Annual maintenance for high efficiency gas furnace

Posted by Jules on October 21, 2009, 3:05 pm

On Wed, 21 Oct 2009 11:53:37 -0500, BillGill wrote:

> Well, my manual has a differential given for the input/output
> air temperature.

Hmm, I'll take a more thorough look again later in case it's there and I
missed it.

I just checked some of the temperatures at the registers and I'm getting
a 17F differential between the ones closest to the furnace and the
ones furthest away, so there's definitely some scope for more insulation
around the ducts, as that seems quite a drop.

> I have been
> thinking of installing a pair of thermometers so that I can measure the
> temps at the input and output plenums. I just haven't seen a pair of
> cheap enough thermometers with a range from about 32 degrees F to 200
> degrees F.

I want to do the same, along with an outdoor thermometer, so I can
correlate indoor temps against outdoor, with it all hooked up to a PC
which does the data logging.

If you're handy with a soldering iron, one of the Dallas DS18S20 chips
will measure in the range of -67F to 257F and should cope with most
things thrown at it. They seem pretty simple to interface to. There seems
to be some useful info and schematic info here:

http://martybugs.net/electronics/tempsensor

although Google coughs up various alternatives... (I'm interested in an
RS232-based interface like the one on that site, but I suspect a lot of
folk would prefer USB these days)

It's one of those things on my to-do list that keeps on getting pushed out
of the way by more urgent stuff! :-)

cheers

Jules

Posted by BillGill on October 21, 2009, 6:30 pm

Jules wrote:

> On Wed, 21 Oct 2009 11:53:37 -0500, BillGill wrote:

>> Well, my manual has a differential given for the input/output
>> air temperature.

>
> Hmm, I'll take a more thorough look again later in case it's there and I
> missed it.
>
> I just checked some of the temperatures at the registers and I'm getting
> a 17F differential between the ones closest to the furnace and the
> ones furthest away, so there's definitely some scope for more insulation
> around the ducts, as that seems quite a drop.
>

>> I have been
>> thinking of installing a pair of thermometers so that I can measure the
>> temps at the input and output plenums. I just haven't seen a pair of
>> cheap enough thermometers with a range from about 32 degrees F to 200
>> degrees F.

>
> I want to do the same, along with an outdoor thermometer, so I can
> correlate indoor temps against outdoor, with it all hooked up to a PC
> which does the data logging.
>
> If you're handy with a soldering iron, one of the Dallas DS18S20 chips
> will measure in the range of -67F to 257F and should cope with most
> things thrown at it. They seem pretty simple to interface to. There seems
> to be some useful info and schematic info here:
>
> http://martybugs.net/electronics/tempsensor
>
> although Google coughs up various alternatives... (I'm interested in an
> RS232-based interface like the one on that site, but I suspect a lot of
> folk would prefer USB these days)
>
> It's one of those things on my to-do list that keeps on getting pushed out
> of the way by more urgent stuff! :-)
>
> cheers
>
> Jules
>

There was a time when I would have given serious thought to building
myself a monitoring system, but I have given up on it pretty much now.
Part of the problem is that I worked too long with professional electronics
equipment and the kind of stuff that you can home brew turns out to
mostly be rather simplistic.

Bill

Posted by Jules on October 22, 2009, 10:01 am

On Wed, 21 Oct 2009 17:30:10 -0500, BillGill wrote:

> There was a time when I would have given serious thought to building
> myself a monitoring system, but I have given up on it pretty much now.
> Part of the problem is that I worked too long with professional electronics
> equipment and the kind of stuff that you can home brew turns out to
> mostly be rather simplistic.

I hear ya - although I don't think it needs to be that complex for a home
anyway. I'm somewhat lucky in that our basement runs the full length of
the house, so it's quite easy to string signal wiring up for things, and
I've already got a PC sitting down there that's left on continuously
anyway.

The one I'm scratching my head over is how to (safely and legally!)
monitor the level in the propane tank - it'd be nice to not have to go out
and check the tank when it's 20 below out and there's a couple of feet of
snow on the ground :-)

cheers

Jules

Posted by Jim Elbrecht on October 22, 2009, 10:34 am

-snip-

>I hear ya - although I don't think it needs to be that complex for a home
>anyway. I'm somewhat lucky in that our basement runs the full length of
>the house, so it's quite easy to string signal wiring up for things, and
>I've already got a PC sitting down there that's left on continuously
>anyway.
>The one I'm scratching my head over is how to (safely and legally!)
>monitor the level in the propane tank - it'd be nice to not have to go out
>and check the tank when it's 20 below out and there's a couple of feet of
>snow on the ground :-)

2 thoughts that might be geeky enough for you.<g>

1. Web cam on gauge.
2. A series of temp sensors arranged vertically on the tank. The cold
ring is where the liquid is.

Jim

Posted by Jules on October 22, 2009, 10:48 am

On Thu, 22 Oct 2009 10:34:44 -0400, Jim Elbrecht wrote:

>
> -snip-

>>I hear ya - although I don't think it needs to be that complex for a home
>>anyway. I'm somewhat lucky in that our basement runs the full length of
>>the house, so it's quite easy to string signal wiring up for things, and
>>I've already got a PC sitting down there that's left on continuously
>>anyway.
>>The one I'm scratching my head over is how to (safely and legally!)
>>monitor the level in the propane tank - it'd be nice to not have to go out
>>and check the tank when it's 20 below out and there's a couple of feet of
>>snow on the ground :-)

>
> 2 thoughts that might be geeky enough for you.<g>

heh heh :-)

> 1. Web cam on gauge.

You might not be surprised to hear that I'd already thought about it ;)
Problem is webcams within a reasonable cost range all seem to be USB,
which has distance limitations - plus they may be prone to fogging and not
even survive the temps down to -30F that we can get in winters up
here. I wouldn't mind paying some serious money for an IP-based camera for
things like security purposes, but the "inconvenience" here just isn't
enough to justify it for something that's just going to be forever
pointing at a tank gauge.

Maybe I can get a remote gauge - I'll prod the tank company about that
sometime. Then it could be put indoors where there are no weather or
cable-distance issues...

> 2. A series of temp sensors arranged vertically on the tank. The cold
> ring is where the liquid is.

Hmm, interesting idea! It'd work in Summer, but I'm not sure if I'd be
able to detect it when the outdoor temperature gets seriously cold...

The tank monitoring's low priority in a way simply because it is more
complex and I don't want to devote the braincells to it when I've got lots
of other stuff to do - but it's still interesting to plan it all out...

cheers

Jules

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Annual maintenance for high efficiency gas furnace - Page 3