My mother's new townhome has an annoying problem on the bottom level. The smoke detector seems to beep at slow intervals when the room gets cold. We've tried replacing the battery, and she had someone come by to replace the detector, but it's still doing it. Do they all do this? So far I've only come across this explanation.

Normally the solution would be simple, just raise the heat in the room. But this is the basement (where the home theater is), it's the summer so the AC is on, and the thermostat is on the top of the three floors on that system. So the heat rises, the thermostat says to cool, and the bottom floor, which was already five to seven degrees cooler than the top, gets even colder. I've been in there when it was 72 on the floor with the thermostat, and 58 in the basement.

She and I always seem to get different stories depending on which HVAC person we talk to. Is it okay to close vents to force the air into different parts of the house? I, for one, close all the vents on my first floor in the summer and open the ones on the second, where it's always 10 degrees hotter.

So this is somewhat two parts: is there anything we can do about the detector, and is it okay to close a large number of vents to control the airflow?

Hi,

If it was non-battery powered, you could place a resistor local to the detector to pre-heat the surrounding air. The resistor wouldn't have to burn hotc at all, just lightly warm in the confined space of the Smoke Alarm cabinet to add a few degrees of local thermal rise.

Unfortunately, it would also drain your battery.

The safety of such an idea would depend on the individual circumstances and would possibly violate the UL certification of the Smoke Alarm - depending on the flamability rating of the Circuit Board (should be 94V-0 anyway) and the assembly should be 94V-2. I don't know what the plastic is rated. The power source for the resistor, resistor placement, insulation, interconnect wiring as well would have to meet UL and probably an need Alternate Construction Letter approved by UL or the certifying body.

If there was a fire, the modification would come into question, the Insurance Company would freak and deny payment because the Smoke Alarm was tampered with, you never forgive yourself because she's destitute and has to live with you because it was your fault ...

Okay, Okay, STOP!!!! Bad idea, go to your room.
Yes, Master. <grin>


Too bad a manufacturer can sell us a product that is THOROUGHLY CERTIFIED and yet have this basic problem isn't it?


Ross

Lithium batteries are supposed to perform better than alkaline batteries at low temperatures. Maybe try replacing the battery with one of those? (9V lithium batteries are a little hard to find, though.)

58?! Damn, that's uncomfortably cold. The coldest I've ever had our house, while I've been in it, is just under 61 (16 Celsius) and we've not had any issues of beeping smoke detectors (wired). They do beep when the power goes out and then again when it coms on.

Apart from replacing the detectors with a different brand, I also recommend making sure to keep room doors open all the time as well as running the HVAC fan at all times to help circulate the air in the house. You're seeing an enormous variation in temperatures between floors, and to me, that's a much bigger problem and implies a poorly designed (and/or implemented) HVAC system.

You can try to close vents strategically to improve air flow to certain parts of the house and you can also try an remote thermostat to monitor temperatures on the top floor. If airflow is low from some vents you can also install in-line duct fans to help pull more air. You may also consider getting in another HVAC company to independently audit the system - it just doesn't sound right to me that you'd have that kind of variation from floor to floor.

Is this a CO detector as well as a smoke detector? I think they are more sensitive to things like cold and humidity and tend to beep a lot more for spurious reasons.

Of course it's OK to open/close vents to control airflow. What do you think those vents are there for, anyway?

But to raise a slightly different aspect here... what kind of a lunatic system does your mother have that has a single control zone (i.e., thermostat) for a three-story house? You are just about guaranteed that anyplace you go in the house you are going to be either too hot or too cold.

In Alaska, the weather conditions are incomparably more extreme than in Virginia (temperatures can vary by 170 degrees F or more summer to winter), and the hvac systems are designed accordingly. My house had two stories, and six separate, individual thermostatically controlled temperature zones. The furnace (no a/c) was a computer-controlled Buderas system that monitored outside air temperature and set the boiler temperature accordingly. The Buderas burned about 25% less fuel for the same size house as a conventional (and far less expensive) system might. See the attached picture. My apologies for the mess, the basement was being remodeled and everything got dumped into the furnace room. The point of this rambling discourse is that I could heat my 3400 square foot house for what most of you would consider a staggering amount of money (average about $3,000 per year) but some of my cow-orkers were spending three times that amount on houses half the size. In Winter time I would frequently have a room 30 degrees colder than the room next to it (all the inside walls had 4" insulation) if I wasn't using that room. No sense in heating empty space! Your mother's system is not only badly designed for comfort, it is badly designed for economy of operation. It's like an ink-jet printer: Cheap to build/buy, expensive to operate.

You may be able to alleviate the problem considerably by judicious adjustment of airflow, but it may turn out to be a continual process as the seasons change.

tanstaafl.

Addressing some comments:

- it's actually a five story townhome, but I left out the top two floors because they don't have these temperature problems, and they're a different system.

- the detectors are not also CO detectors. We had to get some of those and place them around the house as well.

- there are no closed doors anywhere in the house but closets. In fact, there isn't a single door between any two floors in the entire home. There should be a great amount of air flow.

- she recently had a complete audit and cleaning of the entire system. They didn't see anything wrong

- I don't think I'll tamper with the detectors

The reason I asked about closing vents is because while I figured it's okay to close a vent or two (maybe you're sitting near one and don't want it blowing on you), I wasn't sure if it was okay to close entire floors off. The last HVAC guy that came out to her home opened all the vents that I had closed. In the winter I closed the vents on the top two floors of the 3-story system, because no heat was coming to the bottom floor before the top one got warm enough for the thermostat. But this guy didn't like that.

I've had beeping smoke detectors as well. Inevitably, replacing the 9V battery with a new one solved the problem. Of course, they're most likely to start beeping in the middle of the night when you have the heat down in the house...

I should have also mentioned that we replaced the 9v battery first. That didn't do a thing, and the battery that was in there tested as having a nearly full charge.

You did say that.

Indeed. At least for us, battery replacements have worked well.