Brand New Rheem RGPS Gas Furnace Short Cycling........ WHY ??

[Labrat0116]

is this in an attic?

No, it's in a crawl space under the house. The house is 101 years old.

Here's a video I just took.



I believe the model is a RGPS. Gas, updraft. I need to find the papers on it...

As for the registers.... there are 5 downstairs and 4 upstairs. The are all approximately
(did not measure).... 4" x 10" each. One downstairs is kept closed since it's only 4 feet from the T-Stat. The house is pretty small Sq Ft about 1100 or so.

I just remembered..... Here are some pics of the old furnace when we bought the house 17 years ago. I cleaned up a lot of that mess since. You're gonna love how the previous owner had the AC condensation drain set up!!

http://katmanduonline.net/pics/ACFURNACEPics/index.html

To give a better idea of the size house, here's pics of it.

http://katmanduonline.net/pics/NewHousePaint2006/

[Labrat0116]

And here some still pics of the setup.

http://katmanduonline.net/albums/NewFurnace/

[jmac00]

it doesn't look bad, but I have a real problem with the way that duct comes off the backside of the supply plenum. I can't tell if that necessary or not?

I think it would have been cheaper/quicker to install a new plenum and connect directly into the supply at the back, eliminate the down turn short way 90 elbow.

I would also put a supply run in the crawl space

[beenthere]

I don't think so.

Yes, same Rheem furnace.

The Moderator merged these threads. I'm not sure why, the issues aren't related.... it is the same furnace though. ??

Very well may be related.

The 1000 CFM of return may not be enough either.

[Labrat0116]

The 1000 CFM of return may not be enough either.

How much should this should this configuration have ?

How can I add more capacity ?

[Labrat0116]

I think it would have been cheaper/quicker to install a new plenum and connect directly into the supply at the back, eliminate the down turn short way 90 elbow.

I would also put a supply run in the crawl space

I'm not quite sure which one your referring to. ?? The flexible hose and the plenum (before the filter) are all new. The 2 - 12" ducts are from the old setup.

What would installing a supply run in the crawl space accomplish ?? More capacity perhaps ?

[beenthere]

How much should this should this configuration have ?

How can I add more capacity ?

Need full model number of the furnace to tell for sure. Adding another return or enlarging 1 or both of those may be all that is needed.

[beenthere]

I'm not quite sure which one your referring to. ?? The flexible hose and the plenum (before the filter) are all new. The 2 - 12" ducts are from the old setup.

What would installing a supply run in the crawl space accomplish ?? More capacity perhaps ?

Without a return in the crawlspace, it would put your house into a negative pressure.

[Labrat0116]

BTW, the furnace has gone thru several cycles since this AM and appears to be doing much better. No more short cycling or shutting down during startups.

Like I stated before, the ONLY thing the Tech did this AM was bend the aluminum bracket that holds the pressure switch away from hitting the inside of the door.

My question now is How could that bent bracket have any effect on the startup shutdown issue ??

The part looked like this one below......

[Labrat0116]

Without a return in the crawlspace, it would put your house into a negative pressure.

What would a negative pressure in the house do ?

I was thinking a negative pressure may have built up under the house that may have restricted the flow out the flu pipe. Therefore causing the pressure switch to activate and shutting down the system during startup. ?? Is that plausible ?

[Joehvac25]

Did he bend it so it sat like the one in the pic? It should have the diaphragm vertical, not horizontal like the pic.

[jmac00]

I'm not quite sure which one your referring to. ?? The flexible hose and the plenum (before the filter) are all new. The 2 - 12" ducts are from the old setup.

What would installing a supply run in the crawl space accomplish ?? More capacity perhaps ?

I was looking at the supply plenum on top of the a/c coil. In Pix 0306, On the back side it appears there is a 6" x ??? that runs about a foot and then goes into (what looks like) 8" x ??? short way elbow. I think you have much to much restriction there.

[beenthere]

What would a negative pressure in the house do ?

I was thinking a negative pressure may have built up under the house that may have restricted the flow out the flu pipe. Therefore causing the pressure switch to activate and shutting down the system during startup. ?? Is that plausible ?

How big is the crawlspace. And what BTU is the furnace again.

A negative pressure in the house will draw in the cold dry outside air. making you heating cost increase, and your house very dry and uncomfortable.