Heat Pump Guide
including
why it is essential to integrate heat pumps with vacuum solar thermal

100% environment friendly heating – but pay for only 25%

Because heat pumps can extract up to 75% of the heating energy they produce from the environment, the actual running cost is the electrical energy needed to drive the compressor. In other words for every 1kW of energy needed to run the heat pump, up to 4kW is produced giving the heat pump an efficiency of up to 400%

How do heat pumps compare with traditional heating methods?

Non condensing gas and oil boilers are notoriously inefficient typically running at anything from 45-70% efficiency. More modern condensing boilers have far higher efficiencies with the SEDBUK `A` rated ones in excess of 90%, but even so this is only when they are in condensing mode. Therefore in today`s marketplace, heat pumps are unrivalled for economy and efficiency.

What about CO2 emissions?

When a heat pump is used for heating purposes a reduction in CO2 emissions of around 25% (about 1 ton with a typical household) can be expected. This can be increased by a further ¾ of a ton if combined with vacuum solar thermal for domestic hot water (DHW).

Why bother with solar thermal though when heat pumps can provide DHW as well?

Heat pumps work far more efficiently when they are sized to produce constant lower flow temperatures, typically in the range of 35-40c for underfloor heating and up to 55c for radiators (radiators should be low water content high efficiency type or sized 30% larger than standard). DHW requires year round temperatures in excess of 60c which will reduce the performance of the heat pump, measured by something called COP or Coefficient of Performance and significantly increase the householders utility bill. Vacuum solar thermal will typically provide 90% of a households DHW between April and October, and up to 70% throughout the year. This is effectively free (literally pennies per week) and irrespective of the heat pump`s performance, it just cannot compare.

Many heat pump systems are incompatible with solar thermal and therefore this option is not offered to potential buyers by many companies, however, if you want low running costs with virtually free hot water, integration with a suitable vacuum solar thermal system is absolutely essential. We cannot stress this point strongly enough.

Can heat pumps be installed in any property?

The short answer to that has to be no. For heat pumps to perform efficiently the property needs to be insulated to at least the requirements of Part L1B (2006) Building Regulations (Part J in Scotland) which will provide for a maximum heat loss of 50w/m. It is preferable for the insulation levels to be much higher, as the more heat that is retained in the winter months, the less work the heat pump will have to do meaning the HP running at a higher energy co-efficient, which in turn results in lower energy bills for the householder.

So if the property is well insulated and therefore suitable for heat pump consideration - can the gas or oil boiler be completely removed?

Yes. Provided that the design is sized to meet the full peak heating demand of a well insulated building, then the Heat Pump will absorb sufficient energy from the surrounding air or ground to heat the building year round. By connecting to a suitable off peak electricity tariff, the system can be run at least partly overnight at a cost of approximately 30% of normal daytime electricity rates. In well insulated buildings, the majority of the heat is retained ensuring the heat pump does not cycle on and off continuously during the day, although some of the tariff`s now offer off-peak electricity at other times of the day for a total of 10 hours (per day).

As mentioned, for optimum efficiency it is best to integrate the heat pump with solar thermal, which in our opinion and with respect to all other available technologies, is undoubtedly the way forward for our country as a whole.

What is the difference between Ground & Air Source?

The technology is essentially the same, however, with GS a reservoir of low grade solar energy within the ground is used which will normally be at a higher temperature than the ambient air temperature when heating is required most. At 2m below the surface the temperature stays at a reasonably constant 10-12c and this “free” energy can be utilised by the GS heat pump. With Air Source, whatever the temperature of the surrounding air, is the energy source for the compressor within the heat pump to work with. Having said that, the more efficient of the AS heat pumps use refrigerant, as opposed to water, for heat transfer and the refrigerants have a boiling temperature as low as -50c which provides for a highly efficient heat exchange.

Is there much difference in cost?

Quite simply, yes. Ground Source requires either extensive trenches in which to lay the GS loops or alternatively boreholes to be drilled. The GS loops are normally at least 50m per 5kW, 2m deep and at least 5m apart from each other, therefore a lot of land is required. Boreholes can be extremely expensive, we have had quotes starting at £8,000 and ending up at £20,000 plus. Air Source on the other hand can be installed in most properties (it then comes down to a question of suitability) and although relatively expensive when compared with a boiler change for example, are generally considerably cheaper to install than GS. There is a small difference in efficiency, but this has to be weighed up against the lower cost.

Are all heat pumps much the same?

As with all things in life, there are vast differences between heat pumps and we advise anyone interested in one to research them as much as possible. We only install the most technologically advanced, efficient and long lasting heat pumps, there are therefore many that we would not install. Look for a refrigerant based heat pump with an inverter compressor and a long warranty (2-3 years) if you want high efficiency and few problems.

