Browse Forums Heating, Cooling & Insulation 1 Sep 29, 2014 9:42 pm Hi All, Over summer I would like to redo my ducting for heating as the airflow is not setup correctly... Are there any heating experts on here that can draw my airflow for my place if I obatin the house plans from council. Its a 12 year old house and I have full aceess underneath in teh sub floor area. 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 3Sep 30, 2014 6:14 pm One of the main problems with ducted heating distribution isn't the ducts . . . Its the fact that there is only one return air point. This means that if you shut a door between a duct and the return air point the heating will be much less effective in that room. What happens is you pressurise the room with the shut door which then stops the air from being sent to that room. Changing the ducts won't make much difference if the above is your problem. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Duct Heating Expert - Redo Ducting Air Flow 4Sep 30, 2014 8:53 pm Bels What's wrong with it currently? The air flow was not set up correctly and the front part of teh house is much colder due to the duct size sending the air. Bels What are you trying to achieve? I think from memory I will chekc better when I enter the sub floor it has a 6" duct running about 10 meters feeding teh outlets with 6" duct. I need someone who understands airflow or willing to type in ceiling heights and room sizes to get the best for my place. The biggest problem is the unit is located at he rear of the property which was installed before I purchased the place. My other biggest achivement would be to lower my heating bill as I feel the unit is working overtime due to poor layout. 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 5Sep 30, 2014 10:20 pm Handy007 The air flow was not set up correctly and the front part of teh house is much colder due to the duct size sending the air. How many outlets in total? What is the model of your ducted heater? Handy007 Better air flow with some changes to the layout. Are you planning on zoning or anything? Handy007 I think from memory I will chekc better when I enter the sub floor it has a 6" duct running about 10 meters feeding teh outlets with 6" duct. It depends on how many outlets is hanging off the end of this 6" main branch. Increasing the size of the duct will result in moving more air but at a slower velocity unless you're able to increase the output of your fan, i.e. running your fan at high speed when previously it was on low or medium speed, etc. What about using a booster fan to assist in moving more air down to the front of the house? Handy007 I need someone who understands airflow or willing to type in ceiling heights and room sizes to get the best for my place. There's online heat load calculators which could be a good starting point for you to understand what capacity is required for each room. You could get some approximate dimensions with a tape and go from there to give yourself a starting point. Handy007 The biggest problem is the unit is located at he rear of the property which was installed before I purchased the place. That's not that great a concern, what's more important is what your fan is rated for as that's pushing the air around. Handy007 My other biggest achivement would be to lower my heating bill as I feel the unit is working overtime due to poor layout. Again, all this will depend on the capacity of your unit, duct ratings, air losses, what your heating the house to, zoning and location of the thermostat. hth Re: Duct Heating Expert - Redo Ducting Air Flow 6Oct 01, 2014 9:21 am Hi Handy 007. There is a merit in what you are trying to do. During my new install I did a lot of this work to improve the performance of both heating and cooling. In your case if you want advice I think it would be best to draw a plan of what you currently have. I can already suspect one issue is that you have two different rooms that are at different distance from the unit but both have the same diameter pipe. As you have point out these will yield two different performance for each room. If I was to give advise to you in this project you should be trying to achieve the following. 1. Balance out the air flow 2, Removing necessary duct work and ensuring they are kept as short as possible. 3. Make sure and eliminate air leaks 4. Make sure all bends are smooth and not sudden. 5. All straight runs should be straight as possible. To balance out the system in the example given I would be looking at making the long runs and 8inch instead of 6inch. This is reduces airflow speed as someone has already pointed out above but what people always forget to mention(and some fail to understand) that reducing airflow also reduces friction (= airflow loss) So in terms of volume of air you will get more out of the pipe. Which make the unit more efficient. ( This is the part that is difficult for people to understand) Return air can be a bottle neck also so make sure you have the shortest possible run from you unit to the return air. If this is to long and has to many bend try relocating. the r/a. If you want more advice the next step would be to get a house plan and locate all the heating components on it. Re: Duct Heating Expert - Redo Ducting Air Flow 7Oct 01, 2014 9:20 pm Bels How many outlets in total? Bels What is the model of your ducted heater? Bels Are you planning on zoning or anything? Bels It