Browse Forums Heating, Cooling & Insulation 1 Feb 16, 2011 12:26 pm Good Afternoon all, I have gathered up 3 quotes in my local area regarding the Actron ESP Ultima setup. The quotes seem to vary in price by around $2000 and in different zone setups. Controllers etc. But I’m trying to get my head around what will be the better installation because one quote has all bedrooms zoned but I’m sceptical that there will be far too much pressure on some of these rooms due to the small size. I understand that the 17.5kw Single Phase Actron ESP Ultima has a minimum zone duct pressure of 185 Litres per second. What I would like to know is what pressure rating the duct work can withstand for 8inch and 10inch ductwork. I found reference from Google that 8 inch Duct can hold between 50 - 90 Litres per second and the 10 inch Duct 90 - 160 Litres per second but unsure how credible these figures are and would like to ask any installers on Homeone if these values are roughly correct? Some quotes are referring to a common zone that will always be on but from what I gather as long a zone has enough ducting to support the minimum airflow of 185 L/s each zone should be able to run independently without the need for a common zone. Having a common zone defies the whole point to me of installing the ESP ULTIMA is this correct? I have a few rooms in question which I think will possibly be too much for the ductwork. I have an example below of my study from the quote which states an 8 inch duct. Its 3.9 meters X 3 Meters which equals 11.7 SQM, from what I can gather to get KW ratings needed for rough air con cooling is to multiply the SQM by between .125 and .150. Ill use the higher end (11.7 * .150 = 1.755KW) this is roughly the power needed to cool the single room. I also found reference on Google that around 60 Litres of air a second is needed per KW of cooling. Some quick maths on 1.755KW * 60 = 105.3 Litres per second of air to effectively cool a room of that size, this pressure appears to be over the duct rating of an 8 inch duct and under the minimum pressure rating for a single zone on the ESP Ultima. 1) Would this amount of pressure be likely to blow the duct apart or create substantial problems with noise and other issues in the future? 2)Should this room be zoned with my theatre room that will have a 10inch duct allowing over the minimum 185 Litres a second? If the pressure figures I have been using for 8 inch ducts are correct and they can withstand a maximum of 90 Litres per Second and zoning 2 bedrooms together with 8 inch ducts = 180 Litres per second would this be borderline enough to run a single zone on since the ESP Ultima's minimum fan speed is 185 Litres per second or would the extra 5 litres per second be negligible? I would like to stress I’m no expert and my formulas are most probably incorrect. I just would like to see if I’m on the right wave length and get the best out of my install!! It’s a big outlay. Cheers and sorry for the long winded post Steve Re: Actron ESP Ultima and Ducting, Zoning Questions!! 2Feb 18, 2011 7:47 pm I am having exactly the same issue with that system. I'm stumbling around in the dark using formulae from the internet that may or may not be right and I just want the people quoting to explain how they work out that there won't be too much pressure and noise if using one vent, single zone into a bedroom of about 15m2. Someone posted in another group that they were ok with that setup with a 14.5 kW ultima but its minimum flow rate is 150 l/s and I don't know if that will make a big difference or not. My last response from the people doing my quote was "Industry standard for a bedroom is approx 6-8 litres per sq/m via a 250mm duct.". I can't see how that is right?? I suspect that its /s not per /m in which case it comes out close to your rule of thumb at 93.6 l/s on 11.7 m2. I've then looked at http://www.comairrotron.com/airflow_calc.shtml . Using an airflow of 185 l/s with a duct of 12.5 cm radius gives a linear speed of 3.77 m/s or 741.87 ft/min. It looks like systems for bedrooms should be kept below 600 ft/min - I can't find the page where I read that. If you increase the radius to 15 cm then the velocity drops to 2.62 m/s or 515.19 ft/min. There is a relevant post here where someone says "you want to keep velocity in the duct to no more than 5m/s" http://www.*.com/f193/minim ... ize-74682/ . So putting that all together if I I had to guess I'd say we would be OK with 300mm into a single duct and it might not be that noisy. What I have learnt from looking online though is that the calculations aren't as straightforward as I suggest above with friction coefficient, static pressures, face velocities etc etc so I might be off the mark, What I'd really like is for someone who owns the 17.5 kW Ultima to say "forget the calculations I've got one and its quiet enough to sleep when only one zone is on". I suppose I also need to know if there are any disadvantages of using 300mm duct rather than smaller...? Re: Actron ESP Ultima and Ducting, Zoning Questions!! 3Feb 18, 2011 8:27 pm you guys would have done more research than any installer that i know. You guys need to consider duct length in your calculations. The figures you have been quotes for the amount of litres per second suitable for various duct size are recommendation based to reduce the amount of resistance. ie if to much air passes through then resistance increase and it becomes inefficient. However if you go to big of a duct there is too much surface area then you cool air may increase by 1 degree. I have measured this on my own system where i have a combination of 8 and 10 ducts. 10 inch ducts are always one degree warmer. You also need to calculate the air volume in the room. So Ceiling heights come in to the calculations also. Re: Actron ESP Ultima and Ducting, Zoning Questions!! 4Feb 18, 2011 8:52 pm Thanks B Star and yes I recognise it's all a bit obsessive. But its an expensive unit and I just want some reassurance before spending that money that it will perform. It will be in a long time and I dont look forward to explaining to my wife why it is that I got "the noisy" one if I muck it up. Re: Actron ESP Ultima and Ducting, Zoning Questions!! 5Feb 18, 2011 8:57 pm I totally agree peter. I spent (and still not finished) ages optimizing my heating and cooling system. I believe its almost more important to have the duct work installed correctly then it is getting the right size unit. I had spent heaps of time researching is area to work out how I was going to go about it. Re: Actron ESP Ultima and Ducting, Zoning Questions!! 6Feb 24, 2011 11:37 pm PM me and don't confuse the issue! You are not far from the mark but don't over analyse You get what you pay for! Re: Actron ESP Ultima and Ducting, Zoning Questions!! 7Mar 06, 2011 1:12 pm Peter1295 What I'd really like is for someone who owns the 17.5 kW Ultima to say "forget the calculations I've got one and its quiet enough to sleep when only one zone is on". All those calculations lost me! But we have an Ultima 18kW that uses both size vents/ducting and yes, I can tell you that every bedroom is quiet enough to sleep even if it's the only zone on. Never, ever had any problem with air pressure or anything else when only one zone is on. Re: Actron ESP Ultima and Ducting, Zoning Questions!! 9Mar 08, 2011 1:52 pm @ 3m/s velocity the following diameter ducts will carry 200mm (8") 95 l/s 250mm (10") 150 l/s 300mm (12") 210 l/s 3m/s is recommended for the final connection to the vents in residential applications. There are various types of flexible duct and if noise becomes an issue (it shouldn't) their is 'acoustic' rated duct which is typically quieter than standard flex. basic calc for a room / area = L x W x H x 3.54 = l/s x 0.0176 = kW. You can use the 150w/m2 but it doesn't factor the volume if ceiling heights are abover standard (2.45m). This calc factors volume first and then converts to kW This is for a standard application with no North / West facing windows - insulated etc. You get what you pay for! Thanks for that! Yeah, I was thinking timber front door. 10 21641 4 11199 Personally, considering your layout (study/work desks in bedrooms), I don't think you have any other option but to leave NW windows and make them as big as possible e.g.… 7 10470 |