Heat pump / inverter DIY

thechippy

paceinternet wrote: »

Why would you bin the central heating system?
Surely you would consider a heat pump with a heat exchanger, at least to compare with an air to air system?

Not sure I understand your question. It will be an air to air system.

paceinternet

Well if you have had a "ch boiler" it suggests you were distributing the heat around the house with a wet system through radiators. If you change to an air to air system, you have to have a way of distributing that air around the house to the rooms, or have multiple internal units.
If you have an air to water heat pump, you can use your existing wet system to distribute the heat around the house. You may need to review radiator sizing because the system will run at a lower temperature. But it is worth comparing the 2 methods.

Does that help, or have I misunderstood what you want to do?

thechippy

Yes, I see what you mean now. We do not have the space for the wet system believe it or not, so it's not an option. However, we do have the space to install a couple of outdoor units at high level.

The layout of our house is such that we could supply the whole of the downstairs with a single 5kw inverter. The inverter would be in the living room, but the hot air will easily infiltrate to the kitchen. The layout of upstairs is such that, we could use a single 3.5kw system on the landing, which again, will easily infiltrate to the bathroom and both bedrooms (you would need to see the house to understand). Hot water would be via the immersion heater in the cylinder.
I'm getting costs together at present and will let you know the installation costs and estimated running costs. I'm convinced at present, that the cost to heat the house will be a good bit less than gch.

G.

stevehead

thechippy wrote: »

Yes, I see what you mean now. We do not have the space for the wet system believe it or not, so it's not an option. However, we do have the space to install a couple of outdoor units at high level.

The layout of our house is such that we could supply the whole of the downstairs with a single 5kw inverter. The inverter would be in the living room, but the hot air will easily infiltrate to the kitchen. The layout of upstairs is such that, we could use a single 3.5kw system on the landing, which again, will easily infiltrate to the bathroom and both bedrooms (you would need to see the house to understand). Hot water would be via the immersion heater in the cylinder.
I'm getting costs together at present and will let you know the installation costs and estimated running costs. I'm convinced at present, that the cost to heat the house will be a good bit less than gch.

G.

I have a similar arrangement to this:
The downstairs unit is positioned above the archway that ajoins the living room to the kitchen/diner - but in the living room. This blows straight down, and keeps the living room about 1 degree above the kitchen/diner.
The upstairs unit is on the landing, and distributes heat into the bathroom, 3 bedrooms & loft. The upper unit is set to blow on a fixed downward trajectory to max outward thrust, then set to left/right oscillation to push heat in through the open doors of the rooms.
The loft is of an open plan design, and all the heat from the house ends up in there so no need for a 3rd unit.

The coldest part of the house is the front entrance hall; don't really care but no effective way to heat it so it's well insulated and I can live with that.

Energy Usage of my 2 Mitsubishi's Dec 1st - right now:
Downstairs Aircon 76 Units (£7.60)
Upstairs Aircon 64 Units (£6.40)

So December is working out at a quid a day, up on November which was 70p.

Scanario: Location Plymouth UK / 2 Kids / Work from Home / wife works part time / end terrace house / Living room temp 22 day 24 night / Loft temp 22 constant

Hot Water
I use a gas instant water heater for this; don't like water tanks as they loose heat constantly from water that you may or may not use.

thechippy

Thanks Steve,

I'm a 2 bed mid terrace, so yes, not unlike you're setup.
I'm going to install my system next weekend and will try to post some photo's and keep the site up to date with running costs.
As I'm in the trade, I can't say what I paid for the systems, but I'll inform you of what I would have charged to install them if this was someone else's property.

I don't know about others on here, but I'm sick to death of rising energy costs and want the most efficient system possible.

You may see much talk that heat pumps produce vastly reduced heat when the ambient drops below -5c. That was a while back! Now, even at -15c, they will still have a cop of around 1.5. During the recent nippy evenings of -2, they should still have a minimum cop of about 2.6. At the recent daytime temp of 5-7c, they will give around 3.5, so still very economical to run.

richardc1983

Thechippy, i would like to ask you a question as I am unsure if my system is faulty.

