Enjoy your videos, keep it up. Only thing I would add. We run ours midday once the house is warm and I know the heating being off for 1.5hrs won't matter. Also midday ambient temp is usually higher so better efficiency. if people have time of use tariff then probably better to align with the cheap rate.
Very timely video. Just in the process of requesting a larger hot water cylinder than the one we have been allocated from Octopus before our install next month. Probably focused too much on the ASHP sizing and just accepted the cylinder they assigned us. I was reading the Daikin HW manual which stated 'The lower the desired DHW tank temperature, the more cost effective. By selecting a larger DHW tank, you can lower the desired DHW tank temperature'. Your video confirms what I had worked out, that I would be needing to heat our water to a higher temperature so we could blend it down to have enough hot water. Thanks as always for the content.
The rule of thumb 45L per person per day is an ok guide but has one big problem, that is for storing water at 60 degrees! No one makes this clear. One you store at 50 degrees, you should be aiming for 55-60L per person.
My DHW settings are more or less the same as yours with a target temperature of 55C with one 2 hour cycle per day. We typically achieve a COP of 3.6 (not including space heating) which we are very happy with. Very informative video.
Hi thanks for the information. I'm enjoying your videos. We've just had a Vaillant Arotherm plus installed and still trying to get to grips with all the settings. I have one thought to share. Realising that the pump can only do heating or DHW, I didn't want the house to get too cold overnight whilst I heat the water up in the cheap period. I read in one of the Vaillant manuals how long it would take to recharge different size tanks. For my 200L tank it said something like 78 mins. Therefore I've set up my system to do DHW for only 90 mins. So far this seems to have worked for us.
Even though we shower at night, we still have the water heated overnight. This does mean we have to set the temperature a couple of degrees higher because of the longer time for heat loss, but the savings from using off-peak rate more than make up for this. We also do have a couple of extra thermometers in the tank as our tank also use solar thermal, it does mean that we can look at the top one to see if the water is hot enough - we obviously don't bother with that on a regular basis.
Worth considering a Mixergy tank if you worry about how much hot water is left. Loads of data presented in graphs. Works well with our Daikin HP for a full charge, but can also heat from an immersion at the top of the tank. That gives the option of a quick partial reheat to whatever % you specify and also allows a solar diverter to heat the tank in the summer. Probably a more expensive option to install though.
I have the ‘offset’ set to zero and as you said, the system does what it likes and the flow temperature gets to 10 degrees hotter than my hot water temperature target.
@@JohnBrophy-z1c I've seen people with 5kW units having the same problem. Apparently a large enough coil can help this but I can't find any technical info on coil sizing. You would think that a 7kW heat pump with a 250L tank that are designed by Vaillant to go together shouldn't suffer this issue.
@@UpsideDownFork Well, you could have a bigger coil to transfer the heat but then you would have less hot water and more (copper) cost. Engineering is always a compromise.
Hello, I have a question please, the domestic hot water is set to 40 degrees, I made my shower ok, after, my wife was in shower and after couple of minutes , cold water and the valiant eco tec plus that I have was in error, F57. Can you recommend me what to do? Or how to set proper temperature, please. Thank tou
Very good as always. I realise you want to tie in your DHW charging with the cheap rate electric & EV charging, the coldest part of the night tends to be around dawn, some would say just after, I seem to see it being around 04.00/05.00. so it might be an idea to heat the hot water at the start of the cheap period and then charge the car thereafter?
Great tip! It would be a good experiment to run to prove your theory to be true. Would need to factor in any standing losses for the extra hours of storing heated water but probably negated overall?
This is quite a complex and depends on what you're trying to achieve. If you're after highest cop then middle of the day. If you want the cheapest price then likely to be long and slow overnight. I found that 2 hours in the early hours is usually okay, but I found on really cold days it let the house temperature drop too much. So I now run two 1 hour sessions with 1 hour heating in between. Will revert when weather is warmer to a single session.
Thanks for commenting. Hopefully this video guide will help people get in the ballpark of what they want to do and if they want to eek out a little more then reading some of the comments like yours can help them consider further options.
I know this is specific to heat pumps, but I wonder how this applies to a boiler with a vented cylinder. I have my flow set to 60c and the tank thermostat set to 50c. After 20 minutes or so the boiler starts to cycle as it cannot modulate low enough to keep the flow at 60c as it keeps overshooting (12kw boiler can only modulate down to 8kw). To avoid too much cycling I have 2 x 30 minute schedules each day. This means the whole tank is never getting up to temperature, but it's enough for our showers and dishes etc. Do you reckon this is better, or should I have 1 x 1 hour session in the morning to heat more of the tank, but get more cycling on the boiler potentially causing more wear and tear?
