Kev M again thank you so much. Success, just got this from Octopus Energy:

Hi Duncan,

I have spoken to my team and they have assured me that we can in fact remove the gas meter and cap it at the same time. The earliest date I could get for you was the 18th of May from 1-5pm. The engineers will call on the day to confirm when they are due to arrive and be with you.

Love and Power,
Gaby

The Octopus Energy team

Think I owe you a pint for that!

Hi Dan T,

From an efficiency point of view, having your ASHP boost your hot water between 5am and 7am is probably the worst time you could choose.

If you look at the daily weather forecasts, the time around dawn is normally the coldest period of the day, with at the moment, temperatures well below the 7C, below which ASHP's start to become less efficient. Your ASHP will already be working harder to keep your home warm, so also heating your water at the same time will just increase the load on your heat pump when it is operating at its least efficient.

Obviously dependent upon the size of your hot water tank and your requirement for hot water, it would be better to have your water heating cycle or cycles when the ambient air temperature is more likely to be above 7C.

Do you have solar PV or solar thermal, since this would probably be a more efficient way of providing hot water, rather than increasing the water flow temperature from your ASHP which in turn reduces its efficiency.

I am writing some articles at the moment which look at different ways to improve home efficiency, which will hopefully provide more details. 

That is a v good point Derek. Not considered it. Previously we switched off our oil boiler about now (April) and back on again on October. H/w heated via solar PV and a Solic. I hope the Mixergy does the same. Set up as such. 
I was then thinking to heat hot water between 12:30 and 4:30am when my octopus go tariff is cheapest. 
So different Solutions for different circumstances. 
Will have to test the night time ASHP running cost vs day time at 14p

Thanks @derek-m

That's a really good point - we set it 5am-7am as that's when the engineer suggested. He said 5am-7am and midday-2pm. Maybe I should change the 5-7am morning to slightly later. We do have solar panels - tho not sure how we would use them to provide hot water. They currently are being used to contribute to our power demands, then any excess is exported to the grid. I assume they are being used to supply the electricity to heat the tank, but can't be 100%.

That said, if previously our hot water was being heated to 50degrees 24/7 and now is only heated twice daily, I'd expect to see savings each day.

Hi JulianC,

Dependent upon the size of your solar PV and the power required to operate your ASHP, it may be possible to both heat your water and drive your ASHP during the day from your solar PV.

At the moment we are using the heat energy derived from solar gain in our conservatory (see my recent article 'How to train your enthalpy'), along with running our small Air to Air ASHP to provide heating during the day. We are even able to increase the indoor temperature to between 23C and 24C, and so are storing energy for later use. This in turn delays the time at which our gas boiler needs to fire up.

I am also finding that the outside unit of our heat pump periodically shuts down because the indoor is up to temperature. This in turn allows more output from our solar PV to be diverted to the immersion heater in our hot water tank via our Immersun Unit. We therefore have a plentiful supply of hot water (+60C) which is provided by free 'green' energy from the Sun.

Whilst this works well for my wife and myself, it would not work for everyone. 

Since we still have our gas boiler, I doubt that going down the Octopus route would be beneficial. One of the major problems in the UK is the variability of our weather, which makes automating the process of energy conservancy much more difficult.

Hi DanT,

The first priority of any power generated by your solar PV should be to drive your ASHP.

If you have excess generation, which at the moment you are exporting, it is quite possibly to utilise this energy to heat water via a diverter unit.

Our particular diverter is from a company called Immersun, though there are a number of other manufacturers offering similar units. The way a diverter works is that it senses whether you are importing or exporting power from or to the grid, if you are exporting, it diverts most of this excess to a given load (normally up to 3kW), so you end up exporting only a small amount (about 10W with our unit). Our unit works down to an excess of less than 100W, and therefore provides virtually all our hot water from Spring through to Autumn.

If you can heat most, if not all of your hot water from your solar PV, you can then run your ASHP at lower water flow temperatures which improves efficiency.

Hi DanT,

I forgot to mention.

Heating your water all day, as against twice per day, may not make that much difference.

It all depends on how much hot water you use and how well your hot water tank is insulated. If you have your system set to heat your water throughout the day it will probably operate in the following manner.

Your ASHP will heat your water up to the desired temp (say 50C) and then stop doing so. If you then use some hot water and the temperature of the water in your tank falls below the low setting (say 45C), the control system will once more heat the water up to 50C.

If you don't use any hot water the temperature in the tank will gradually fall (due to heat loss) until it reaches the low setting and is then heated back up to 50C.

Having your system heat your water twice per day, could cause the water in your tank to be cooler for longer periods, which would reduce the rate of heat loss.

