Jane Galt <
Ja...@whoisjanegalt.net> wrote:
> The problem is, by the time [the humidifier] comes on, it can stay on
> for hours. This causes what they call "stacking" in the water heater,
> as it draws a tiny stream of hot water from the top, causing cold
> water to come in the bottom and trigger the gas burner, but then the
> top water overheats and gets WAY too hot, if it keeps running for
> hours.
Are you sure the humidifier is operating correctly and is sized
correctly for the house? Assuming the humidistat is operating
correctly, if it wants to run the humdifier for long periods of time,
maybe the humidifier isn't working as efficiently as it should be. Or,
maybe the humidistat isn't working right, and replacing it would help.
> And yes, we've thought of turning the water heater down - the problem
> is that when the humidifier isn't running, then the hot water is the
> minimum temp we need it, so it would be too cool to sustain a shower
> if we set it any lower.
You can get a small electric circulator pump that connects to the hot
water line and pumps water back to the water heater. This would
probably even out the temperature in your water heater, and also give
you hot water quicker at the faucet.
Or, you can get small water heaters that are designed to run a single
hot water faucet, either tank-type (a few gallons) or instant. Maybe
installing one of these to serve just the humidifer would help.
> So what I'm thinking, is we could put a timer in series with the
> humidistat, which uses 120VAC in the series loop.
You could use a plain old light timer - the kind that lets you set an
on or off for every hour of the day - in the 120 V supply to the
humidifier. Set it for 1 hour on, 3 hours off, around the clock.
This is easy to do (it doesn't need current sensing), but has the
disadvantage that when the humidistat calls for humidity, the timer
might be in its "off" cycle for a few more hours.
On the other hand, adding the timer is probably going to make the timer
the dominant variable in the equation. If the humidistat calls for
humidity for several hours, the timer will prevent the humidifer from
ever satisfying the request, unless the humidity in the house goes up
for some other reason. So the humidifer will just cycle on and off
with the timer.
> It would have to be a series thing - sense that 120vac current was
> going through it, let it go for an adjustable time, then shut off for
> an adjustable time, then let it go again.
The timer also has to default to the "on" (contacts closed) state, so
it can tell if the humidifier is drawing any current or not. It doesn't
start the clock until it sees the humidifier drawing current, but the
contacts have to be closed so the humidifier *can* draw current.
I don't know if you can get a timer that does this all on its own. I
know you can get current sensing relays that close a set of contacts
when they detect current in another wire; Aprilaire even makes one for
enabling the humidifier with the furnace blower on furnaces that don't
have separate humidifier terminals, and "general purpose" ones are
available from Functional Devices
http://www.functionaldevices.com/building-automation/currentsensors.php
and probably others. Once you have the current-sensing relay, you'd
have to add a timer to it, maybe using a time-day relay. Amperite
http://www.amperite.com/search/search.aspx and other vendors make
these.
Again - if this is a widespread problem, I think Aprilaire would
probably sell it as an add-on box, or as a feature on a high-end
humidifer. So maybe adding a timer isn't the way this typically gets
solved.
Standard disclaimers apply; I don't get money or other consideration
from any companies mentioned.
Matt Roberds