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

[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.

[jtrammel]

And here some still pics of the setup.

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

Looks like a hack job, duct tape on the vent pipe! I hope you didn't pay much for the install because it needs to be redone by a professional.

[jtrammel]

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

I guarantee he has enough duct leakage to amount to an 8" supply or two and an 8" return.

[jmac00]

Looks like a hack job, duct tape on the vent pipe! I hope you didn't pay much for the install because it needs to be redone by a professional.

I guarantee he has enough duct leakage to amount to an 8" supply or two and an 8" return.

I was trying to be nice I still want to get a better look at the backside of that supply plenum, something is not right back there

[Labrat0116]

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

I'm not clear on what you're asking. ??

[Labrat0116]

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.

RG PN 07 I believe.... I need to find the papers to verify that.

[Labrat0116]

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.

You mean in the red box area ? BELOW

This was original duct work from who knows how long ago. ?



It's a pretty bizarre setup. That particular run goes into a very large diameter duct (maybe 12" x 12") and runs about 35 feet under the house. Believe it or not, it only feeds to small registers. The air is luke warm by the time it gets to them.

More can be seen here.....

[Labrat0116]

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.

The crawl space I would guess to be around 5-600 sq ft. ??

The house is rather well insulated. Not drafty at all. It is however, very dry. We keep several small humidifers running most of the time.

Furnace is 75,000 btu 80% efficient.

[Labrat0116]

Looks like a hack job, duct tape on the vent pipe! I hope you didn't pay much for the install because it needs to be redone by a professional.

Are you refering to this pic ?



They didn't do that. I taped that about (10) years ago. I saw a gap between the (2) pipes and went to town with the duct tape.

The outer (bigger diameter) pipe appeared to be double-walled. It looked really odd to me so I taped the crap out of it and sealed it tight.

EDITED..... I just found an OLD pic of what it looked like BEFORE I taped it up.