Hmmm. I'm not sure to be completely honest with you. This video is the result of me experimenting with the Vaillant heat pump and invented cylinder in my own house over the last year.
@@UpsideDownFork Yeah I wasn't expecting you to have an answer, don't worry 😀 Just makes me wonder. Not sure if cycling is as bad for heat pumps as it is for boilers. Obviosuly bad for efficiency, but in terms of long term damage...
@egocd from my understanding boiler cycling isn't as bad as heat pump cycling due to the compressor starts. Hopefully someone more experienced will come along to offer you some advice 👍
@@trailblazer7108 radiators on a heat pump gets much closer to UFH comfort levels. Still not quite on par but our kitchen tiles for example aren't stone cold anymore because of the low and slow heating which feeds thermal mass into things like that. The difference between gas boiler on/off heating and heat pump weather compensation is night and day. Between rads and UFH it's a much smaller margin.
I never have and never will. There is already virtually no risk of legionella in a domestic setting, before we consider that it won't grow if you store your water above 45 degrees and even more critical is how quickly you're turning the water over. We empty our cylinder every day so there is no risk.
Same for me. I don’t believe there has ever been a documented domestic case of legionella. The only place legionella has been isolated from in a domestic settings is shower heads so it’s probably more important to run showers that are not used on a regular basis.
@@UpsideDownFork don't know, sorry. Mine's a 7kW, 250l cylinder, 6m coil. Will track at 4-5deg, but no lower, even if set to zero. There was a suggestion on HG that it should be able to track lower, but I've not seen any evidence.
@@71brp84 well you have literally the perfect setup. 7kW and 250L is the ideal pairing according to my contact at Vaillant. 👍 5 degrees is pretty good though. Many people stuck with 10 degrees and can't get any closer with smaller coils.
If you are charging in a much smaller window you will need to set the charge hysteresis way down. Ours is set to 1 degree as it only gets a 2hr window for the cheapest Octopus Agile slot in the day. Without that we would miss an entire day before the next recharge window.
@@UpsideDownFork Yup, because it has to last 22 hours without a reheat (after much arguing I got a 300l tank even though "you don't need that much" specifically for this reason). The sensor is half way down the tank so doesn't really read the average temperature of the tank properly due to stratification. By the time its dropped by 5 deg your already a long way thought the tanks hot water, and with a setpoint of 45deg you really don't want the stratified level to be much lower temp than that. If its already warm the reheat doesn't really last that long. The cost differential is so extreme that it makes sense (in a day you have 7p, 16p, 33p / kWh). I can't really see any downsides to just running it each day, there is the heat loss from the tank but that is so minor.
It's important to know how many kWh of heat the DHW cylinder (& any buffer tank) loses in 24hrs and to think where that heat is going, especially if you're about to install & considering putting the kit in a place that's not heated & not insulated. Your DHW tank & ancillarys are a heat battery - a useful leaky space heater OR a waste of heat and primary energy
Yep, exactly one of the reasons that I pushed to keep my buffer tank and cylinder in a first floor cupboard rather than the garage or the loft that the installers preferred. In this video I intentionally suggest that people should heat the hot water closest to the point of use to avoid those standing losses as much as possible. Thanks for commenting!
Enjoy your videos, keep it up. Only thing I would add. We run ours midday once the house is warm and I know the heating being off for 1.5hrs won't matter. Also midday ambient temp is usually higher so better efficiency. if people have time of use tariff then probably better to align with the cheap rate.
Great tip! 👍
Very timely video. Just in the process of requesting a larger hot water cylinder than the one we have been allocated from Octopus before our install next month. Probably focused too much on the ASHP sizing and just accepted the cylinder they assigned us. I was reading the Daikin HW manual which stated 'The lower the desired DHW tank temperature, the more cost effective. By selecting a larger DHW tank, you can lower the desired DHW tank temperature'. Your video confirms what I had worked out, that I would be needing to heat our water to a higher temperature so we could blend it down to have enough hot water. Thanks as always for the content.
The rule of thumb 45L per person per day is an ok guide but has one big problem, that is for storing water at 60 degrees!
No one makes this clear.
One you store at 50 degrees, you should be aiming for 55-60L per person.
My DHW settings are more or less the same as yours with a target temperature of 55C with one 2 hour cycle per day. We typically achieve a COP of 3.6 (not including space heating) which we are very happy with. Very informative video.
Good going. 👍 I wince every time I see someone in the owner's group on Facebook sharing their DHW COP of 2🫣
Hi thanks for the information. I'm enjoying your videos. We've just had a Vaillant Arotherm plus installed and still trying to get to grips with all the settings. I have one thought to share. Realising that the pump can only do heating or DHW, I didn't want the house to get too cold overnight whilst I heat the water up in the cheap period. I read in one of the Vaillant manuals how long it would take to recharge different size tanks. For my 200L tank it said something like 78 mins. Therefore I've set up my system to do DHW for only 90 mins. So far this seems to have worked for us.
Thanks for commenting!
Thanks I will try that . I have mine to come on when temp falls 10 deg below 45 so comes on twice a day normally.
If you can get away with once a day you should see overall gains. 👍
Even though we shower at night, we still have the water heated overnight. This does mean we have to set the temperature a couple of degrees higher because of the longer time for heat loss, but the savings from using off-peak rate more than make up for this.
We also do have a couple of extra thermometers in the tank as our tank also use solar thermal, it does mean that we can look at the top one to see if the water is hot enough - we obviously don't bother with that on a regular basis.
Thanks for commenting!
Worth considering a Mixergy tank if you worry about how much hot water is left. Loads of data presented in graphs. Works well with our Daikin HP for a full charge, but can also heat from an immersion at the top of the tank. That gives the option of a quick partial reheat to whatever % you specify and also allows a solar diverter to heat the tank in the summer. Probably a more expensive option to install though.
Thanks for commenting.
Mixergy is a great option for those who can afford it and will value the extra data!
I have the ‘offset’ set to zero and as you said, the system does what it likes and the flow temperature gets to 10 degrees hotter than my hot water temperature target.
Thanks for commenting!
This is because the heat pump cannot modulate down far enough to achieve the desired offset.
@@JohnBrophy-z1c I've seen people with 5kW units having the same problem. Apparently a large enough coil can help this but I can't find any technical info on coil sizing.
You would think that a 7kW heat pump with a 250L tank that are designed by Vaillant to go together shouldn't suffer this issue.
@@UpsideDownFork Well, you could have a bigger coil to transfer the heat but then you would have less hot water and more (copper) cost. Engineering is always a compromise.
Now i have to shot a video to show the correct settings - don't make me too busy, please 🤣
Get on with it already! 🤣
Hello, I have a question please, the domestic hot water is set to 40 degrees, I made my shower ok, after, my wife was in shower and after couple of minutes , cold water and the valiant eco tec plus that I have was in error, F57. Can you recommend me what to do? Or how to set proper temperature, please. Thank tou
I'm afraid I can't offer any advice on boiler settings.
@ ok, thank you
I decided to go mixergy tank so this allows me to see the level in the tank, but even then when its at 0 it still has some hot water.
That's definitely the big advantage of a mixergy tank!
Very good as always. I realise you want to tie in your DHW charging with the cheap rate electric & EV charging, the coldest part of the night tends to be around dawn, some would say just after, I seem to see it being around 04.00/05.00. so it might be an idea to heat the hot water at the start of the cheap period and then charge the car thereafter?
Great tip!
It would be a good experiment to run to prove your theory to be true.
Would need to factor in any standing losses for the extra hours of storing heated water but probably negated overall?
@@UpsideDownFork My flimsy belief of the coldest time is based on the Vaillant (app) outdoor temp graph.
@FRZ5951 that's good enough for me 👍😁
This is quite a complex and depends on what you're trying to achieve. If you're after highest cop then middle of the day. If you want the cheapest price then likely to be long and slow overnight. I found that 2 hours in the early hours is usually okay, but I found on really cold days it let the house temperature drop too much. So I now run two 1 hour sessions with 1 hour heating in between. Will revert when weather is warmer to a single session.
Thanks for commenting.
Hopefully this video guide will help people get in the ballpark of what they want to do and if they want to eek out a little more then reading some of the comments like yours can help them consider further options.
I know this is specific to heat pumps, but I wonder how this applies to a boiler with a vented cylinder. I have my flow set to 60c and the tank thermostat set to 50c. After 20 minutes or so the boiler starts to cycle as it cannot modulate low enough to keep the flow at 60c as it keeps overshooting (12kw boiler can only modulate down to 8kw). To avoid too much cycling I have 2 x 30 minute schedules each day. This means the whole tank is never getting up to temperature, but it's enough for our showers and dishes etc. Do you reckon this is better, or should I have 1 x 1 hour session in the morning to heat more of the tank, but get more cycling on the boiler potentially causing more wear and tear?
