It's probably worth mentioning that 70C hot water is a scalding risk and is higher than anyone would want, even 60C is fine for legionella. It would be more efficient to heat the tank a couple of times per day to 45-50C rather than heating to 70C.
Thanks Glyn, I did mention both of those points in my previous 2 videos but neglected to cover it again here. If you don't mind, i'll pin your comment for others to see in the future.
I’m happy for you, very persistent in proving a point. I’m having my heat pump installed next month your journey has inspired me to move into a cleaner environment. Thank you 👍🏻
Your robust 200-litre DHW tank with a 17Kw coil output is functioning properly; there is no need to spend money unnecessarily. Starting at a temperature of 24 and finishing at 69, your tank consumed 10.48 kWh of energy to reach the desired temperature.
Hi again, that looked much better... Just a point, the charging offset is added to the target tank temp to set the target flow temp, not added to the actual tank temp, so for you the target flow temp will have been 72 deg. (assume 2 deg offset). The heat pump will seek to achieve that target flow temp and you will see the actual flow temp increase as the tank heats up depending on how much heat can be released by the coil. Better to have a larger output heat pump as the compressor modulates down, and should have much better efficiency at lower speeds. Glad you got up to temp!!
I have the same ashp but a Mixergy 150L cylinder. With thse cylinders you can set a smaller % of hot water required eg 10% to 100%. Much greater control as it doesnt use the normal coil but a heat exchanger with pumps top and bottom. Ie the return temp will always be at a cooler level than the standard coil design due to more precise stratification. It is more complicated but xtremely efficient. COP is usually around 5.
we have a similar setup and been running out of water on our two cycles off 2.30am -5.00am off peak heat and 2-3pm top ip with 4 of us in the house installer recommended legionnaires cycle during off peak and the 5.30pm-8.00pm cycle so will see... runs out after two 10 min showers at the moment weird valiant has setback on heating but not hot water... great info
@@UpsideDownFork 250l new one from heat geek.. temp set at 50 then two test 10 min showers and the temperature was down to 15degrees Was told 10min is 110l water so in 20 sounds about right? I could and probably am wrong
@@AnotherBoring43yearold Where is the temp probe located in that cylinder? In my vaillant cylinder it's at the bottom third, so even when my temp readout is down at 15 degrees I still have enough water for another good hot shower above that cold water. If you have 250L of 50 degree water and most showers are at approx 38 degrees, you will have a lot more shower temperature water once it mixes down with the cold from 50 degrees. At 48 degree store temp, we have enough hot water for 3 showers from our cylinder which is labelled as 200L but only stores 170L as the rest is taken up by the coil. That's tested until our digital shower display starts flashing to let me know that it cannot maintain the 38 degrees any more, rather than relying on the Vaillant temp readout which appears very low even after just one shower.
Thanks for sharing! Can I ask what your standard settings are for your Vaillant ASHP? For your information I have a Heat Geek Cylinder are full of quality issues… awful. Our cylinder started leaking after a few days and the coil in the actual tank is not distributed evenly throughout the tank… it welded onto a cage and the a flexible solar heating pipe attached to a mesh cage inside the cylinder. I would stay well away and go for a larger cylinder from Vaillant or another good brand name.
Remember that the temp sense probe is only around a third of the way up the tank; the actual temp at the outlet will be a few degrees higher. The heat pump gives up due to the hot water flowing back to it. It modulates down as much as it can (which is not a lot on a HP when compared to a modern gas boiler) before it has to stop and just circulate what it already has in the loop.
I hear this comment a lot that HP don't modulate very well. If you just look at the ratio and compare that to a boiler then it's true. 3:1 or 4:1 looks pretty terrible compared to a boiler that will manage 10:1 or better. But. Because of the boiler oversizing epidemic, a property may have a 30kW boiler that modulates down to 3kW. The heat loss is probably 5kW so you can fit a 5kW HP which can modulate down to 1.5kW or better in some cases. Just an example of my thinking and why HP modulation isn't that important. Thanks for commenting!
I have a vailant gas boiler with vailant controls i dont know if its the same for your heat pump but it actually stops heating the cylinder around 2 degrees lower than the set point .You think its broken but sure enough about 3 to 5 minutes later its at the correct temp .you got close maybe heat losses in the pipes at that temp could explain the 0.5 c . Also the wider the flow temps would suggest the cylinder is soaking up the energy very well
A very informative series. Did you find that with the higher DWH stored temp, you had enough hot water for day on a single heat up (to the higher temp?)
@@BuiltOverJam yes! 👍 I alluded to this in my previous videos. I would like to run the store temp lower for efficiency reasons but can't compromise comfort so I've been trying to dial in exactly how much we need. Unfortunately the external temperature can make a big difference so finding the right number has been a moving target.
