Can you use a programmable therostat with a boiler?

Sweet_Lew

Hello!

My wife and i moved into a 1912 farm house that has a hot water boiler\radiator heating system (Bryant Legacy BW series boiler made in 2002). We swapped out the old Honeywell mercury manual t-stat with a Honeywell RTH230B programmable model. I have been told that a programmable WILL work with 2-wire boiler systems. It is working, but it's working much differently than the manual was. For one, when the old t-stat was set to 71, it was toasty. When the new one is set to 71, it is fairly cool. The boiler is also kicking much more frequently and the radiators are not as warm as they were with the old t-stat and I'm hearing more banging noises in the basement.

Lastly, heating cycles..In the manual it says to set the CPH to 3 for hot water systems. I currently have the cycle set to 3. Should it be changed to a different setting?

So I'm looking to see if I should just get a "heat only" thermostat and ditch this pprogrammable.

Thanks,

Lew

Peter_26

Anticipator Setting

I think you have the same problem I had and I think it has to do with the anticipator setting on your old Honeywell. From what I know the programmable ones don't have anything to help with that setting. I think the anticipator setting has to do with the current from your control.

Look here: [u][color=#810081]http://www.ehow.com/how_5073336_adjust-honeywell-thermostat-heat-anticipator.html[/color][/u]

  

Can anyone help out here?



It's funny because this forum is called heating help and I've noticed that I'm the first to try and help out.



 

Hope this helps. I just stuck with my old honeywell. If anyone has any advice on a programmable, please let us know.

Pete

Sweet_Lew

Thanks

Thanks for the reply Peter!

I ended up purchasing a RobertShaw RS3110 t-stat that has a adjustable temp differential:

[url=http://www.prothermostats.com/product.php?p=robertshaw_rs3110&product=172265]http://www.prothermostats.com/product.php?p=robertshaw_rs3110&product=172265

I haven't installed it yet, but if it sucks too, the old mechanical is going back in.

Better yet, what Peter said. Is ANYONE out there using a digital t-stat with an anticipator feature?

Peter_26

Let me know

Let me know how that goes, but I think from what I've read on the internet the Honeywell is your best bet.

 

I still can't believe no on else has answered. It's happen to me before, unbelievable!



Pete 

Sweet_Lew

Will Do...

This one DOES have an anticipator feature which I passed on for the less expensive RobertShaw:

[url=http://www.prothermostats.com/product.php?p=white-rodgers_1f80-0471&product=110089]http://www.prothermostats.com/product.php?p=white-rodgers_1f80-0471&product=110089

I mean, someone could go crazy trying to figure out what to buy.

Peter_26

I think....

From the specs you were probably better off getting that one, but who knows and it's more expensive too.



Pete

Gordy

Room temp?

 You stated that with the old t stat was set to 71* and it seemed warmer then now at the same srtting with new t stat.  With the old one being set to 71 what was the actual room temp on the t stat when the heating cycle ended?  It may have been 72-74*. Thats why you may notice a difference.



 My electronic t stat has what they call the "swing" which is the same thing as the anticipator setting. I think the swing is in to tight of a range is why the boiler is kicking on more frequently.  Its staying in that 71* range so when the room temp drops below that slightly the boiler kicks on. Then it shuts down only heating the room a little over the 71* setting.  The higher the swing number the more the temp varies from the t stat setting. Raise your swing number to 4.



Gordy

Sweet_Lew

Hey Gordy

With the mechanical t-stat it was consideralbly warmer downstairs and especially upstairs. Example: I would turn the corner going up the stairs and you could feel the rise in heat. Now, I do the same thing and it feels colder than downstairs. Before my wife and I would kick the sheets off at night. Now, we are fighting for them. My sons room was super cosy and now he needs a space heater. It's really weird. I'm wondering if the old t-stat was really that out of whack and maybe it was reading waaaay higher than 71. I never did measure the temp before I swapped out the t-stat. =/

I'm thinking I may pass on the Robershaw and would be better off with the old one or a replacement mechanical. I really think not having an anticipator is hurting my heating system by running it more frequently and not heating the house as evenly.

Peter_26

Thanks for the help Gordy!

I just looked up the owners's manual and the way to do that is the following:



DIFF Setting

Your thermostat is set at the factory to cycle at 2ºF (1ºC) above and below the set temperature (DIFF = 2). This setting has been designed to provide a comfortable room temperature under most conditions. However, if you find your system cycling too often, the DIFF can be adjusted to modify the cycle time.

• Press and hold BOTH up and down keys for three seconds. The display will flash, and DIFF will be displayed on the LCD.

• Press the up key to raise the DIFF to 3. This setting INCREASES to cycle time by allowing your system to run LONGER.

• Press the down key to lower the DIFF to 1. This setting DECREASES the cycle time by causing your system to run SHORTER.

The DIFF settings remain the same for both HEAT and COOL. The DIFF can be changed at any time and is independent of program times or temperatures. When batteries are installed in the thermostat, the DIFF is reset back to Setting 2.

Let me know if this helps. If it wasn't for Gordy this would've been overlooked.

PeteYour thermostat is set at the factory to cycle at 2ºF (1ºC) above and below the set temperature (DIFF = 2). This setting has been designed to provide a comfortable room temperature under most conditions. However, if you find your system cycling too often, the DIFF can be adjusted to modify the cycle time.

