Air Source Heat Pumps

Swipe

Yep, I'd definitely turn it off at that cost. That's ridiculous. I don't use more than 100 units in a week with my two aircon air to air units. Get yourself a few cheap heaters. You'll save yourself a fortune and still be warm at half the cost.

zeupater

@Bazz@rr

A couple of things which come to mind having read the previous couple of pages ...

Firstly, the property .... After you gave the size of the system, Geotherm asked for the floor area to see if it was correctly sized - this will indicate whether 100kWh/day would be expected. Also, what's the level of insulation and the type of building (ie is it solid stonework/high thermal mass ?)

Secondly, 100kWh/day (4.2kW continuous load) input is massive even at a COP of 1.0, so what's the temperature in the house - you've mentioned the thermostat temperatures, but what's the actual temperature .... also, are the radiators/underfloor warm ? ... is the temperature gradually increasing each day ? ...

Thirdly, is there a possibility that the meter could be feeding another property as well as the one you are renting ? ... this is not unknown!

Here's one for the HP techies ... If the heatpump is effectively turned off, does the frost protection switch the circulation pump and the immersion heater on ? ...

HTH
Z

lovesgshp

Have had a look through the manual and tech specs, from what the OP has been saying. This Grant pump, if the info given is correct, is below a 9kw output. Sizing without the thermal details, would normally put the house size circa 100sq mtrs, with normal insulation levels.
My thoughts are that it is undersized. Without floor area and thermal requirements it is difficult to tell.
If the pump is switched off, then no component circuits would normally work, as the sensors would not have power. This set-up is hard to get your head around!!!

albyota

zeupater wrote: »

Here's one for the HP techies ... If the heatpump is effectively turned off, does the frost protection switch the circulation pump and the immersion heater on ? ...

HTH
Z

Ze, see my post 1240

from the manual, it suggests that the first stage of frost protection runs the circulating pump until it sees a lift in return temp, then second stage kicks in.

AL

merlinonline

I heard today about a new build estate just south of Bedford called Wixams, its been a troubled place ever since they started the development.

They tried to fit this heating into the houses but didn't use approved installers and consequently it was a disaster as it didn't work so they ended up ripping out every install and replacing it with gas boilers which has cost £20K for each property! (bear in mind this is a new estate (village)).So just goes to show even new builds can be a disaster if not fitted by competent (and I mean suitably trained) person.

albyota

Yep, another developer that still thinks cheap is best, cutting costs, I hope these arrogant people learn their lesson.....fast..... And not at the expense of the occupants.

Harryo

The literature states the unit consumes a maximum of 28 A at 240V (that will be the heat pump, electric heater, integral circulating pump (if it has one) and condenser fan) . Therefore the absolute maximum consumption (cannot determine from the literature at what conditions that would be though) of the 110 heat pump package unit, excluding immersion heater, over a 24 hour period equates to 90 kW. The heat output at -2 deg.C / 50 deg. C flow (the rads will require this rather than the more advantageous 35 deg C Flow). is about 8.5 kW. It looks as though it is -2 at 08.30. What do you estimate the minimum and max temps are over a 24 hour period where you are? Was the heat pump left on continuously during the 24 hour period? I would suggest switching off all electric immersion heaters in the system, making sure the underfloor heating is switched off if it is electric and turning off the solar thermal system if both the heat pump and STS serve the same hot water cylinder. You say the STS is not functioning correctly. There is a possibility it is acting in reverse at night and discharging heat to atmosphere.

Baz@rr

Apologies for the delay in replying folks, my mother was admitted to hospital late on Friday, so things have been a bit chaotic.

Thanks for all your efforts to help me out here - it's much appreciated. To answer as many of your questions as I can...

The floor space of the house is approximate 160sq m. I don't know what it's made of, but there's roughcasting on the outside, if that's any help? One of the people working for the building company told us previously that "it's insulated to the hilt".

I'll get a thermometer today to check temperatures, but over the past 48 hours here the outside temperature min has been about -2 (briefly), and max about 10. I'd say it was averaging around 4deg overall.

I've been keeping a close eye on the meter readings and this is what I found.

Between 07:30 and 11:30 yesterday with the heating turned off at the control panel upstairs and some light usage of lights, kettle and toaster, the system went through 22 units of electricity.

Between 11:30 and 19:30, the ASHP was switched off at the mains. During this time we had TV/Sky on, an iPad charging, kettle boiling four times and dinner cooked in an electric oven. We also put the hot water boost on for an hour and used a little fan heater in the living room for half an hour. Total units used: 9.

At 19:30 I put the pump back on outside, worried we might wake to a freezing cold house. I checked the meter at 08:30 this morning. Units used: 70!

Worryingly, the temperature in the hot water cylinder never seems to make it above 37deg or thereabouts, hence me putting the boost on yesterday to try to bring it above 60 for legionnaires protection.

I'm assuming the ASHP should be bringing it up to above that level, otherwise surely it's a health hazard?

The problem with the solar pump is that it's literally doing nothing, although I dug around in the settings and think I've found out why, so hopefully when (if) it brightens enough today I should see it kicking in, but as it's currently very overcast it may well not do a thing.

My theory is that the 8.73kW just isn't enough to heat the house and hot water, so the built in immerser is kicking in all the time. These units are being racked up despite the fact the UFH is off and the radiators in three of the four bedrooms are turned off at the rad stat.

I spoke to the landlord yesterday and to his credit he actually swore in shock at the electric usage, and is getting the company who designed and installed the system to come down and check it. He has said if it was going to cost that much he'd "rip the f****** thing out with his bare hands" if necessary and have it replaced, as he had been sold the system on the understanding it would be cheap to run.

I'd like to have as much info as possible for when the installers come down so I can fend off any suggestions that it's working as it's supposed to be. All the advice you guys are giving is hugely appreciated.

Swipe

I wouldn't worry too much about the legionaries threat. It's really over exaggerated and takes weeks for them to build up and even then they thrive best at around temps of 30C. I've only ever heated my immersion heater to around 55C for over 3 years. To be on the safe side I'd heat it to 60C every couple of weeks if you really must and even then you only need to maintain that temp for around 15mins.

zeupater

@Bazz@rr

Looks like you're trying to run the HP like normal GCH. The efficiency of the unit will be much lower at ambient temperatures of -2C than at +10C, running during the day could give you 'up to' 40% more heat per unit energy input than doing so at night.

The important information which you missed out was the temperature inside the house ... is it getting warmer ? ... as it stands, the system will be running continuously until the thermostat temperature is reached, but the problem with heatpumps is that they aren't powerful enough to raise the temperature of the thermal mass as quickly as normal GCH. A house of the size you mention would normally have a ~30kW gas boiler which can raise the temperature of the air much faster than the structure can absorb it (unlike a smaller HP unit) .... If it was me, I'd be turning the house thermostat down to slightly above the air temperature to see if/when it cuts out and then edge the thermostat up by say 1C at a time, also knocking the temperature setting down at night, this way you would be able to measure the energy required to achieve the new setting and only raise the temperature of the thermal mass when the ambient temperature is high enough for the HP to be operating efficiently ...

HTH
Z