My new furnace plus tankless install with pix!

[johnt2_2002]

I didn't have a good look at pic 2, its clearly 2"--my bad!

[commerce48]

Ok, if you say so. I guess its the angle of the pics that's throwing me off in regards to the vent size for the furnace. But to me its very strange that the furnace is as wide as it is for only a 40000 btu unit. Perhaps you can verify by pulling the front cover off and looking at the data plate--just to ensure the input is 40,000btu and not larger--just for peace of mind

I'm OK, remember I saw the air pathway before the furnace was installed. But for your peace of mind, here is the sticker picture.

[johnt2_2002]

I'm OK, remember I saw the air pathway before the furnace was installed. But for your peace of mind, here is the sticker picture.

LOL, alright thanks. I'm sure you spent a lot of money on your installation and expect the best performance and service---just want to make sure you got what you paid for!!---As long as your happy, I'm Happy!

As for the tankless unit, and I know you have water treatment, ensure it is flushed and maintained annually as well.

[commerce48]

Such fun. What size return air at filter into furnace, 20 x 25? What reduced size before filter, 12 x 25?

The original return drop was 16 x 20. The new return drop is swedged down over 5" to 10 x 20 rectangular piece for 8 inches and then widens to 25 x 10 for 4" before the final transition into a 16 x 25 filter box (and a 16 x 25 Merv 10 media filter).

It is a little strange, but it is pretty much what they had to do. The installer called in what he wanted to the company shop (this is a larger local company) and installed the new return the following day - they hadn't originally planned on replacing the final drop until they realized how strangely this furnace is configured. In hindsight, they could have made the new drop a few inches wider, say 12 to 14 instead of a 10 inches, but it is still more than sufficient for the furnace return requirements.

They also originally brought out a larger filter box and would have installed it if I requested it. But that would have been a bit silly as the 16 x 25 filter box matched the return cutout on the furnace box.

[commerce48]

LOL, alright thanks. I'm sure you spent a lot of money on your installation and expect the best performance and service---just want to make sure you got what you paid for!!---As long as your happy, I'm Happy!

As for the tankless unit, and I know you have water treatment, ensure it is flushed and maintained annually as well.

I'm happy so far (crossed fingers). As to the tankless maintenance, I'm going to keep my eye on it, but I'm hoping annual flushing can be lengthened to two years or more. I live alone (sigh) and probably use less than a fifth of the water of a typical install annually.

[hvacvegas]

I'm happy so far (crossed fingers). As to the tankless maintenance, I'm going to keep my eye on it, but I'm hoping annual flushing can be lengthened to two years or more. I live alone (sigh) and probably use less than a fifth of the water of a typical install annually.

Which is exactly why a tankless is perfect for you. How do you like it so far? How long does it take for the water to get hot at the facet?

[commerce48]

Which is exactly why a tankless is perfect for you. How do you like it so far? How long does it take for the water to get hot at the facet?

I like it fine so far. The water is a much more stable temperature than the old tank heater. I take showers with hot water only, seems a bit silly to me to heat water up and then cool it down by diluting it with cold water. So I can set my shower temperatures to the exact temp I like, and change it for dishes or clothes.

Water takes the same exact time to get hot at the faucet as stored water with a few twists. I can enable or disable the internal circulating pump and storage tank from the thermostat. Enabled, hot water is ready with no more delay that an ordinary tank, just the static volume in the pipes from the heater to the faucet have to be flushed as normal.

Disabled, the Navien, just like every other tankless heater, requires a half a gallon of flow before it starts heating. So that means that an extra half a gallon of cold water in addition to the pipe volume before hot water hits the faucet. This is where the so-called cold water sandwich comes from. If hot water has reached the tap, and you turn it off briefly, there will be a half a gallon of cold water that "sandwiches" the hot water.

In addition, all tankless water heaters require a half gallon per minute minimum flow to operate. Except for the Navien if the internal buffer tank and circulation circuit is enabled. Then you cannot have a cold water sandwich and the water will be hot at any flow rate, even a drip. This feature also allows a slow and intermittent filling front loading washer (such as I have) to get hot water - otherwise I'd be stuck with only cold water washes.

So why would I ever disable the Navien's cool internal circulating pump? Because as small as it is, I resent the energy loss of the internal buffer tank. In addition, the cycling is potentially annoying with the burner fire up routine and somewhat noisy spinning of the circulating pump. The Navien has a programming feature in the remote stat to limit circulating to certain times of the day. This is probably especially useful to those people who set up an external return circuit to, say, their bathroom or other taps. Then there is zero delay in hot water to the tap, but this luxury means a significant energy hit because of hot water continually circulating in the pipes. So you can limit that loss to the times of day when you are likely to be awake and at home.

For me, my schedule is erratic and I find it easier to just turn it on and off manually when I'm washing dishes or clothes (both of which are weekly or longer periods typically for me). Showers don't matter as I'm not stopping and starting flow.

[beenthere]

Known furnace output. Timed the runs over two hours while outside temp stayed a consistent 5 degrees.

Guessed at furnace output.

You didn't check CFM, temp rise, and colorimetric value of the gas while using the old furnace, to check what the True BTU output was.

They could have installed the air filter in the drop, then they wouldn't have had to reduce the return. Not a big deal. But wold have been better for getting the most usefull life span from the air filter. While maintaining a low ESP. Not a big deal though.

Would have been better to transition to the A/C coil, instead of setting it on the furnace and blocking the side of the furnace off. Not a big deal.

If your running a .46 ESP at 700 CFM in heating mode. If your A/C wants to move 800 CFM, then your ESP will be above .7 in cooling mode with a clean/new air filter.

Overall. looks like they did an above average install.

[energy star]

If your running a .46 ESP at 700 CFM in heating mode. If your A/C wants to move 800 CFM, then your ESP will be above .7 in cooling mode with a clean/new air filter.

Isn't that a bit high?

[kenney t]

Isn't that a bit high?

yea beenthere how bout when coil is wet?

[beenthere]

Isn't that a bit high?

Do you mean that you think I said the ESP will be higher then it really will be. Or that .7" is too high?

.7" on a clean filter is ok, under .7" would be better, and allow the air filter to load up more.

Vanes in the return ell would/will help to reduce the ESP.

It would have been better if they had taken static readings on the old furnace, before installing the new one. And then taken static readings of the supply and return after installing the new furnace. So that they could tell which duct is the most restrictive.

Obviously. The old duct system was NOT good for 1200 CFM unlike they told him. Or his A/C coil is a lot more restrictive then it should be.

[beenthere]

yea beenthere how bout when coil is wet?

I allowed/added .1" for a wet coil.

[energy star]

I think the fan may be working a bit hard but will compensate. I also think if a restriction exists it's at that return fitting.