ASHP - E7 or not E7?

[Geoff-Belgraver]

10 hours ago, Geoff-Belgraver said:

yep - probably - that's why the MCS survey is so important (if they are up to doing the calc for the thermal store)

Yes -thermal store heat loss data from the supplier will be important and many do not even specify the type and thickness of the insulation.

[SteamyTea]

5 hours ago, Geoff-Belgraver said:

thermal store heat loss data from the supplier will be important

You have to be careful with the manufactures HLD, they have a quirky way of calculating it.

It assumes the cylinder is cold, then heated up as fast as possible, then drained of useable hot water.  The losses are are calculated in that small usage window.

The rest of us heat things up and use it hours later.

[ollie]

On 05/08/2021 at 21:19, PeterW said:

Yes it’s called load shifting - works really well. 
 

Probably one of the better reasons for solar PV although in winter you need a lot of panels to offset the usage 

Hi PeterW , due to recent electricity price hikes i'm desperately looking into cheaper ways to use my ASHP - i'd love to hear more about your experiences of load shifting - annoyingly i can't get on octopus go tariff as our smart meter wont communicate due to poor signal in the area, so i'm now looking into standard eco 7 tariffs and want to ensure there is an actual saving to me made by switching my ashp to operate on off peak times. 

 

 

 

[Luke1]

I've had an ASHP installed this year, so fairly new to the game and can't offer much advice, but thought I'd chip in with regards to E7 tariffs.

My tariff has two off-peak periods oddly! 23:30 - 01:30 & 3:30 -08:30 (due to change by 1hr when the clocks change).

 

These off peak periods are 5X cheaper than the day rate so I've been running the ASHP over night during these periods to pre-heat the DHW.

I have been heating my tank to 55C. Whilst I am getting a lower COP heating the tank this high, I guess that I am still saving overall as I do not need to heat the cylinder during the day at 5X the cost. 

I'm just awaiting delivery of a Shelly EM to monitor our electricity usage so that I can try and maximise any savings of the E7, especially when it comes to heating. 

[SteamyTea]

1 hour ago, Luke1 said:

These off peak periods are 5X cheaper than the day rate so I've been running the ASHP over night during these periods to pre-heat the DHW

Worth looking at the current rates on E7/10 as they are not so attractive.

Think mine are 14p and 24p.

I use around 80% of my energy at 14p. But my usage is low at ~5 MWh/year for everything.

Usually only use about 2 KWh/day at 24p.

[Luke1]

5 hours ago, SteamyTea said:

Worth looking at the current rates on E7/10 as they are not so attractive.

Think mine are 14p and 24p.

I use around 80% of my energy at 14p. But my usage is low at ~5 MWh/year for everything.

Usually only use about 2 KWh/day at 24p.

I signed up nearly a year ago now in a 2 year fix with EDF.

I'm on 5p and 24p. So my night rate is very favourable compared to the recent price hike! 

[SteamyTea]

2 minutes ago, Luke1 said:

I signed up nearly a year ago now in a 2 year fix with EDF.

I'm on 5p and 24p. So my night rate is very favourable compared to the recent price hike! 

I am with EDF and never got offered 5p for night rate, not even 20 years ago.

[Luke1]

6 minutes ago, SteamyTea said:

I am with EDF and never got offered 5p for night rate, not even 20 years ago.

No idea how I wangled it, but I'm even more happy with my 4.99p now! 

Before the recent price hike I did see an Octopus deal that was 5p & 15p ish which I nearly changed to! 

 

My E7 hours are a little strange though:

Day: 0030-0230 & 0730-2230
Night: 2230-0030 & 0230-0730

 

[SteamyTea]

4 minutes ago, Luke1 said:

My E7 hours are a little strange though:

Day: 0030-0230 & 0730-2230
Night: 2230-0030 & 0230-0730

Mine are similar.

 

I have disabled the late evening times as I only need about 3 hours.  That way it heats the water later, or closer to when I need it.  As long as I use it after the shut off time, I reduce the standing losses.

[Luke1]

9 minutes ago, SteamyTea said:

Mine are similar.

 

I have disabled the late evening times as I only need about 3 hours.  That way it heats the water later, or closer to when I need it.  As long as I use it after the shut off time, I reduce the standing losses.

I'm doing exactly the same. I may have to set it to shut off earlier during the week as the water is normally being charged whilst its used and then I end up with a hot tank that doesn't get used all day!

There is a sweet spot though, to have enough time to recharge it sufficiently in the morning. Especially now the ASHP is going to be doing heating as well!

[SteamyTea]

3 minutes ago, Luke1 said:

There is a sweet spot though, to have enough time to recharge it sufficiently in the morning.

Do you have an electrical energy logger?

[Luke1]

6 minutes ago, SteamyTea said:

Do you have an electrical energy logger?

I'm just setting up Home Assistant. I've managed to extract some info via an API from the Bright app, however this is only on overall electricity use per hour. (I've attached the kWh info that is imported into Home Assistant. 

I have a Shelly EM with a couple of CT clamps on order, which I hope to use with Home Assistant. They've just released an Energy panel, and it looks like I can use multiple tariffs to help monitor cost. 

[SteamyTea]

3 minutes ago, Luke1 said:

I have a Shelly EM with a couple of CT clamps on order

Let us know how you get on with them, I made my own.

 

 

 

 

 

[Luke1]

Those graphs are interesting. Hopefully I'll have similar data in a year to understand things a bit better myself. (I presume the monitoring has helped you make informed choices on how to programme your system?)

I presume you have UFH and ran the heating at night only in general.

I'm hoping my kitchen slab will act like a storage heater, pumping in heat overnight, in the hope it releases the heat gradually over the course of the day. I fear it won't hold the heat for long though and will need topping up during the day. 

 

Time will tell!

[SteamyTea]

30 minutes ago, Luke1 said:

(I presume the monitoring has helped you make informed choices on how to programme your system

Yes, and it can quickly highlight a problem, like when my fridge went permanently on.  I saw the rise in usage and got a new fridge within  days.  Was also useful when the element in the water cylinder went, could see that it was only partially drawing power as it failed.

I use basic storage heaters and a 200lt water cylinder.  I just control the times with secondary timers.

I did muck about with removing elements from the large storage heater (21 kWh), but decided that using just timers (cheap from eBay and have lasted years) was easiest, and can get them to fit in with times of low emission generation.