Thermostat, Cycling and Steam System

sean_b

Hi, I recently bought a home with a steam system, and I have never seen such a technology before!  I have had nothing but issues, questions, and stress - and as a result I have found, then referenced this site over the last 2 months an uncountable number of times!  What a great resource this wall and all of you have been. 



I plan to take some pictures and post a more lengthy question later re: some operational issues i continue to experience but for now while at work I figured I could ask a more simple one about thermostats.



The boiler is brand new Smith series 8 3-section oil fired.  When they put in the new thermostat with the new boiler they put in a digital but manual Honeywell 5000 series.  I read in some other posts that this is a good manual option. 



I understand deep setbacks (w/ a programmable t-stat which mine is not) for a steam system arent a good idea having to bring everything back up to temp from being ice cold takes a long time and uses a lot of fuel.  However, this thermostat drives me crazy.  It turns the boiler on if the temp falls just a fraction of a degree.  It seems like during cold days that it shuts off for 10 minutes then turns on again for 5 minutes.  And does this all day/night long.  Is this called short cycling?  What is considered short cycling?  Also, can this be fixed by adjusting the number of cycles per hour the t-stat does?  I am a little confused by this concept of setting the cph and what the objective is by doing so (seen in another thread).   Also couldnt figure out how to do it on my t-stat.



I find that when the system turns on and off so much, it ends up just adding a little heat at a time which finds the closest radiators to the t-stat (also closest to boiler), and then the other further away (2nd floor in particular) radiators end up going cold because the system isnt running long enough at any given stretch to really heat them.  Is this normal operation?  I try closing down the vents on the near radiators a little bit (all rads have all brand-new vent-rite adjustable vents)  and it seems to just make the frequency of firings increase a bit.  



I understand some t-stats have something that will let them drop a degree or two from the setting  before turning on the boiler. essentially resetting set-backs all day long.  Is this a bad idea for steam?  My thinking is that it would make the system run much longer and heat would go to all rads at that point.   but is this wasteful?  what would this feature even be called? 



Thanks in advance for any help or advice anyone has to offer.



-Sean

AlexR

longer thermostat cycles

You're correct that the thermostat should be calling for heat for a longer period.  Reducing the "cycles per hour" setting on the thermostat should help (I think 1 cycle per hour is normal for steam).  Some thermostats don't have a CPH setting but do let you set the type of system (eg, hot air or steam).  Others have a deadband or swing setting, which tells the thermostat how many degrees the temperature can fall before it calls for heat.  Mine works like this and I set it to a 3 degree swing.  So if the thermostat is set at 65, the temperature has to fall to 62 before the thermostat calls for heat; it then calls for heat until the temperature reads 66 (which probably means 65.5 or something) and cuts off. 



Running for just a few minutes at a time is bad.  As you observed, it doesn't get all the radiators hot.  You probably want the thermostat to call for heat for 30 to 60 minutes or so, unless that results in the boiler short cycling (the boiler cuts on and off every minute or so).

BobC

Venting, etc

I installed a Honeywell 6450 that also controls the temperature within a degree and I wished it could be adjusted to 2 degrees but that ain't gonna happen. My manual gives me a Heat Cycle Rate choice of furnace (5) - electric (9) - hot water (3) - steam or gravity hot water (1)



My system comes on about once every 60-90 minutes on very cold days and probably runs for 6-7 minutes initially and then a minute on and a minute and a half off for 3 or 4 cycles. All of my radiators heat up fine . i should mention that my boiler is really to big for the house.



Make sure that thermostat is set up for steam so that it has a CPH of 1. The next item on the checklist is to see how ell your venting is working. How long does it take for your main vents in the basement to close? You want them to close within a few minutes of the time your boilers header gets hot. If the main vents fast then you should be able to get steam to all the radiators at about the same time. Then you have to adjust the venting on each radiator so they heat up at about the same rate. You might try throttling back the VentRites on the first floor to encourage the steam into finding the radiators upstairs - especially on the radiator in the room with the thermostat. I use Hoffman 1A's on my system and I keep the venting rate on the first floor at a bit less than two while some of the upstairs radiators are on 4.



Buy some of Dan's books so you can get a clear idea of how these systems work. I've bought "The Lost Art of Steam Heating" and "Greening Steam" and they have paid for themselves many times over.



Bob

Charlie from wmass

Sean get those photos up here

It sounds you have more than thermostat issues. Have you purchased Dan's book "Got steam" yet?

David Nadle

Check the installer manual

Check the installer manual and make sure the thermostat is setup for steam/gravity. If it's a FocusPro 5000 the installer manual is here:



http://customer.honeywell.com/techlit/pdf/69-0000s/69-2026.pdf

sean_b

Thank you!

Thank you guys!  It is a focuspro 5000 t-stat, and I have been going nuts trying to determine how to adjust anything on it!   I have a couple unopened Home Depot t-stats to return now.  the manual the installer left for me must have been the "for dummies" edition!  Honeywell seems to hide the real manuals on a different website.  I will verify CPH and change to 1 tonight when I get home and update.



Also, re: venting/piping and all my other issues, I do plan to post a longer question under a different thread hopefully tonight or this week - but I want to take some pictures first.  I can say however the mains are venting ok and heating up rather quickly.



I have all sorts of issues going on but I think this t-stat issue is somewhat of a separate one (still related I know), and if i can effectively get a wider swing temp. by lowering the CPH it might answer a couple other concerns of mine...  The whole house would heat a little more comfortably if only the system would stay on a bit longer between firings instead of constant on/off every 10 min to keep it within +/- 1 deg!!! 





 

Mark N

FocusPro 5000

Press and hold up arrow button and fan button(bottom left )



This puts you into the set up mode. Setting #5 is for the CPH setting

NY_Hammer

here is the manual

the simple one



http://customer.honeywell.com/techlit/pdf/69-0000s/69-2026.pdf

sean_b

thanks so much!

With the help of the manuals i changed the CPH to 1 and works like a charm.  When the new system was installed the heating company left it at 5 (the default?)