SteamyTea

No, I am interested in why there is a reluctance to fit them. I think so, and usually undersized, or customers told that an ASHP cannot get the temperature high enough, so they fit gas or oil because It is the same, pumps and pipes valves and distribution manifolds. The emitters (radiators, UFH pipework) may be a different physical size, or spacing, but is hard to design a wet system differently that it already is. I think there is a lot of confusion with terminology, my favourite being the names used to store hotwater, is it a cylinder a thermal store, am unvented cylinder or a vented one, buffer tanks, accumulators (though I think they are to buffer mains waiter pressure), feed and expansion tanks, pumped showers, mains pressure showers. About time some of the plumbers put up some diagrams showing the difference. But when it comes to heating the actual house (space heating), this is where a proper thermal model of the building, and local climate, is needed. Would probably save money on all installations regardless of fuel type.

It may be worth you doing a sketch of your system, bit like a London Underground map (topological). Probably all become clear how it works then.

It may not, if the return temperature is too high, the boiler may cut out as it assumes that the need is satisfied.

Shame they use W for work and power, even if work is intalised.

Can you copy the pages from his books. Be interesting to see how it is explained. I am not sure if an oversize system would overheat a house. The control system should take care of that. It would probably not be very efficient though.

This is the 2020's not Caxton's 14070's. I think I did a bit about phase change materials on this thread:

Yes they must. But we have to put a cost on the externalities to. The servicing issue is a problem at the moment. But it is with some gas boilers, and definitely oil ones, even down here. Generally, ASHPs are reliable and are low maintenance. But you know that from the one you have that heats the water.

Only took a few days for mine to turn up. China warehouse in Southampton probably. I have used an ordinary relay in the past. Just hook the coil up to the switched supply, then sense the contacts closing.

If only this forum had a way to easily direct people to decent static resources. There is a second part to the whole energy, power and temperature bit that is more relevant to heat pumps and that is phase change materials. This is how heat pumps work efficiently, but also gives that looks like a deficiency. As the gas used in the units has a fixed temperature, like all gases, at phase change, this puts an upper limit on how high it can raise the temperature, off say, water. The gasses are chosen to be as high as possible, without causing other problems i.e. extremely high, or low pressure, too large a difference in temperature between liquid and gas states, power need to change the state via the compressor etc, and other things like the need to lubricate moving parts, not so cold that they instantaneously free the moisture out of the air. It is the differences in specific energy capacity, and reversibility, of gasses and liquids that allow heat pumps to run with high efficient. Oddly, combustion can also be thought of as a phase change, from gas to plasma and back to a gas, but not the same gas, it is not easily reversible though, and this causes pollution problems. The efficiency cannot be as high as a heat pump, ever.

Energy is the ability to do work. It can take one of two forms. Potential or kinetic. Those words just mean stored or moving. The unit of energy is the joule [J] and the definition of that, in SI units is kg.m-2.s-2. Power is the actual work done, and is the rate that the energy is being used. The unit is the watt [W] kg.m-2.s-3 or is simpler English, a joule per second j/s. Temperature is a relative value with the 0 point set where there is no kinetic movement within an atom. This is known as 'absolute zero'. Temperature can be thought of as how fast atoms are allowed to move when unimpeded. The hotter they are, the faster they can move. So taking a very simple example, if you have a box with sided each 1 metre long, with lots of smaller cubes in it, 1000 of them, that have a mass of 1 kg each, and you move each smaller cube out of the box and place then on a table 1 metre away, if you disregard friction and gravity, for each mass you move you have used a J of energy. The temperature of the masses has not changed (though the person, or machine doing the work will get warmer. Now if you move each mass at a rate of 1 a second, the power you are moving those masses is 1 W. It will take 1000 seconds to empty the large box and 1 kJ of energy will have been used. For some reason we do not use joule as a unit of energy, we use the kilowatt hour. But that can be easily broken down in derived SI units. kilo = 1000, W = J/s and hour is 3600 seconds. Writing out in long hand. 1000 x 1J.s-1 x 3600s = 0.00027777777777778 kWh.

In what way, operation, design, installation, maintenance?

