New thermostat not allowing boiler to stay on long enough to heat radiators on house third floor?

RonnieO

For about 22 years, we have lived in Chicago in a 1906 3-story single-family brownstone with steam radiator heat. The system has been maintained by a well-known HCAC contractor with a lot of steam heat knowledge/experience. Several months ago the house's programmable thermostat failed; it is located in the middle of the second floor. I installed that thermostat myself, maybe 10 years ago. When the old thermostat failed, I installed a Honeywell RTH7600, and programmed into it essentially the same temp settings that I had on the old thermostat. In prior years, the temperature on third floor, where my wife and I sleep, has been just fine. The radiators were sufficiently warm/hot and so they radiated a sufficient amount of heat. But now the third floor is staying uncomfortably cold because the radiators on the third floor are no longer sufficiently warm/hot, and so they are not radiating a sufficient amount of heat. Those third floor radiators only seem to be getting sufficiently warm/hot first thing in the morning, when we are transitioning from the nighttime temperature (62, I think) to the morning wake-up temperature (66)—a shift that necessarily keeps the boiler on longer, allowing those third floor radiators to heat up. I "blame" the uncomfortable third floor temperatures on the new thermostat. Granted, I'm an uninformed lay person, but I am used to my boiler/radiator sounds after so many years in the house, and it seems as though the boiler isn't staying on long enough. Maybe that's a consequence of greater efficiencies in the thermostat, but, again, it's making the third floor a place we go only to dive under the (extra) bed blankets. Other than that, it's sort of become unusable space. I called Honeywell this morning and they said there's nothing I can do. Is that true? If so, any other solution—different thermostat, get a contractor in to check it out. etc? Thanks—and Happy New Year!

BobC

Have you got that thermostat set up for steam? Someplace in the initial setup it askes you what kind of system you have - hot air, baseboard, or gravity hot water /steam. You want to be sure ut's set for gravity hot water / steam so the boiler cycle will be about 1 hour.

Most thermostats come set for hot air (4 - 6 cycles per hour), you have to make sure it's still not set for the default. I use the RTH6450 and I had to change my defaault setting.

Bob

KC_Jones

setting 0240 should be at "1". This is in system setup. If I have the right manual it's on page 18 of your installation instructions.
https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-2206ES.pdf

Abracadabra

A setback on a steam system is not really saving you much money. When I hear that "radiators are not really getting hot except in the morning during recovery from setback" I think a venting or wet steam. What type of a steam system is this? Pics of near boiler piping? What's your main vent situation? Vents on 3rd floor good?

RonnieO

Thanks. First I'll check to see if my heating cycle rate is at 1. I don't recall whether I set it at 1. if that doesn't seem to result in any improvement, I'll provide further data and/or pics. And in response to Abracadabra, I haven't noticed any venting or wet steam issues at the third floor or at any other floor. Generally speaking, but for one past boiler failure and one past radiator crack, this system has been very reliable. Thanks, again.

vaporvac

You may also have mis-wired the new Tstat and thus, you won't be able to set to one CPH. I had a similar thing with mine. The setting wouldn't hold. They also have multiple internal sensors so don't bother testing the temp against another measure as they won't match. It gives an ambient temp based on temp, humidity and radiant temp (or something like that). I called and talked to their tech support. Don't bother with the regular customer service people. They had someone check out a pic of my wiring, etc. EXTREMELY helpful.

RonnieO

Yesterday may not have been the ideal day to tinker with the cycle settings, with temps around 0, and it also may not have been the ideal day to try to gauge whether changing the cycle setting fixed the problem, but it was set at 5 when it should have been set at 1, it was easy to effect that change, and making that simple change seemed to effect a near-immediate change in the third floor temp as those third floor radiators actually did become warm and radiate heat when the boiler cycled on. So--bottom-line--thanks so very much for what seems to have been key, correct advice (when the Honeywell representative told me there was nothing I could do to address the problem!).

Dave_154

You might find a setting of 2 keeps you more comfortable. I find that 1 creates a bit too much of a temperature swing.

SWEI

Any particular reason they don't have a 1.5 setting? Seems reasonable to me, given the huge step between one and two...

norb

i have a Honeywell , i believe, rth4100d----after reading this, i checked mine ( I had recently had a new WeilMclain boiler installed and they also installed this thermostat). Upon checking the mode it was in---it turned out it was set at 5 ( the default mode "for boilers with an efficiency below 90%)---this must be a catch-all mode------I changed it to the Number 1 setting for steam gravity systems per the instructions and per this heating help forum. The heat seems to be even better , getting to all the rooms very well. What exactly is going on here with the cycling of the boiler with a setting of 1 versus the default setting of 5? or is the heat better due to the very cold weather we are now having ( causing the boiler to run more) ?

Fred

The setting of 1 means the boiler will run 1 cycle every hour. That cycle will be long enough to heat all the Mains, the radiator runs and the radiators more evenly. The boiler may run anywhere from 10 to 20 minutes and use the hot radiators to continue to heat the romms for the remainder of that hour but allow the mains and rads to cool down enough to allow the vents to all open and be ready for the next heating cycle.
A setting of 5 means 5 cycles per hour, twelve minute cycles, usually 6 minutes on, 6 minutes off. Just not enough time to really heat the mains, runs and rads like they need to be for effecient operation. That 5 setting is designed for forced air furnaces. Enjoy!

norb

thanks----what a difference with the setting of one

Dave_154

Setting of 5 on a steam boiler equates to 'heating the basement', nowhere else.