As you can see from my previous posts I have 1 x FM25Ah outdoor multisplit unit connected to 2 x MV12AH (3.5kw) indoor convertible units, (lounge and bedroom)

The outdoor unit is RATED at 1990 watts going down to 1194watts (maintaining setpoint) when both indoor units are on cooling when maintaining setpoint (inverter ramping up and down). This is as per the product specification databook based on certain operating conditions outdoor ambient etc. This figure is pretty spot on though and very accurate.

However in heating mode its a diff situation totally. It says that to have both units turned on in heating and set point of 20C outdoor ambient 7 which is what it has been last few days here in Leeds that the outdoor unit is rated at 2280W, dropping to 1368W (i assume when only maintaining set point)

I checked this yesterday and today and it only ever gets to 1368W if one unit is operating maintaining setpoint. WHich apparently if only one unit is operating it should drop to 800w. It doesnt seem to be ramping down to the 800w so the unit cycles when mainting setpoint. It cycles in cooling but am not bothered because it is costing next to nothing to run.

If both units are running at max power on heating i.e room temp diff of 3C (inverter ramped fully up) the quoted max rating of the outdoor unit is 2500W however its registering on my energy monitor as 2900W even when only maintaining set point, this drops perhaps to the rated input when its maintaining setpoint.

When only one unit is operating in heating mode the max it will ramp down to is 1300W when its maintaining setpoint. This is no where near the 800w mark that is quoted in the specs? So im dissapointed as yes its cheaper than electric heaters but having checked with the energy meter its using more than I was expecting it to. Cooling is very cheap and within the specs quoted, heating is always like 2280W when both units are on and maintaining set point. No where near the 1368W quoted for the min input on the sheets.

We pay 18p per unit of electric and were putting in about £5 a day in coins when were using it both units, and prob about £3 when using just the one unit.

To say an electric heater uses 2kw well this is using an extra 500w when both units are on (yes it heats the whole flat using 2500w as apposed to one room but I want the quoted specs. The units are oversized a little but all doors are left open so it also heats our large hallway so the doors are never closed. Its like it doesnt ramp down early enough so it goes overset point. Cooling mode it sometimes maintains setpoint of .5C but in heating it seems to always be 1C before it clicks back in and 1C oversetpoint before shutting off its not as precise. When its 1C off setpoint it should be pretty much ramped right down but it still doesnt seem low enough for it to go over set point. Once its reached the set point point it stays on until its gone 1C over but doesnt seem to slow down.

For instance it just cycled back on in both rooms and was using 2300W but then cycled back off and didnt seem to ramp down.

Can you shed some light on this for me? The equipment is LG and before u say it has been great in the summer no probs at all, I know LG dont have a good reputation and all that but this is what ive got!

The link is here to the specifications data book. Scroll to my model of outdoor (FM25AH) on the combination tables and you can see the figures for heating and cooling below the cooling. http://mylg.co.uk/data%20for%20site/multi%20f%202008%20outdoor.pdf

The installer who put it in did it as a favour and i got it a lot cheaper than normally but I feel if i keep asking him out and saying its not performing properly in heating that im being a bit ungrateful really. he has connected his ampmeter to it and he says its running properly but I dont think he left it long enough he only measured it on 30C flat out which I think is still using more than it should.

Any help appreciated matey.

Rich.

thechippy

Hi Rich,

Just going to bed, but will read your post more carefully tomorrow and try to help.
LG is an ok system, so don't worry. In fact, unknown to many, they are the single largest manufacturer of split a/c's in the world!

G

richardc1983

Yes this is what I was told when I said to him "lucky goldstar" its gonna drop to pieces in a week!

The build quality of both indoor and outdoor is very good i think. And outdoor unit is very quiet too which is good. I was told LG make loads of compressors that go into other manufacters units.

stevehead

thechippy wrote: »

Thanks Steve,

I'm going to install my system next weekend and will try to post some photo's and keep the site up to date with running costs.
As I'm in the trade, I can't say what I paid for the systems, but I'll inform you of what I would have charged to install them if this was someone else's property.
quote]

Can you tell us what system(s) you intend to install?

stevehead

Here's my setup - I made this today and dropped it on Youtube for U
http://uk.youtube.com/watch?v=79UAPRI6p-M