depends on how many outlets is hanging off the end of this 6" main branch. Increasing the size of the duct will result in moving more air but at a slower velocity unless you're able to increase the output of your fan, i.e. running your fan at high speed when previously it was on low or medium speed, etc. What about using a booster fan to assist in moving more air down to the front of the house? Bels There's online heat load calculators which could be a good starting point for you to understand what capacity is required for each room. You could get some approximate dimensions with a tape and go from there to give yourself a starting point. Bels That's not that great a concern, what's more important is what your fan is rated for as that's pushing the air around. Bels Again, all this will depend on the capacity of your unit, duct ratings, air losses, what your heating the house to, zoning and location of the thermostat. BTW thank you for your reply and help. Are you a duct installer? 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 8Oct 01, 2014 9:32 pm B STAR Hi Handy 007. There is a merit in what you are trying to do. During my new install I did a lot of this work to improve the performance of both heating and cooling. In your case if you want advice I think it would be best to draw a plan of what you currently have. I can already suspect one issue is that you have two different rooms that are at different distance from the unit but both have the same diameter pipe. As you have point out these will yield two different performance for each room. I want to scrap what I currently have in place and start fresh but keep the heating unit. Sometimes its best not to work with a dogs breakfeast and get teh formula the way it should be. B STAR If I was to give advise to you in this project you should be trying to achieve the following. B STAR 1. Balance out the air flow B STAR 2, Removing necessary duct work and ensuring they are kept as short as possible. B STAR 3. Make sure and eliminate air leaks B STAR 4. Make sure all bends are smooth and not sudden. B STAR 5. All straight runs should be straight as possible. B STAR To balance out the system in the example given I would be looking at making the long runs and 8inch instead of 6inch. This is reduces airflow speed as someone has already pointed out above but what people always forget to mention(and some fail to understand) that reducing airflow also reduces friction (= airflow loss) So in terms of volume of air you will get more out of the pipe. Which make the unit more efficient. ( This is the part that is difficult for people to understand) B STAR Return air can be a bottle neck also so make sure you have the shortest possible run from you unit to the return air. If this is to long and has to many bend try relocating. the r/a. B STAR If you want more advice the next step would be to get a house plan and locate all the heating components on it. I have got house plans which I have to convert the files to upload. Btw thanks for your reply... Are you in the field? 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 9Oct 01, 2014 9:39 pm A couple fo other questions; Where in Melb can you buy good quality ducts? I don't mind spending the extra dollars as I would like to get a fiar bit out of it plus once the unit dies I don't want ot worry about the ducts that are in place. I have heard of companies such as Westaflex and Metaflex are their any better products than these companies. How can I work out in the thermostat is working correctly... It is a Honeywell CT2800 https://customer.honeywell.com/resource ... 9-0767.pdf Can anyone suggest a good thermo heating engineer and what are the fees to do this? Thank you everyone for your input..... 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 10Oct 01, 2014 10:00 pm Hi Handy007 sounds like you are very determined. Regarding your one main question on the return air. There is no real need to have two. Just one in a good location that is unrestricted. If you are going to go the trouble of changing on all ducts consider if you will ever be adding refrigerated cooling to the system as this will change things. Also if you could be changing the heating unit to a more modern type in the future consider if you will want to add zoning later and if this is the case design the duct network accordingly. Regarding good quality ducts then one u mentioned are better ones. But you will need to compare the price difference as see if the price difference is reasonable. You asked if I am in the field. The truth is I am not. But I am an engineer that spent many years designing rf (Radio frequency) distributed antennas systems for a major telco for large office building and when I started looking into the airflow theory I discovered that theories and concepts are very similar for RF in coax and Air flow in ducts, so I picked it up pretty quickly. I found many installer don't understand the airflow concepts as well what I did which I thought was interesting. Subsequently I redesigned my system and significantly improved performance and efficiency for both my heating and add on cooling systems - but it did take a while to make all the changes. Re: Duct Heating Expert - Redo Ducting Air Flow 11Oct 02, 2014 8:45 pm B STAR Hi Handy007 sounds like you are very determined. B STAR Regarding your one main question on the return air. There is no real need to have two. Just one in a