You Can't Set Cycles per Hour on a Nest Thermostat

Rod

I got an email ad for Nest thermostats today with an email address for asking questions.

You apparently can't program cycles per hour on this thermostat. (See attached reply)

- Rod

ChrisJ

Nest

Boooo!!! Hissss!!!!!

Mark N

Nest

I don't know $249 for a thermostat. I watched the video who actually plays with their thermostat that much. I have steam I set it to 70 over a month ago. It will stay there till spring.

David Nadle

CPH ain't the only way

I don't think the Nest is going to work out for other reasons, but the lack of a CPH setting only means that they're not using the Honeywell style P+I algorithm. The Nest does have a hydronic/steam setting, and it's entirely possible that it is capable of controlling a steam system as good as or better than a Honeywell thermostat. Whether its opportunistic, "learning" setback feature will be enjoyed by many is less certain. 

jpf321

i wonder if the nest...

algorithm .. figures out that it costs waay more to recover in steam than to just leave it as it was before it setback (at least for setbacks less than 24hrs)...at which point you may as well have spent $15 on a round non-programmable wall unit.

Firsttimeboileruser

Nest/Cycles per hour

I saw your post regarding your steam radiator and Nest.  I noticed that you posted your comment in 2011.  Have they solved this issue? I have the same problem with my boiler.

Thank you,

Jason

ChrisJ

Nest

Has a setting called "True Radiant" which is said to be for radiant heat as well as radiators, though it doesn't specifically say which type. 



Have not tried one my self and due to all of the reviews talking about software glitches causing problems I don't think I will be.

AlexR

can you set the swing or deadzone?

Does it let you set the deadzone?



My thermostat doesn't have a cycles per hour setting either, but setting a 2 or 3 degree deadzone achieves a similar result.  Using a 2 degree setting means that if the thermostat is set to 70 in heat mode, it won't turn the boiler on until the temperature drops to 68.  That effectively prevents more than one cycle per hour and it's a small enough change in room temp that you can't tell unless you look at the thermostat.

Jamie Hall

I suppose...

that this thread is as good a one as any on which to pose the question I have about the Nest thermostat... which is...



Why?



As far as I can figure out, the only type of heat which responds fast enough to warrant moderate to large setbacks is forced air.  Radiant surely doesn't, and steam seems to tolerate small setbacks after a fashion, as does hydronic.  So it might be OK for forced air...



but then...



if you have anything temperature sensitive in the place, whether it's a plant or fine furniture or a piano, you don't want to change the air temperature much; a few degrees, that's all.



So why, unless you are iFreak of some kind, would you have a Nest?



Just askin'

David Nadle

"Learning"

The supposed value of the Nest is that it incorporates a motion sensor and learns when you're home and not home to deploy setback. It seems to me if you have a high mass system like steam there are going to be many episodes where you'll be disappointed with the Nest's choices.

Joe V_2

Here is a photo of usage

on a one pipe steam system in NYC.  Owner is happy with performance.  Boiler operates between 3 &4 hours per day.  I'll let the experts here exploit the pros and cons.

ChrisJ

Yikes

63F at night to 71F in the morning and then back down to 63F?  I consider my system to be pretty well matched and I wouldn't even consider a schedule like that.  I do a 3 degree recovery in the morning (67F to 70F) and then maintain until bedtime and then it drops back down to 67F.

Joe V_2

nest

schedule

nicholas bonham-carter

Fluctuating temperature

If the customer is happy with the performance, is the customer right? Most people with unbalanced steam systems have to rely on bumping up the temperature to get the cold spots warm, and maybe as a bandaid for a badly maintained system, needing this treatment, the nest would be alright. If you do not know what your old system is capable of, then it would seem normal to have to rely on these methods of heat management.

If you have a balanced system, then the constant temperature would be best--NBC

Joe V_2

Not a customer; a relative.

The house is well insulated and comfortable throughout.  Second floor apartment slightly warmer ( 1 degree)  throughout.  Boiler system is well maintained.  No issues.  He likes it cool during the night and noone is home during the day.  He is just saving money.



And, he has a baby grand piano that doesnt mind the temperature swings. But that is probably not relevent.

Other bennies include wifi that also monitors outside local temperature and remote control and monitoring via smart phone which is where photos are from.  I'm in NC and can raise or lower his house temp at will.  Plus, there is the obvious trending capability as seen in the photos.

ChrisJ

pressure

How many times does the burner kick off due to pressure during that 8 degree recovery?   Even my system will cycle on pressure at least once doing an 8 degree recovery on a 20F day.

Jamie Hall

Yike

I beg to differ.  It is highly unlikely that your relative is saving money with that large a setback.  Running the boiler 3 to 4 hours, which I believe you mentioned, should be necessary only on a day very close to design temperature; on a "normal" day (today, for example) the boiler in the building I super may run as long as an hour and a half; it may not even run that long...

On the baby grand.  All I can say (I should note here that part of my charge here is to see to the care and maintenance of three Steinway grands) is that I'm very happy for your piano technician; I'm sure he can use the money...

Joe V_2

Don't know

Pressuretrol is set to 2psi and heat is delivered in 15 minutes.  I would say not too often but I dont know.

Joe V_2

nah, the piano does fine.

No sour notes.

He will wait and see his fuel bill soon.  The nest was a gift so time will tell.  But, to be fair, that is an operator issue.  It seems the nest is capable.

nicholas bonham-carter

Remote access

The Internet/smartphone capabilities are a plus for this, but that schedule of raising the temperature at 6 then lowering it at 8 seems counterproductive to me. If he would try a constant 67 degrees for a few days, he might be pleasantly surprised.

