Allied gas heater question

[surenuff]

Hey, I have an allied gas geater made I guess by lennox with model number:
080UH1DO70A12-02
I am needing some technical info about it, specifically the blower info for this heater. I have been called in behind an installer to find out why it has been freezing up since install. Everything I am seeing points to poor airflow across the coil. I need to know what the blower on this model is rated at, so I can confirm or rule out my theory. thanks.........

[BaldLoonie]

Starts out CG80.

12 means 3 ton or 1200 CFM with reasonable static on high. If you have a 3 ton or less and still think low airflow, someone needs to take a static pressure reading on the coil, filter and duct system.

[surenuff]

Thanks. I have a 3.5 ton trane a/c attached to this furnace. instantly on start up we are flooding back. No superheat. 25*-30* split across the coil. Duct system is a furr down that has been in there since the days when a swamp cooler was on the roof. Customer says they had no trouble out of a/c until this new heater was installed. Furr downs offer little to no resistance to airflow because they are in most cases oversized for the amount of airflow coming from a furnace even on high speed. I even took the blower cover off to let it have all the air it could get cause the returns were pretty small, but even though it helped a little, it still did not stop the flooding. Do you think this 3 ton blower would offer enough airflow for that 3.5 ton?

[cuchulain]

Do a static pressure test on the blower/heater by itself then take the system airflow data (which should be in the install manual somewhere) and find out what the actual cfm of the system is based on that static.

[surenuff]

No blower data in the installation manual left by the installer. That is why I was hoping someone on here had online access to information on this particular unit.

[BaldLoonie]

I don't think it would be that bad to have a 3.5 ton A/C on it unless you had really high static and were moving closer to 1000 CFM. Lotta units out there not running 400 CFM a ton!

If rundawg or someone doesn't come up with a chart for it before Monday, I should be able to find something then.

[surenuff]

I did not check static pressure while I was there last night, because as I said, it is using a furr down as the duct system, and those inherintly have very low staic pressure because they were not designed to handle these types of air flows. In most cases, they were built to handle 4500-5500 cfm of a swamp cooler blower. They worked just ok for the heater, but this is certainly not a system built to work with approx. 1200 cfm. My concern is the fact that the home owner said that it worked fine until two weeks ago when a new heater was installed. She said that she used to feel a lot more air coming out of vents. Now little air is coming out of the vents, and the airflow across the coil seems very low. I will be back out there Monday. I will check static pressures, and try to find some blower data for this particular unit.

[rundawg]

I will check static pressures, and try to find some blower data for this particular unit.

Check your e-mail.

[surenuff]

Thanks rundawg for the blower data. It appears that with this unit, it should be delivering enough air if the static is not too high. I can't believe that it would be with that furr down, but I will verify actual static pressure Monday morning. One other thing I am worried about is the fact that the old coil was quite a bit larger physically than the new furnace discharge opening. THey made an adapter that is about 10" high on top of the furnace to accomidate the difference. The coil is flush on the right side of the unit while the offset is all on the left. This is just an old standard "A" type coil, but I wonder if that offset is causing a large part of the coil to not have sufficient airflow through it. Oh well...... If anyone has any more to offer, I would enjoy hearing them before my trip back Monday. Just recieved news that my brother's wife has passed away today. Long struggle for about 7 years now. I will not be worried any more today about this problem.

[BaldLoonie]

Sorry to hear of your loss :(

[rundawg]

Very sorry to hear of the loss of your brothers wife. We are all thinking about you.