No need to do anything with the exhaust/flue pipe of your furnace.

 

except remove the silicone from the joints.

 

Hello all,

I'm in the process of quoting an add-on central A/C system install to an existing ducted forced hot air oil heating system. The oil furnace & duct work was all newly installed about 6 months ago. Furnace is a Thermopride OH6FA072D48B, down-fired to 60K BTU (smallest unit I could find). House is 750 sq ft with 5 rooms, each having its own duct and MV4. Home is in the southern Poconos in NE Pennsylvania.

Two quotes I've received so far. One is calling for a 2-ton Amana ASX13. The other is calling for a 1.5 ton Amana ASX14, but with a custom duct coming off of the furnace due to the location of the heating exhaust pipe which connects to the chimney. The location of this pipe is practically touching the right side of the duct that extends above the oil furnace (where the A/C coil needs to be installed). He wants to make this duct smaller so that the coil is not exposed to the heat coming off of that exhaust pipe. Pictures are attached below. The current size of the duct coming off of the oil furnace is 18"W x 22"H x 19"D.

Questions:

-Are there any heat tolerance concerns when it comes to installing encased A/C coils which sit on top of oil furnaces, and/or which sit right next to oil furnace exhaust pipes? I can't seem to find heat tolerance specifications from any coil manufacturer.
-Moreover, if the size of the duct is reduced, won't this introduce higher static pressures to the heating system, which can cause excess stress to the furnace and/or exchanger?

Naturally, I don't want to void out my install warranty with the HVAC company that installed the heating system, nor do I wish to void out my Thermopride 10 year parts warranty, and lifetime heat exchanger warranty. But it seems a shame for me to have to install a separate mini-split inversion A/C system (much more expensive), when everything can be tied into my new & existing system (along with Nest thermostat integration, which I also already have in place).

Comments appreciated. Thanks in advance.

 

Goodman/Amana recommends installing their high temperature drain pan when mounting on a oil furnace.

https://www.acwholesalers.com/Goodman-Air-Conditioner/HTP-C-High-Temperature-Drain-Pan/30391.ac

Product Specifications page 12 shows the different model numbers for size of coil/furnace.

http://www.goodmanmfg.com/products/air-handlers-and-coils/coils/capt-series

Sorry did not notice this is a down flow, when I first posted info but possible this may help anyway.

 

Goodman/Amana recommends installing their high temperature drain pan when mounting on a oil furnace.



Product Specifications page 12 shows the different model numbers for size of coil/furnace.



Sorry did not notice this is a down flow, when I first posted info but possible this may help anyway.

This definitely answers the first question (of two) in the first bullet point in my original post. Thank you for this information.

Comments appreciated with regards A/C coil heat tolerances when heating exhaust/flue vents run close to the side of the encased coils. I'm wondering if the main air duct needs to be customized (made smaller) so that the A/C coil is not right next to the heating flue vent. I'm thinking no as if it was too hot, my existing air duct would have melted by now.

 

http://thermoprideregistration.bh-portal.net/

You may want to double check to see if the furnace was registered initially ( unless you personally registered it ) as your parts and limited lifetime HX warranty will be decreased if not registered. Things like that fall through the cracks sometimes...

Same applies for the Amana, http://www.amana-hac.com/product-registration if and when you install A/C if whoever quoting you the Amana and they participate in offering the extended labor warranty from Amana called Asure, you can extend your labor warranty for up to 10 years ( if interested ) and the labor warranty is backed by the manufacturer unlike a labor warranty from the Installing Contractor, which is only as good as long as they do not go out of business.

http://www.amana-hac.com/support

http://www.hvacdist.com/warranty/Amana-Goodman Warranty Guidelines.pdf

Did the Contractor who quoted the A/C say anything about the ductwork, ( if it's not insulated ) about possible sweating near the furnace?

 

Thank you for the warranty heads-up. I just submitted it now...hopefully they will retro-date my registration to within 90 days of the install.

"Did the Contractor who quoted the A/C say anything about the ductwork, ( if it's not insulated ) about possible sweating near the furnace?"

Neither of them mentioned this. I will ask tonight. Thanks Joey!

 

Thank you for the warranty heads-up. I just submitted it now...hopefully they will retro-date my registration to within 90 days of the install.

See,... if you never registered the furnace your 10 year parts and limited lifetime HX warranty would probably have gone to 5 years parts and a basic 20 year HX warranty. Typically many contractors do it for their customers but not all but they should have told you to register it yourself helping you do it or showing you where to go. If that was the case ( failed to tell you or they where going to register it ) to me the Contractor dropped the ball......IMO

 

All I can add is they will probably have to insulate the plenum box ( sitting on top of furnace ) from the inside as the flue duct looks to be practically touching the plenum duct now. In regards to the indoor coil they can have the connection hookup ( Liquid line, suction line, drain pan condensate line ) on the rear of the furnace. As the flue will not be in the way. ( if the lineset can be run without to much problem due to duct )

To me the barometric damper looks to close to the return duct in case you need to adjust/move the knob. Can't see how they can access that adjustment knob. Probably was installed after the duct guys finished, as the vertical return duct should be moved right say a foot or so ( viewing first photo ) to have access to the barometric damper knob. The inspector was OK with that?

https://www.googleadservices.com/pa...Ku52XzoTw9fzQbVnA&ctype=5&q=&ved=0ahUKEwjp7czpkNLTAhVXzmMKHZEEDDYQwg8IIw&adurl=

Yes I was referencing only as an example my fiberglass water filter in my basement. I have it elevated off the basement floor and it sits in a auxiliary pan, as stated even with my dehumidifier running the body still condenses and drips into the pan.

There are two types of indoor coil types, a cased and uncased, a case has the the coil built into a factory insulated box. Yours looks to be the uncased type, as they will be sliding one into the existing plenum box.

http://www.goodmanmfg.com/products/air-handlers-and-coils/coils/capf-series

Hit product specifications to see the cased and uncased Amana/Goodman coil with dimensions. You can pick one out yourself to get an idea of tonnage size heights and width.

Your looking at the CAUF model ( uncased ) with a factory piston metering device. They make a field install OEM TXV to replace the simple piston metering device. Do not know what the Amana Contractor bidded. But the sizes are on page 12.

My mistake I thought you had the ID coil already installed.

 

-Yes, the flue duct is very close to the plenum duct. Yes, I believe the rear of the furnace is the ideal spot for the connection hookup.

-The barometric damper is 3" away from the return duct. Yes, it passed inspection (I think the standards in PA are looser as compared to other states like NY and NJ).

-Luckily (knocks wood), I have no condensation issues going on in my basement to this point. Your basement definitely seems to be more of a challenge with regards to humidity, but mine does as well if I don't run the dehumidifier.

-Interesting, as my contractor appears to be proposing ordering me a pre-made cased coil from Amana. Says he can do either cased or uncased, but prefers the cased one. I'll have to get clarification on this. What I know for certain is I need a custom duct to properly fit the coil on top of the furnace. Looks like there's a size mis-match between my Thermopride furnace and the Amana coils.

Two final questions sir:

-Is the field install OEM TXV necessary? Factory piston metering device is no good?

-Do you think it's wise for me to insulate all of the trunk ducts in the basement (past the plenum, all the way up to the vertical trunk connection)? Or is this something I can try without at first, and then insulate if a condensation problem surfaces? The latter is what my contractor is recommending, as he feels my basement doesn't call for it (which will save me on labor costs). He will be quoting me this separately so that I know what to expect price-wise.

 

Looking at the original photos you provided looks like the Barometric dampers has access room for adjustment. The 2nd sets of photo ( different angel ) looks like the damper is only an inch or two away from the return duct, which I was basing my concerns about the damper, once again my mistake.

Looking at the website gives about the coils the picture of the CAPF cased coil shows the insulation on the inside of the factory outer shell.

 

if there is head-room; there should always be a 4 to 6" or more transition above the furnace on which the evap coil is installed.

Many of those Thermo-Pride OIL HEAT-EXCHANGERS are large & close to the top of the furnace which can also cause an airflow restriction, when the coil is put directly on top of the furnace, considerably reducing REQUIRED airflow. They need adequate transitions...!

 

Not much head room. Only 3" of play is what I'm being told. That's how far off from the top of the furnace the coil will be.

Thanks for the feedback.

 

Post 17 gives you the web site to check dimensions of cased coils, so you can get an idea if you have the room for a transition piece. CAPF is the piston metering device or the CAPT is the factory built INTERNAL TXV. They can also remove the existing piston on the CAPF and install a OEM EXTERNAL mounted TXV. Again even if you have the room and go with a cased coil/transition piece you need to replace the factory drain pan and install the high temperature one. Decisions, Decisions...

 

Definitely will be going with the CAPF model.

 

At 795 sq', what about a ductless system?

Could use a heat pump to offset the oil cost in winter.

 

Hey Pac,

Thanks for the suggestion.

Thought about it, but decided to pass for a few reasons:

-Up front install cost (big difference as you know)
-No Nest thermostat integration (it's all freshly wired up for A/C)
-Rather large and unpleasant looking duct in my living room ceiling, which is already crammed with high hats, the heating MV4, and ceiling speakers. Wife will also not allow a wall unit.
-Summer season is not long enough to realize the energy savings

P.S. Love your forum signature. =D

 

Just wanted to thank everyone here for responding. This was my first experience on the HVAC-Talk forum, and I have to say it was a great one. Lots of friendly and helpful people.

Have a great day everyone!