Programmable thermostat changes

Hatherly_2

We have steam radiator heat which has never worked particularly well - parts of the house would get overheated and in other parts the heat barely reached the radiators. Meanwhile, the basement where the boiler is located was really hot and the boiler would kick on and off fairly often. Our house is very well insulated. We have had people come to check out our system but never had any good help - steam heat is extremely rare in our state and most HVAC guys have said we should fly in someone from New York to help as they have no experience! (we are in New Mexico)



We have had a regular thermostat which we used to adjust manually and the heat would only come into the colder rooms if we cranked it up really high - over 80 degrees. Meanwhile the other rooms would become far too hot.



Last week we installed a programmable thermostat and from the moment it was installed the whole system has worked fabulously. The boiler kicks on twice a day for maybe 45 minutes and the entire house gets evenly warm, even the radiators that never seemed to work are now working perfectly all the time. The basement is no longer overheated and the boiler isn't cycling on and off. The house holds the heat and stays comfortable for much longer than previously, because the whole house is now getting heated.



So my question is why this would happen? The only thing we did was take off the old thermostat and put the new one on. I had prevously tested the old thermostat's temperature settings with a wall-thermometer to see if it was calibrated correctly and it seemd to be just fine.



I'm happy it is working so well but confused as to why. Any thoughts?

Mike Kusiak_2

Matching the system

A heating system will only work properly if its operational characteristics match and complement those of the thermostat used. More than just the temperature setting, its how the cycles are

actually timed relative to the systems needs.



Since most homes in the US are heated by forced hot air, typical thermostats are designed to match their characteristics. Hot air systems only heat air and therefore can cycle on and off several times an hour to provide comfort.



Steam heating is totally different. It takes a long time for all that water and iron to come up to temperature, and once the radiators are hot, a long time for them to cool down. So a thermostat set up for hot air will make a steam system almost unusable. Sounds like you had such a situation with your previous thermostat which was most likely optimized for hot air systems.



Your new thermostat settings seems perfectly suited for a steam system, running long heating cycles much less frequently. Consequently, the system operates properly, and you are enjoying all the comfort a steam system can provide.

jpf321

can you tell us ...

what thermostat you installed? brand and model?



You are right to be confused, and Mike may be onto the reason why .. but I'd like to know what you installed so that we can see if more if either confusion or an "attaboy" to Mike are in order.

Hatherly_2

Thanks

Thanks so much - that makes sense!

Hatherly_2

Lux

The kind we installed is a Lux TX9000TS programmable. The old one was a small round older model (sorry, I threw it out) - but it is a kind I have seen often before in older houses with a dial that you turn. 

jpf321

well here's the manual

http://luxproducts.com/support/TX9000TS_ENG_LARGE-SIZE.pdf And the only thing that says anything about cycles is 6.2 SWING ..



the Lux says nothing at all about Steam ..



there is a very strong possibility that your old t-stat was simply broken and needed to be replaced .. and you didn't even know it. now you have one that is not broken, although there doesn't seem to be anything "special" about it in terms of "steam".



btw, can you look to see what your "swing" setting is .. i'm curious .. i'm guessing it's 0.75 or 1 .. fyi, my "swing" is 0.5 (the smallest it can go) ..

Hatherly_2

Swing settings

How do I find the swing settings? I don't understand the broken thermostat scenario. How would a broken thermostat still manage to heat half the house but not all the radiators? The boiler would come on and some rooms would get quite hot while in others there was no heat at all. Now when the boiler kicks on all the radiators heat evenly and the once-hot rooms are comfortable and not overheating.

Mike Kusiak_2

Honeywell mercury thermostat?

Sounds like you had an old round mechanical thermostat. These had a device called a heat anticipator, which allowed you to adjust the cycle length. If the installer set it up as he would for the usual hot air system,  it would short cycle on a steam system as yours did.



Actually, that same thermostat works great on a steam system if the anticipator is adjusted properly. In this case, the anticipator is set for the long cycles appropriate for steam.

jpf321

as per manual ..

Touch MENU.

SCROLL to SWING VALUE.

Touch YES. Adjust Swing Value will appear.

Use UP/DOWN arrows to adjust.

