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macsierra8
Baby Newfoundland
Premium Member
join:2003-11-30
Minden, NV

macsierra8

Premium Member

Another HVAC Question Regarding a New Condensing Unit

My HVAC contractor got into financial trouble and sent over some inexperienced installers to install a Rheem/Rudd RARL-024 JEZ condensing unit about 70' from the heating/cooling modulating unit. Sloppy install, too much heat near the valves when brazing etc...

I'm using a Multi-Stage Rheem thermostat # UHC-TST401 with the modulating furnace.

They used an 18/3 cable from the heater to the condensing unit. Don't I need at least an 18/4 cable for the 2 (second stage) condenser? The condenser runs the AC OK but only runs on the first stage and the thermostat calls for 2 stages.

My contractor sez one stage is fine????????

Y1---Y2---common---24vac

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

1 edit

SandShark5

Premium Member

According to the installation instructions the outside unit needs at least 4 wires (Y1, Y2, C, R). If you have a communicating thermostat (I don't believe yours is a communicating thermostat) with ICC Fault information, the unit would need 5 wires.

Edit - Corrected link. Thanks cdru See Profile!

cdru
Go Colts
MVM
join:2003-05-14
Fort Wayne, IN

1 edit

cdru to macsierra8

MVM

to macsierra8
According to page 19 here, 4 or 5 wires would need to be hooked up to E2 at the condenser. Perhaps they cheated and jumpered Y1 and Y2 and it's always running both stages?

Edited: Damn, beat by Sandshark. At least I linked to the right manual though for (R)ARL-JEZ condensers.

macsierra8
Baby Newfoundland
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join:2003-11-30
Minden, NV

macsierra8 to SandShark5

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to SandShark5
SandShark and cdru, I very much appreciate your help!

I didn't want to bug my HVAC guy again and we agreed to hold out $800 for the thermostat ($260) and the registers + labor. He came and checked the R-410A so I'm good there.

The place is drywalled and just about ready for final inspection so no easy way to add the 4th control wire as the condenser is outside under an open stairway.

To gain a wire?? I disconnected the common and the meter showed 26 vac between R terminal and equipment ground. That would be a nice way to gain the Y2 wire but if something shorted to ground I'll bet the circuit board would fry by way of the common before the breaker opened. Could I fuse the common for protection?

Another way, could I add a 24 vac transformer at the condenser unit??

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

SandShark5

Premium Member

Isn't the cable from the condensing unit to the furnace run with the refrigerant lines? Are the refrigerant lines inside walls/ceilings?

macsierra8
Baby Newfoundland
Premium Member
join:2003-11-30
Minden, NV

macsierra8

Premium Member

said by SandShark5:

Isn't the cable from the condensing unit to the furnace run with the refrigerant lines? Are the refrigerant lines inside walls/ceilings?
Yep, inside the walls most of the way and the control cable is taped to the refrigerant lines. I could come through the 2nd story attic, but I'd still have to drop down the outside of the building and under the stairs.

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

SandShark5 to macsierra8

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to macsierra8
said by macsierra8:

To gain a wire?? I disconnected the common and the meter showed 26 vac between R terminal and equipment ground. That would be a nice way to gain the Y2 wire but if something shorted to ground I'll bet the circuit board would fry by way of the common before the breaker opened. Could I fuse the common for protection?

Another way, could I add a 24 vac transformer at the condenser unit??
I have used the equipment ground to gain common when I had to have Y2 on two-speed units and the cable didn't have enough wires, but these systems didn't have electronics in them. I'm not going to say you can't do it this way, but I'm not going to say you can, either. As far as adding another 24V transformer, that's something I've never tried. Again, we're dealing with electronics, so that's a gamble, too.

I'd recommend your installer (or you) try talking to someone at Rheem/Ruud technical support. You should be able to get the number from the local Rheem/Ruud distributor in your area.

