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There is a DDC controller modulating the dampers, thus ensuring that there is enough air passing through the DX evap coil so that it does not freeze up. Am I too understand that : - the suction pressure will drop as there is less cold gas flowing ? -The temp of the refrigerant evaporation...

I have been told if you By-Pass some air around the avaporator coil, you will dehumidify the air while not needing to reheat it. What is more, the fact that you reduce the air flow through the evaporator coil, you reduce the suction pressure of the cold gas, thereby reducing the evaporating...

DrRTU this is a comfort cooling case in a private residence for elderly people. What do you mean by 'Many codes /standards prohibit non cycle rh for comfort cooling. ' in this situation? Back of the envelope calcs : In dehumidification mode, run only first stage compressor. Therefor : 67% x 3...

DrRTU, Thx for the RAWAL suggestion...Therefor you are saying the RAWAL device + an electric coil c/w SCR is the more efficient solution to build and operate ? The idea of recouperating the heat was enticing, but if I understand you correctly, you are saying it's too complicated to properly...

Hello, Is it possible, with a heat pump, to do a Hot Gas Reheat, by diverting some of the Hot Gas from the Condensor to a reheat Coil. The goal is to respond to a call for dehumification without further cooling. Please see attached diagram. Equipment: Heat Pump : (New-To Be supplied)3 Ton, 2...

Given the amount of welding and hot dip galvanizing, I wouldn't be surprised if the base plate would curl if it didn't have this tear. Therefor, maybe it's there to ensure that that base plate can yield enough so as to be tightly sandwhiched between the leveling nut and tightening nut during...

....from what I remember, in driven (hammered) piles, buckling is discounted as the soil is assumed to be bracing laterally the pile. Materials are heavily factored because of dubious quality.

Just thinking out loud -if the concrete column is exposed; Add a full height reinforced concrete collar to the column and weld the rebars to the steel capital collar to ensure development and transfer of stresses.

I came up with this arrangement for mechanical components of an Air Handler (Please see attachment) Plenum Fan + N-Coil +Discharge Plenum. Following everyone's suggestions, 1.I placed the N-Coil after the Fan Motor so as to remove the risk of a damp Fan-Plenum environment. 2.I use a Discharge...

I came up with this arrangement : (Please see attachment) Plenum Fan + N-Coil +Discharge Plenum. Following everyone's suggestions, 1.I placed the N-Coil after the Fan Motor so as to remove the risk of a damp Fan-Plenum environment. 2.I use a Discharge Plenum so as to do away with transitions...

....sorry Maurice, not sure what you mean ?

Post-script : If you are installing duct heaters, you need a minimum of 50 cfm per KW of heat. Other wise your ductheaters will overheat. So there is a minimum, or lower limit, you could work off of !

Here is the uploaded schematic !!!http://files.engineering.com/getfile.aspx?folder=ecd5f19b-2b20-4e5f-94ca-d9fc098dfb9f&file=ControlDiagram.jpg

If anybody cares to comment I am uploading a system schematic. I am new at this, feel free to comment or correct my schematic. This design revolves around the use of three thermostats. T1 has a room temp sensor and controls the heat pump and at times signals the need for aux-heat. T2 has a...

Thanks maurice, what do you mean by in-duct detector? Is that a thermostat or temperature sensor in the duct ? Do you have a specific device model # I can quote to someone ? What value did you use as a discharge temperature ? Thanks

Guys...thanks for your comments ! This is what I've found so far. There isn't any thermosat capable of controlling a 2 stage heat pump with auxilliary heat (Emergency Heat)with a 0-10VDC output required for the electric duct heater with SCR. Be very kind of someone to prove me wrong. Regards

Tys90... Just so you know, the fan is a plenum fan with a VFD with up to 8 preset speeds. Do you know of a thermostat model by name ? I don't understand what you mean by 'Also, 90.1 allows reheat of up to 30% of the design airflow' why do they base it on flow rather than on cooling or enthalpy ?

Does anybody have experience using electric duct heaters that can modulate using an SCR. This is supposedely an improvement to staging. I am proposing a 12 KW duct heater in a residence. I wasn't sure if I sould divide it in 2 or 3 stages or specify modulation using an SCR. My questions are ...

BlueSandman, Thx for your reply. Actually I share your concern and yes there will be dehumidification. This is how I address the problem : I cannot put the coil after the fan because there is no room. I am hoping that by ensuring that the air flows through the coil at a speed of < 450 fpm, I...

Thx for your feedback everyone ! I will install a VFD too. As you can see, the installation is tight and I want to minimize system effects. Like many of you mentioned, I am seeking noise reduction which I am hoping the backward curved blades and direct-drive motor offer. Once it's...