Touch EXIT to return to main display



I'm not sure it will ever be known as to why changing the t-stat made your system better .. but consider yourself blessed .. there are a myriad of things that could have fixed/improved your old system .. but swapping the t-stat would have been waaaay down on the list.

Hatherly_2

Honeywell

Yes it was a Honeywell mercury thermostat - I remember now. And the anticipator makes sense.



Also, the swing setting is set to .5 degrees F .



I'm so glad it is working better! Now if only there were a really experienced steam guy in the state I would love to get a more efficient boiler - ours is really old and huge - a Slant Fin G-225 cast iron 180,000 BTU output. Having read some on this site, however, I am far too nervous about getting just anyone in to change it out!

jpf321

thanks

thanks for checking on the swing .. if it's working well, don't change a thing .. by increasing the swing ... you may lose comfort ..

  0.5 means modulate between for example 70.5 and 69.5 (if setpoint is 70) ..

  if you change to 1 that would mean 69 and 71 ..

  changing to 2 would therefore be 68 and 72 ..

and so on based on the limits of the swing.

Hatherly_2

Thanks

Thanks jpf321 - I didn't understand that before but now I do.

jpf321

yeah the manual

doesn't really make it very clear huh .. 

Mike Kusiak_2

Thermostat cycling

With a problem like short cycling and uneven heating, the thermostat should be near the top of the list. If the boiler only runs for a few minutes and then shuts down, there is no time for steam to reach the furthest radiators during the cycle, so uneven heating results. Steam systems were never designed or intended to operate that way.



Remember this thread?



http://www.heatinghelp.com/forum-thread/133063/Help-Desperately-Seeking-Solution



Aside from all the bad piping and poor installation, the real problem was the thermostat.

Rod

Steam Books

Hi - You probably need to do what a lot of us have done. Just read up on steam. I was forced to do this as my house is in rural Maine and no one local seemed to have a clue when it came to steam. I would suggest you start with "We Got Steam Heat!"

http://www.heatinghelp.com/products/Books/5/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence

It's a very good introductory book on steam heating. It's written for the homeowner and is easy, humorous reading. In an evening or two of reading you'll be light years ahead in your knowledge of steam heating.  After you have read "We Got...! I would then read  "The Lost Art of Steam Heating".  Both these books are available in a package in the Shop section of this website.

http://www.heatinghelp.com/products/Super-Deals/14/129/A-Steamy-Deal



These books will save you a lot of money as you will be able to do a lot of the maintenance yourself. Mine have saved me at least 100 times their cost since I got them

- Rod

jpf321

don't we have...

some folks here from Denver? How far could Denver be from N.M. :-)

Hatherly

Books

Thanks for the books suggestion - I'm ordering them for myself for a christmas present!

Kevin_in_Denver_2

Cycles per hour

The new thermostat may just have a "steam" mode, which is one cycle per hour.



That mode would explain the long cycles you're now seeing. (A good thing)



Did you have an experienced guy install the new stat, or were you just lucky?

Mike Kusiak_2

Adjustable differential

It appears that the Lux thermostat does not use any fancy algorithm to adjust the cycling. but simply a differential or "swing" setting to determine the cycling rate. Its operation will be more dependent on the characteristics of the system it is used with. For example if used with a high mass system, there will be a long time lag between when the burner is fired and when the thermostat senses the heat. This will result in long cycles, which can be modified by the adjustable differential setting. Conversely, if the same thermostat is used with forced hot air which responds quickly, the thermostat will sense the heat more quickly and repond with short cycles.



In any case, if the differential is set too high, over and undershoot of the setpoint temperature will result with this type of thermostat, so the minimum setting which provides the desired cycle rate should be used.



From the results obtained though, the Lux certainly seems like a good choice for a steam system.

Hatherly

Lucky coincidence

Well, it was pure luck - I bought the Lux as it had a lot of positive ratings on Amazon, and installed it myself.

jpf321

i'm very happy...

with my CPH-less swinging Ritetemp T-stat ... i oscillate between 69.5 and 70.5 with a setpoint of 70 .. no over/under (at least not at the stat) .. the stat thermo display resolution might not be that great though .. it sits at 69.5 for a long while before it trips the circuit for a call.



and i don't need any of that fancy intelligent recovery stuff since I don't run any setbacks. 

jpf321

last year...

last year I had a datalogger sitting on t-stat ... it maintained 69.5-70.5