Heating

hieoin

Hi I know this question has been posted many times but we are still no closer to a decision. We are starting to build soon and have been looking into heating systems for awhile now. We were all set to go with a thermal store with oil, back boiler and solar feeding into it. Some suppliers are suggesting an air to water heat pump in particular a mitsu***** one. The prices for both are coming in around the same. We know oil is expensive up but also aware that heat pump can lead to expensive bills and its efficiency decreases when the temperature drops. Does anyone have any particular experience with this certain heat pump pm only!

sydthebeat

can i ask what the attraction of a heat pump is?

if you are able to reduce your heat demand down to its minimum, you wouldnt need such an expensive piece of kit to provide heat energy

hieoin

No real attraction to a heat pump,its just that the price for oil,solar(6sq m) and buffer tank if coming in only a couple of grand cheaper-not much in the grand scheme of things. We were just thinking with the way oil is going should we go with a heat pump. We are planning on lot of insulation anyway.

fclauson

From my research a HP is considerably cheaper than solar+oil+thermal store specifically in a well insulated build - and is better suited to a well insulated house as it can proivide continous low levels of heat (i.e. at 25 degress into the UFH)

just do it

fclauson wrote: »

From my research a HP is considerably cheaper than solar+oil+thermal store specifically in a well insulated build - and is better suited to a well insulated house as it can proivide continous low levels of heat (i.e. at 25 degress into the UFH)

Is that an air to water HP? From what I've seen from regular posters on here this type of hp doesn't have many fans.

beyondpassive

just do it wrote: »

Is that an air to water HP? From what I've seen from regular posters on here this type of hp doesn't have many fans.

From my own research, if your on the gas grid or need gas for cooking and fires then Natural gas or LPG are the most viable. Air source inverter Heat pump is worth considering if you have a low energy build, (heating and hot water bill under €800 per annum, not 60mm insulation in the cavity and a bit of cosyboard lining with so called 'a-rated windows' )

Air to water can be viable where you have a low grade heat source such as underfloor and the return temp hasn't lost too much heat. With the cost of PV substantially reduced due to the reduced tariffs in the UK, this can now also be considered to work with your 'electric' heating system. Heat pumps are simple to operate, but you need to have a good warranty from the manufacturer. If anything happens a gas boiler its simple to fix.

If you have a thermal store, you have plenty of input ports and can always add heat pump later. For the moment concentrate on insulation, airtighness and eliminating cold bridges.

Do-more

When you are looking at air to water heat pumps there are a number of important points you need to look at.

"Old school" pumps generally drop rapidly in efficiency when ambient temperatures drop below zero C.

So you need to look at the amount of heat the pump is capable of supplying when it gets really cold outside.

For example an 10kW pump may only be capable of producing 6kW of heat at -7C and many switch off completely if it hits -11C.

So you need to consider if this can satisfy your heat demand when it's really cold and you need to consider if you require a back up heat source if it is extremely cold. (Could be just a couple of large immersions at the top and bottom of your tank).

The latest generation heat pumps (like the one you are being offered) are a different scenario, because they use different refrigerants and in many cases are a "split" system where the compressor is inside the house sometimes integrated with the water tank.

Because of this they have different operating properties and do not fall in efficiency so rapidly when ambient air temps are under zero. Some advertise that they will produce useful heat down to -25C.

The difficulty you may have with using this type of pump is in integrating it with your solar panels. If the indoor unit has a water tank they normally don't accept a solar coil and in any case the tank is probably of too small a capacity (200L) to be really useful with solar, so you will have to dock a second solar tank beside it. This is something you will need to discuss with the supplier.

A better solution IMO is a split system where the indoor unit doesn't have it's own storage tank and can therefore be hooked up to directly to your solar tank. This makes the controls a lot easier and it also means that any low grade solar production in the winter time can be used by the UFH.

Dancealot

hi,i am new to this. i am looking to replace the heating system in my 12 year old 4000sq ft house over 3 storey. i have ufh on 2 floors and rads on the top floor. At the moment i am considering a mescoli 34kw pellet boiler or a kostrzewa 40kw pellet boiler with fuzzy logic and lamda sensor. Just wondering if anyone has any experience of these boilers and if they are reliable? Also will 35 to 40kw be enough to heat house?

JD6910

Dancealot wrote: »

hi,i am new to this. i am looking to replace the heating system in my 12 year old 4000sq ft house over 3 storey. i have ufh on 2 floors and rads on the top floor. At the moment i am considering a mescoli 34kw pellet boiler or a kostrzewa 40kw pellet boiler with fuzzy logic and lamda sensor. Just wondering if anyone has any experience of these boilers and if they are reliable? Also will 35 to 40kw be enough to heat house?

what system are you replacing??????

engineermike

I think if you design the build to meet the heat pump output, i.e low temp and uF heating distribution. Insulate - Insulate - Insulate the home and get what solar gains you can from the south face of the build.
You will reap the rewards in years to come & get a BER rating that's high up there.
Most people have issues with heat pumps due to 'Chinese crap' / or poor installation of pumps - or not matching the demand correctly. Its a false economy to think that you can have a heat pump and save a few grand because its not a brand name, the Mitsi pump or a number of other pumps are tried and tested technology with 20, 30 , 40 years of engineering and success behind them in the cooling sector and commercial sectors and applications.
The heat pump - air source or ground source is just the same technology in reverse.
They need maintenance like any heating system and choose your installer / installers carefully by getting a number of quotes and opinions.

And in the interest of clarity I am in the sector, but I firmly believe if it ain't broke, don't fix it.
Mike F

air

OP, I don't see the point in a buffer tank if you only have a back boiler and 6sqm of solar panels feeding into it.
IMHO buffer tanks / accumulators only make sense where you are using a batch system such as a wood gasification boiler or a heat pump which runs on night rate electricity perhaps.
Solar won't make any (useful / economic) contribution to a space heating buffer at the time of year you need it, especially just 6sqm of solar.

I would suggest the following:
1. Estimate (or have your architect estimate) your annual heat load in kWh.
2.Get the local prices for all energy sources available to you in cost / kWh.
3.Get full quotations for the capital equipment required to use each energy source considered in (2) above. Push the suppliers of each for annual maintenance costs and expected lifetime projections.
Add the cost of financing the capital expenditure if you will be funding the build on credit.
4. Work out the annual cost in euros for fuel from each source and for the capital cost for each source. Add the two of these together for the full cost picture from each source.

The best option for you will be the lowest cost option based on these calculations.
The answer will be different for everyone as every house has a different heat demand and fuel costs vary with location.
The cost per unit may be much lower for some capital intensive options but if your heat demand is low then you will never realise enough savings to make back the capital outlay.
The relative costs of different fuels may fluctuate slightly but historically they have all generally ran close enough to inflation.