Lurch77
Premium Member
join:2001-11-22
Green Bay, WI

Lurch77 to macsierra8

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to macsierra8
said by macsierra8:

...as the condenser is outside under an open stairway.
Not to get off topic, but this may become an issue as well if they did not follow minimum clearance set by the manufacturer, open steps or not.

macsierra8
Baby Newfoundland
Premium Member
join:2003-11-30
Minden, NV

macsierra8

Premium Member

said by Lurch77:
said by macsierra8:

...as the condenser is outside under an open stairway.
Not to get off topic, but this may become an issue as well if they did not follow minimum clearance set by the manufacturer, open steps or not.
I don't think that's too far off topic, and actually is a good question. I discussed the placement issue, both with the HVAC contractor and the building inspector. The larger unit has over the recommended clearance and the smaller unit is just a couple inches under specs but only has 1200 sf to cool with R38 ceiling insulation and R26 wall insulation.

At 92 degrees ambient I did a test the other day running both units steady for about an hour after the house temp went to 77 F. The smaller unit (heat gun temp) actually runs slightly cooler than the big unit. Room temperature cooled to under 70 F in a short time in both areas.

The big condenser unit showed 6 amps per leg at 240 volts and the small one (Y1 stage one) used 4.3 amps per leg with the ACD-14fx Amprobe. Add a little tho, for forced air circulation..

As a comparison, my old 6000 CFM swamp cooler at high fan used 10 amps (one leg) at 120 volts.


cowboyro
Premium Member
join:2000-10-11
CT

cowboyro to macsierra8

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to macsierra8
As a side note I think that's a really bad location for the units. The stairs will restrict the airflow creating a pocket of warm air - and reduced efficiency.

guppy_fish
Premium Member
join:2003-12-09
Palm Harbor, FL

guppy_fish to macsierra8

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to macsierra8
Units are WAY to close to the house, you have effectively cut the air flow by on third as they look almost flush against the siding, not even getting into the smaller one being shoe-horned under the steps

Msradell
Premium Member
join:2008-12-25
Louisville, KY

Msradell to macsierra8

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to macsierra8
said by macsierra8:

The place is drywalled and just about ready for final inspection so no easy way to add the 4th control wire as the condenser is outside under an open stairway.

To gain a wire?? I disconnected the common and the meter showed 26 vac between R terminal and equipment ground. That would be a nice way to gain the Y2 wire but if something shorted to ground I'll bet the circuit board would fry by way of the common before the breaker opened. Could I fuse the common for protection?

Another way, could I add a 24 vac transformer at the condenser unit??
No matter how you look at it to have the unit operate how it's intended you need a minimum of four wires to the thermostat, the fifth is just to show diagnostic codes. I certainly wouldn't recommend using the common ground. Who knows what else could end up putting signals to the ground plus lightening could induce current to the ground.

Also the idea of putting another transformer at the condenser unit won't work. You are switching voltages to make the outside unit operate and providing the common from a different transformer is unacceptable both for code and operational considerations. I would also be very surprised if either of your proposed solutions were acceptable to the local AHJ.

Before we had electronic controllers you could get away with some unusual arrangements now days that's not possible. Also, do you not have heat? If you do the thermostat would need another wire for that bringing the total up to five or six.

On the subject of clearances it recommends 12" between the units and the wall and allows it to go to a minimum of 8" if space is limited. It also saves you are required to have 60" above the fan minimum without exceptions. From your pictures I'm sure you're much closer to the wall and don't have acceptable vertical clearance. Your measurements may have been acceptable but I certainly wouldn't accept the units until this is corrected. It will make them work much harder in the long run and limit their life. Also it's hard to tell what do you have 24 inches between the Units? That is the minimum required to allow access for repairs and actually is a code requirement in many municipalities.

