16 July 2009
1117 the high road
Mr. David Patricks
3005 west 29th,
Dear Mr. Patricks :
I received your June 6th letter requesting consultation an am providing my recommendation in the following.
First, let me review my understanding of your inquiry. The question you raise revoives around whether the heading registers should be located in a low sidewall, or in the ceiling, and, if ceiling registers are used, which type—step down or stamped-faced—will deliver the best results. Additionally, the problem concems whether there is any benefit to having heating registers near the floor,whether moving heated air “down” in ducts negatively affects blower performance, and whether adequate injection that can be achieved on the low spped of a two stage fumace.
my recommendations are as follows :
- I can find mothing in either carrier, Trane, or ASHRAE design manuals that indicates drop as being a factor in duct design any different from normal static losses, if you have different information on this, I would like to have references to it.
- I cannot see any advantage to low sidewall application. The problem is injection an pattern. I do see an advantageto low sidewall return; carrier design manual air Distribution is a good reference on both items.
- I recommend step down diffusers with OBD because they have pattern and volume control that is superior to stamped faced diffusers.
- I am opposed to low sidewall diffusers or floor diffusers in the application you describe. The increased static losses that result from trying to get the ducts down through the walls will only increase installation cost and reduce efficiency.
If there is anyone in your organization whom is uncomfortable with these recommendations, let me know. I’d be very interested in reviewing any actual documented test results. Let me know if you have any futher questions or if I can be of any further assistance.
sincerely,
Jane A McMurrey, P.E.
HVAC Consultans