I is easier than working out the volume. Timber has a specific energy of ~4.5 kWh/kg. Another thing worth looking at is the number of rings showing on logs, that gives a good indication how long it takes to replenish that resource, quite frightening that you can burn a ten year old log in a few minutes. But that is another topic. Without knowing the heat losses of the building, it is hard to work out the cot of any type of heating system. You can do a simplified calculation by working out the U-Value and areas of all the exposed components, then find some local weather data, that will give a fairly good estimate of what is needed. Then you can look at different technologies and how they compare on capital and running costs. Which do you think is more complicated, your gas oven or your fridge? Heat pumps are really very basic and have been around, unchanged, for about 50 years (the first heat pump was about 1940). The only major change is the transition from reciprocating 'piston' compressors to rotary 'scroll' compressors. Though is some CO2 HPs they are going back to reciprocating pumps. The reason for this is that even the 'best' R32 refrigerant gas is still several hundred times worse that CO2. This is legislation driven, not a technology change as such. Heat pumps can use tap water as the refrigerant, but as water is 'the universal solvent' it does not have the longevity desired, though the performance is very good. While a useful basic comparison of technologies, the running costs can vary way too much in individual households i.e. the standard deviation is very great. When looking at the technology side, it is easy to get side tracked by the fuel costs. These vary, and vary greatly around the world. Japan, which has no naturally occurring coal, oil or gas, uses heat pumps. Russia has about 150 year worth of natural gas at current consumption rates, so uses basic technology and they control temperature by opening windows. The running costs do not change the efficiency of a system and can very easily be a distraction when trying to work out the best there is.

Out of interest, could you weigh the logs you burn in a typical day, then we can work out the energy that is used.

Can't really be answered. Like saying what is an average house, 60, 120, 180 m2, 1, 2, 3, 4, 5 bedrooms, 1, 2 3 bathrooms, but only one actual bath. Really comes down to discarding the cost of the common components i.e. cylinders, radiators, UFH pipe, then comparing gas, oil, and ASHP units that, and this is important, deliver the correct output. That rated output may be different for the different technologies.

This is really what this thread is about. I say that correctly designed systems work perfectly fine. Badly designed systems will not work as expected. There is also a slight difference in how they are opperated. In the past we had basic boilers and controlled the output with a combination of on/off temperature control, and a timer. This was because 'gas was expensive' in the days of town gas. Natural or North Sea gas changed this, and technology/legislation moved on, so now we have quite sophisticated modulating and condensing gas boilers, with temperature control in each room. Coupled to that the controllers can also adjust each room to have a different temperature, at different times, and different days of the week. This can also be done without machine learning, saves RTFM. But at the heart of any heating system is a machine that raises temperature and transfers it to a transfer medium, usually water. This is what the sizing is so important, and like cars, you cannot always gauge the performance on engine power alone. My bosses car is about the same power as mine, but faster. How can that be. Well it is three quarters of the mass, has a lower drag coefficient, and is petrol. But my car does more miles to the gallon (not the best way to work out efficiency, should really be kJ/km), is quieter and more comfortable. And cheaper.

This is a very hard one to generalise. Mainly because houses are different, and the occupants live differently. It does not change the underlying physics. Another problem is 'what does a heat pump cost'. Some people play top dollar, others buy off eBay.

Just looked it up on Google Earth, seems to be the place.

She lives in Whitchurch. She took me to a pub by a lock a couple of years back. Can't remember the name. Had a large carpark other side of the canal. But that is not unusual for canalside places.

The efficiency is not set by the type of building, it is set by the load cycle. So the question is wrong really.

Next time I am up seeing my best mate, I shall have a wander along the canal and have a peak at your place.

Was a tenner, but after I ordered hound them cheaper. They also do DC activated ones, could be useful for PV 'suff' i.e. diverting power. https://www.ebay.co.uk/itm/SelfSupply-Adjustable-Normally-CloseAC-Current-Sensing-Switch-SZC25-NC-AL-CH/114352241908 I got it to turn a fan on so that I can put my new oven under my induction hob.

Why not find another smaller one, then plumb that in for upstairs and the DHW. And it is kWh, not kwh. Probably not the best way to go with an old house, more radiators would be easiest, and cheapest. Probably not, but having two smaller ones could work out cheaper and give more options.

Yes, and the blame often goes to ASHPs, not the sizing of them. This is the whole point of this topic, it is to stop this happening. So everytime we see someone say something like "I thought of an ASHP, but they are no good in old houses" or "I know someone that has one, and it is rubbish", maybe my favourite "they are not there yet", which I have no idea what it means. it should always be pointed out that they will work if they the design size and installation is correct.

Isn't that mixing up skill and qualification/accreditation. I have the skills to calculate heat loss, but no certification to prove that. But if there was a way for the equipment manufacturers to say 'show us your workings' then they should not be able to sell the wrong component knowingly.

That was the case if a MCS installer did the job. The system had to supply 99% if the time. So 3.65 days if the year you may need supplementary heating i.e. a fan heater.