good location that is unrestricted. B STAR If you are going to go the trouble of changing on all ducts consider if you will ever be adding refrigerated cooling to the system as this will change things. B STAR Also if you could be changing the heating unit to a more modern type in the future consider if you will want to add zoning later and if this is the case design the duct network accordingly. B STAR Regarding good quality ducts then one u mentioned are better ones. But you will need to compare the price difference as see if the price difference is reasonable. B STAR You asked if I am in the field. The truth is I am not. But I am an engineer that spent many years designing rf (Radio frequency) distributed antennas systems for a major telco for large office building and when I started looking into the airflow theory I discovered that theories and concepts are very similar for RF in coax and Air flow in ducts, so I picked it up pretty quickly. I found many installer don't understand the airflow concepts as well what I did which I thought was interesting. Subsequently I redesigned my system and significantly improved performance and efficiency for both my heating and add on cooling systems - but it did take a while to make all the changes. Thanks for your feedback. 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 12Oct 02, 2014 10:25 pm Hi again all, I'm also thinking of adding three more extra duct point if teh unit can handle the capacity one for each bathroom and the other for the kitchen/dining area. One other question how does one check if the thermostat is working correctly? When I unscrewed the thermostat off the wall [Honeywell CT2800] https://customer.honeywell.com/resource ... 9-0767.pdf There are two wires like speaker wires plugged in which run under the sub floor and I assume they go to the heater unit or are they meant to be in the duct? Thanks. 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 13Oct 03, 2014 12:46 am Handy007 Are you a duct installer? No, I'm an electrician/refrigeration mechanic. I cut my teeth in the commercial and industrial air conditioning service industry but nowadays work more on commercial refrigeration although I still do bits and pieces in commercial HVAC. The IHE120S is rated at 1100L/s air on high speed although at what pressure isn't specified. It does list some sort of boost mode where it provides 1200L/s air @ 125Pa but not sure the fan is rated to run at that all day long. Unsure of the size of your house but assuming a conservative 100L/s to each outlet taking into account 10% loss which is regarded as acceptable. In reality you'll have more air out of some outlets and less out of others depending on location in various rooms, etc. To consider adding 3 additional outlets, you'll need to consider the size of each room; ceiling heights; insulation (if any) in walls, ceilings; and thermal losses through windows, etc. It works out to be a bit over 75L/s for each outlet which seems inadequate from a glance. You could consider zoning to only heat the rooms you require at different times which would give you a bit more capacity out of your unit. Otherwise the inline booster fan would work here. With ducts, my suggestion is to get as high an R rating as you're able to afford. The increased insulation means you less likely to lose your heated air to infiltration or ex-filtration and thermal losses leading to an increase in efficiency as long a all the joins are sealed correctly. For the long straight run of ~10m, you'd need to run a minimum of 14" flex to move the required air at an adequate pressure (~650L/s @ 100Pa is a good starting point). Else you could run it in a straight length of solid spiro duct and then only require 12". That main branch will need to be 14" from the fan. From the 14~ you can branch down to 3 10" ducts and then to 2 6" ducts off each 10" and one to each outlet. If you went with the inline fan route, depending on what the fan flows, you could even upsize your ducts to 8" to each outlet. Where in Melbourne are you roughly? There's a few other places able to supply ducts and things scattered around. Westerflex is generally good duct so you can't go wrong with it even if you don't bother to shop around for anything else. Generally Honeywell digital thermostats have a pretty decent control loop and fuzzy logic. They obviously are mass produced to work in nearly all applications so they won't try to squeeze every last bit of efficiency out of the control loop. Unless it's really acting up, I'd not be inclined to condemn it. You could always change it out for something else down the track if you so choose. In terms of cost of running, what setpoint have you set on your thermostat? If your house is not able to reach the setpoint you set then the heater will be running all the time trying to heat the house to the setpoint contributing to high heat bills. An example I run the setpoint on the ducted heater at 20 or 21 and the heater will cycle on and off as required and the house is comfortable. Everyone opinion of comfortable is different though so what's comfortable for me may not be for you. The 2 wires you see behind the thermostat are the control wires which are switched through the thermostat's heating relay to start the heater. Like with anything take the advice and suggestions here with a grain of salt. As helpful as we all are, we don't know all the details of what you're