as far as I am concerned, a big freaking boondoggle in line with consumer credit - with all these independent energy producers playing fast and loose with "come on" rates and then, after the honeymoon period, lowering the boom, and hoping they get a few people who miss the transition to a "screw you" rate.

Friday, November 21, 2014

Winter Heating: Humidity and Apparent Temperature

Having problems getting and staying warm this winter? Finding yourself pushing the thermostat up past your usual comfort range?

The problem might be related to low relative humidity. The colder the outdoor temperature, the more heat must be added indoors for body comfort. However, the heat that is added will cause a drying effect and lower the indoor relative humidity, unless an indoor moisture source is present.

As an example, a comfort level of 70°F at 50% RH feels more like 65°F at 20% RH, a very typical humidity for a home without humidification.

Apparent Temperature for Values of Room Temperature and Relative Humidity
Many central heating systems incorporate automatic humidity controls; however there are often non-functioning or in need of service. Alternately, you can purchase a warm-mist or cool-mist humidifier.

Finally, there are solid (and cost-effective / green) tips to be found here: 6 Ways to Humidify Your House (Without a Humidifier)

See also: