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High air source heat pump running costs – Vaillant AroTherm Plus

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Colin
(@colin)
Beginner Member
206 kWhs
Joined: 9 months ago
Posts: 30
 

@webcmg Glad to help. If you only charge up the cylinder once at night and you might be able to save a little more. Something doesn't seem quite right as our consumption is less than half of yours,  30kwH vs 71kwH so far this month but you may use the hot water much more than us (family of 4 with 2 small kids).

IMG F58E7D4FEF9C 1

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webcmg
(@webcmg)
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173 kWhs
Joined: 6 months ago
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Topic starter  
Posted by: @webcmg

@colin Hi Colin, we've certainly reduced our Kwh usage for the hot water based on the settings. We now currently use between 3-4 Kwh per day to heat the water. 2kwh in the morning and 1-2kwh in the afternoon depending on usage (n.b. flat rate tariff). The anti legionnela cycle seemed to reach the required temperature when I checked this week which is also good. Thanks for your help. 

SmartSelect 20220616 070624 VRC 700

Interesting, I'd like to get to the bottom of the efficency because we're seeing high usage for DHW and heating which is why I started this thread. I did insulate the cylinder (which sits outside the thermal envelope of the house in a store room area of the garage) on 5th June and this seems to have had a minor impact (although it could also be the warm weather). This and recharging twice per day will accounts for some of the difference (up to 18 kwh?) . 

In terms of usage, we are a couple without kids and we each have a shower per day, one of us in morning and the other at night. My wife does seem to like having long hot showers and we have large high capacity rainfall shower heads. I suspect this could be a factor. If I have a relatively quick shower in the morning the cylinder temp drop off is around 10-15 degrees, so the cylinder does normally need recharging during the day to avoid a disappionted wife.

A few questions, if I may? 

  1. Do you all have showers at a similar time of day? 
  2. What style showers do you have? 
  3. What is the orientation of your heat pump unit (ours faces westerly) - pictures of installation would be helpful if possible? 
  4. I thought a recharge during the day might result in a higher yield ad the air temperature is typically higher, is this likely to make a difference? 
  5. Is anyone aware of any other reasons why our heat pump might not be acting efficiently?

 


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webcmg
(@webcmg)
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@colin one thing I have noticed is that we have a secondary return on the hot water circuit. It has a timer which activates a pump to circulate the water. This is to reduce the hot water run off time in the extremities of the property. I haven't ever switched the pump timer on do the pump isn't active but I have noticed that the pipework on the return is often very hot. Could it be convecting/syphoning which means the water temperature is reducing more quickly thank normal?


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Colin
(@colin)
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Joined: 9 months ago
Posts: 30
 

@webcmg We don't have showers at a regular time each day, also we have the same style showers as you. Our pump is pointing in an east-north-east direction. Recharge during the night will consume a little more because it's cooler outside but that's when our tariff is 3 times less so makes sense in our case.

Your cylinder could be heating up multiple times per day because of usage which may explain the higher consumption? If you can figure out if your 300L cylinder only consumes 2 to 3kwh to do a single recharge, if not then there's something not right. Easiest way would be set it to charge for a couple of hours each day. Ours only takes about an hour to charge up the 300L tank, even in winter.

I'm not sure if I've got the circulation pump. I've included a graph of my cylinder temperature over the past few days so maybe you can compare temperature loss etc during the day. 

Screenshot 2022 06 18 at 13.28.07

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webcmg
(@webcmg)
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@colin thanks, what are you using to monitor the temp of the tank and produce the graph? 


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Colin
(@colin)
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Joined: 9 months ago
Posts: 30
 

@webcmg Hi, I'm using a free bit of software called 'Home Assistant' that can run on almost anything including old PCs. link: www.home-assistant.io/

I'm using the below Home Assistant Vaillant integration to monitor the all the Vaillant kit, Pump/Cylinder/Controls.

Link: github.com/thomasgermain/vaillant-component

It's helped me a lot by getting a bit more understanding about what was happening under the hood and optimising our consumption but I appreciate it needs a wee bit of technical know how. 

This post was modified 2 weeks ago 3 times by Colin

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webcmg
(@webcmg)
Primary Member
173 kWhs
Joined: 6 months ago
Posts: 65
Topic starter  
Posted by: @colin

@webcmg Hi, I'm using a free bit of software called 'Home Assistant' that can run on almost anything including old PCs. link: www.home-assistant.io/

I'm using the below Home Assistant Vaillant integration to monitor the all the Vaillant kit, Pump/Cylinder/Controls.

Link: github.com/thomasgermain/vaillant-component

It's helped me a lot by getting a bit more understanding about what was happening under the hood and optimising our consumption but I appreciate it needs a wee bit of technical know how. 