Had a Vailliant 12kw heatpump and 15 radiator system with 210ltr cylinder fitted a couple of months ago and solar with 5kw battery. Tuesday morning it does a legionella cycle taking it to 69° for hot, water normally 43C All automatic don't need to play with settings at all. In Aberdeenshire so far or electric bill is less than it was and not getting £400 worth of oil every 2,1/2months on top of the electric. I don't think there will be much in it in December/January as there will not be much from the solar. Over a year it should work out less in total. I did ask Vaillent what was the coldest they had tested to as Breamar 1 hour from us holds the cold for UK record at -29deg C. Did not get an answer.If you did not have the solar they would be very expensive to run.M😀
Even without solar, a well setup heat pump will still make financial savings compared to oil. The heat pump max output is tested at low temperatures for a period of 24hrs. What is your design temperature? Mine is -1.8 degrees because I live in the warmest part of the UK.
@@UpsideDownFork I used to install oil heating and a good condensing oil boiler with proper controls will give 93% efficiency uk standards 105% European so they can be economical to run. Our electric for yesterday as the heating was on a lot was £10.14 for one day. in the warmer weather £2.40 -£4.00p/d. Most systems here are set for designed for -3C I could not tell you exactly as it was put in by a installer.I would not be surprised if it was up to £15 a day in the coldest months. Bet you are happy you live in the warmest place. Scotland can be very cold. M😀
@@MarshallSmart how did you measure the boiler efficiency? You should be provided with the documents that state the design temperature, usually along with the heat loss.
Excellent, keep up the good news. I've just finished my self install of an Arotherm 7kW and have kept (for the time being) my original hot water cylinder, as it also has a solar thermal coil at the bottom. So the heat pump is connected to what was the oil boiler coil, I want to see how well it works on that coil and I might copy your experiment!
I am looking at self installing an Arotherm 7kW - seems to be the only one that fits my needs and has headroom - my cylinder is an old Megaflo which only has a 0.9m2 coil but I use the immersion from PV for 70% of the year...
@@Umski My solar water heaters are three thermal panels, not PV to immersion, so it has a separate solar coil at the bottom and the 'traditional' oil/gas coil mid way, this is the one i have connected to the heat pump.... you can follow my progress... www.youtube.com/@UFZ7482/videos
Yes. 100% worth it. We needed a new boiler and cylinder. Cheapest quote for us was near £6k for that work. Heat pump came in at nearly half that. It's cheaper to run and more comfortable in the house. We disconnected the gas so don't pay the £100 per year standing charge there as well. All round excellent and there are loads of videos on my channel around this.
I have my DW offset set to zero and like you it makes no difference and the circulating temp always gets to around 10C higher than the HW set temperature.
Is this your DHW strategy (heating to 70°C) going forward or is this just for the legionella hygiene cycle? Or is this to compensate for small cylinder in combination with profligate usage?😉
I think it was in response to mis-information saying ASHP can't get the water very hot and/or needing immersion to do the DWH cycle. I very much doubt he will be running it like that all the time, as in the video, ECO mode does a better job for the vast majority of people.
I don't run a legionella cycle. This is just a test to prove the naysayers wrong. It does show that you can effectively double your stored hot water by increasing the temp up to these temperatures.
@@UpsideDownFork That is a really big improvement. I currently use a hybrid heat pump that leaves the DHW job to the gas boiler and it uses about 80 kWh of gas a month for that. The gas boiler also kicks in when the heat pump either can not do it alone or if the gas price beats the electricity price at the actual COP. There is a full electric option coming this winter, which basically replaces the gas boiler with an R290 water/water heat pump and a DHW cylinder. It can take energy from the low temperature heating system after the ASHP and before reaching the radiators and also give energy back from the DHW system so that it is basically also a heat battery for low COP conditions. And there is a backup heater in there as well, just in case. Reading your reply comforts me that this system will be enough for DHW needs, but I think getting the biggest cylinder that I can fit may be a good idea to make sure no one gets a cold shower and the COP 1 backup heater is used as little as possible. This system by Quatt is currently only available in the Netherlands, but Germany is next and it will not stop there. The installation of the hybrid system cost me about €3000 after a €2775 government incentive fully installed and commisioned. The full electric option is a bit more expensive at about €5000 after government incentives, but that includes everything, even removing the gas boiler and closing off the gas pipes.
It's probably worth mentioning that 70C hot water is a scalding risk and is higher than anyone would want, even 60C is fine for legionella. It would be more efficient to heat the tank a couple of times per day to 45-50C rather than heating to 70C.
Thanks Glyn, I did mention both of those points in my previous 2 videos but neglected to cover it again here.
If you don't mind, i'll pin your comment for others to see in the future.
I’m happy for you, very persistent in proving a point. I’m having my heat pump installed next month your journey has inspired me to move into a cleaner environment. Thank you 👍🏻
Great to hear!
