Nibe (or any heat pump) water scheduling

[mary]

OK

 

I’ve no idea what’s going on to be honest - we have got a smart meter and it randomly goes up when we aren’t doing anything different.  For example, it keeps going from 0.15p a hour to 0:22p a hour without anything being turned on or off

 

The instructions refer to controlling the secondary hot water loop which is optional but this isn’t on the controller so we don’t have that anyway

 

I just don’t understand the immersion part to even check unless it’s the plug saying cylinder immersion?  The instructions say the buffer tank  is to prevent the pump from short cycling so not sure if that needs to be on (it’s a plug labelled buffer immersion)?

 

this is probably a daft question but are there trades people who actually deal with helping getting the system set up to suit you?! 

 

 

[marshian]

33 minutes ago, mary said:

OK

 

I’ve no idea what’s going on to be honest - we have got a smart meter and it randomly goes up when we aren’t doing anything different.  For example, it keeps going from 0.15p a hour to 0:22p a hour without anything being turned on or off

 

 

 

You have fridge and or freezer? - they randomly top up and cause a spike without you even noticing you are doing anything different.

 

Difference from 0.15p per hour to 0.22p per hour based on say a 35p per kWh for electric is around 200W so it's not enough to be an immersion heater

[sharpener]

 

5 hours ago, mary said:

Thanks all

 

i have the instructions so I’ll try to work it out - I think there are 2 switches saying cylinder immersion and booster immersion / both are on

 

So turn them off, there is no risk and you will learn what happens

 

20 minutes ago, mary said:

The system was put in 8 yrs ago and previous owners didn’t really give us much information but they had a teenager so their usage would have differed I guess

 

this is probably a daft question but are there trades people who actually deal with helping getting the system set up to suit you?! 

 

Do you know who installed the system for them/who has serviced it since?

 

Do NIBE have a "find an expert" service or can they send their own engineer out?

 

Is there a NIBE help forum?

 

Have you tried to locate a heatgeek specialist near you  https://www.heatgeek.com/find-a-heat-geek/

[mary]

That’s all!

 

yes it’s been serviced every year and we have all the docs 

 

I’ll try and few things - not even tried the heating yet so lord help me!! 😅

[SteamyTea]

@mary

Just as an example of heating water I have a basic E7 cylinder of 200lt.

The bottom 3 kW element comes on at 3AM, and goes off at 4:30 AM. I have the thermostat set to 50°C.

That heats enough water for 1 bath, 1 short shower and all the washing up.

The cost is about 50p/day.

 

The thing with an electric element is that it gets very hot, well over 100°C. This does not cause the water to boil because eddy currents are set up in the cylinder, these replaced the very hot water with cooler water.

With a heat pump setup, the coil that transfers the energy is at a much lower temperature, often below 60°C. Even if it has a large surface area, it can still take longer for the cylinder to get up to the set temperature.

This is because as the water in the cylinder approaches the coil temperature, less energy is transferred. It is not unusual for the last 5°C rise in temperature to take as long as the first 20°C rise i.e 25 to 45°C.

That is an important point about using low temperature heating systems and why they are not used like a normal gas boiler.

You will hear the term 'slow and steady' with regards heat pumps. They are designed to deliver energy that way.

Edited Tuesday at 18:24 by SteamyTea

[mary]

Thanks

 

I've turned off the cylinder immersion but can’t really see any difference

 

One other thing I’m unsure about is that I can hear the air pump coming in sometimes randomly?  Is this normal?  For example, this morning when  I got up at 7am the heat pump was going outside and meter showed 50p a hour.  We only have only git hot water scheduled 4am for 30mins and no heating scheduled?  The air pump stopped after a hour??

[IGP]

HPs are great and can easily be cheaper and more comfortable than gas central heating, but they are different beasts vs gas boilers. They can be a bit of a learning curve as you don’t run them the same way. 

 

I would get someone like a heat geek as mentioned earlier to come round, and explain and setup the system in an optimal way for you. It’s just not worth the stress IMHO. 

[mary]

Thanks everyone - I’ll get some advice.

 

It’s all just so different coming from a combi boiler set up !

[SteamyTea]

4 hours ago, mary said:

 Is this normal

In a properly set up system yes.

As heat pumps deliver water for the heating at a lower temperature, the tend to deliver (switch on) when they sense the house getting colder. They can do this by sensing the return pipe temperature, rather than use a room thermostat.

 

A combi boiler is sized to deliver hot water and is often in the region of 20 kW or more. A heat pump is sized to heat the house, so often 6 kW or more. This is why it takes an hour or two to heat up a water cylinder.

The calculation for heating water is quite simple, once you know what the words mean.

If you know the size of your ASHP and the size of your water cylinder, it only takes a minute to work out how long it will take to heat up.

[mary]

OK I can check that information 

 

I just don’t understand why the pump is ‘pumping’ when I don’t have anything scheduled to be on

[SteamyTea]

6 minutes ago, mary said:

OK I can check that information 

 

I just don’t understand why the pump is ‘pumping’ when I don’t have anything scheduled to be on

'pumping' is a bit vague, it may be just the circulation pump.

[PhilT]

4 hours ago, mary said:

Thanks everyone - I’ll get some advice.

 

It’s all just so different coming from a combi boiler set up !

Or maybe there's a forum member who can help if nearby, in which area are you?

[mary]

1 hour ago, SteamyTea said:

'pumping' is a bit vague, it may be just the circulation pump.

Sorry I mean I can hear the pump making a noise outside 

[sharpener]

2 hours ago, mary said:

Sorry I mean I can hear the pump making a noise outside

 

If the fan is running the HP will be producing heat. One or both pipes coming into the house will be warm under the lagging.

 

If the fan is not running any continuous noise will be the circulation pump in the outdoor unit pushing the water round the system. Even if there is no heat demand this can be quite normal, the HP needs to measure the water in the house (at least periodically) so does this to sample the return pipe temperature as @SteamyTea says upthread:

 

4 hours ago, SteamyTea said:

They can do this by sensing the return pipe temperature,

 

[mary]

Thanks - not sure if it’s the fan running or just a noise to be honest - it just seems to happen randomly so maybe it’s the circulation thing.

 

I’ll try a local a local geek!  I’m in Sheffield so must  someone around here  

[sharpener]

15 minutes ago, mary said:

Thanks - not sure if it’s the fan running or just a noise to be honest - it just seems to happen randomly so maybe it’s the circulation thing.

 

Well the fan blows cold air out of the front of the machine (as fans do). So that is how you can tell.

[mary]

OK thanks - next time I hear it I’ll go out and check!  Another stupid question / if it’s the fan why would it be producing heat if I’ve only programmed it to heat water (no heating on)?

[sharpener]

It needs to produce heat to heat the water which is the heat transfer medium. I was not intending to draw any distinction between heating and hot water, the fan blows cold air out in either case.

 

The air comes out colder than when it went in at the back of the unit bc the heat in it has been tranferred by the refrigeration cycle in the HP from the ambient air to the water pipe which goes into the house. This initial process is the same whether it subsequently heats the house or the hot water. See here https://en.wikipedia.org/wiki/Air_source_heat_pump.