Thanks, will have a go at getting this set up. Hope it works with the installation here. 


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Colin
(@colin)
Beginner Member
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Joined: 9 months ago
Posts: 30
 

@webcmg If you're able to pair it with your Smart Meter it starts to make much more sense as well. 

Below is my typical daily evening power usage during the cylinder heating.

image
This post was modified 2 weeks ago by Colin

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Gurugurugravity
(@gurugurugravity)
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@colin how do you go about pairing your smart meter to home assistant?


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Colin
(@colin)
Beginner Member
206 kWhs
Joined: 9 months ago
Posts: 30
 

@gurugurugravity If you check the following link it details the many ways you can do it.

www.home-assistant.io/docs/energy/electricity-grid

I've done it a couple of different ways. I have a Geo Trio IHD with Wifi so integrated that with Home Assistant with the following integration

github.com/mmillmor/home-assistant-components/tree/main/geo_home

There're other ways that don't rely on IHDs, e.g.  I'd bought a SMETS2 monitor which also works well but you need to buy the monitor plus a Zigbee dongle/controller. www.amazon.co.uk/gp/product/B08WXT6HHJ 

These dashboards helps me to see what's going on under the hood at a glance.

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This post was modified 1 week ago 3 times by Colin

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Gurugurugravity
(@gurugurugravity)
New Member
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@colin thank you, that’s very helpful. I have this IHD, so I suspect I’ll need some extra equipment to do this as it’s not on the list of integrations https://chameleontechnology.co.uk/solutions/smart-in-home-displays/#ihd6


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Colin
(@colin)
Beginner Member
206 kWhs
Joined: 9 months ago
Posts: 30
 

@gurugurugravity It's certainly capable of it with a bit of fiddling. 

community.home-assistant.io/t/uk-smart-energy-meters/16545/173

You don't even need any hardware if you use the free Glow/Bright App but only get delayed 30min stats.

github.com/HandyHat/ha-hildebrandglow-dcc


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Aceshigh
(@aceshigh)
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63 kWhs
Joined: 1 month ago
Posts: 5
 

@webcmg 

 

From the pictures on your first post it appears that the DHW outlet and secondary return inlet are piped straight up into your ceiling space, no doubt that pipework then runs horizontally and then upwards to your taps / bath / showers upstairs.

 

I am not a plumber, nor a heating engineer, but I have recently had a similar piped system installed and I can see that I can have a 300l cylinder cool itself due to syphoning in a day, without any hot water drawn off for household use.

 

If you have your system programmed to maintain a certain temperature in the cylinder, or one or two times programs a day, you will be unnecessarily cooling the cylinder continuously with the secondary return which then needs to be reheated.

 

If you want to test this, ensure the DHW return pump is turned off and then close one of pump valves. Yes, you will have to wait longer for hot water at the outlets during the test, but I think you will find that your cylinder doesn't take as much energy.


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webcmg
(@webcmg)
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173 kWhs
Joined: 6 months ago
Posts: 65
Topic starter  

@aceshigh thanks, that is helpful to know. Are there likely to be any risks associated with this?

@colin I have a small form factor PC on the way to get home assistant setup. The water board fitted a smart water meter to other day too, so should be able to get good visibility of a range of data


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webcmg
(@webcmg)
Primary Member
173 kWhs
Joined: 6 months ago
Posts: 65
Topic starter  

@aceshigh @colin I isolated the secondary return at the weekend and today the DHW has not had to recharge following yesterday's anti legionnela cycle. The temperature has remained above 50 degrees even though we've both had showers. It does take marginally longer to get hot water, but I prefer this if we're saving energy. So this is a positive sign. I wonder if this issue has impacted the ASHP performance for the heating. We had our DHW on constant and can imagine it would need to keep cutting in to recharge the DHW. When it did this perhaps the flow temp for heating dropped, incurring greater consumption to get back to desired temperature. Something to monitor but positive signs. I just wanted to say many thanks to you both for taking the time to help me. It is greatly appreciated. Thank you. 

@aceshigh Do you know if it is possible to plumb in a secondary return so it does not syphon? It might be nice to circulate on demand at particular times of day (which is what the pump with attached timer is supposed to do, but it didn't ever need the pump. A motorised control zone perhaps?

@colin it sounds like we have similar setups and houses (minus 2 children). What is your current daily electricity kwh usage for the house? I'm looking for a comparison because ours is still 6 kwh without any ASHP usage. I don't think we have several tvs on standby, two fridge freezers and a lot of Philips hue devices on standby. Not sure if 6 kwh is good or bad... 


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