Coanda

Are they not the same thing?

I'd like someone to check my mathematics. It's a long time since I left school. I'm using 90mm ducting, which has an ID of 78mm so the radius is 39mm 39 by 39 by 3.14 gives an area of 4775.94 mm2 Divide by 1,000,000 gives 0.00477594 M2 Call it .005 cause my anemometer only has three decimal places. Extract from the kitchen shows 0.7 CMM and same from the bathroom. Total extract 1.4 CMM Supply to the living room. bed room and junk room is 0.5,0.4 and 0.5 CMM also for a total of 1.4 for the sake of balance I'm going to leave it there meantime. Multiply these numbers by 60 and presto total out, 84 CMH and total incoming the same. I'm going to leave it like that for few hours to see what the numbers at the unit look like regarding temps in out etc. Tomorrow I'll try opening the ceiling vents to see if any more comes through. 84 CMH, if my maths are correct is probably good enough for ventilation but I'd need something in reserve for boost.

Are you using it on it's own or part of a mvhr set up?

Velly intellesting. I searched for mvhr core. There doesn't appear to be any great bargains at present but keep looking, I did, If he had bought it off the shelf, four years later he would have wished he made it himself or something else, such is human nature. Yes I agree, I'm retired with time on my hands, a small workshop and a reasonable amount of tools so why not have a go. At the same time if I found a complete unit for a knock down price I would buy it and pass my time some other way.

Like my wheelie bin vacuum. I put a perspex lid on it and now I can be mesmerised by the saw dust swirling round and round and,,,, It's 227 by 227 by 383 on the small side I would agree but I may manufacture a second one from corriboard and put them in series. Fans are definitely a problem, although I am looking into ones recommended earlier by Johnmo. The two I am using now are repurposed inline fans, one Monrose and another similar. They are rated <> 180- 230 M3h but they are not doing that and they are not balanced, I only have one duct going to each Plenum, I'm wondering would two allow more air with the same fan speed or would better fans be a better bet.

Yeah, thinking along those lines None at present but carbon on way from Temu.

I get that. But I'm old school, I heat all of my house to 15/16 deg which is comfortable for the bedroom and kitchen and enough to keep unused rooms from going stale. The living room has a wood burner which keeps me cosy in the evenings.

The exchanger/core is 227 by 227 by 383. I looked those fans up, they look like a possible solution, Do you happen to know what their flow rate is?

May I enquire what formula you used?

It would but I doubt I could be dedicated enough, unless I could automate a system. Here's a couple of pics I took when I was building it. I built it big on the idea that the longer the air was inside the better. That may or may not be true. It's 820 by 800 by just under 500. It could have been quite a bit smaller and possibly worked as well. I made the enclosure from 50mm polystyrene. I wouldn't do that again. The polystyrene is cheap, light and easy to cut but born out of wedlock to glue. After I've monitored and or tweaked it a bit I may make the box again from something more substantial. I'd like some suggestions, maybe MDF or good quality plywood. Not that I've seen but I'm a newbie Here you go.

There's a problem, though I don't know how serious it is. Certainly not life threatening at this stage. The fans I am using are not equally matched intake pushes through about 20% more than extract, so I'm going to, at some point have to replace one or both. Where does one locate suitable fans, they don't come up in google searches.

Thank you for your reply. Looks like we were posting at the same time. One of the bits I read said about the heat from the room having an effect so although in my case it wouldn't matter cause it's in the cold attic space I didn't use it and opted for the passive house one.

I had hoped some wise person would have commented on the efficiency or lack there of. So in the absence of that I searched for a formula online. I found a formula for a PHI test. My house is nowhere near a PH but I applied the formula which gives 74% Now that the temp outside has lowered it gives a rating of 80.7% not to shabby considering it's held together with titebond and duct tape. The formula used is extract air minus exhaust over extract air minus intake.

I bought a core cheap on a well known online auction site and made a polystyrene housing for it and a couple of inline fans which I had removed from extractors in the house. I then bought a batch of ducting, connectors etc from BPC and jerry rigged the whole thing up as a test. The ducting, etc is all good and will be staying, I just need to decide if the unit is good enough, needs improving or replacing. The temperature sensors are not exactly state of the art but will give an indication. Thlevel 4x Digital LCD Thermometer Temperature Monitor with External Probe for Fridge Freezer Refrigerator Aquarium (4x Black) : Amazon.co.uk: Large Appliances

I don't travel the M6 very often, so much as I'd like to I probably won't get to see yours. I was hoping someone would comment on the numbers or more importantly, as you say the difference between them. I'm not totally dissatisfied as the extract ducting is laying on top of the insulation and I know that temp will improve once covered and give a little more heat to be recovered. But I don't think that will make any difference to the basic efficiency of the exchanger.

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Finally got the DIY MVHR running yesterday. It's just taped up to make sure everything fits. Today I checked everything over and fitted thermometers. Here's what it looks like after running a couple of hours.

Since I posted this, I contacted the company which fitted them. A very helpful lady texted me back in minutes to say that the vents fitted to my roof are C5. A quick search online tells me that C5 vents are good for 2000mm2 of air. My schoolboy mathematics tells me this is more than ample for the 125mm round intake/exhaust pipes I will be using. (correct me if I'm wrong.) I have located two vents in close proximity to where I will place the exchanger. Unfortunately they are both intersected by a rafter. This makes things a little more awkward, but I have fashioned vents which will straddle the rafter and seal against the felt. I will monitor the installation and should any problems arise, I can change them to the soffit which will be a bit more work, but hay, ho if it's needed.

No more nails didn't work out so good. It was still not set after 18/19 hrs. So my plans for gluing up today had to go on hold. So with nothing more pressing on the calendar, I took a wee excursion to BPC in Larne. I may not have everything I need but it must be close to it. Great guys, very helpful and keen prices. I'd highly recommend them. For your info a 50m roll of 90mm semi rigid can be shoe horned into a Ford Kuga and, it not as easy to get out again. Just saying.

As the title says. How have you or how do you suggest insulating the semi rigid ducting in the roof space?

BTW any suggestions for glue anyone?

The temperature/ RH logger would be nice. But plenty to do before that's needed.

I can't disagree. But this is my first attempt, which I am treating as a learning curve. Using what I have as far as possible and the crossflow core which didn't cost much at all.

I'd be really interested in that. Fill me in.