Heating a room with no central heating.

[David]

Hi there,

I am open to suggestions about heating and cooling a 10m x 5m room. We were looking at using an air to air heat pump but I am slightly confused about how these work. Ideally we would like an energy efficient electric solution to heat the room in winter and cool it in summer..

Suggestions and advice please :)

Thanks.

[Andrew Gabriel]

I've installed two of them, IIRC some 4 years ago. They have a 3.5kW cooling capability and 3.8kW heating. (You get more heating, because you also get the unit's power consumption in addition to the pumped heat.)

They both cool just fine.

For heating, they have different capabilities. Both work down to about 6C outside. Below this, there's a problem in that the outside evaporator can ice up, and this means they have to perform defrost cycles, and I suspect when they're doing this, you are probably not getting any more than you would from a direct fan heater. However, when it's gone below zero outside, one of them will then work without doing defrost cycles and it again becomes viable.

These were B&Q Airforce units, one an older design than the other (ironically, the older one seems to be better).

Also see:

think all the units you can buy nowadays are inverter proportional control units (looked that way when I looked in B&Q last year). Mine aren't proportional control and hence cycle on and off.

I work quite a bit from home, and being able to heat (or cool) just the one room where I'm spending most of the day, rather than the whole house, seemed like a good idea. That one is plugged into a power meter, which seems to have gone 6 months since last reset. It's clocked up 84 units used in that period (which will be part cooling and part heating). That's around 10 quid in electricity cost.

In case anyone is interested, I decoded the IR remote control for my unit, and consequently, it's driven mainly from my house automation system, rather than directly from the remote.

[David]

Hmm, how long does a de-frost cycle last and will it make the room feel significantly cooler on colder days? These units will be needed all day in winter and in weather like this when temperatures struggle to get over 1C I'm just wondering how effective there will be.

Are units made by Daikin, Fujitsu etc any better? In our school ICT labs they have Toshiba ceiling cassette units; I have tried using heating mode on them by setting the temperature to around 23C, the unit seems to do nothing for a few minutes and a symbol appears on the control unit display after a while this disappears and the unit gives out heat, the symbol appears and re-appears quite frequently. However I have never been able to test them properly because the heat from the

30 or so PC's and projector cause the unit to go into cooling mode even on cold days.

Hmm, I see you mention insulation, this is a old building and this

50m2 room is upstairs which has quite a few double glazed and also small(ish) single glazed windows at a higher level. It has a suspended ceiling but I'll ask my Dad regarding insulation.

Does this give any particular advantage?

Mine aren't proportional control and

Seems quite impressive.

Slightly OT here but is this home automation system like a BMS? Our school has one and after talking to the caretaker and going for a tour around the plant room etc it appears that it wasn't done properly and it's a total c*ck up; boilers would appear to be ON on the BMS when they are really OFF so it defeats the purpose and the caretaker has to walk to the plant room to check himself. Also silly things like the air handlers and chiller kicking in for cooling operation when you turn the UFH in certain areas ON!

Thanks for your reply.

[Andrew Gabriel]

Just did a test this morning, and need to retract some of that. It's -3C at the air inlet to the outdoor unit, and both of them work without doing defrost cycles. My guess is that they only do the defrost cycles if it's above freezing outside AND the cooling of the outside evaporator would take it below freezing, so there's a risk of ice build-up. That's probably when outside temp is in the range something like -1C to +5C. When it's below freezing outdoors, defrost cycles are no longer performed as the outside (absolute) humidity is going to be so close to zero that there's no moisture to form ice.

Probably 5 minutes. The unit switches into cooling mode but all fans are off, so although the inside pipework gets cold, no air is blown over it. The outside unit gets warm. After a while, the outside fan comes on and blows the water off the unit - being warm and wet when it's around freezing outside, it generates a large cloud of mist across the back garden. Then the unit switches back to heating mode.

At the time, they were professional fit only. There were many other companies manufacturing DIY install units though and that's now a big market (because cost of professional installation is much more than the cost of the units), so I wouldn't be surprised if they did DIY install ones too now, but I haven't had any reason to look.

My reason for going B&Q was they had a special offer with a very large amount off the price. Otherwise, you want to use a specialist supplier who goes to the effort to supply at 5% VAT (rate for heat pump heating appliances), which B&Q didn't bother to do. Some of these will also lend you the kit to install the precharged professional units, so you aren't limited to just DIY units.

If you drive to warmer parts of Europe, might want to check prices there. In areas where aircon is more common, the price tends to be much lower. It's still seen and charged for as a luxury in the UK. It's even cheaper in the US, but not very pratical to bring units back (although one colleague did back around 2001, and it's apparently still working fine).

It heats up the internal pipework before switching on the fan, or you would start by getting a cold draft effect from it.

Don't know if that's cycling on room temperature, or defrost cycles, based on what you've said. I haven't seen ceiling cassette units for DIY install, but I haven't looked recently. I had one professionally installed at a previous workplace. They only really make sense if you have a false ceiling with enough clearance above to flush mount the unit.

I recall saying at the time I wouldn't pay extra for inverter proportional control, which at the time, you had to. Now you don't as it looks like they all work that way. I would guess you get better room temperature regulation.

remote.http://groups.google.co.uk/group/comp.home.automation/msg/4e9e6615489...> Slightly OT here but is this home automation system like a BMS? Our

Yes.

I am not at all surprised. Getting a building management system working means you need to be expert in all the fields it interfaces to; heating, aircon, cooling, hot water supply, alarms and occupancy sensing, environmental sensing, remote monitoring, etc. That expertise doesn't come cheap, and I guess the installers weren't up to the job. Then you have to educate the occupants in how it works and feedback their requirements into the fine tuning, so they aren't fighting it, not to mention changes in building use. That often isn't done either. If it does work well, they are brilliant.

[David]

,

Like this?

is this mist seen as a nuisance like condensing boiler plumes?

I see, I think we are looking to get them installed.

see:

> Hmm, I see you mention insulation, this is a old building and this

Good point.

remote.http://groups.google.co.uk/group/comp.home.automation/msg/4e9e6615489...> > Slightly OT here but is this home automation system like a BMS? Our

Thanks for all your help.

[Andrew Gabriel]

(First time, I thought it sprung a leak and lost the refrigerant;-) I couldn't see much mist in that video - I see much more from mine, depending on outside conditions. I drain mine into the soakaway, and don't just run the condensate onto a path to make an ice rink outside the door!

It's a one-off whoosh, not continuous like a boiler.

People worry more about the noise (large or old units can be quite noisy). When my new neighbour moved in, he saw it and asked over the fence "Is it noisy when it's on?". I said "It is on!".

6 feet away and over a fence, it is inaudiable given normal background noise level. When I had one put in at work, the landlord specified a max noise, and it was way below that.

With professional install, you have more options, e.g. one outside unit driving two (or possibly more) inside units. Also, more flexibility on positioning of the inside and outside units as they will be able to add to the gas charge for longer pipework, and compensate for more widely mismatched heights of the inside verses outside unit. They may offer a service to do the heat calcs too to work out what size units you need. Of course, this will cost.

[David]

Thanks for your help :)

Much appreciated.