There is more to heating comfort than mere air temperature with any radiator system. The radiators are not just raising the air temperature, but also that of the colder walls in the room. You could have the "cold 70degrees" phenomenon in a situation like this.

Of course some people like the sound of the radiators hissing air as they wake up to remind then they should soon feel warm shortly. Feelings of warmth and coldness are very subjective, and heavily influenced by other factors besides the true air temperature.

For myself, I keep the bedroom at 65, which is more exposed, resultI in the rest of the hous being 68.--NBC

Sil

Isnt the proof in the gas bill?

Joe V: 

Can you speak to what your gas usage has been before and after the nest?  Isnt that really the "proof in the pudding"?

Joe V_2

Sil, that

is what we are waiting for.  He just received it for Christmas.

As I said earlier, time will tell and we can't fault the Nest if the owner runs it the way he wants to.  He is comfortable and if his fuel bill is lower then he will be happy too.  I believe that is the way his Honeywell was programmed.

ChrisJ

Yep

My Honeywell VP 8110 was programmed for I think 62 at night then 72 or something wake then back to 62 then back to 72.



Thats for forced hot air, and even then I wouldn't use it because its just too much in my opinion.  You are right, his schedule isn't the fault on the Nest, but its still wrong for a steam system either way.



Now, how does the Nest do with overshooting after the recovery?  Also if it is about to do a setback, say at 10PM and it calls for heat at 9:58PM will it fire up the boiler just to shut it off 2 minutes later never even producing steam?

I ask because these are the things I've wondered about the Nest.

nicholas bonham-carter

fuel bills

when i had a new boiler installed, and undid deferred maintenance, i had to wait until the meter was read at the end of winter to find out the fuel savings. luckily our gas company included the degree days for the month with an historical gas consumption printout for the past 2 years; although they did not take a reading every month.

the new nestling will probably not see anything informative on just one bill.--nbc

PMJ

Meter Readings

The gas company converted our meter to electronic read about 2 years ago. Now all monthly readings are actual and since daily HDD data is easily available good monthly feedback is pretty easy. Reading your own meter it is possible to say something intelligent about yesterday's results if you wanted to.

It would seem that given the large changes in actual demand on the heating system from day to day that fuel used/HDD is about the only way to reasonably compare efficiencies of two different calendar periods. 

Joe V_2

..

Chris, Temperature overshoots are almost non existent if you compare the schedule to the actual temp/on/off photos.  In the beginning the overshoots were large but the device "learned" how the steam system responds.  I interpet the first photo as a call for heat just prior to set back but it is hard to tell if it is long enough to create steam or a waste of fuel.

NBC, we have to start somewhere and Jan1 is where he started.  I believe Con Ed provides detailed fuel usage online.  He is the only person I know to have a nest on a steam system and willing to let us learn.   

Joe V_2

Update

So, here is an update on the nest performance.  My relative agreed to raise the setback from 63 to 67 and left the "occupied" temp at 71.

This was done on the evening of Friday, Jan 18.

Joe V_2

Unsegmented graph

May add info

Mark N

Graphs

Joe



The graphs that you are posting are quite interesting. How many different ways can you display the data? It looks like you can display when the boiler runs and also total daily run times. Very helpful to track fuel consumption. Can it also display actual on and off times?

Joe V_2

these are the only two graphs

the first, is the solid bar that just tells total run time.



tap on any day and get a segmented graph where each red segment is "on" time.

nicholas bonham-carter

Burner run-time

It looks like the system is firing up to one third of the time in total.

I don't have an hour meter on my burner, but I think I am not firing such a large percentage of each day.

If the graph is showing us the call for heat timing, then there must be some short-cycling going on-maybe on pressure. How is the venting on this system?--NBC

PMJ

Total Run Time

Pretty tough to compare this for two different structures isn't it? Different total demands (outside temps) and different heating system capacities sized for different temp zones maybe?

Joe V_2

The graph is

Showing a calls for heat.  It is a one pipe system and all radiator/ riser vents work well.  Heats fast and quietly.  Could very possibly trip on pressure which is set for 2psi.  Outside temps that week were in the teens.  As you can see, the nest is holding temp well and it appears that the boiler comes on at least once an hour throughout the day for about (hard to interpolate) 30 minutes which is more than enough time to deliver heat, but I do not think long enough to trip on pressure. 

Kjmass1

please explain

what happened on the Monday. Throughout the previous days there were calls for heat 12+ times. On the monday it drastically dropped...was that because the outside temperature rose? Or has it adapted in some way?



Any update since last January in any fuel savings? Santa may be leaving me a Nest this year.

Joe V_2

update

you would have to google historical temps in NYC for those posts and use the date of the original posts which go back to early 2013, I think.



My brother has taken some advice from this board regarding setbacks. He likes the ability to tell if the boiler is working correctly from work and adjusting the temps higher via cell phone if he is out of town and the temps drops. He likes that the nest now has smoke detectors that can communicate with him via phone if one detects smoke.

He told me to date his average winter gas bill is $125.00/ month to heat 1800sqft. That includes his oven and hot water heater which is large enough for him and the four tennents who share the apt above him.



It's all good. he loves it. It works as well as any thermostat but if you have issues with the nest, I saw in home depot recently that Honeywell now sells a tstat with comparable features at a comparable price

jpf321

Degreedays.net will

Have the historic degree days..