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    • CommentAuthorowlman
    • CommentTimeNov 9th 2015
     
    Does anybody have any experience with these units in a domestic interior?
    • CommentAuthorbarney
    • CommentTimeNov 9th 2015
     
    Not air to air HP, but I did live in a flat that had ducted air heating - bloody hopeless in my opinion

    No significant radiant component, dusty, quite high temperature air if close to the vents, noisy (fan and duct noise) and generally something I would avoid at all costs

    In a highly insulated dwelling where the air volumes and velocities involved are perhaps smaller and the delta T to the room can be smaller then maybe - but I wouldn't want it as my sole means of heating

    Regards

    Barney
  1.  
    Posted By: owlmanDoes anybody have any experience with these units in a domestic interior?


    Yes ... sort of ...

    Posted By: barneyNot air to air HP, but I did live in a flat that had ducted air heating - bloody hopeless in my opinion

    No significant radiant component, dusty, quite high temperature air if close to the vents, noisy (fan and duct noise) and generally something I would avoid at all costs

    In a highly insulated dwelling where the air volumes and velocities involved are perhaps smaller and the delta T to the room can be smaller then maybe - but I wouldn't want it as my sole means of heating

    Regards

    Barney


    My experience is ducted water-to-air, but the experience should be the same. It's true there's no radiant component, yet I am sitting here in comfort with all interior surfaces close to air temperature. There's no dust, as there's a decent MERV10 filter in the supply duct - if you have a good filter there shouldn't be an issue, but often the filters that come standard are very poor. If anything, I can see the air coming out of the vents (in sunlight) has less dust than the general room air.

    There's next to no noise, especially in the bedrooms as these are the furthest from the fan. The main supply ducts are all lined with acoustic absorbents and a all the main "turns" have turning vanes to also help reduce noise. Noise is often due to air velocity that's too high which is often caused by ducts that are too small.

    My house is not well insulated (1898 solid brick/stone construction with between 1 and 2cm of insulation here and there). The heatpump has no problem keeping me warm, even when it's -25C and lower outside (though auxiliary resistance heating kicks in when it's below -15C). I

    I'd highly recommend this type of system ONLY if you have the space to put in the correctly sized ducts required. If you skimp on these, you will have noise. Air temperature coming out of the ducts should not ever be high enough to give a "burnt dust" smell.

    Paul in Montreal.
    • CommentAuthorringi
    • CommentTimeNov 9th 2015
     
    In the UK you are unlikely to find a company that will install a system to the standard Paul has without making a UFH refit seem cheap!
    • CommentAuthorowlman
    • CommentTimeNov 9th 2015
     
    Posted By: ringiIn the UK you are unlikely to find a company that will install a system to the standard Paul has without making a UFH refit seem cheap!


    Except that I don't want to rip up decent flooring for UFH and discrete ceiling grilles seem a much better idea. I've been quoted about £2500- £2800 for a 10kW system on a supply only basis plus fitting guidance, and an extra approx. £500 for checking and commissioning.
  2.  
    Posted By: ringiIn the UK you are unlikely to find a company that will install a system to the standard Paul has without making a UFH refit seem cheap!


    That's sad as it's easy to design the correct sized ducts. However, most houses here have basements so it's much easier to run the large "trunks" than it is with a solid floor. Some people use "high velocity small diameter" ducts in retrofits where there is no space - but these have to be carefully designed to avoid noise, though it is possible. There are lots of resources on US A/C sites to help you calculate the correct ducts to minimize noise.

    Posted By: owlmanExcept that I don't want to rip up decent flooring for UFH and discrete ceiling grilles seem a much better idea


    It's actually quite normal to use ceiling registers, especially for systems that do A/C (cold air falls after all) - in my house we have registers on the ground downstairs (fed from the basement) but ceiling registers upstairs. Both work well for heating.

    Paul in Montreal.
    • CommentAuthorowlman
    • CommentTimeNov 10th 2015
     
    Thanks Paul, I'm doing a bit of pre-planning and looking to the future, when hauling logs for my biomass boiler is beyond me, and the thought of spare solar energy plus the new home battery storage is a distinct possibility.
    Combining that lot and going down the A2A route seems easy and attractive without very much disruption as I have good accessible loft space, at least over the main living area plus wood stove to supplement.
    • CommentAuthorringi
    • CommentTimeNov 10th 2015
     
    It may be easier to put a small A2A unit in each room rather then ducts back to a large central unit.
    • CommentAuthorowlman
    • CommentTimeNov 10th 2015
     
    I'd thought of that ringi and in some respects you're right. The internal units, handy as they are with remote control, are a bit too big for my liking and intrude on limited wall space for artwork etc.
    •  
      CommentAuthordjh
    • CommentTimeNov 11th 2015
     
    Posted By: owlmanThe internal units, handy as they are with remote control, are a bit too big for my liking and intrude on limited wall space for artwork etc.

