Ground Source Heat Pump at Nowty Towers

[AE-NMidlands]

Fittings are pretty variable in quality that's for sure, personally I solder all copper work,I only use compression if I cant use poly plumb or the pipework wont drain out enough for a solder joint.
Desp

Same here. Love a Yorkshire fitting and the smell of flux in the morning!

A friend convinced me to change to endfeed fittings: he said "If you can do a Yorkshire joint you can do endfeed, save a lot of money and space!"
I did and it has been OK. I was really surprised that when I disassembled one Yorkshire joint the inner end hadn't wetted / soldered the pipe at all, despite me being almost obsessive about cleaning both surfaces.
I have tried the "no need to clean" solder but didn't like it: it cleaned the copper perfectly but I couldn't assemble the joints. I put it down to the metal being so clean that it fused on first contact. I like the lubrication that you get with old-fashioned flux.
A

[Oliver90owner]

Going off topic, but what the hell eh,

It would be better(?) If other comments were posted on a different thread? It would make this most useful thread easier to follow if there were no interruptions to the flow. Personally, I’m very much enjoying the write-up - just not the bits that are ‘diluting’ it.

[Joeboy]

Going off topic, but what the hell eh,

It would be better(?) If other comments were posted on a different thread? It would make this most useful thread easier to follow if there were no interruptions to the flow. Personally, I’m very much enjoying the write-up - just not the bits that are ‘diluting’ it.

What a fun night out you must be pal.

[nowty]

Then as my heatpump did not come with any built in water pumps, I had to work out what size of water pumps I needed. I found this graph from Yorkshire Pipes,



The effective length of the pipe run was quite difficult to work out because of the different diameters of pipe and the numerous 90 degree bends and of course the heat exchanger in the evaporator also had to be added. Then the graph was for water at 13 degrees with no glycol in it. So after some more calculations I came to a pressure head value of 9 metres.

Well I had already bought a couple of standard 6m head pumps (cos their cheap) before even doing the calculations so had to press on trying them out. I tested it with a single pump and I measured a flow rate of 800 litres per hour. I was about to bite the bullet and purchase a more powerful pump but as I had two of the pumps I tried both in series and the flow rate improved to 1,200 litres per hour so decided to go with that.

I measured the flow rate by pumping from one bucket into another and measuring the time taken to fill the bucket.

[nowty]

So the actual testing time came, I connected the cold circuit with two water pumps and a couple of full bore flexible connection hoses and gate valves to the pumps for easy replacement. I filled the cold circuit with a 20% mixture of food grade glycol and pressurised it to around 1 bar. The glycol is required to lower the freezing temp of the liquid but it comes with an operational cost. The specific heat capacity of glycol is less than water and it makes the liquid more viscous, especially at low temperatures, so makes the flow rate drop and the pump work harder.

For experimental purposes, I simply connected the hot circuit with a single water pump running into a 35 litre builders bucket filled with water. I placed a thermometer in the bucket so I could measure the temperature over time and I also measured the power input to the heatpump.

I switched on the unit, first it did a system check, then the cold circuit pumps started up, followed a minute later by the hot circuit pumps. Soon after the compressor started up. Almost instantly the gauges on the exterior of the unit move in opposite directions, the evaporator is getting colder under the partial vacuum as the refrigerant gas boils as it turns from a liquid into a gas and the condenser is getting hotter under higher pressure as the refrigerant gas is compressed and turns from a gas back into a liquid thus giving up its latent heat. The hot water output feels slightly warm, with the cold circuit gets colder with condensation forming on the ground loop pipes.


Test setup



Water temperature is rising



Pressure gauges showing the high pressure condenser (hot) and the low pressure evaporator (cold) temperatures



A constant increase of 2 degrees per minute in the 35 litre builders bucket, from 18 degrees all the way up to 58 degrees in 17 mins when the high temperature tripped out the compressor. I have calculated that equates to a constant 5.7kW of heat output. The electricity consumption gradually increases in line with the compressor pressure, thus reducing the COP value. The ground loop rapidly drops in temperature for the first 5 minutes, then becomes constant.

[spread-tee]

Fittings are pretty variable in quality that's for sure, personally I solder all copper work,I only use compression if I cant use poly plumb or the pipework wont drain out enough for a solder joint.
Desp

Same here. Love a Yorkshire fitting and the smell of flux in the morning!

A friend convinced me to change to endfeed fittings: he said "If you can do a Yorkshire joint you can do endfeed, save a lot of money and space!"
I did and it has been OK. I was really surprised that when I disassembled one Yorkshire joint the inner end hadn't wetted / soldered the pipe at all, despite me being almost obsessive about cleaning both surfaces.
I have tried the "no need to clean" solder but didn't like it: it cleaned the copper perfectly but I couldn't assemble the joints. I put it down to the metal being so clean that it fused on first contact. I like the lubrication that you get with old-fashioned flux.
A

Same as that, yorkies have way too much solder in them for my liking, stalactites and snots galore, also when buying a couple of hundred quids worth you really feel the expense of yorkies. Also another bonus of end feed is they're easier to file the stop out of to create a slipper.

Desp

[nowty]

From a plumber selling up for £500, I picked up a brand new 300 litre stainless steel indirect hot water cylinder with a very large internal coil specifically for heat pumps. Internally it has 28m of 22mm corrugated stainless pipe rated at 57kW, about twice the amount of a standard cylinder. Also had twin immersions for my solar diverter too.




Decided to install it outside to be close to the heatpump and free up space inside my house.



And placed masses of insulation around it in fact there is now even more since that photo was taken.



Other pipes went through the wall of my house to connect up with my central heating system.



And zone valves were added so I could have either hot water or heating or both together controlled via WiFi sockets.

[nowty]

The heatpump has now been operating for 3 years, during this time I have had a few problems but so far non have been anything to do with the actual heatpump unit itself.

My main problem is silt build up on the under water copper pipe coils, this is usually only a problem in times of little rain in winter. The silt acts as an insulator therefore the cold circuit temp drops and if the return flow to the heatpump drops below zero degrees it shuts down. I can monitor the return flow temp from the controller in the house so I don't have to venture out to measure anything.




Silited up coils.



The remedy is simple, I give the coils a pressure wash for just a few seconds with a 2 meter lance so I don't even have to go down the manhole. The washing usually recovers the return water temperature by at least 2 degrees.




But if it rains hard then its self washing.

[nowty]

And the total cost for it all as a DIY job was around £3k, but a lot of work !

8kW heatpump (real world 6kW) - Ex-display but as new £1,000.
300 litre stainless steel heatpump cylinder with twin immersions - bought brand new from bankrupt plumber for £500
Bespoke home made copper ground source heat exchanger (heat extracted from underground water source) - £250
Water pumps - £300
Control valves, thermostat, etc, - £100
Pipe and fittings - £300
Additional radiators in house to increase efficiency. - £200
Timber, insulation, etc, - £200
Additional immersun (second hand) for diverting excess Solar PV - £200

Total - £3050

[nowty]

The other problem I have had is failures of the the external water pumps, about 1 per year but they are cheap and easy to replace. Generally easy to diagnose the problem but unless both failed on the same hot or cold circuit, the heatpump still runs, just less efficiently. Except for my recent failure where a failed water pump occasionally tripped the heatpump circuit breaker.