Probably the main difference between heating your water only twice per day, as against all day, would be how efficient your ASHP is operating when the heating of your water takes place. You could set your system to heat the water throughout daylight hours, say from mid morning to mid evening, when your ASHP is probably running at its most efficient.

Posted by: @duncan-mac

Kev M again thank you so much. Success, just got this from Octopus Energy:

Hi Duncan,

I have spoken to my team and they have assured me that we can in fact remove the gas meter and cap it at the same time. The earliest date I could get for you was the 18th of May from 1-5pm. The engineers will call on the day to confirm when they are due to arrive and be with you.

Love and Power,
Gaby

The Octopus Energy team

 

Think I owe you a pint for that!

excellent news, happy to help!

@mike-patrick,

Hi Mike,

I read with interest your recent review of the Grant Aerona 3 ASHP.

Are you still experiencing the loss of pressure within your system? This would indicate to me that you may have a leak somewhere.

If you would care to share some information I may be able to help you locate and rectify the problem.

My first question would be how quickly does the pressure fall, is it fairly quick or over a longer period of time?

It would be useful if you could provide a list of all the equipment within your system, so that I can possibly identify where any leak may be located.

Pressurised systems obviously need to be airtight, but also require some form of expansion vessel to accommodate the fact that water expands and contracts as it heats up and cools down. A leak does not have to be on the water side, so may not be apparent.

Regards,

Derek.

@derek-m

Derek,

Yes, there's been no pressure in the heating expansion vessel for some months.You can see the gauge on the red tank in the picture. The most recent engineer to visit attempted to deal with this by letting in water via the filling loop (this is downstairs in the kitchen, the cylinder in the picture is upstairs). This worked but the pressure fell away again very quickly. I was watching while he did it.

More recently we have had a leak. A pressure valve at the top of the pipe shown started leaking  (see other photo). On texted instructions from the engineer who had attempted to deal with the pressure issue I screwed down the valve to stop the leak. It remains like that. The heating continues to work  (but clearly not as correctly as it should) but I've been holding off calling an engineer until I'm sure I have one who can sort the problems.

The heating is underfloor upstairs and downstairs and each floor has its own manifold. There are heated bathroom towel rails which also won't heat at present as they are perpetually full of air which I can vent off for only a temporary fix.

Thanks,

Mike

That’s a whole lot of expansion vessels - 3?  I’ve got one for the Mixergy tank. And the Daikin has an internal one

Hi Mike,

Thanks for the info.

Because liquids cannot be compressed, it is necessary to have an expansion vessel in pressurised systems.

Inside the expansion vessel is a flexible membrane (probably neoprene) that separates the bottom part from the top part. The bottom part is connected to the water side of your heating system and the top part has air in it.

When you add water from the mains into your heating system, it eventually starts to fill the bottom part of the expansion vessel with water. This in turn pushes the membrane upwards, and pressurises the air above the membrane until it reaches the required pressure, at which point you would stop adding water.

So the fact that you are losing pressure would indicate that there is a leak.

The leak could be on the air side, either a pin hole in the membrane or a pin hole in the upper part of the expansion vessel, but the fact that you are getting air in your towel rails would indicate it is more likely on the water side.

The fact that you have not discovered a leak, could be as simple as the pressure relief valve is set much too low or is passing, or it could be that you have a leak within your hot water cylinder between the primary circuit and the secondary circuit.

It is not easy fault finding via messages, but lets give it a try.

Here is a link to the manual for the cylinder, download it and check that it is the same as yours.

GRANTUK.COM "https://www.grantuk.com/media/3844/grant-monowave-system-hp-cylinder-with-buffer-installer-and-user-uk-doc-0133-rev-1-3-dec-2020.pdf"

Try the following and let me know what you find. You may need someone to assist.

1) Having checked and made a note of which pipes are hot/warm and which are cold before you start, try gradually refilling your system whilst trying to maintain the desired pressure, then see if any of the cold pipes are now warmer. If you do find a pipe that has changed temperature then try to identify where it is going.

2) Try gradually refilling your system with water up to the required pressure and then time how long it takes for the pressure to fall. Obviously look for any sign of leaks.

3) Try refilling and bleeding the towel rails at the same time. Again, time how long the pressure takes to fall.

4) Find your Pressure and Temperature Relief Valve and see if it, and the pipework around it are getting warm. when your heating system is on. This would indicate that the valve is passing and hence your are losing pressure.

5) Make some soap solution (washing up liquid and water) and using a small brush coat the solution on the expansion tank. Refill your system and check for air bubbles as the pressure decays.

Is your secondary circuit (the water that comes out of the taps) fed directly from the water mains supply, or via a cold water tank in the loft?

How long have you been losing pressure? Did you notice if it started gradually or fairly sudden?

Try the various test and let me know what you find.

Regards,

Derek.