People Saying Heat Pumps are Rubbish - Are They?

QrizB

BoYaNY73 said:

matt_drummer said:

sohekim said:

I live between 2 houses that both have Air Source Heat Pumps fitted and both of them exceed the sound pressure levels. The Law states they must be 42dB or less and there is a good reason for this but we have recorded both units running at over 70dB. The manufactures do sound level tests but these I have found out to be flawed as they quote a "free field" test sound level which means that during the test there are no reflective surfaces for sounds to bounce off and the unit is basically clear of any obstructions and they manufactures do not have to record lower frequencies.  Nor do they take into account that rural village sound levels are lower than 40dB during the night so when calculations are made the manufacture uses the urban sound levels instead However these units when running emit deep frequency hums that can disturb the sleep. Also the colder or lower atmospheric pressure is the longer the Air Source Heat Pumps run for.  They can be a nuisance for people living near to them. At night prior to the fitting of the ASHP the sound level at night was 29.2dB but now it is between 60db and 75db when they are running and it is agony at night. All measurements have been taken using professional equipment and you can see there is a big difference between the normal quiet village life and when the ASHP's are running. It is so easy for these units to cause health problems as the sound grinds a person down. 

I don't believe you, sorry.

Next door’s fans from their air conditioners are driving me crazy! They certainly grind you down ! I feel the only thing to do is sell up and move house.

So they're air conditioners now, not "heat pumps"? Are they portable units or permanently installed?

You've had a couple of suggestions in this thread. You can complain to your neighbours, or you can complain to your council (building control and/or environmental health). Have you tried that?

Reed_Richards

BoYaNY73 said:

Next door’s fans from their air conditioners are driving me crazy! They certainly grind you down ! I feel the only thing to do is sell up and move house.

• So we have established that these are air conditioners (which very probably are a type of heat pump but not an ASHP).
• There is no noise from the fans if you are outside.
• But you hear a noise inside your house that you struggle to tolerate.

This is a strange and inexplicable problem; unless you can establish how it is happening I doubt that you will find a solution, so selling up and moving may indeed be your best option.    

Strummer22

hairydog said:

6. ASHP systems don't seem to last very long. A decent gas boiler lasts 15 to 25 years, with a service every 3-5 years. I know of a few people whose ASHP unit has had to be replaced before it was ten years old (one of them twice in ten years). This has a huge embedded carbon cost.
So in summary, ASHP do work, but they probably won't save you money and they are no greener than mains gas.

Embedded carbon cost of installing an ASHP is apparently around 1.5 tonnes CO2e. I had a quick search for a comparable figure for a gas boiler and didn't find anything, so we'll be generous to gas and say it's zero.

According to OFGEM a 'typical' household uses 11,500 kWh gas, the vast majority being for heating and hot water. Say 10,000 kWh (producing about 9,000 kWh heat). Burning natural gas releases about 0.183 kg CO2e/kWh (for gas consumed, not energy produced). That's 1.8 tonnes CO2e per year from burning gas. 

For a COP of 3 to produce 9,000 kWh an ASHP uses 3,000 kWh electricity. It's probably not realistic to use grid average carbon intensity as ASHP demand is likely to be highest when carbon intensity is high (very cold weather tends to be dark, and not very windy). Say 200 g/kWh. So 600 kg CO2e from the electricity consumed.

Based on the above, CO2e from boiler ~1.8 tonnes per annum, CO2e from heat pump ~ 0.6 tonnes per annum. 1.2 tonnes per annum difference. Just over 1 year to pay back the 1.5 tonnes embedded carbon from ASHP. Therefore not a huge embedded carbon cost unless you have to replace your heat pump every year.

"no greener than mains gas" - rubbish, seems like you have an axe to grind!

matelodave

Strummer22 said:

hairydog said:

6. ASHP systems don't seem to last very long. A decent gas boiler lasts 15 to 25 years, with a service every 3-5 years. I know of a few people whose ASHP unit has had to be replaced before it was ten years old (one of them twice in ten years). This has a huge embedded carbon cost.
So in summary, ASHP do work, but they probably won't save you money and they are no greener than mains gas.

"no greener than mains gas" - rubbish, seems like you have an axe to grind!

There's no reason why a heatpump should be any less reliable than a gas boiler - after all its only a fridge working in reverse and fridge's last a long time. In fact the expected life of a heatpump is around 15-20 years.

TBH modern gas boilers don't last anywhere as long as those with minimal controls and a cast iron heat exchanger.  The electronics, fans, low water content heat exchangers, acidic condensation etc means they've actually got more to go wrong than a compressor, fan and flow valve in a heatpump. I know many people who's gas boiler has lasted well short of ten years

Hopefully I'm not tempting fate but my ASHP is coming up to 15 years old and still chunters away quite happily.

