High velocity furnaces - http://www.hvacmechanic.com/ Forums
Original message
| problems
 |  "High velocity furnaces"
, posted Sat 9 Feb 01:10  
Still winter but I have a couple of residences with reportedly the same problems. I have never had anything to do with high velocity furnaces, 2 inch vents, they tell me the airconditioning has never worked, always freezing up, now I have not looked at them yet, I was just hoping to see if anyone had encountered this or worked on a similar system. Spring should happen by July this year I am hoping but never the less both friend jobs, we will see, any ideas ?
In the Trade for a long long time !
Things a bit different than before !
Refrigeration still doesn't have a "d" in it does it ?
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Replies:
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| problems
| "Re(1):High velocity furnaces" , posted Sun 10 Feb 00:08
Thanks for all the insight and experience, static when I check and verify the charge (txv) should I expect 20 degree's of subcooling and if it is a piston style evap should I look for 20 degree's superheat @ the condensing unit.
Again, thanks again, especially for all the heads up info.
In the Trade for a long long time !
Things a bit different than before !
Refrigeration still doesn't have a "d" in it does it ?
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| | static
| "Re(2):High velocity furnaces" , posted Sun 10 Feb 01:39
Hello,
On the sub cooling, 20º should be okay, no more though, I usually stay in the range of 12 - 15 when charging one.
On superheat...I've never seen one of these that used a piston. If it did, I'd expect to see a pretty low superheat number.
With a TXV, head pressure should look pretty normal, but don't be suprised to see suction pressure below 60 psig, an SP in the low to mid 50's is how these seem to usually run. How they don't all freeze up like that, I haven't a clue.
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| cyberbeagle
| "Re(1):High velocity furnaces" , posted Sat 9 Feb 16:33:
High Velocity are low cfm and high static pressure unlike traditional systems that are high cfm and low static pressure. They still have the same volume of air circulating. What makes the name "high velocity" is when the air is released from the vent because of the pressure. 2" ducts are ok, but the 3" ducts work better. Noise is related to poor instalation. The minimum number of vents must be respected for the fan unit/settings. Also, leaks in ducts are another cause. EVERYTHING MUST be sealed TIGHT with aluminium tape to eliminate/reduce noise.
As for the TXV, its in the coil of the blower. The circuit board is also located inside the blower where you'll find the freeze stat connection. Atleast that's the way my setup is.
I have a Hi-Velocity unit (3" outlets) in my home with a Waterfurnace geothermal R410A. Noise was eliminated be doing what I just said. I love my system and I'ld never go back to traditionnal.
Good luck
[this message was edited by cyberbeagle on Sat 9 Feb 16:35] |
| | marchvac
| "Re(2):High velocity furnaces" , posted Sat 9 Feb 17:05
The houses that I find to be noisy are the long narrow homes such as town homes with all hard surfaces like hardwood and ceramic floors. Don't take it the wrong way because the systems that I have installed work great but there are some people that are very sensitive to noise.
Be careful sometimes you don't get a second chance
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| | problems
| "Re(3):High velocity furnaces" , posted Sun 10 Feb 16:24
THANKS again guys, if you are ever up Brooks, AB - Canada way .............. ITS MY TURN TO BUY !
Just A/C Refrigeration and AirConditioning Services
In the Trade for a long long time !
Things a bit different than before !
Refrigeration still doesn't have a "d" in it does it ?
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| marchvac
| "Re(1):High velocity furnaces" , posted Sat 9 Feb 11:04
I have installed a few for reno's but don't like them because the noise. What make and model# is the air handler and A/C. Alot of the ones I put in have a terminal on the board for a freeze stat. I also prefer to use a tx on those systems. Most have a speed control and multi speed motor that you have to change the speed tap.
Be careful sometimes you don't get a second chance
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| | static
| "Re(2):High velocity furnaces" , posted Sat 9 Feb 15:05
The ones I have installed / serviced have always come with a TXV from the factory. And most definitely I agree with Marchvac about the freeze-stat.
The thing about these is, they're high velocity but low volume...done this way to dehumidify better...they want to run a colder coil. If you try to charge one by one of the "rule of thumb" methods (set suction pressure @ indoor temp, head pressure = ambient + 30º, etc.) you will screw up every one. They MUST be charged by subcooling (if it's TXV equipped).
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| | northernfitter
| "Re(3):High velocity furnaces" , posted Sat 16 Feb 23:10
I ran into one of these for the first time this winter and once I did some research was pretty discouraged with what I saw. A/C contractor comes in after the house is built and sells them a basic keeprite 2 ton. Coil keeps freezing up so instead of contacting the manufacturer they charge the guy to put in a new return air and gut all the ductwork costing him a couple thousand dollars. This winter the guy looses control of his 4 wheeler while plowing his driveway and takes out the condenser(1year old). Condenser is trashed and I dont have the heart to tell him how badly they have butchered his system. Going to put in another Condenser for him this spring with no markup and just the labor charges. Some guys just have no luck.
14years as a service tech in Ottawa and the valley. www.reliableheating.ca. For furnace manufacturer ratings go to
http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/gas-furnaces/furnaces-repair-history-205/overview/index.htm?resultPageIndex=1&resultIndex=1&searchTerm=furnace
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