dealing with. If you do engage someone, you could run all the suggestions past him/her. hth Re: Duct Heating Expert - Redo Ducting Air Flow 14Oct 03, 2014 8:35 am Some good advice there Bells. One thing I want to know more details about is your recommendation to to favor bigger duct work. While I agree this will vastly improve airflow I found that in my test increasing duct size from 8 to 10 inch increased the aircond temp by 0.5 to 1 degree when I measured it. I suspected the increased surface area (from bigger duct) exposed to the roof cavity caused this. Because of this I wasn't overly keen to increase the duct work excessively. Re: Duct Heating Expert - Redo Ducting Air Flow 15Oct 03, 2014 8:13 pm The suggestion of the larger duct work is its volume of airflow it's able to carry. The fan in the above mentioned ducted heater is rated at 1100L/s of airflow and 60% of that is 650L/s. I took a guess of 100Pa of static pressure as a starting point as that variable is unknown. The main branch supplying the 6 outlets at the front of the house is 10m of 6" duct. To realistically supply 650L/s through that size duct to 6 outlets you'd be running at a ridiculous static pressure and it would sound like there was a 747 jet under the house with the velocity noise of that much air being moved. It's probably why the OP doesn't feel the installation is working very well and he's right, it isn't. Being able to supply the adequate amount of air at a reasonable static pressure will allow that air to then be used for heating without disadvantages as noise or drafts. To supply 650L/s of air @ 100Pa will require duct work with a diameter of 335mm. As duct work sizes step in set sizes, the recommended size in this case is 14" or ~350mm diameter. The increase in temperature you're seeing is more likely due to the reduced velocity of the airflow allowing the air to pick up more heat than when it was flowing quicker. More surface area won't matter as much if the duct is insulated correctly or insulated with a high enough R rating to minimize or stop heat infiltration. The OP has also stated that the duct work will be run under the house so isn't going to be affected by the heat in the ceiling space. With increasing the size of the duct work from 8" to 10" you're effectively flowing the same volume of air at a reduced velocity. hth Re: Duct Heating Expert - Redo Ducting Air Flow 16Oct 03, 2014 11:19 pm Bels and B Star thank you for your replies and input. Im got a better understanding with your help and Im looking forward tio fix this problem. Couple of questions; Who else sells duct heating supplies that are very good quality and I don't mind spending that liitle bit more. Im going to try and avoid a inline booster fan for numerous reasons but interested what you guys think about them BTW do these inline fans run all the time while the heater is on or do they have a trigger unit for this. WIth my thermostat I did take if off the wall to see the wiring setup which it does have speaker type of wires. Solid black is wired to R on the back of the thermostat and black wire with white strip is wired to W. How do I know if they have doen this correctly? Once again Im really greatful for your help on this guys. 'It's not the size of the dog in the fight, it's the size of the fight in the dog.' Re: Duct Heating Expert - Redo Ducting Air Flow 17Oct 05, 2014 12:43 am Handy007, PM me your location and I'll direct you somewhere in your area. I'm personally neither for or against using booster fans. My experience is generally commercial so if a booster fan is required then it generally gets installed. The downside of it is the additional cost to buy initially, the power consumption when running and noise or vibration when not installed correctly. If you require a certain volume of air and you're not getting it, you'll either need to install a booster fan to satisfy the requirements or contend yourself to knowing the system isn't going to heat as designed due to the shortcomings. To operate correctly, the booster fan would need to be wired to run when the main fan runs. To have it running constantly will cause draughts when the heater is in the off cycle and not firing. You'll require an electrician to wire this for you or you could get an electrician to wire a plug base where you could then plug in the fan. Yes the thermostat is wired correctly. hth Re: Duct Heating Expert - Redo Ducting Air Flow 19Oct 09, 2014 8:41 pm Agree with you to some degree but what's the alternative if you don't have enough air for your living space? It's either make do with what you have, replace the fan in the heater (if able to) or replace the unit with a larger one. Options 2 and 3 will both cost money and require handy engage someone in to carry out the work for him. With the booster fan, he'll be able to install it himself and only require someone to come in to tie it in with the main fan. Horses for courses and there's more than one way to skin a cat. DIY, Home Maintenance & Repair Hi everyone Question about Brevis gas heating undergound - was recently installed by previous owners (<1 year old) but live in a relatively large house - 4 bdr - and only… 0 2152 Good luck with it. I don't know what the cost of a nice bidet seat with a 25mm air gap will be but you are obviously deducting the cost of a RPZ valve and its… 9 6985 You may still have a case, but your next step is to speak to a lawyer. 3 1649 |