I know you stated you don't want to bug the contractor but making sure things are installed according to specifications for your own protection. If they are not the manufacturer could and quite possibly would deny any warranty claims you make of the units. You're much better off correcting the problems now.

macsierra8
Baby Newfoundland
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join:2003-11-30
Minden, NV

macsierra8 to guppy_fish

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to guppy_fish
said by guppy_fish:

Units are WAY to close to the house, you have effectively cut the air flow by on third as they look almost flush against the siding, not even getting into the smaller one being shoe-horned under the steps
Sorry to disagree with you guys. There's 10" clearance to the siding and it's not at all "shoe-horned" under the steps. All clearances are within inches of what Rheem requires in the installation specs. Pictures can be deceiving and they appear sometimes to be what you want to visualize. I'll take one from another angle..

Temperatures at 92 F ambient at one hour steady running time told the story as well and that's why I did the testing. These condensers are not working hard at all in this dry humidity area.

mattmag

join:2000-04-09
NW Illinois

mattmag

said by macsierra8:

Temperatures at 92 F ambient at one hour steady running time told the story as well and that's why I did the testing. These condensers are not working hard at all in this dry humidity area.
I personally believe that is a great location. You have clearances that are working fine for your application, and as a secondary benefit those units are probably enjoying some shading effect as well. Plus it is aesthetically pleasing the way they are located, almost looks like it was designed that way.
Tyreman
join:2002-10-08
Cambridge, ON

1 edit

Tyreman to macsierra8

Member

to macsierra8
On the small unit how much clearance is between the condenser top(fan) and the landing in inches or feet.
Top clearance is to avoid any recirculation of discharge air at a high temperature into the inlet air stream

macsierra8
Baby Newfoundland
Premium Member
join:2003-11-30
Minden, NV

macsierra8

Premium Member

said by Tyreman:

On the small unit how much clearance is between the condenser top(fan) and the landing in inches or feet.
Top clearance is to avoid any recirculation of discharge air at a high temperature into the inlet air stream
I measure 52" on the small one and 65" on the big one. Heat gun checks don't appear to be showing any recirculation. The stairs allow air to penetrate to a certain degree..

SandShark5
Long may you run
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join:2000-05-23
Santa Fe, TX

SandShark5

Premium Member

I've seen units shoe-horned in much tighter locations and in locations where the ambient air temperature exceeds 120 degrees. These clearances are recommendations and, in your case, I think their location and clearances are fine and I don't think the efficiencies will be affected too much, if at all. However, as a service technician, I would like to have seen a few more inches between the two units. Otherwise, nice installation. I'd like to see the indoor installations. That will tell the tale.

macsierra8
Baby Newfoundland
Premium Member
join:2003-11-30
Minden, NV

macsierra8

Premium Member

There is 26" between the 2 units. Here's some more picts with a couple of the attic installation of the modulating furnace. Don't ask me how those clowns burned the label on the cover, I have no idea..







The downstairs AC (larger unit) and air handler is in an older thread. Picture of work in progress and temporary expansion tank hang and electric and plumbing not finished.
»Tankless water heaters?


SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

SandShark5

Premium Member

Thanks for the photos. It may just be the angle the photo was taken, but is the condensate drain in the first photo running uphill? Do the drains need to be insulated? In the second photo, I'm a little concerned about the gas piping being run in front of the blower compartment in case the blower has to be removed for service. Also, are those trusses going to affect servicing the system in any way? Is that a hydronic heating coil in the downflow unit (last photo)?

Ken
MVM
join:2003-06-16
Markle, IN

Ken

MVM

It does look like it's going uphill about a 1/2"

macsierra8
Baby Newfoundland
Premium Member
join:2003-11-30
Minden, NV

1 recommendation

macsierra8 to SandShark5

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to SandShark5
I'll check that pan for level today. The return air plenum on the right side unscrews to gain full access to the blower area and I extended the floor to that area myself. The trusses clear well but the pict brings things to appear smaller and magnified.

The hydronic heating coil is part of the Rinnai air handler. It works surprisingly well in conjunction with the hot water system.