First post noob...
Before I get nailed as a DIY, let me say that I have a professional HVAC contractor (mostly commercial) that does anything I need around freon - or copper for that matter. He installed the complete system in my existing house and happens to be a good friend and neighbor.
Now to my technical question. I've looked at drawings / pictures of bullhead tees haven't seen any kind of splitter to help turn the air column at the back of the tee. Is this because its too difficult or expensive to integrate into the tee - or is it just a bad idea? This is a high-velocity Spacepak application.
The air just smacks the back of the tee and makes its way out the two 90s. (This is 8" PVC with 1000 cfm in / 500 cfm out on both sides.)
Would a radiused back to back quarter turn at a height of half the pipe ID be a good idea? (The inside of the turns where the side entry joins the tee would be radiused as well.)
Just wondering if there is anything counter-intuitive about this...
high velocity (SpacePak, Unico) system has their own set of rules when it comes to ductwork. If you deviate from the design, fittings, # of outlets etc. you're asking for trouble.
GO NAVY, BEAT ARMY!
A DECADE OF DOMINANCE! +3
Corncob, you installed one of those systems with a jet engine for a fan
With all of that HP and static pressure and you want to install efficient fittings?
Sounds like a contradiction in terms!
I guess you can tell I am not a fan of the HV systems that need3ed their own category to avoid the "standard equipment" energy standards
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
Well, that makes sense because thats generally what I do.
Originally Posted by gregp
I've followed their design rules closely though and everything seems to be working just shy of expected numbers. I'm right at 700cfm (borrowed friend's anemometer) out of 22 ports - about 32cfm per port average. Ports close to the plenum are 36 and ports on long runs are 28. They spec 33 to 44 as a range. I'm opening up 8 more ports today - shooting for 1000cfm or so.
I took the tee out this morning and found one problem. I included their air control module in my system and the valve that adjusts airflow (600-1200cfm range) could not open fully as it was hitting the edge of the blower exit port.
My neighbor told me I should chunk their valve and he would replace my blower motor with an ecm dc motor to adjust total cfm. Sounds like a better plan.
The valve causes a problem ahead of the tee anyway (unless you have several feet between them to get a nice air flow established) where it puts more pressure on one side of the tee than the other. I've only got 18" between them.
He claims the splitter I have in the tee might reduce a little turbulence but only testing would prove it.
Hope to get this tee ironed out and have him over here to hook up the heat pump. He is also drilling two 50ft holes and putting loops in ahead of the HP.
Sounds like you have it going. Hope your installing it as per manufacture first then getting your measurements written down before making your changes. Otherwise your changes are just moot speculation.
I'm curious as to your results though.
If you think our goverment is screwed up. You haven't lived in another country.
The installation of the tee as done is acceptable. I'll be real curious just how and why your friend is going to replace that motor with an ECM motor.
Remember too that there is a reason they want that return within a few feet of the unit.
What is the "50 ft. holes" referring to? Is this a ground source "split system" installed on a high velocity air handling system? If so, is there a match up chart for this system (like AHRI)? If not, then what kind of warranty (or efficiency) are you expecting on this system??
He mentioned the ECM when I was complaining about the orientation of the valve in the ACM. As the ACM rotates to adjust blower cfm, the valve induces higher pressure on one side or the other of the airstream depending on which side you restrict flow.
Originally Posted by Glennhvac
Since my tee is close to the ACM (18"), the airstream is still higher pressure on one side or the other of the splitter at the back of my tee. Thats why I was asking about possibly removing the splitter - an effort to not reinforce the existing bias.
My return air path is < 8ft with two slow 90deg turns.
The ECM motor he described would be mounted as required where the existing 1HP motor is. Have to match shaft dimensions and motor RPM range. Since the motor in the blower now is just off or on 230v, the ECM would be configured for the same.
