I'm back and want to do another diagram!

Javelin

Dear Heating Pros,

A couple of years ago this group was kind enough to look at my diagram of a new boiler system I was planning on putting together myself and with your expert guidance, I got it in and it's been running like a charm (after some tweaking -

My new project is putting in a 1.5 ton traditional ducted heat pump in an apartment above a garage. I think I have all the CFMs correctly calculated (with the help of a friend, but he's hard to get a hold of recently, so thought I'd put up the drawings here). Would you all be willing/able to have a look to tell me if I have anything massively wrong?

I love new challenges and am looking forward to running all this rigid pipe (which I'm told is easier than square), but would really like to pass it by some old hats first.

Would anyone here be willing to weigh in?

Thanks in advance!

Jay

Techman

I think more than a few "anyone" will.

RobG

Where is the design?

Techman

Yeah!! What RobG said!!!!!!!!!!!!!

Paul48

It must be a very, very small system. I can't see it.

Javelin

Heating Pros,

Ok.. here it goes.. Please don't judge my sketch-up skills, but attached is a basic model of this 2+ room area above my garage as well as some photos all with some basic labels.. What I'm asking of all of you is guidance in putting together a properly sized rigid duct system..

A few notes:

1) Air handler will be in a separate room UNDER the living area next to the garage, but no sharing the same space/air as the actual garage.

2) There is not a lot of room, but my plan is to put the duct work in the triangular space above the false ceiling

3) From what I've read on line for a 1.5 ton system, I need 14" round duct from the air handler to start. I then hope to pull a 4" hit off into the bathroom (ROUND RED A), allowing me to drop to 12" duct to make it fit better going into the turn and into room B. In room B, I would have a bigger 8" hit (ROUND RED allowing the drop to 10" going into room C, where I would Tee off to 2 7" hits (ROUND RED C1 and C2) on either side of the room.

Specific Initial Questions:

1) For the 4" hit into room A, would I use something like a Saddle tap:?
http://www.thesheetmetalkid.com/saddle-taps/

2) Same for the 8" into room B?

3) Though I'm planning on running the duct inside insulated space (I'm insulating the diagonal roof rafters all the way up to the ridge), I still need to insulate to prevent condensation right? What sort of insulation should I be thinking about? What thickness?

4) For the return can I just use the actual triangular void as the return duct? I've seen that done with regular stud cavaties in the past.. not sure about using this whole triangular space.

5) Going into Room C, plan on just using a T and going to both

I've also attached a couple of photos of the actual space in case they help. I know this is very rough, but hopefully it's enough to get the discussion started and get some feedback from you pros.

Thanks in advance!

Jay

PS - I could just forget the ductwork and run ductless minisplits, but I was told by an "old school" HVAC guy that the mini-splits might not get warm enough in the winter (Philadelphia area) and the lack of a return means staler, less conditioned air. That, plus it's more expensive to install (even if I run myself) and probably more expensive to maintain over more "simple" air-handlers. Thoughts?

unclejohn

1.5 ton heat pump you need 600 cfm. That's a 12" @ .8 static to start. A 4" at .8 gets you 120 cfm. Now we are dealing with 480 cfm so reduce to 10" and your @ .1 static. So I would run a 7" off the ten and reduce to 8" for room c and hope it can be balanced at the registers or put a damper in the 8" after the reducer. With the round ducts you can't get the odd 1/2 sizes to keep the pressure the same through out the run like you can with rectangular duct. I would run hard pipe for the return and just size it the same as the supply. 8" to room C and 10" room B and the rest 12"

Empire_2

Love the room to room set up. Looks great and get's the visual picture across. While I agree with Unclejohn, reducers cost, money and in this example may be a wash, but money is money and since the job is quite small, and seeing least load is the first 2 rooms(bath and kitchen) if you want to call it that first load, reduce from 12, pick up the bath, and what looks like a kitchen or gathering room, then from there you can be safe finishing the room "C" with 10" round which give you 400cfm or 1 ton for what looks like the living area.
I really like the program you are running Javelin... Where may I find such a program?

Peace;
MPT...

Javelin

Empire and Uncle John,
Thanks so much for your replies.. So it sounds like the diagram is mostly correct, but I can reduce the sizes a bit which will actually help me a lot in running through the triangular space. Two questions:

1) How do I go "off" the main trunk for my registers? With the saddle taps?