Your robust 200-litre DHW tank with a 17Kw coil output is functioning properly; there is no need to spend money unnecessarily.
Starting at a temperature of 24 and finishing at 69, your tank consumed 10.48 kWh of energy to reach the desired temperature.
Hi again, that looked much better...
Just a point, the charging offset is added to the target tank temp to set the target flow temp, not added to the actual tank temp, so for you the target flow temp will have been 72 deg. (assume 2 deg offset).
The heat pump will seek to achieve that target flow temp and you will see the actual flow temp increase as the tank heats up depending on how much heat can be released by the coil.
Better to have a larger output heat pump as the compressor modulates down, and should have much better efficiency at lower speeds.
Glad you got up to temp!!
I have the same ashp but a Mixergy 150L cylinder. With thse cylinders you can set a smaller % of hot water required eg 10% to 100%. Much greater control as it doesnt use the normal coil but a heat exchanger with pumps top and bottom. Ie the return temp will always be at a cooler level than the standard coil design due to more precise stratification. It is more complicated but xtremely efficient. COP is usually around 5.
we have a similar setup and been running out of water on our two cycles off 2.30am -5.00am off peak heat and 2-3pm top ip with 4 of us in the house
installer recommended legionnaires cycle during off peak and the 5.30pm-8.00pm cycle so will see...
runs out after two 10 min showers at the moment
weird valiant has setback on heating but not hot water...
great info
What size cylinder is running out after 20 mins of showering?
@@UpsideDownFork 250l new one from heat geek.. temp set at 50 then two test 10 min showers and the temperature was down to 15degrees
Was told 10min is 110l water so in 20 sounds about right?
I could and probably am wrong
@@AnotherBoring43yearold Where is the temp probe located in that cylinder? In my vaillant cylinder it's at the bottom third, so even when my temp readout is down at 15 degrees I still have enough water for another good hot shower above that cold water.
If you have 250L of 50 degree water and most showers are at approx 38 degrees, you will have a lot more shower temperature water once it mixes down with the cold from 50 degrees.
At 48 degree store temp, we have enough hot water for 3 showers from our cylinder which is labelled as 200L but only stores 170L as the rest is taken up by the coil. That's tested until our digital shower display starts flashing to let me know that it cannot maintain the 38 degrees any more, rather than relying on the Vaillant temp readout which appears very low even after just one shower.
@@UpsideDownFork good to know we have one one the new heat geek cylinders so hopefully good 😬
Thanks for sharing! Can I ask what your standard settings are for your Vaillant ASHP? For your information I have a Heat Geek Cylinder are full of quality issues… awful. Our cylinder started leaking after a few days and the coil in the actual tank is not distributed evenly throughout the tank… it welded onto a cage and the a flexible solar heating pipe attached to a mesh cage inside the cylinder. I would stay well away and go for a larger cylinder from Vaillant or another good brand name.
Oh wow, I did not expect that.
It seems that the grass really isn't greener.
Thanks for sharing and I hope your issues all get resolved.
Remember that the temp sense probe is only around a third of the way up the tank; the actual temp at the outlet will be a few degrees higher. The heat pump gives up due to the hot water flowing back to it. It modulates down as much as it can (which is not a lot on a HP when compared to a modern gas boiler) before it has to stop and just circulate what it already has in the loop.
I hear this comment a lot that HP don't modulate very well.
If you just look at the ratio and compare that to a boiler then it's true. 3:1 or 4:1 looks pretty terrible compared to a boiler that will manage 10:1 or better.
But.
Because of the boiler oversizing epidemic, a property may have a 30kW boiler that modulates down to 3kW. The heat loss is probably 5kW so you can fit a 5kW HP which can modulate down to 1.5kW or better in some cases.
Just an example of my thinking and why HP modulation isn't that important.
Thanks for commenting!
I have a vailant gas boiler with vailant controls i dont know if its the same for your heat pump but it actually stops heating the cylinder around 2 degrees lower than the set point .You think its broken but sure enough about 3 to 5 minutes later its at the correct temp .you got close maybe heat losses in the pipes at that temp could explain the 0.5 c . Also the wider the flow temps would suggest the cylinder is soaking up the energy very well
A very informative series. Did you find that with the higher DWH stored temp, you had enough hot water for day on a single heat up (to the higher temp?)
@@BuiltOverJam yes! 👍
I alluded to this in my previous videos. I would like to run the store temp lower for efficiency reasons but can't compromise comfort so I've been trying to dial in exactly how much we need. Unfortunately the external temperature can make a big difference so finding the right number has been a moving target.