• Press and hold BOTH up and down keys for three seconds. The display will flash, and DIFF will be displayed on the LCD.

• Press the up key to raise the DIFF to 3. This setting INCREASES to cycle time by allowing your system to run LONGER.

• Press the down key to lower the DIFF to 1. This setting DECREASES the cycle time by causing your system to run SHORTER.

The DIFF settings remain the same for both HEAT and COOL. The DIFF can be changed at any time and is independent of program times or temperatures. When batteries are installed in the thermostat, the DIFF is reset back to Setting 2.

Let me know if this helps. If it wasn't for Gordy this would've been overlooked.

Pete

Sweet_Lew

I knew that... =P

I've read the instructions a few times to make sure I install it correctly. However, is that feature similar to an anticipator. I'm wondering if the temp will dip too much and make the house colder before it warms up again..What the hell, I'll install it this weekend and post back after a few days. I think you were right Pete and I should of got the White Rogers. Worse case I give the RS to my parents..

cattledog

Thermostat

Lew--



I think that you have several things to sort out to help you get your system tuned correctly.



First, there is the temperature at the thermostat location and in the different rooms in the house. I do not think that you can compare the 71F from the old thermostat to the new one, especially if you are comparing a mechanical dial to a digital readout. You may need to ignore the reading for awhile, tune the new controls to your comfort, and monitor fuel usage to see if you have really shifted the overall temperature and heat loss from your house.



I would also leave the use of "setback" and daily programming for later refinement once you have worked out the basic temperature and control strategy. Recovery from setback is a separate issue.



Second, once you have settled on a temperature, there is the stability of that temperature and the running behavior of the boiler.



There is one method of control which uses "differential" or "hysteresis" settings to control the turn on- turn off behavior. This may also be referred to as "bang-bang" operation. As others have said, you can usually extend run times by making the differential larger, but the downside is overshoot and undershoot of the desired temperature.



The other method of control uses "cycle time" or "cycles per hour" . This may also be called Proportional, Proportional-Integral (PI) or Proportional-Integral-Differential (PID) control. This is also called pulse width modulation (PWM) by some manufacturers. These thermostats control overshoot and undershoot by varying the boiler run times based on the difference from the setpoint ( within a proportioning band) and cycle time chosen. These thermostats usually give better temperature stability (less overshoot/undershoot) but tuning them for optimal boiler run times to heat all radiators and avoid short runs can be difficult. Some controllers allow you to set minimum run times and lock out times between runs which gives you more ways to tune the system.



I believe that your original Honeywell digital replacement used this second method, and if you wanted longer cycle times you should have changed the cycles per hour setting from 3 to 1.



You should be able to tune a digital thermostat to replace an older model. The Robertshaw may not get you there with its limitation to only adjusting the differential.

Some thermostats can be configured for alternate modes of operation--either differential or modulating to give you more freedom, but if the Honywell is really "cycles per hour" proportioning, and the Robershaw is variable differential, you should be able to experiment.



Good Luck

Sweet_Lew

WOW...

Thanks so much for that informative reply.

Yes, the Honeywell digital t-stat that I am currently using has a "CPH" setting. Currently it is set to 3 as specified in the manual for my type of heating setup (hot water boiler). So should I change the CPH setting to 2 and see how that works?

Also, as for t-stat set temp and room temp. Here is where I think the old mechanical was out of whack. I would set the mechanical to 71 and it was SUPER toasty downstairs and upstairs. I set the new digital to 74 (and then swings to 75 as it should) and the entire house is much cooler. I now need to run a space heater in my sons room where It would get almost too warm with the old t-stat.

I really appreciate all the help. I will change the CPH setting to 2 and see how that works. Then I will up the temp a couple more degrees to see if that helps as well. If that fails, then I may splurge and get a Honeywell Pro model or I'm going old skool and getting a mechanical with a heat anticipator.

Cheers!

Lew

Sweet_Lew

Update

So when I got home last night, I raised temp on the t-stat and lowered the CPH to 2 (that was as low as it would go). Woke up this morning the the house was indeed warmer and the rads felt warmer too. However, it was one of the warmest nights in a while (32 degrees). I'll keep the settings as is during the weekend and post back. It's supposed to dip into the teens at night...Along with an ****-ton of snow.. >=(

Cheers,

Lew

Sweet_Lew

Success

It has been in the upper 20s during the days and upper teens at night this weekend. The house is MUCH more comfortable now. Other than swapping out the Home Depot t-stat with a Honeywell FocusPro model, I think I'm good to go. Thanks again for all your help!



Lew

Peter_26

What model..

Glad to hear it! What model number is the new Honeywell? I'm thinking of changing my thermostat too.



Thanks,

Pete

Sweet_Lew

Models

I am currently using the Honeywell RTH230B:

[url=http://www.amazon.com/Honeywell-RTH230B-5-2-Programmable-Thermostat/dp/B000EW5U86/ref=sr_1_1?ie=UTF8&s=hi&qid=1265638013&sr=8-1]http://www.amazon.com/Honeywell-RTH230B-5-2-Programmable-Thermostat/dp/B000EW5U86/ref=sr_1_1?ie=UTF8&s=hi&qid=1265638013&sr=8-1



I will be replacing it with the Honeywell FocusPro 5000:

[url=http://www.prothermostats.com/product.php?p=honeywell_th5110d1006&product=100934]http://www.prothermostats.com/product.php?p=honeywell_th5110d1006&product=100934