Hmmm. I'm not sure to be completely honest with you.
This video is the result of me experimenting with the Vaillant heat pump and invented cylinder in my own house over the last year.
@@UpsideDownFork Yeah I wasn't expecting you to have an answer, don't worry 😀 Just makes me wonder. Not sure if cycling is as bad for heat pumps as it is for boilers. Obviosuly bad for efficiency, but in terms of long term damage...
@egocd from my understanding boiler cycling isn't as bad as heat pump cycling due to the compressor starts.
Hopefully someone more experienced will come along to offer you some advice 👍
Quick unrelated question: is underfloor heating worth the effort and the money?
Financially? No. You will never see a return.
Comfort level? That's subjective.
@ thank you. Can similar comfort be achieved with radiators you think?
@@trailblazer7108 radiators on a heat pump gets much closer to UFH comfort levels. Still not quite on par but our kitchen tiles for example aren't stone cold anymore because of the low and slow heating which feeds thermal mass into things like that.
The difference between gas boiler on/off heating and heat pump weather compensation is night and day.
Between rads and UFH it's a much smaller margin.
@ thank you so much! I wouldn’t be doing this without you and your channel, so I’m ever so grateful.
What do you have your DHW mode set to? I tried ECO but it was taking quite a while to heat up our 300 litre cylinder, so I’ve stuck with with NORMAL.
I do run mine on eco, because the time taken overnight doesn't matter to me.
The efficiency difference between eco and normal is fairly small anyway.
When do you do your 60c cycle
I never have and never will.
There is already virtually no risk of legionella in a domestic setting, before we consider that it won't grow if you store your water above 45 degrees and even more critical is how quickly you're turning the water over.
We empty our cylinder every day so there is no risk.
Same for me. I don’t believe there has ever been a documented domestic case of legionella. The only place legionella has been isolated from in a domestic settings is shower heads so it’s probably more important to run showers that are not used on a regular basis.
Cylinder charging offset can make a difference IF you have cylinder with a big enough coil to dissipate all the energy.
Do you happen to know what size coil that happens at for a 5, 7 or 12kW pump?
@@UpsideDownFork don't know, sorry.
Mine's a 7kW, 250l cylinder, 6m coil. Will track at 4-5deg, but no lower, even if set to zero.
There was a suggestion on HG that it should be able to track lower, but I've not seen any evidence.
@@71brp84 well you have literally the perfect setup. 7kW and 250L is the ideal pairing according to my contact at Vaillant. 👍
5 degrees is pretty good though. Many people stuck with 10 degrees and can't get any closer with smaller coils.
If you are charging in a much smaller window you will need to set the charge hysteresis way down.
Ours is set to 1 degree as it only gets a 2hr window for the cheapest Octopus Agile slot in the day. Without that we would miss an entire day before the next recharge window.
@@TheBaron0000 so if the temp drops from 50 to 48 for example, you reheat the tank?
@@UpsideDownFork Yup, because it has to last 22 hours without a reheat (after much arguing I got a 300l tank even though "you don't need that much" specifically for this reason). The sensor is half way down the tank so doesn't really read the average temperature of the tank properly due to stratification. By the time its dropped by 5 deg your already a long way thought the tanks hot water, and with a setpoint of 45deg you really don't want the stratified level to be much lower temp than that. If its already warm the reheat doesn't really last that long. The cost differential is so extreme that it makes sense (in a day you have 7p, 16p, 33p / kWh). I can't really see any downsides to just running it each day, there is the heat loss from the tank but that is so minor.
@@TheBaron0000 Ah, got it.
It's important to know how many kWh of heat the DHW cylinder (& any buffer tank) loses in 24hrs and to think where that heat is going, especially if you're about to install & considering putting the kit in a place that's not heated & not insulated. Your DHW tank & ancillarys are a heat battery - a useful leaky space heater OR a waste of heat and primary energy
Yep, exactly one of the reasons that I pushed to keep my buffer tank and cylinder in a first floor cupboard rather than the garage or the loft that the installers preferred.
In this video I intentionally suggest that people should heat the hot water closest to the point of use to avoid those standing losses as much as possible.
Thanks for commenting!