Had a Vailliant 12kw heatpump and 15 radiator system with 210ltr cylinder fitted a couple of months ago and solar with 5kw battery. Tuesday morning it does a legionella cycle taking it to 69° for hot, water normally 43C All automatic don't need to play with settings at all. In Aberdeenshire so far or electric bill is less than it was and not getting £400 worth of oil every 2,1/2months on top of the electric. I don't think there will be much in it in December/January as there will not be much from the solar. Over a year it should work out less in total. I did ask Vaillent what was the coldest they had tested to as Breamar 1 hour from us holds the cold for UK record at -29deg C. Did not get an answer.If you did not have the solar they would be very expensive to run.M😀
Even without solar, a well setup heat pump will still make financial savings compared to oil.
The heat pump max output is tested at low temperatures for a period of 24hrs.
What is your design temperature?
Mine is -1.8 degrees because I live in the warmest part of the UK.
@@UpsideDownFork I used to install oil heating and a good condensing oil boiler with proper controls will give 93% efficiency uk standards 105% European so they can be economical to run. Our electric for yesterday as the heating was on a lot was £10.14 for one day. in the warmer weather £2.40 -£4.00p/d. Most systems here are set for designed for -3C
I could not tell you exactly as it was put in by a installer.I would not be surprised if it was up to £15 a day in the coldest months. Bet you are happy you live in the warmest place. Scotland can be very cold. M😀
@@MarshallSmart how did you measure the boiler efficiency?
You should be provided with the documents that state the design temperature, usually along with the heat loss.
Excellent, keep up the good news. I've just finished my self install of an Arotherm 7kW and have kept (for the time being) my original hot water cylinder, as it also has a solar thermal coil at the bottom. So the heat pump is connected to what was the oil boiler coil, I want to see how well it works on that coil and I might copy your experiment!
I am looking at self installing an Arotherm 7kW - seems to be the only one that fits my needs and has headroom - my cylinder is an old Megaflo which only has a 0.9m2 coil but I use the immersion from PV for 70% of the year...
@@Umski My solar water heaters are three thermal panels, not PV to immersion, so it has a separate solar coil at the bottom and the 'traditional' oil/gas coil mid way, this is the one i have connected to the heat pump.... you can follow my progress... www.youtube.com/@UFZ7482/videos
@@FRZ5951 nice one, thanks 👍
To cut a long story short...are they worth it and do they completely replace gas boilers? Whats the full cost including installation
Yes. 100% worth it.
We needed a new boiler and cylinder. Cheapest quote for us was near £6k for that work. Heat pump came in at nearly half that.
It's cheaper to run and more comfortable in the house.
We disconnected the gas so don't pay the £100 per year standing charge there as well.
All round excellent and there are loads of videos on my channel around this.
Do you think a Heat Geek tank would justify the extra cost?
Short answer? Nope.
I have my DW offset set to zero and like you it makes no difference and the circulating temp always gets to around 10C higher than the HW set temperature.
Is this your DHW strategy (heating to 70°C) going forward or is this just for the legionella hygiene cycle? Or is this to compensate for small cylinder in combination with profligate usage?😉
I think it was in response to mis-information saying ASHP can't get the water very hot and/or needing immersion to do the DWH cycle. I very much doubt he will be running it like that all the time, as in the video, ECO mode does a better job for the vast majority of people.
I don't run a legionella cycle. This is just a test to prove the naysayers wrong.
It does show that you can effectively double your stored hot water by increasing the temp up to these temperatures.
@@UpsideDownFork OK understood - thank you for the prompt reply and a consistently informative channel .😀👍
Looks like it is working well. Does going up to 70 celcius help to meet your family DWH needs?
Yes it does! It gives us roughly double the amount of hot water.
@@UpsideDownFork That is a really big improvement.
I currently use a hybrid heat pump that leaves the DHW job to the gas boiler and it uses about 80 kWh of gas a month for that.
The gas boiler also kicks in when the heat pump either can not do it alone or if the gas price beats the electricity price at the actual COP.
There is a full electric option coming this winter, which basically replaces the gas boiler with an R290 water/water heat pump and a DHW cylinder. It can take energy from the low temperature heating system after the ASHP and before reaching the radiators and also give energy back from the DHW system so that it is basically also a heat battery for low COP conditions. And there is a backup heater in there as well, just in case.
Reading your reply comforts me that this system will be enough for DHW needs, but I think getting the biggest cylinder that I can fit may be a good idea to make sure no one gets a cold shower and the COP 1 backup heater is used as little as possible.
This system by Quatt is currently only available in the Netherlands, but Germany is next and it will not stop there. The installation of the hybrid system cost me about €3000 after a €2775 government incentive fully installed and commisioned. The full electric option is a bit more expensive at about €5000 after government incentives, but that includes everything, even removing the gas boiler and closing off the gas pipes.
@@SolAce-nw2hf that sounds like a brilliant option! Thanks for letting me know about it 👍