    The internal units are typically designed to sit above doors, aren't they? So don't really get in the way of anything.
    • CommentAuthorowlman
    • CommentTimeNov 11th 2015
     
    I don't know, are they?? I suppose they go wherever you've got space. All the pictures seem to show them on a plain wall.
    • CommentAuthormike7
    • CommentTimeNov 11th 2015 edited
     
    There are internal units designed to be at floor level, and I think this is more appropriate when intended use is for heating provided they don't blow directly at a seating area.

    I use wall mounted units at low level with bookshelves in front to disguise. Leaves space above for my Modigliani.
    • CommentAuthorowlman
    • CommentTimeNov 11th 2015
     
    Modigliani!!

    If you can afford one of those then surely you have a spare flunkey or two knocking around to worry about the heating.
    :bigsmile:
    • CommentAuthorGarethC
    • CommentTimeNov 11th 2015
     
    So it was you that bought it. Think you outbid me by a hair.

    Not just low wall and high wall, quite a few different types of indoor unit including slimline and "single duct" or something I think. Should be able to get something that works.
    • CommentAuthormike7
    • CommentTimeNov 12th 2015 edited
     
    Actually mine's a Modigliani calendar - hoping to sell all months for a similar price once the year is over. Looking forward to the £1.3bn. If I get it in £50 notes and put them through one of those paper log making machines it should heat my home for about 4 years.
    • CommentAuthorowlman
    • CommentTimeNov 12th 2015
     
    I've got one too, on my workshop wall. At least that's what the rep said they were. He must bring one out every year. :wink::bigsmile:
    •  
      CommentAuthordjh
    • CommentTimeNov 12th 2015
     
    Is Modigliani greek for Pirelli?
    • CommentAuthormike7
    • CommentTimeNov 12th 2015
     
    If GarethC or anyone is interested I'll have April going at a bit of a discount. We managed to rub out the dental appointments, holiday dates etc pretty well on most months, but April has 'Mum's Bday' in heavy black ink and we've had a bit of trouble with that. I showed it to a Christies valuer and pretended it was part of Modigliani's work and related to his mum - thought it might even add to the value a bit- but unfortunately he must have been a bit of a pub quiz champion, and knew exactly when Modigliani's mum was born, so that scuppered the plan.
    • CommentAuthorowlman
    • CommentTimeMar 15th 2018
     
    Well, 2.5 years on from my OP and I think this year may be the action year. I had a very helpful chat with a tech sales guy from Mitsubishi electric and I think I'm going to opt for a split system.
    I intend putting in a ducted system for the sitting/dining room, and a standard wall mount unit in the sun room, with one outdoor unit powering the lot. I have a large loft space to house all the ductwork etc. so no problem there,-Any tips for ductwork size?, rigid or insulated flexi?, I kind of imagined about 6" but with no real evidence, It was just SWAG. I believe standard ceiling grilles are available at 12" x 12".
    For paul i M. You mentioned " vanes" in the ductwork are they simply so you can "balance" the system airflow.
    • CommentAuthorTimSmall
    • CommentTimeMar 15th 2018
     
    Duct sizing depends on heat load, but is likely to be bigger than 6" I'd have thought? Larger means lower air flows and lower operating temperatures (so higher heat pump efficiency).

    Ducted systems are very common in North America, and you can almost certainly find a plethora of duct sizing calculators online.

    Did you consider multiple smaller "mini split" units like the Mitsubishi MSZ-LN35VG or MSZ-LN25VG (both available for under 900 inc VAT), which may be cheaper?

