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manders

New heating system up and running

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Outdoor Unit
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Indoor Unit (with emergency backup fan heater).
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Looks very interesting, please explain.

Phil

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It's an air source heat pump (air conditiong unit in other words), produces 3.2 kW of heat for power input of 0.58 kW, theoretically.  

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Wow! That sounds amazing, I'm familiar  with ground source heat pumps but less so with air source. I' d be really interested at how you go on as it seems the perfect solution for heating a greenhouse.

Phil

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Had been thinking about this for literally years, admittedly its a bit of an experiment, albeit a potentially expensive one.  All being well it should payback in 2-3 years.  I'm quite happily setting higher temperatures and not worrying about leccy bills.

there are a couple of limitations, can only set either 10C or 16C+ as a minimum.  I think there is a way around this though.

Also theres some electronics inside the indoor unit, so getting it wet wouldnt be a good idea.

Anyway, if i can go for three years without breaking it (and parts are warranted for that period) it will have covered the cost of it!

 

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Certainly looks like the future. What is the minimum temperature that it can still extract heat from the air?

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Supposedly -15C, the efficiency will probably drop off a bit by then.  There are some videos on utube with these working at -10 or lower and not pulling a huge current.  I need a few cold nights to properly test it, but we only get to -4C once a year at most here (2010 excepted!!).

 

 

 

 

Edited by manders
Bad spellinng

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And to think I started off years ago with a parrafin heater...

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I think the temperature control is sorted, the wifi app lets you set any temperature between 10 and 30C!

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What is the noise level like - I had read they could be noticeable, going on intrusive?

Interested in the details - what's the make & model, and was it a DIY job to fit?

Thanks,

Dave

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It's extremely quiet, on the outside unit i have to look at the fan or put my hand on the unit (it gets cold) to know if its working.  The inside unit is quieter or similar to a fan heater.  I suppose it might get noiser with old age.

If you had it in a bedroom then it could be irritating at night, but most poeple would get used to it, i used to have one in Japan and thailand in the bedroom, irritating at first but only for a few days.  Not a problem in a greenhouse or for the neighbours.

The one i got was Mitsubishi M, the High COP version, MZFH25VE.  I got the smallest unit, puts out a maximum of 3 or 4 kW, i'm not sure exactly as max power is not stated.

Definately not a DIY installation, i was tempted to get a cheap unit and diy it (cheap ones are all chinese junk).  Its not actually legal to DIY it.  In the end i went for the high end Mitsubishi, it has the best COP and probably the best reputation (Daikin are ok also).

Got three quotes for installation, quite a bit of difference between the three.  The guys who put it in did a great job.

There, are units specifically designed for greenhouses that can be diy (i.e. Marjuana growers), a bit too big and expensive for most amateur greenhouses i suspect.

the only aspect that does bother me slightly is keeping the electronics dry, it us fairly well protected, but if course there is some risk of damaging it.

If i had a big enough greenhouse(which i dont), safer option would be air to water heat pump, so you pump hot water round the greenhouse and the electronics is kept sealed in the outside unit.

Anyway, so far, especially with the temperature problem sorted, i'm really happy with it.

 

 

 

 

 

 

 

 

 

 

 

 

 

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Thanks for the info.

The pdf below says the (average/typical/) UK heating capacity for that model is 2.65kW, giving a range of 1.49 to 4.57, which probably covers most of the time in all but the largest greenhouses, and in any case I'm sure it would always need a backup heater anyway

https://www.air-heatpumps.com/pdf/MSZ-FH_Inverter_Heat_Pump.pdf

How did you calculate ROI?

A number of years ago I calculated I spend around £300/year on electricity to run a 12 x 8 greenhouse, heated to around 14oC

If I saved half that, as a conservative guess (assuming the heat pump does not cover all heating needs, and there are other things using electricity), the payback on this would be something like 6 years

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Why would you need backup heating except for emergencies?  Heat pumps are normally reliable, basically its just a fridge in reverse.  I had one for a two years in Japan, it never failed to work as the only source of heating in a flat.

In my case i'm heating a very well insulated 18x10ft greenhouse and leccy costs for heating are about 600£ per year (I have it logged), with a COP over 5, that reduces the bill to around 110£/yr.  Therefore 1800-330 = 1470£ saving in three years, more than enough to cover cost+installation.

What I wouldn't do is put one of these in a small greenhouse, as you say the payback would be much longer and the heating duty would probably be well oversized, ideally you want the inverter controlling the temperature rather than the unit switching on/off every few minutes.

I'm curious to see what the COP actually works out to be in practice, it could either be higher or lower than the figure quoted.

The rated conditions are 7C outside 21C inside.  If your heating from UK winter average of 5C to greenhouse of say 14C, the COP should be higher than 5.5 rated value.

Anyway so far its proving extremely cheap to run so i'm happy.

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Maddy,

The points is that its a lot cheaper to run than an electric fan heater.  About 5 times cheaper.  However, to make it worthwhile, it would really suit a large greenhouse, or one you want to keep hot.  It would be a great way to heat a hot orchid house or lowland nepenthes house.

For a small greenhouse it would not be worth the installation cost.

The immediate difference for us was i now heat the greenhouse to 20+ C daytime even in cold winter weather and I dont worry about the heating cost.

 

 

 

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I have the same aircon unit in my conservatory bought it at Wickes 7/8 years ago lovely in the summer,

It keeps it cool, it's controlled by remote unit but not wifi but only cost £299 I fitted it myself.

been very reliable.

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