Another T-stat setting question

[Mikepier]

I posted a few days ago about setting temps in an apt building. This is in NYC, and the gudelines are as follows:

6AM-10PM 68 degrees ( if outside temp is below 55) 10PM-6AM 55 degrees (if outside temp is below 40)

Now I'm just wondering, if you set your T-stat to 55 at night, doesn't the heating system have to work longer to get the temp back up to 68 in the morning?

I would think if you drop it to like 64 or 65 at night, it would not take much to get it back up to 68 again. And plus 55 at night seems low, but thats the rules they post on the website.

[dpb]

Overall there's less time at heat so it is a net savings.

Not sure whose guidelines you're speaking of; I'd presume those are minimums, not maximums.

--

[salty]

stated another way - Lower average temp over time = savings

[Peter]

See this link for an analysis of why it is energy efficient to set back the thermostat at night in the winter:

and this one:

Also, a lot of energy is needed just to get the duct walls and air, or water (or steam) hot to begin with. When you have the heating system running for a good while, that only is done once during that heating cycle. Our local utility company claims that you save 3% on energy use for every degree F you set the heat lower than 68 degrees. Do a little search engine browsing on "analysis thermostat set-back efficiency" and you'll find pages of hits. This is a real phenomenon, not some urban legend.

[ransley]

You can lower it and save a bit but if you have steam you have several issues. A steam boiler should idealy be set to 1.25lb maximum pressure, [ checks yours]. I found running a long long cycle to reheat, I reheat unevenly compared to steady heat, plus its alot harder on the boiler if its cycling by high pressure limit, which it will do on a big temp difference makeup. If your pressure is set alot higher than optimal-normal its alot harder on the boiler. I found mine cutting out at 5lb and I got a few leaks. I also dont lower it because the tenants correctly argue they work or are out late and are only home when I would be cutting back the temp, so you will get unhappy tenants. If they are unhappy they move and in winter you dont want vacancies, getting a good new tenant in winter is not easy nobody wants to move when its near 0 and snowy out.

[Colbyt]

I would never do more than a 10 degree setback and in that coldest 30 days I might not do that much. I actually only do five at that time.

Yes it works harder. The harder it works the greater the efficiency. Overall you save money. If the system can not recover to the higher setting within 2 hours you need to adjust your numbers. That is why I only do five for the coldest 30 days.

[Ed Pawlowski]

I'm guessing the guidelines are some sort of minimum by law. 55 is too low for most people, especially elderly.

The more you set it back, yes, the longer it takes to get up to temperature. It may take an uncomfortably long time to reach temperature again and that does not make for good relations with the tenants. I'd go with a minimum of about 62. What I found works well in my house is 62 at night, 70 first thing in the AM, then drop back to 68 for the rest of the day. That gives you time to wake up, have breakfast, start moving before the temperature drops a bit. Sometimes in the evening I'll bump it a degree if we are just sitting and reading or TV watching.

What works will depend on your tenants too. If they are elderly, they will want warmer, working people won't care during the day as they are not home. If they are all from Europe, they will think 65 is extravagant.

[The Daring Dufas]

I remember back in the 70's when all this turn back the thermostat to save energy mantra started. The Federal Government in all its wisdom, issued a mandate that all government buildings would have the thermostats set back to 68°F. The federal workers at government sites in Hawaii were freezing their butts off because the air conditioning was running wide open. :-)

TDD

[trader4]

.

There are two seperate issues. One is the lower you set it back, the more energy you save. Yes, it then takes longer to heat it back up, but that doesn't effect the energy savings. But it does lead to the issue of whether you want to wait that long for the heat to get back to an acceptable level.

Also, those guidlines sound like the minimums, not what you'd want to maintain reasonable tenenants.