Air Source Heat Pump

deantrina

I have just read that you turn off your ASHP in the summer , can anyone advsie if that is correct / a good idea & if i do turn my ASHP off how do i get domestic hot water to wash with ? 

matt_drummer

Turn off  the heating but leave the hot water on, just like you would with a gas or oil boiler.

Reed_Richards

I don't know where you read that but it's mostly wrong.

• You would have to rely on your immersion heater to heat your hot water and that would be much more expensive unless you have free solar power.  And depending on how the immersion heater is wired, it may not be possible to turn it on if the heat pump is off.
• I suspect that heat pumps are happier with at least occasional use than when they are turned off and standing completely idle.
• But a minority of heat pumps have a significant "vampire load", a power drain when the heat pump is doing nothing.  In the worst case this "vampire load" can be of the order of 100 W or 2.4 kWh per day for which you derive no benefit.  So I think some people with these "bad" heat pumps do turn them off in summer.    

MultiFuelBurner

Unless you have solar thermal for your hot water then the cheapest thing to do is heat your hot water with your heat pump.

I was reading your previous thread did you eventually get on top of the costs and perhaps set the system to use weather compensation as that one setting saved us over 30% a year.

https://forums.moneysavingexpert.com/discussion/6248170/high-electric-bills-with-new-ashp/p1

matelodave

My heat pump is now getting on a bit at 13 years old and is one where the sump heater is on continuously and therefore consumes around 3kwh when its not doing anything. I'm sure that later units are a lot better in this respect.

Because of that, I do turn the unit off for most of the time in the summer and just run it for an hour or so every couple of days to give us hot water. If it didn't have a standing load, then I'd leave it on and just turn off the heating.

We find that our 200l tank will last around two days (although the last shower on the second day is perhaps a bit cooler than it should be but is adequate.. The Heatpump consumes around 2-2.5kwh to heat our water every two days when used this way. 

We are fairly frugal with our hot water use, we only heat it to 45 degrees and our shower (no bath) has a low flow 6lpm Eco shower head and I can managed to shower in less than 2 minutes so I can get a decent shower out of less than 12 litres of water.

Even Mrs Matelo can shower in less than four minutes. Washing up goes in the dishwasher and if we need really hot water we just boil what we need in a kettle.

When the temp drops to the point when we need heating, around the middle of October it just gets left on 24/7 until around April.

The heating uses Weather Compensation and runs at a flow temp of around 33-35 degrees, unless its ever so cold outside when it can increase up to 40 if the temp drops to around -5 degrees. The controller sets back the flow temp overnight by around 3 degrees, to avoid the house getting too cold.

Because we have underfloor heating, its pretty slow to respond at these low flow temps so the unit idles for most of the time which seems to be much more efficient that letting it cycle on and off under control of the room thermostats. 

matt_drummer

My new Daikin Altherma 3 consumes 15 watts on standby so about 360 watts a day, not bad I think.

We have a 250 litre tank that is heated to 48c once a day, It also tops up if the tank temperature drops below 39c.

Yesterday the heat pump used 650 watts to heat our tank and it took around 30 minutes.

Our heat pump is consuming around 1 kWh per day to heat our water including the standby use.

We also heat to 60c once a week and that uses an immersion heater to boost the temperature. This consumes between 4 and 5 kWh but once this is done we don't heat for a day or sometimes two.

In August our heat pump consumed 47.36 kWh to heat our water and that includes the standby use and four weeky legionella cycles.

matelodave

Yes, I guessed that more modern kit uses a lot less, probably just the power consumption of the controller etc.

We also have the sterilisation cycle but I dont really think it needs to be done every week, especially if you've got a non-vented tank - the amount of chlorine in our mains water water would kill almost anything so I only do it once every couple of weeks. Like yours we don't need to heat the water the next day after a sterilisation cycle.

AFAIK some heatpumps allow you to set the frequency yourself but my Daikin can only be set to do it once a week or not all.

matt_drummer

The weekly sterilisation cycle was set by the installer, Octopus, and I think it is an MCS requirement.

I don't know if it can be programmed any differently to yours as I haven't looked.

I doubt it is necessary at all but I am going to leave it alone for the time being, the cost is minimal so I don't really care.

Spoonie_Turtle

I've just checked our usage (needed to anyway, but this thread reminded me) - ours is from 2019, and heating apparently used 66kWh in July and 70kWh in August, for outputs respectively of 0kWh and 13kWh.

