Annual maintenance for high efficiency gas furnace

[blueman]

We have a couple of high efficiency, condensing gas furnaces with forced hot air used to heat our home.

So far, every year at the start of the heating season, I have been doing the following for maintenance.

1. Thoroughly vacuum out the interior
2. Clean the condensate pump of accumulated crud
3. Wash the air filter (it's a simple low-end washable one)
4. Inspect for cracks, loose wires, funny noises, etc.

I have a CO detector mounted near all the heaters.

- Do I need to clean the burners, igniters, heat exchanger, etc? Or are they best left alone if everything is working properly

- Is there anything else I need to be doing from a regular maintenance perspective?

- Is there any need to call in an official HVAC person for (additional) preventive maintenance?

Thanks

[ransley]

Wont a cheap air filter bypass alot of dirt and coat the heat exchanger reducing its efficency, at least thats my thought so I use the 4" media, have you ever cleaned the heat exchanger, are burners burning right, is exchanger temp in the proper range, how about the blades on the blower fan, are they clean, if dirty that would indicate a inefective air filter. Im no pro but im sure there are even more things to do.

[ransley]

I had a friend buy a house, I dont know if it the furnace was run without a filter or just a bad one, but the AC coil was so clogged he was getting almost no heat. We removed the AC coil until he cleaned it next spring. A crappy air filter can trash an AC unit. With a condensing unit checking exaust temp should tell you alot about the unit, I dont know what range it should run at, but to high would indicate its not efficent. I think poor-cheap air filtration is the quickest way to ruin a furnace and cut its efficency way down.

[RBM]

I would expect the manual that came with the unit, or goes with the unit will answer your questions. If you don't have it, you can probably get one online. Personally, I would never open up a condensing furnace/boiler, unless something goes wrong

[BillGill]

I'm not sure what kind of furnace you have, but the pros aren't going to inspect the fan, at least not in the one I have. Inspecting the fan requires rather extensive disassembly. I don't know about the burners, but I don't think they are easy to get at. In all about all the pros can do would be to check flow and temperature rise. And I'm not sure about temperature rise. There is no convenient place to put a probe just before and after the furnace. They would be pretty much limited to the air at the return vent and a supply vent.

In fact I think almost all they can do is to replace the filters with their overpriced filters.

Bill

[Big_Jake]

I can get a pretty good look at my fan just by taking the door off the blower compartment. Temperature rise is a snap to check, with a probe type thermometer. You just use a sheet metal screw (1/2" x #6) like they use to install the bulk of the sheet metal around the furnace, to punch a hole in the cold air drop and plenum, and test with the thermometer. A meat thermometer could be used in a pinch.

JK

[BillGill]

Well, taking the cover off of the blower compartment on mine involves removing the air intake and exhaust lines that run down in front of it, and then unmounting the control circuit board that is mounted on the cover. Not something to be undertaken lightly.

I realize that I could do something like your description of the temperature test, but the average tech isn't going to take the time to go punching holes in the plenum to do it.

Bill

[Jules]

JOOI, how do you know when it's good or bad (other than obvious cases!) - do manufacturers typically publish plenum temps for their furnace against a range in input temps, or is there a rough rule of thumb for a given furnace size? Or is it a case of monitoring it year to year just so you know when performance is off against previous years?

I've got a temp probe on my meter so could easily measure mine, but it doesn't tell me much other than that it's producing warm air (which of course I know anyway :-)

cheers

Jules

[Bob Villa]

a range in input temps, or is there a rough rule of thumb for a given furnace size? Or is it a case of monitoring it year to year just so you know when performance is off against previous years?

If the furnace guys left the installation guide (or asked them for it).

I installed the Carrier I have (all work except sheet metal)...so I know the information is there.

I also worked at a hardware store once and the boss had a new gas boiler delivered...he left for the day and said to install it! (I didn't have to go far for pipe)

bob_v

[Jules]

Yeah, I have it - doesn't list plenum temp from what I can see, though. I think I'll measure and make a note of it anyway, then I can check in susequent years (the furnace was installed in 2007, just before we bought the house, so it *should* be operating pretty much optimally right now!)

Actually, I need to insulate around some more of the ducting anyway (much of it runs through the basement, which gets pretty cool) so it'll be a useful exercise for seeing how much heat is getting lost before it even gets as far as the rooms...

cheers

Jules

[BillGill]

Well, my manual has a differential given for the input/output air temperature. There is a range for normal operation. There is also an absolute maximum for the output. I assume that the output temp is going to be the same as the plenum temp. 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. That range is so I can also do a confidence check on the cooling in the summer.

Bill

[Jules]

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 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:

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

[BillGill]

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

[Jules]

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

[Jim Elbrecht]

-snip-

2 thoughts that might be geeky enough for you.

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

[Jules]

heh heh :-)

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...

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

[ransley]

I just drilled a hole and was carefull about the AC, getting it at the top of the exchanger is important, go up maybe 1ft and temp drop is alot

[blueman]

If tank is above ground, you could add a strain gauge and measure weight...

[blueman]

Interestingly, one of our 3 units is a York and they seem to have good quality downloadable manuals. The other 2 units are American Standard and I can't find any manuals online. American Standard has also yet to reply to an email request for manuals. Note: we don't have the original since the previous homeowners didn't pass it on.

[DerbyDad03]

re: "how to (safely and legally!) monitor the level in the propane tank"

1 - Call your delivery guy and have him fill the tank up to the max. On that day you can write down "Full" in your book.

2 - Keep track of how many hours you use the appliances that use propane.

3 - Use the propane until the stove and furnace will no longer produce any heat. At that day you can write down "Empty" in your book.

4 - Call your delivery guy and have him fill the tank up to the max. On that day you can write down "Full" in your book.

5 - Don't use your appliances for as many hours before calling for a refill.

QED