What sort of efficiency can I expect?

As mentioned above somewhere between 300% and 400% depending upon the property and maximum heat demand. This compares very favourably with condensing boilers that perform around 90% when at their best (in condensing mode). One reputable air source heat pump manufacturer, Daikin, have a test house in Sweden 250km from the Arctic Circle. With winter temperature averages of -18c their Altherma heat pump recorded an efficiency of 240% between January and April. This figure was closer to 300% when combined with vacuum solar thermal for the hot water which is something we highly recommend.

What is the maximum water temperature from heat pumps?

Normally 55c. Once you go above this figure the CoP (Coefficient of Performance) drops dramatically which simply means your energy bills will be far higher.

Is 55c water hot enough to heat my house?

We need to calculate the maximum heat loss of your home to determine that. Most properties that have good cavity wall insulation, double glazing and at least 200mm (8”) of loft insulation will have a maximum heat loss of less than 50w/sqm and can therefore be considered suitable for a heat pump. Underfloor heating can be designed with a flow temperature as low as 25c so is very suitable to integrate withheat pumps. Radiators on the other hand need to be oversized by 30-35% to allow for the lower temperatures and additionally low water high efficiency radiators (ie Jaga Strada DBE) warm up 9x faster than a conventional radiator, so again are well suited to heat pump applications.

Can I have cooling?

Yes, but it normally has to be stated at outset. The cooling function is an option and a reversible version of the heat pump is required.

How big are they?

A Ground Source looks like a small to medium fridge and an AS is similar to an air conditioning unit.

Are they noisy?

No, around 50db – A library is about 25db, so it is somewhere between a fridge freezer and an electric fan?

Technical

What is the equilibrium point?

It is the point at which the heat pump capacity matches the heating demand at which no additional heat source is required

How do I know where the equilibrium point is?

The equilibrium point is not fixed. Most quality heat pumps have a back up heater that will switch ON if the heat pump cannot reach the set point water temperature within a certain time period independently of the ambient temperature (as long as the back up heater is not disabled by field setting)

What is a floating set point?

When the floating set point functionality is enabled, the set point for the leaving water temperature will be dependent on the outside ambient temperature. At low outside ambient temperatures, the leaving water temperature will increase to satisfy the increasing heating requirement of the building.

What is the benefit of a floating set point?

The floating set point ensures that the heat emitter temperature is never higher than necessary and this leads to the highest possible comfort level. A heat pump requires more energy input the higher the water temperature, which means that the floating set point also ensures the lowest possible energy consumption.

What is an inverter compressor?

An inverter compressor will gradually increase or decrease its capacity based on the duty needed to cool down or heat up the room, ie modulates. Most heat pumps have non inverter compressors and therefore have to literally stop and start to change capacity. This is inefficient as each time they start without an inverter there is a power surge.

What are the benefits of an inverter compressor?

• The comfort temperature is reached much faster
• The start up time is reduced by one third
• 30% less power consumption
• There are no voltage peaks
• The heat exchangers become over sized in partial load which increases the efficiency
• Additionally there are no temperature fluctuations

Miscellaneous

Oil increased from $10 per barrel in 2001 to over $140 in the summer of `08 – 1300% in 7 years, although admittedly it has fallen back considerably since. We all know it is only a matter of time before we see these huge rises again.

The Chairman of Gazprom, Alexei Miller, says “to expect $250 a barrel oil within a few years” June 2008

Heating oil per litre is increasing at a rate of approximately 1p per $1 increase per barrel, therefore, £1.50 - £1.70 per litre should be expected. 18 months ago it was approximately 32p

Oil fired AGA`s burn on average 10 litres per day with the CH system doing the same for an average 4 bed house.

Anybody with money in the bank earning 6% or 7% pa should seriously consider protecting themselves against rampant energy inflation that is currently in excess of 50%pa. Heat pumps combined with vacuum solar thermal will go a long way to achieving this, we just wished our Government had the foresight to see this and assisted more with grants or subsidies.

Energy price increases summer - 2008

100% energy inflation in 3 years – when will it end?

Back in 2005 we paid £675 for gas and electricity on average, according to OFGEM. Now, extrapolating from the latest OFGEM figures we can find, we calculate we pay £825 on average for gas alone. Combined with electricity we pay approximately £1300, so roughly double the 2005 amount.

Florian Ritzmann from Xelector agrees that £1300 is the official figure but, as he says, no one believes that. He believes the real average figure we pay is closer to a huge £1600 and rising, with £5000 pa predicted within 10 years.