2) What about insulation? Is there a standard or term I should search for? Please talk to me like I'm a child.. I'm a web designer by trade and a handyman by necessity with my 1911 house

Empire, the program I used is called Google Sketchup - it's free (at least for home use/tinkering) - http://www.sketchup.com - you can download it for free and there are a ton of tutorials online if you'd like to learn more (I didn't which is why my mock ups look the way they do

Thanks in advance for all this help - I really like the opportunity to learn a new skill (sort of)

Best,

Jay

JUGHNE

I believe an inverter/variable motor system of mini-splits will deliver hotter air (although the inside CFM will decrease as it gets colder outside) than the standard single speed heat pump.

I have a nursing home here in northern NE (20+ rooms) with mini split heat pumps, there have not been complaints of cool air being delivered, rather not enough heat and then the base board heater kicks in.

I would guess in your location that you will need supplemental heat regardless of which heat pump you chose.

I would suggest you check the installed price of multi mini split heat pumps. Your back up/supplemental heat would be resistance heat for either system. You could add cove heat or baseboard heaters in the 2 large rooms. For the bath I would add a light-heat-vent unit. Or a small cove radiant heater would be comfortable for a bath.

There would be no ductwork and any loses.
You could insulate the ceiling and knee walls and gain vented attic spaces above the ceiling.

As far of no return air, with either system the same air will be recirculated through the rooms.

Inside units could be installed on inside walls with line sets concealed in these walls going down into the garage perhaps.

The mini-split could be somewhat oversized to gain more heating capacity and then modulate down for the cooling.

Just a thought.

unclejohn

The saddle tap is fine. I would just get a tee or Y fitting from the supply house so I wouldn't have to cut the hole. There are insulating sleeves that slide over the round duct.

Techman

Flapping jaws here. the Heat pump. The "indoor" section being in a garage has to be sealed, car exhaust and all, the AHU has to be raised off the floor a certain distance, gasoline fumes and all.The AHU "room" would HAVE TO BE "air tight "from the garage, not just separate, as in height/sealing requirements. The "attic" space insulation cannot block off the roof ridge vent if there is one, or if not then there has to be "air vents" in the walls for ventilation above the ceiling.. This then means,"technically" the attic duct will be subjected to outdoor air temps, or damn close to ambient temps, summer/winter.

A HP most times deals w/ 450cfm/ton, so 1 1/2t =675cfm, Going from a 14" supply@ .10 static(1000cfm) , then taking off a 4" supply (35cfm) for bath, then dropping down to 12"(700cfm) doesn't make sense. Then an 8"(260cfm) drop into (b), leaving the rest of the cfm (380cfm) for (c) being fed by 10'(420cfm) going into two 7" (160cfm x 2= 320cfm). There was a load calc performed? The return is usually sized a size larger (or two) and at a lower static press , usually .06-.08.

Where is "Spence" he's a good "jaw flapper" and smart too.

Javelin

Thanks Techman...

The room where the air-handler will be is separate and will be "air-tight" from the garage. Right now the only way they are connected is through the joist bays above both which will be removed once drywall is added and insulation added.

As for the installation in the roof to vent the ceiling, I just finished cutting in new ridge/soffit vents, and the roof is now being ventilated with vent baffles behind the insulation.. That insulation goes all the way up the diagonal space to the ridge which should keep most of the cold/hot out, but still allows for venting (see attached mockup I just made).

Regarding the sizing of the ducts - that's why I started this post - looking for you pros to weigh in on what makes sense? I know when I did my boiler, someone from this group did a "manual-J" for my BTU needs.. Does something similar exist for duct sizing?

Is there anyone on this board that I could pay for an hour service call to come see the space in person and tell me what supplies to get to properly size things?

Thank you all!

Jay

Bob Bona_4

Manual J results can be translated to cfm and duct sizing.

unclejohn

Sorry the eyes are getting old and you get vilified. Should have picked it up as I know you get about 100 cfm from a 6" round. @ .1 SP. so other then that 4" error. Run the rest just like I said and it will work fine. And if you want the system to heat best keep the cfm at 600.

Javelin

Just wanted to give everyone on this thread a heart-felt THANK YOU for your advice on this project. I was able to run all the duct-work myself.. had a plumber/hvac(ey) friend install the condenser and air handler and it's cruising away, keeping the apartment warm even in this current mid-atlantic cold snap.

I love doing things on my own (with a little guidance) and you all make that possible.. so THANK YOU.