As to whether its greener, yes it is insofar as it uses less energy than a gas boiler for the same heat output. Although it may well be a moot point whether the leccy it uses is green when a fair proportion of it is produced by burning gas or  twigs brought all the way from the USA on a diesel powered boat.

The cost of the leccy it uses costs around four times the cost of gas, so although greener, not necessarily cheaper.

Strummer22

matelodave said:

As to whether its greener, yes it is insofar as it uses less energy than a gas boiler for the same heat output. Although it may well be a moot point whether the leccy it uses is green when a fair proportion of it is produced by burning gas or  twigs brought all the way from the USA on a diesel powered boat.

Still greener even if all the electricity is from burning gas. Gas turbine (CCGT) ~60% efficient, gas boiler ~90% efficient.

COP of 3, CCGT leccy is 180% efficient, so an ASHP running on gas-generated electricity will have half the carbon emissions of a gas boiler. 

matelodave

You also need to take into account the electricity transmission losses which are about 8% which often gets overlooked when discussing the energy efficiency of leccy. https://www.nationalgrid.co.uk/smarter-networks/losses/electrical-losses

grumpypensioner

Any one know what the temperature these new systems give you for hot water for showering, bath etc.? My old system is set for 55ºC which seems fine.

Alnat1

grumpypensioner said:

Any one know what the temperature these new systems give you for hot water for showering, bath etc.? My old system is set for 55ºC which seems fine.

Heat pumps can normally heat the tank to around 52-55C. We have ours set to 47C once a day, plenty for our 2 showers and a bit of cleaning. It can be set up to keep reheating the water when the temperature drops below a set level, for those that use more. There's a boost option that uses the tanks immersion heater and can quickly reheat it if needed. This can also be used to take the temperature above what the heat pump can manage.

benson1980

Alnat1 said:

grumpypensioner said:

Any one know what the temperature these new systems give you for hot water for showering, bath etc.? My old system is set for 55ºC which seems fine.

Heat pumps can normally heat the tank to around 52-55C. We have ours set to 47C once a day, plenty for our 2 showers and a bit of cleaning. It can be set up to keep reheating the water when the temperature drops below a set level, for those that use more. There's a boost option that uses the tanks immersion heater and can quickly reheat it if needed. This can also be used to take the temperature above what the heat pump can manage.

What you do need to be mindful of is that thermostatic shower valves will generally need a 10oC differential in temperature i.e. if HW supply from cylinder is 47 or 48, the max outlet temperature will be 37-38. The instructions for one of ours actually says that the HW supply needs to be 60oC (which is slightly ridiculous as stored water in the tank does not need to be this hot to provide sufficient warm water to a household). Outlet temp of 38 gives a comfortable warm shower.

We initially had our cylinder temp set at 45 but we had to turn it up to 48 as one of our showers really struggled with sufficient outlet temperatures, and this was on full adjustment.

Risk of legionnaires in domestic properties is negligible to non existent so we personally don't bother with the immersion cycle either. Just stays at 48. That does plenty of HW for 4, set at reheat during peak shower times.

michaels

benson1980 said:

Alnat1 said:

grumpypensioner said:

Any one know what the temperature these new systems give you for hot water for showering, bath etc.? My old system is set for 55ºC which seems fine.

Heat pumps can normally heat the tank to around 52-55C. We have ours set to 47C once a day, plenty for our 2 showers and a bit of cleaning. It can be set up to keep reheating the water when the temperature drops below a set level, for those that use more. There's a boost option that uses the tanks immersion heater and can quickly reheat it if needed. This can also be used to take the temperature above what the heat pump can manage.

What you do need to be mindful of is that thermostatic shower valves will generally need a 10oC differential in temperature i.e. if HW supply from cylinder is 47 or 48, the max outlet temperature will be 37-38. The instructions for one of ours actually says that the HW supply needs to be 60oC (which is slightly ridiculous as stored water in the tank does not need to be this hot to provide sufficient warm water to a household). Outlet temp of 38 gives a comfortable warm shower.

We initially had our cylinder temp set at 45 but we had to turn it up to 48 as one of our showers really struggled with sufficient outlet temperatures, and this was on full adjustment.

Risk of legionnaires in domestic properties is negligible to non existent so we personally don't bother with the immersion cycle either. Just stays at 48. That does plenty of HW for 4, set at reheat during peak shower times.

How big is your cylinder?  Lets say you want a shower temp of 38C (probably more like 40) and cold water is 8c (can be les sin winter) then a 250l tank gives you about 340l of water so about 4 80l showers.