GSHP - I need help with making it as efficient as possible!

countryhouse39

In good news  - having switched off the underfloor heating at source, our overnight usage WAS significantly lower: 3.7kwh at 7am.
So maybe the HW usage is not the issue after all (although I'm still thinking there are efficiencies to be made there)

Reed_Richards

countryhouse39 said:

So maybe the HW usage is not the issue after all (although I'm still thinking there are efficiencies to be made there)

Most of us have our hot water cylinder inside the house so if it loses heat most of that will go towards heating the house (which is a good thing except in summer).  It also means that the air temperature outside the cylinder is room temperature or greater.  Your hot water cylinder is in an outbuilding which is unheated so the cylinder will lose heat faster and all the heat it loses is wasted. You really need a very well insulated cylinder connected to very well insulated pipes.      

matelodave

Perhaps you need to sort out what controls you've got (apart from the specific heatpump controller), especially if you underfloor heating has been burbling away in the background un-noticed. Has it got a thermostat to control the u/f pump and any zone valves. Some u/f systems have a by-pass or mixing valve to reduce the floor temp together with their own dedicated pump, especially if you've got rads upstairs which frequently run at a higher flow  temperature.

Likewise if you've got radiators, do they have a separate room stat, TRVs and possibly another pump.So you need to know wha'ts controlling it all

It's quite likely that you've got several pumps all running at different times and controlled by timers or stats - one or more for the ground loops, one for the buffer tank, possibly one between the buffer tank and hot water cylinder for the hot water and one or even two for the heating circuits

I think I'd sit down and draw out a schematic of your plumbing, showing where all the valves and pumps are, together with an indication of where the controls are connected, what they do and how they interact with each other so you can understand what is controlling what and when.

As R-R says having all that hot water in a cold outhouse doesn't improve system efficiency and you need to ensure that all the pipework is really well insulated. Bear in mind what I said about drawing off short amounts of hot water, if the pipe runs are fairly long then you'll be wasting a lot of hot water sitting in the pipework.

markin

countryhouse39 said:

Magnitio said:

And does it have an integrated hot water cylinder or a seperate hot water cylinder, or both? If a seperate hot water cylinder, is it located in a different part of the house to the heat pump?

See attached pic - L-R: HW tank, buffer tank & heat pump - all housed in the pump room, which is a store area attached to our house, but the room isnt insulated -  accessed from the garden. 

All the exposed copper on the tanks wants rapping up, And screw foam board to the external walls and door.

Magnitio

Reed_Richards said:

countryhouse39 said:

So maybe the HW usage is not the issue after all (although I'm still thinking there are efficiencies to be made there)

Most of us have our hot water cylinder inside the house so if it loses heat most of that will go towards heating the house (which is a good thing except in summer).  It also means that the air temperature outside the cylinder is room temperature or greater.  Your hot water cylinder is in an outbuilding which is unheated so the cylinder will lose heat faster and all the heat it loses is wasted. You really need a very well insulated cylinder connected to very well insulated pipes.      

The specification for the hot water cylinder states that it loses 2.24kWh of heat per 24 hours as per following: ( https://downloads.acv.com/SLE+ Tech 040113 - HWA Logo.pdf ) which is fairly normal for a large modern tank. As you say, the actual heat loss will be higher when the ambient temperature is low.

In the installation instructions, it says that the thermostat for this cylinder can be set in the range 60 to 85 C, although it can be modified. It would be interesting to know what it is set to; if it is higher than the output temperature from the heat pump, it will run continuously and may only reach the required temperature once a week.

1961Nick

Reed_Richards said:

countryhouse39 said:

Whether we have the auxillary heater that is part of the pump set up correctly I have no idea though. pic attached of the info for that on the heat pump controls. I think we were told a while ago (years ago now) by a valiant engineer that 4 deg was about right for the temp for coming on, but maybe its not right? Also attach image of stats for how often its on ( i think this is since installation, but no idea tbh!)

Well the compressor hours is equivalent to about 3.25 years.  During those hours the auxiliary heater is on about 8% of the time which should mean that about 8% of the time your heat pump is running it is 4 C or less outside.  That seems a lot to me.  Check that the auxiliary heater hours is not going up, or only going up when the Legionella cycle takes place, as you think it used then.

You should also be able to read the temperature of your hot water cylinder.  You could check that this is not falling too rapidly when the hot water is not being used.  There might also be a setting for how low below the set temperature the cylinder has to get before it is re-heated. 

There could also be a fault with the outside temperature sensor resulting in the auxiliary heater working above 4C? If there was a way to switch the auxiliary heater off for a couple of days, that could eliminate it from the list of potential suspects for the excessive consumption.

matelodave

My ASHP has three isolating switched one each for the heatpump, one for the tank immersion (which is controlled by the heatpump) and one for the auxiliary/backup heater so I can shut all the heaters down so they aren't used if I dont want them to be.
Likewise the controller has the option to activate or deactivate them and set the temperatures at which they operate when activated. Another case of finding out how the controls work, what they do and setting them appropriately

ccbrowning

countryhouse39 said:

In good news  - having switched off the underfloor heating at source, our overnight usage WAS significantly lower: 3.7kwh at 7am.
So maybe the HW usage is not the issue after all (although I'm still thinking there are efficiencies to be made there)

My system was doing the same thing! I had all the zones (underfloor) at like 14C even though the ambient temp has been showing 20 on the thermostats. They'd not been showing the symbol for heating, either. However, it seems like the heating was still running somehow - found a summer setting on my GSHP (Heliotherm) which puts in DHW only.

EricMears

ccbrowning said:

countryhouse39 said:

In good news  - having switched off the underfloor heating at source, our overnight usage WAS significantly lower: 3.7kwh at 7am.
So maybe the HW usage is not the issue after all (although I'm still thinking there are efficiencies to be made there)

My system was doing the same thing! I had all the zones (underfloor) at like 14C even though the ambient temp has been showing 20 on the thermostats. They'd not been showing the symbol for heating, either. However, it seems like the heating was still running somehow - found a summer setting on my GSHP (Heliotherm) which puts in DHW only.

Very likely the system is running due to 'thermosyphon' : i.e. the hot water from tank downstairs is lifting itself up and displacing colder water in the floors.  You'll only stop that if you can put a valve into the line.

ccbrowning

EricMears said:

ccbrowning said:

countryhouse39 said:

In good news  - having switched off the underfloor heating at source, our overnight usage WAS significantly lower: 3.7kwh at 7am.
So maybe the HW usage is not the issue after all (although I'm still thinking there are efficiencies to be made there)

My system was doing the same thing! I had all the zones (underfloor) at like 14C even though the ambient temp has been showing 20 on the thermostats. They'd not been showing the symbol for heating, either. However, it seems like the heating was still running somehow - found a summer setting on my GSHP (Heliotherm) which puts in DHW only.

Very likely the system is running due to 'thermosyphon' : i.e. the hot water from tank downstairs is lifting itself up and displacing colder water in the floors.  You'll only stop that if you can put a valve into the line.

We have a meter which shows just heating electricity usage and I checked 24 hours after changing to summer mode and it’s not gone up at all. Hope it doesn’t cause issues later. So maybe the installers did a passable job? lol