    Daikin also do similar units for a little more.
  3.  
    <blockquote><cite>Posted By: TimSmall</cite>Duct sizing depends on heat load, but is likely to be bigger than 6" I'd have thought? Larger means lower air flows and lower operating temperatures (so higher heat pump efficiency).</blockquote>

    You have it a bit backwards - larger ducts means *higher* air flows, but lower velocity - too much velocity leads to noise. Lower air flows would lead to higher temperatures in fact as you're putting the same amount of heat into a smaller volume of air. It's the delta-T between the condenser and air supply that determines the efficiency to some extent. 6" ducts are fine for the final branches, but the trunk will need to be much larger. Once you know the capacity of the blower, you can calculate the size of the main ducts and the branches to supply the total airflow required to supply the heat. Oversizing gives lower velocities which are usually quieter, but I've heard people say that a lot of the noise in such systems is due to the return duct being undersized, rather than the supply. As others have mentioned, there are plenty of resources available on-line to calculate duct sizes - e.g. here's a simple one: https://ductcalc.ca/ - there's also apps you can download for your phone.

    <blockquote><cite>Posted By: owlman</cite>For paul i M. You mentioned " vanes" in the ductwork are they simply so you can "balance" the system airflow.</blockquote>

    The vanes I mentioned are installed in 90 degree bends to "help" the air turn the corner without creating a lot of turbulence (which leads to noise).

    Good luck!

    Paul in Montreal.
    • CommentAuthorowlman
    • CommentTimeMar 15th 2018
     
    Hi Tim, Thanks, I had looked at various high wall units; Mitsubishi Zen, Daikin Emura, both with a greater degree of design element than most. I hadn't looked at the particular ones you mentioned and one of them may work in the sunroom. However with all such internal wall hung units it's all about available wall space and an unwillingness on my part to compromise/spoil the whole room design with add on boxes however nicely designed. The sun room was a different matter.
    • CommentAuthorowlman
    • CommentTimeMar 15th 2018
     
    Hi Paul, Thanks, the large indoor unit I'm considering has long rectangular inlet and outlet slots so I'm guessing a plenum of some sort needs to be made from which, (in my case), there would be two round duct spigots each side. I think some sort of removable cleanable filtration provision on the inlets may be a good idea?
    The vanes you mentioned are obviously in rigid ductwork, does that mean in insulated flexi they wouldn't be needed?
  4.  
    <blockquote><cite>Posted By: owlman</cite>The vanes you mentioned are obviously in rigid ductwork, does that mean in insulated flexi they wouldn't be needed?</blockquote>

    Yes, they wouldn't be needed in flexi duct.

    As for air filtration, definitely! The slots that are usually on the indoor unit for 1" thick filters are useless - you need a decent pleated filter. I use this model: https://www.aprilaire.com/whole-house-products/air-purifiers/model-2210 - the filter needs to be changed once a year (in theory) but I usually do it about every 18 months on average. When the sun shines in the right spot I can see the air coming out of the vents has less dust in it than the ambient air. You can build a plenum from sheet ductwork to incorporate such a unit.

    Paul in Montreal.
    • CommentAuthorowlman
    • CommentTimeMar 15th 2018
     
    Hi Paul, I've already spoken to some ducting fabrication guys and creating the two plenums is easy for them. They can also incorporate slots for the filter cassettes. I also found a company that supplies equipment/machinery insulation mounting pads. My idea was to build a platform off the woodwork in the loft and simply sit the unit and plenums on it with the mounting pad underneath.
    • CommentAuthorowlman
    • CommentTimeMar 28th 2018
     
    Hi Paul,
    On advice from Mitsubishi Electric ,(V. Good BTW) The 5kW indoor unit has an airflow of 22/242/283 (l/s) lo, med, hi. I used your online calculator, thanks for the link, converted medium flow to cu ft min and it resolved a duct of 10.45". I'm guessing that's for one duct.
    I intend, I think, using two maybe three outflow ducts which logic seems I should divide the sq area of the 10.45" to arrive at the appropriate smaller duct sizes, with multiple plenum outlets.
    I'm guessing the inflow side of the loft unit should match the outflow, what I can't figure out is how to size that duct allowing for the additional filtration, you feel may be advantageous.
    The Mitsubishi unit comes with a filter installed but I'm guessing that's as much to protect the fan as it is the air quality.
  5.  
    Hopefully this photo shows how our air filter is installed in the return plenum. You're right that the filters that come with the unit are just to project the fan and coil.

    Paul in Montreal.
      Filter.jpg
    • CommentAuthorowlman
    • CommentTimeApr 1st 2018
     
    Thanks Paul, I've managed to find a good, well informed, one stop shop for all the ducting, grilles, filters and plenum stuff. With a second supplier for all the air/air components and then the "F Gas" fitter for commissioning, I've just got to find the time and money.
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