As far as control he said the ECM can be ordered with 5 or 6 control wires which select speed (cfm in my case) which we would configure for similar numbers expected from the ACM (ie 600cfm low speed / 1000 cfm high speed). Upside is no airstream path disruption, adjustable cfm and lower operating current in the motor. Since the Spacepak unit in designed to drive the ACM through a 6 pin molex, I can just measure those control signals and translate to drive the ECM. Think he said they could be had with 0 to 10V control too - even easier.
I was considering taking over control of the ACM anyway (and may still) and use the (east side tee exit / west side tee exit) cfm bias as a crude zoning control - have a thermostat on both sides of the house and pick the higher cfm side as needed. The Belimo control on the ACM is 0-95 degrees with 2 to 10V.
Yes ground source. He claims as much as 1/2 a ton per hole depending on density of the subsoil. My heat pump is a 3 ton 16 seer Coleman (York). I got the big Spacepak (4 to 5 ton) which was recommended to me by their engineering people as they had just done testing with my identical heat pump.
Originally Posted by wahoo
Efficiency? Who knows. HV is better although it is worse right? )
All my ducting (including the plenum) and the blower is in a sealed / insulated / heated & cooled crawlspace. Walls in the house are 6" stud R19 with 1/2" plywood / housewrap / brick all around.
Alright. Found enough info on the web to conclude a radius on the outside of a turn alone won't cut it. The inside radius is critical so I removed the tee and added a 2.25" radius turn on both sides. Reduced tee source leg area at same time (Spacepak ap engr didn't like the opening volumn behind the ACM). Turning vanes would also work but I don't have the metal.
Reinstalled the tee and (properly) aligned the ACM on the blower exit (pre-drilled holes). Set the restrictor plate to straight vertical (no restriction) and leveled the Spacepak back up. Added last 8 ports the other day so have 30 total now.
Was out of time but ran the blower long enough to read 4 ports that I had previous numbers for (when there were 22 ports and the ACM was misaligned). It was pretty obvious as I moved the anemometer over the ports - it was spinning up like a turbo. I was over 35 on all 4 ports, 43 on 1. I'm up 2 or 3 cfm compared to the first test on these 4 ports - this with 8 new ports added.
I'll still have the issue with the restrictor plate increasing cfm on whichever leg of the tee its pointing at but I decided to make lemonade and add a second thermostat - one for the east side of the house and one for the west. Share control of the ACM with the Spacepak. Keep the blower motor original.
I reset max travel position of the restrictor plate to about 20 degrees ccw of vertical. Full cw rotation stops at about 15 degrees short of horizontal. Tomorrow I'll run cfm on all 30 ports at full ccw, vertical, 20 degrees cw past vertical, and full cw.
The ports are super quiet even with this velocity. You can hear the blower down in the crawlspace but I have no floor coverings, sheetrock etc.. My ducts are 100% sch40 pvc with long turn 90s where needed and pvc mufflers at port exits.
DIY. I read what you said in your first post. What your doing, is DIY.
Originally Posted by Corncob
"Better tell the sandman to stay away, because we're gonna be workin on this one all night."
"Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."
"Just get it done son."
Well, the only question I've asked was technical in nature (splitter in a tee?) and didn't get answered. I have an HVAC contractor that will handle everything to do with connecting the Spacepak to the compressor and starting the system up. All I'm doing is blowing air down a pipe.
Actually, I've designed several (electronic) controls for hvac companies under contract in the past which would qualify me as an hvac pro! Heh heh maybe not - but I was paid.
I'm only doing as much as I am on this system because I've had 3 contractors out here to quote me on my spec (crawlspace installled) and all 3 proceeded to quote me on systems in my (12/12 pitch) attic for $ to $. The closest any of my (I-beam) floor joists gets to the (30 mil white plastic covered) ground is 41" - and they wouldn't even look at it. So here I am.
After todays effort I'll be supplying technical information if anyone cares to see it.
Last edited by beenthere; 03-18-2012 at 06:46 AM.
Reason: price range