Thankfully the cost isn't horrendous as we're on Tracker with a low average unit rate, but I am gobsmacked at the wastefulness.  It's even worse than last year (34 and 50kWh used for 'heating' in those two months, for 0 output).  But the smart meter data doesn't shed any light, the only spikes are heating water or otherwise explained by our activity.  Unless it really is just a constant vampire load.

I don't know if I even have the courage to turn it off next year though - I live here but my parents are the tenants, and the heat pump was put in by the HA.  I really don't want to make anything go wrong!

matt_drummer

Spoonie_Turtle said:

I've just checked our usage (needed to anyway, but this thread reminded me) - ours is from 2019, and heating apparently used 66kWh in July and 70kWh in August, for outputs respectively of 0kWh and 13kWh.

Thankfully the cost isn't horrendous as we're on Tracker with a low average unit rate, but I am gobsmacked at the wastefulness.  It's even worse than last year (34 and 50kWh used for 'heating' in those two months, for 0 output).  But the smart meter data doesn't shed any light, the only spikes are heating water or otherwise explained by our activity.  Unless it really is just a constant vampire load.

I don't know if I even have the courage to turn it off next year though - I live here but my parents are the tenants, and the heat pump was put in by the HA.  I really don't want to make anything go wrong!

Where are you getting this information from?

What heat pump do you have?

Do you use it to heat your hot water?

My standard Daikin monitoring is good but not detailed enough for me.

I will be having a more sophisticated monitoring system fitted soon (something that Octopus could have fitted at the installation but never offered but that's another story, a bit annoying) but in the meantime I have fitted a ct clamp monitor to the supply cable of the heat pump.

The ct clamp monitor has two inputs so the other is connected to the supply to the house. This means I can cross check with my solar monitoring and energy account and reconcile the total to make sure my figures for the heat pump are correct.

I don't think 2 or 3 kWh a day of standby costs are acceptable, I wouldn't be happy with that.

A ct clamp monitor is pretty cheap and easy to install.

My heat pump is on a separate supply in my meter cabinet so I can turn it off there or at the isolator switch next to the heat pump.

I would try turning it off if I were you, it's no different to a power cut, I can't see what could go wrong.

Spoonie_Turtle

matt_drummer said:

Spoonie_Turtle said:

I've just checked our usage (needed to anyway, but this thread reminded me) - ours is from 2019, and heating apparently used 66kWh in July and 70kWh in August, for outputs respectively of 0kWh and 13kWh.

Thankfully the cost isn't horrendous as we're on Tracker with a low average unit rate, but I am gobsmacked at the wastefulness.  It's even worse than last year (34 and 50kWh used for 'heating' in those two months, for 0 output).  But the smart meter data doesn't shed any light, the only spikes are heating water or otherwise explained by our activity.  Unless it really is just a constant vampire load.

I don't know if I even have the courage to turn it off next year though - I live here but my parents are the tenants, and the heat pump was put in by the HA.  I really don't want to make anything go wrong!

Where are you getting this information from?

What heat pump do you have?

Do you use it to heat your hot water?

My standard Daikin monitoring is good but not detailed enough for me.

I will be having a more sophisticated monitoring system fitted soon (something that Octopus could have fitted at the installation but never offered but that's another story, a bit annoying) but in the meantime I have fitted a ct clamp monitor to the supply cable of the heat pump.

The ct clamp monitor has two inputs so the other is connected to the supply to the house. This means I can cross check with my solar monitoring and energy account and reconcile the total to make sure my figures for the heat pump are correct.

I don't think 2 or 3 kWh a day of standby costs are acceptable, I wouldn't be happy with that.

A ct clamp monitor is pretty cheap and easy to install.

My heat pump is on a separate supply in my meter cabinet so I can turn it off there or at the isolator switch next to the heat pump.

I would try turning it off if I were you, it's no different to a power cut, I can't see what could go wrong.

Ooh good point.  Though our power cuts are not quite that prolonged.

I'm getting the info from the … I don't know what it's called.  This, on our hot water cylinder, the panel that controls everything

Yes we do use it for hot water (that August usage of 33kWh delivered 96kWh for hot water - thanks to our smart meter information I know that yes we definitely need to turn it off when we go away as it heated it every day despite none being used *facepalm*)

It's a Mitsubishi Ecodan, 9.5kW I think?  I have an old thread where I put all the info, lemme dig it out … ah, PUZ WM115VAA  (I think the VAA stands for Vaampire … !)