# with all bedroom doors shut does thermostat read correct temp?



## Scuba_Dave (Jan 16, 2009)

windowguy said:


> Here's a scenario. Thermostat is in hallway of 3 bedroom second floor forced air system. I usually leave all the bedrooms open for good airflow throughout the second floor. We had relatives stay over recently so all three bedroom doors were shut at night. In the middle of the night when the thermo kicks on its blasting those bedrooms with heat (the hallway has no supply registers, only return). Isnt there a lag between the heat of the bedrooms and the hallway thermostat when the doors are closed?
> 
> If my thermostat is set at 70 i'm imagining those bedrooms with the doors closed must get to 75 before the heat "reaches" the hallway. I think almost all houses have a similar set up (supply in bedrooms, thermostat in hallway).
> 
> ...


Without a supply duct in the hallway the bedroosm could go much higher then 75. If the doors are solid wood it will take a while for heat to go thru the doors. Usually there is a space under the door - but you will be sucking the cold air near the floor out.
Most houses have the thermostat in an area with a heat supply or one nearby that can't be blocked


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## windowguy (Jan 27, 2009)

I have hollow masonite doors with about a half inch clearance on bottom of each one. So i'm right, those rooms are sweltering with the doors closed. What happens when i have a baby in that room with the door closed so he can sleep???

Seriously, do most houses have a supply in the same hallway that the thermostat is in? i don't think i've ever seen it before (or common).

If i find this to be pretty bad i guess i'm going to have to tee off of one of the bedrooms and put a supply in the hallway. How come my house wasn't built that way? (3 years old). There has to be a reason why the thermostat is in the hallway, it's because it's centrally located for temperature "even-ness" right? But that idea is worthless if the doors are closed. What family doesnt have children who want their doors closed?


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## Grampa Bud (Apr 6, 2009)

I used to have much the same problem. My stat was down a 3' hallway between three bedrooms. The living room and kitchen were the only permanently open rooms to the hallway and the only return was in the ceiling at one end of that hall. I had the stat anticipator adjusted so the temp in the bedrooms followed the stat as long as the doors were open. Problem was that i could not balance the temp between the bedrooms and the livingroom. I almost went to zoned heat. Instead I moved the stat to the livingroom and readjusted the anticipator to make the livingroom track the stat. Now the general living areas of the house track the stat for both heat and A/C and the bedrooms are 3-4 degrees warmer in winter and 4-6 degrees cooler in summer; just the way we like it.


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## kenmac (Feb 26, 2009)

I like some of the older homes where they had a return in every room.




We use to have alot of old floor furnaces around here.. They would install a thermostat in the bedroom.. Floor furnace would be in the living room. With the door closed the heat would never reach the t.stat to turn furnace off. Code stated thermostat couldn't be installed in a room with a door that would seprate t.stat from floor furnace .. While not exact wording.. it's close


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## Scuba_Dave (Jan 16, 2009)

I think I'd be tempted to just move the thermostat into the largest room. Our current 2nd floor setup will be mostly a Master bedroom. Radiant heat in the Master Steam bath & directly outside along the window. Then a 600w towel heater in the 2nd bathroom
Most of our heat will simply be hot air rising up the stairs from the 1st floor. We have forced HW heat


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## beenthere (Oct 11, 2008)

I'd just balance the air flow to those bedrooms.
Install or have balancing dampers installed if the supply lines don't already have them.


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## windowguy (Jan 27, 2009)

balancing sounds like a good idea, but if you really think about it that doesnt solve the problem, it just makes it slower. slowing the heat to a bedroom just brings that room up slower, it's not like it makes the hallway warmer (remember no supply to hallway). So same situation, bedroom 75+ degrees (with door closed) before thermostat (in hallway) hits 70.

Its a 2nd floor with 3 bedrooms and a bathroom on its own zone. No big open spaces like living ro0m or kitchen. What you're basically heating is 3 closed boxes and the thermostat is outside that box. 

Grampa yours sounds good, warmer in winter, colder in summer but my room temp differences are way more extreme than yours. I think i'm going to research a hallway supply a bit more, and i'll set it up so i can adjust the hallway supply because i don't want the hallway supply shutting off the thermostat too soon (by blowing too close to it).

Uggh.. what a pain.


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## beenthere (Oct 11, 2008)

By slowing the air to the bedrooms. You increase the air to the other rooms.

So the other rooms heat up quicker. Which in turn heats up the hallway quicker.
So the thermostat shuts off the heat quicker, so you don't end up over heating the bedrooms.


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## windowguy (Jan 27, 2009)

beenthere said:


> By slowing the air to the bedrooms. You increase the air to the other rooms.
> 
> So the other rooms heat up quicker. Which in turn heats up the hallway quicker.
> So the thermostat shuts off the heat quicker, so you don't end up over heating the bedrooms.


How am i increasing air to the other rooms? What other rooms? There is no other supply on the entire floor besides the bedrooms. (not counting bathroom). I said above its 2nd floor, seperate zoned, 3 bedroom + hallway space. The supply for the entire floor is THROUGH the bedrooms. There are no other rooms to heat up quicker to heat up the hallway.


