Does anybody have any experience with these units in a domestic interior?

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.

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.

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.

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.

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.

Modigliani!!

If you can afford one of those then surely you have a spare flunkey or two knocking around to worry about the heating.

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.

Is Modigliani greek for Pirelli?

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.

<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.

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?

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.

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.

I'm close to starting installation on the A2A ducted system for my sitting/dining room , I've decided on the following, but with a few reservations:-

1.) I have to have ceiling supply and return grilles because of solid floors. I realise that it's not ideal, but has anyone got ideas on the best design of supply grille. I'd like to avoid an "air curtain" effect so I guess some sort of angled deflector seems appropriate although there are lots of variations on the theme. There are also perforated variations, normally only available for suspended ceiling tile module fitting . Any help would be gratefully received. Return air grilles are less of a problem.

2.) I've kind of decided on smooth rigid ductwork, theoretically this should be better, but with relatively short runs, ( 2 x approx 5M ) and large bore 10/12" ? is it necessary and would the friction losses not matter if I used the semi-rigid stuff. I'll be insulating with 50mm ductwrap.