We're at design temperature in NYC.

JohnNY

It's getting interesting around here.



Mod cons running at 90%-100% today.



A snow melting system of ours was being challenged.



Frozen pipes.



It's supposed to be 1° when I get up in the morning...



I predict no lunch for JohnNY again tomorrow.

Rich_49

What is design temp

Lots of my competitors are lost sleep last night and will lose more in the coming days . They design to 14* . I will be sleeping like a baby . Good night !  Johnny , good luck and hope you don't have too many that were cut close .

JohnNY

ACCA put design at 15 for NYC very recently.

We usually use 0-10.



Either way, it's close.

Total1

figured

When I was figuring out me heat loss , I adjusted the program down to -50 C , the boiler has  plenty of btu's to spare  with the turndown .  Happy that I did this  . In the next couple of days with the wind we are suppose to hit - 76 F .... 

icesailor

-76 degrees/Wind Chill:

There's a difference between OAT (Outside Air Temperature, and "wind chill" Temperature.



OAT is the temperature measured outside on a thermometer. Wind Chill Temperature is the theoretical rate in which exposed human skin will freeze and be damaged due to the severity of the wing. It has nothing to do with how fast a house will cool down other than through infiltration (drafty windows, doors and structures).



Check out this PDF from NWS/NOAA and you will see how low the actual OAT will have to go to get to -76 degrees.

A lot of weather prognosticator exaggerate wind chills like crazy because no one understands what it is and is giving the public a good scare.



http://www.nws.noaa.gov/om/windchill/images/windchillchart3.pdf

Weezbo

i have seen the bottom drop out of a thermostat out side...

that has jack to do with anything other than when it is that cold you ought to be smarter than me and not be out there in the first place lol..

*~//: )





Good Luck Jhonny . we got plenty cold here if you ever need any i will round some up and put it in a box send it right along....

: )



yesterday i fired up some thing it could be Caribou or reindeer, maybe goat or moose might even be musk ox i dunno .... buh it didn't kill me so its all good . : )))

knotgrumpy

Weezbo

"yesterday i fired up some thing it could be Caribou or reindeer, maybe goat or moose might even be musk ox i dunno .... buh it didn't kill me so its all good . : ))) "



It didn't have a Red Nose, did it Weezbo?  Tell me it didn't have a Red Nose...

knotgrumpy

JohnNY

How is everything going in NY?  Everything holding up?



Temp in Illinois is dropping throughout the day to a low of -20°.  Tomorrow a high of -15°.  Not looking forward to the extreme cold but am interested on how my own system does.

ChrisJ

Design temp

I've got what may come across as a "dumb homeowner question".  I'm assuming design temperature is when the system will run continuously to maintain temperature?  Meaning if the design temp is 0F at that temp the heating system should run nonstop to maintain 70F or so.



If that is the case, what happens under those conditions if the customer uses a programmable thermostat and does something like a 5 or 10 degree setback?  I have to assume being these thermostats are common including learning ones like the Nest that this could be a common problem?  Or would the reduced heat loss under those conditions allow the system to actually slowly raise the temperature to 70F?

Mark Eatherton

Setback not recommended..

especially at design conditions. If it is left intact, and the system recovers well, it is an indication of a grossly oversized system, which most older systems are any way.



I'd also be surprised if your boiler is doing a 100% duty cycle at that point in time. In my 36 years of hanging out in boiler rooms, some of which I constructed and know for a fact that they are not grossly oversized, I have yet to see more than a 50% duty cycle.



Even n my own home, where I intentionally cut the boiler size by 50%, I have never seen the boiler at 100% burn capacity even at design condition.





ME

wrxz24

At below design temp

My system ran at 100% for the entire night. The house maintained the temp though but the boiler could not reach it's setpoint. I have combined slab and baseboard return water temps.

meplumber

Below design conditions

Just an FYI to our colleague Mr. Eatherton.



I spent the bulk of the day Friday at a research facility that we built last year.  The building is LEED Certified (Platinum I believe).  Engineer designed mechanical systems.  The boiler plant was struggling to say the least.  It had run at 90%-100% since Wednesday night.  I finally got the train driver on the phone and asked him about his design.  He told me that he used -6 F because he didn't think it got that cold on the coast.  Our usual design temp is -10 F.



The air temp at the time was -21 and the wind was howling off the water.  While I don't dispute ice's comments, I can tell you that in my years of experience, wind chill does effect the building's heat loss.  To top it off, the contact temps on the bulk LP storage tanks was -38 F.  We were struggling with vaporization and with the boilers keeping up. 



Made for a really long day.

ChrisJ

Wind

Wind must effect heat loss of a building otherwise a condenser fan would have no effect on the heat loss of a condenser.



Might be a poor example, but it makes sense to me.