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## beenthere (Oct 11, 2008)

I missed that its a completely separate zone/system for those bedrooms and bath only.

A supply in the hallway would help then.

But, many times, relocating the stat to the master bedroom does better.


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## windowguy (Jan 27, 2009)

beenthere said:


> I missed that its a completely separate zone/system for those bedrooms and bath only.
> 
> A supply in the hallway would help then.
> 
> But, many times, relocating the stat to the master bedroom does better.


 
Which would you try first? i'm guessing a remote thermostat? because that doesnt involve cutting open any walls and ducts first. i'll try the thermostat first, i'll give that a whirl for a season and if that doesnt work i'll add another supply. i did a quick google on thermostats and i think i can retrofit my existing one with a a "duel" one that's wireless to my bedroom or something like that.. if anybody has any links or suggestions i'd appreciate it.


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## beenthere (Oct 11, 2008)

Honeywell has some wireless ones.
A bit expensive though.

A thermostat with a remote sensor would work as well, and cost less.

I'd do the thermostat first.


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## Grampa Bud (Apr 6, 2009)

How big is the attic space above your 2nd flr hallway? Can you easily getup there and work up there? Is the return at one end of the hallway? Is the other end of the hallway ceiling free of light fixtures or scuttles or drop down stairways to the attic? Since you seem to have a single stat for the entire 2nd floor if you have access to the furnace supply plenum(s) for those rooms and the return is on one end, you could possibly cut in a register the size of one of the registers in one of your bedrooms at the farend of the other end of your hall. The heat coming up your stairway would have to be disregarded for this and you would have to adjust your anticipator on the stat so the hallway thermometer would track the stat temperature setting with the three doors closed, but I think you will wind up much more comfortable in those rooms with the doors closed or open.


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## windowguy (Jan 27, 2009)

Grampa Bud said:


> How big is the attic space above your 2nd flr hallway? Can you easily getup there and work up there? Is the return at one end of the hallway? Is the other end of the hallway ceiling free of light fixtures or scuttles or drop down stairways to the attic? Since you seem to have a single stat for the entire 2nd floor if you have access to the furnace supply plenum(s) for those rooms and the return is on one end, you could possibly cut in a register the size of one of the registers in one of your bedrooms at the farend of the other end of your hall. The heat coming up your stairway would have to be disregarded for this and you would have to adjust your anticipator on the stat so the hallway thermometer would track the stat temperature setting with the three doors closed, but I think you will wind up much more comfortable in those rooms with the doors closed or open.


 
I answer yes to almost all the above questions. very open access to atic. return is at end of hallway same side as thermostat. i could pretty easy cut a supply at other end of hallway and tee off somewhere. But i would be tee-ing off of one of the bedroom supplies because the furnace is ALL THE WAY at the opposite side of the where the new register would be.


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## Leah Frances (Jan 13, 2008)

Ask a silly question.. get a silly answer.. but why not just set the hall temp to 65? 

According to your estimate then the bedrooms should get to 70 (if that's your desired temp.).


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## Grampa Bud (Apr 6, 2009)

Are all the bedroom supplies individual (homeruns) runs from the furnace, or is there a trunk line 
-about 10x16- extending part way down the length of the hall? You can actually branch off of either, but depending how gianormous the hall is the trunk would be better. Or just run another homerun supply from the supply plenum at the furnace. However you pick it up make sure it is as far away from the stat as the return, adjust the stat so the hall temp tracks the stat with the doors closed, and then check the temp in the closed bedrooms. They should all be within a degree or so of the hallway.


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## DUDE! (May 3, 2008)

Leah, nice answer, to me anyway, this is one of those times where it seems to have gotten lost in the shuffle, if its too hot at night in those closed off rooms, turn the stat lower, done deal. This arose after having guests stay over, we all have our own comfort levels.


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## windowguy (Jan 27, 2009)

Leah Frances said:


> Ask a silly question.. get a silly answer.. but why not just set the hall temp to 65?
> 
> According to your estimate then the bedrooms should get to 70 (if that's your desired temp.).


 
It does sound simple enough, and worth a try as a the simplest fix, but for your idea to work you are assuming that then the doors are closed to the BRs all the time, in real life it just doesnt work that way. (yes i know programmable thermostat at 10 pm assuming everyone is sleeping with closed doors). Also with your way i'm creating a colder hallway then. but of course that's better than uncomfortable BRs.

i'm willing to put in the effort to get an even temp in the hallway as well as the BRs.


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## Grampa Bud (Apr 6, 2009)

All I was assuming -right or wrong- was that the hall volume with the doors closed is about the same as one of your bedrooms + the stairway. If you do not want to move the stat then a quicker heat up of the hall, will over two or three heat cycles, leave the bedrooms cooler. A lot of people make the mistake of figuring a heat cycle covering a temperature range from the outdoor temp to the desired set point on your stat. Hopefully that only happens on initial start up. The rest of the time you are only dealing with 4-6 degrees during any one heat cycle.


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