Unfortunately in my drafty 150 yr old house wind has a tremendous effect on it but this is due to heat being pushed out of the building rather than just cooling the walls and windows. Little by little I'm making things better but its going to take a long time.



I would assume when someone calculates a design temp wind is already factored into it and you can't use windchill. All in all it seems I am agreeing with icesailor though knowing almost nothing about this I'm in no position to disagree with anyone.

Gordy

Wind chill

Is a big player in infiltration. As far as windchill temps air temp is air temp. I can not find anything to the contrary of ices post.

Jean-David Beyer

My system ran at 100% for the entire night.

Mine does that quite often when it is cold enough outside. (It will not modulate down far enough in warmer weather). I too have radiant slab downstairs (big zone) and oversized baseboard upstairs (tiny zone). And it does not have to be below design temp (14F) for me to do it, but it sure will not do that when it is 50F outside either.



Mine always reaches very close to the room thermostat set point. On these digital Honeywell thermostats, they say I am right at the set point, but I am not as it is still calling for heat. And it does not usually reach the set point until the sun comes out or I turn on the oven of my stove. It does that because of pains taking adjustment of the reset curve. And this works only on cold days because my boiler is about twice the size I actually need. They do not make them small enough for 1150 square foot houses in New Jersey.

SWEI

We get below desgn temps most years

for an hour or three.  Thermal mass hides it completely for most of us.



Days of that is another thing altogether.

icesailor

Wind Chill/Infiltration:

BINGO.



If you look at the wind chill chart, the higher the wind, the greater the chill factor. But it is caused by the wind. In dwellings, wind chill and infiltration are cousins. But it is the ability of the cold draft to "infiltrate" the structure.

Take Massachusetts and the cities of Springfield and Boston and the Towns of Nantucket and Provincetown. The old IBR heat loss tables gave out Boston as say +10 degrees and Springfield at +01. But Nantucket and Provincetown had 0 (Zero) as a factor. Because although Nantucket was almost always warmer than Boston and almost NEVER colder, the wind blows constantly at high rates. It is common to have winter storms that blow 60 to 80 MPH a couple of times per year. It never blows that hard in Springfield, but it is colder. The correction is for the wind.

Clock Thermostats manipulate the outside air temperature. If it is at design temperature (Zero) and you drop the inside thermostat by 10 degrees (60 degrees inside), it is the same as raising the outside temperature 10 degrees while the thermostat is off, and when it comes back on and tries to get to 70 degrees inside, it is "seeing" -10F degrees. Because the heating medium isn't flowing during this longer off period, pipes can freeze where they wouldn't stop if the circulator hadn't been paused.

Another way of looking at infiltration and wind chill is when I would be ice sailing. Infiltration is my hands and body getting cold through my sailing gear. Wind Chill is what I felt on my face because I had to keep the visor on my helmet cracked enough to keep condensation from forming on the inside of the visor and blocking my vision. Not cool at 40+ MPH across the ice. Its important to see where you are going and who is around you.

JStar

Design

I have 100,000 BTUH's worth of baseboard element. Running my hot water boiler at 35,000. Based heat loss at 8F OAT. Maintaining 72F all week. It's 30F outside right now and my Target Supply is 145F.



Haven't had one single complaint from any of our customers. And we are always using equipment that's half the size of our competitor's quotes.

Jean-David Beyer

P.S.

I did not mean it was firing at maximum firing rate. Quite the contrary. But it was firing the whole time, perhaps at minimum firing rate (depends on outside temperature). I think it is an achievement to get it to fire contiinually for a long period of time without firing so low that the house gets cold.

Gordy

Another example

Snowmobiling,



The gear you wear is definitely not designed for -96* while it's -10 oat and flying at 80+ mph. But forget to zip something up you'll know it. Actually had my eye lashes freeze shut once when my visor malfunctioned and flew off.

Mark Eatherton

Sorry, I should have given a caveat….

"On RESIDENTIAL systems…"



Commercially, sure you WILL run into those problems. Especially with DOAS ventilation systems, and a lack of internal assumed gains, and a lack of commissioning, testing and balancing. Our discussion was directed at residential applications. I should have clarified.



And I should state that I have run into it occasionally on poorly constructed, poorly designed residential systems, but it was usually a case of infiltration running rampant through the home.



Check you make up air. It will draw a system backwards faster than you can call the engineer up.



Happy Cold New Year. So much for global warming



ME

ChrisJ

global warming

Prolonged temperatures this cold as well as colder were very common during the little ice age.

ChrisJ

End result

Did a lot of people in NJ / NY have busted pipes?



I have two friends that did one of them being my next door neighbor. I had one just start to freeze but luckily I paid attention to it as we have not lived in this house long and I just insulated all of the steam piping and returns. I'll be doing some modifying now to prevent the possibility in the future.