Storage heater alternative.... Infrared vs lpg vs Air source heat pump 12 April 2021 at 9:50AM in LPG, heating oil, solid & other fuels 83 replies 3.2K views

Reed_Richards

I think the penalty for lack of an annual inspection is that you void the warranty.  @lohr500 has negotiated an excellent £80 per year to have their boiler serviced; I just wanted to point out that if that covers an inspection of the hot water cylinder, duly noted on the report, that would be even better. 

In my last house I had an unvented hot water cylinder that went uninspected for 18 years until I started to get water coming out the overflow.   I got it fixed and no harm was done, AFAIK.  At that time I was unaware of any requirement for servicing if there was one.  I got the gas boiler I had then serviced every two years, as required by the manufacturer.  The service engineer who did that never suggested that it might be prudent to give the cylinder a quick once over. 

lohr500

Reed_Richards said:

The OP (who has not yet returned to comment) wants to replace storage heaters.  If I was installing any radiator-based central heating from scratch I would try to future-proof it by designing it to run with a water flow temperature of no greater than 50 C.  That way whatever boiler you choose now can later be replaced by an ASHP without the need to change the radiators.    

That is a very good suggestion and the OP should give it serious consideration. Far easier to put higher output capacity radiators in during the initial installation than retrofitting them later.

lohr500

Mickey666 said:

Reed_Richards said:

My LG ASHP has a 7 year warranty.  My installer will perform an annual service at a cost of £150.  I'm not sure how necessary this is but an annual inspection of any pressurised water tank is mandatory, whatever is heating your water.

Really?  What legislation is this then?  What's the penalty if you DON'T have an annual inspection?

The old setup was an unpressurised, open vented system. I stuck with it as I didn't want the extra complication of a pressurised system or a combi boiler. More to go wrong and given the age of the plumbing and lack of access to the pipework, the last thing I wanted was loads of pressure in the system. The annual service also includes an annual inspection of the oil tank which is a requirement for the 10 year tank warranty.

Reed_Richards

I switched to a pressurised hot water in 1998, the cold water was already at mains pressure.   The biggest advantage was that the house had an incredibly noisy electric motor for a power shower which I was able to make redundant.

Cardew

shinytop said:

Isn't it a bit like EVs?  For most people changing from their existing ICE car to an EV doesn't make economic sense but plenty do it.  It's a lifestyle choice (and there is nothing wrong with that). Being eco-friendly costs money.  

Certainly for most people an EV doesn't make economic sense; however I still suspect the lure of low running costs is the primary reason.

It is much like people pay £thousands to upgrade their perfectly serviceable ICE car for another ICE because the newer model gets an extra 5mpg.

Cardew

shinytop said:

lohr500 said:

@ shinytop. I have no doubt that your ASHP system will be cheaper to run than a house full of storage heaters.
But one has to wonder how the running costs would compare if you had opted for an oil system.
It would be interesting to know how many kWh you have used over the 10 days and what the cost of that electricity was including a proportion of any standing charge based on ASHP usage vs total usage.

With a modern condensing oil boiler running at 93% efficiency and heating oil at £0.40 per litre inc VAT, the cost of 1kWh of heat works out at £0.042. For an ASHP with a generous COP of 3:1, to get 3kWh of heat out, you would need to be buying electricity at less than £0.126 per kWh to match the oil cost per kWh of available heat.
And I do worry about the claimed COP values for ASHP, particularly when its cold outside, the very time you need more heat in the house.  

I agree 100% that oil is not environmentally friendly and if we could have switched to an ASHP or some other form of renewable supply for at or around the same cost, I would have done it.
I was also a little worried about the fact that the RHI grant is linked to the property, not the individual, so if we were to downsize within the 7 year grant window we would stop receiving the payments despite making the full up front commitment to the installation.  

@Iohr500, over the 10 days, the ASHP used 326 kWh at a COP of 3.16 so used 1030kWh.  I'm paying 11.6p per kWh plus 23p per day. 

A technical question if  I may please.

How do you determine that the system COP over those 10 days was 3.16?

I assume you mean the input was 326kWh giving an output of 1030kWh. Do you have heat meters for both CH water and hot water and does your system have a backup immersion? Would your measurement of input kWh include any defrosting if required?

Reed_Richards

Cardew said:

Would your measurement of input kWh include any defrosting if required?

Yes.  Anyone claiming RHI now requires a meter than measures the power drawn by the heat pump.  It's a regular electricity meter but just on the one circuit.      

Mickey666

Reed_Richards said:

I think the penalty for lack of an annual inspection is that you void the warranty.  @lohr500 has negotiated an excellent £80 per year to have their boiler serviced; I just wanted to point out that if that covers an inspection of the hot water cylinder, duly noted on the report, that would be even better. 

In my last house I had an unvented hot water cylinder that went uninspected for 18 years until I started to get water coming out the overflow.   I got it fixed and no harm was done, AFAIK.  At that time I was unaware of any requirement for servicing if there was one.  I got the gas boiler I had then serviced every two years, as required by the manufacturer.  The service engineer who did that never suggested that it might be prudent to give the cylinder a quick once over. 

Ah, a warranty requirement, not a legal one.

Had me worried for a while there as I've never had my pressurised system checked, never mind annually.  I'm not really sure what there is to check anyway - it's pretty obvious if the system loses pressure.

shinytop

Cardew said:

shinytop said:

lohr500 said:

@ shinytop. I have no doubt that your ASHP system will be cheaper to run than a house full of storage heaters.
But one has to wonder how the running costs would compare if you had opted for an oil system.
It would be interesting to know how many kWh you have used over the 10 days and what the cost of that electricity was including a proportion of any standing charge based on ASHP usage vs total usage.

With a modern condensing oil boiler running at 93% efficiency and heating oil at £0.40 per litre inc VAT, the cost of 1kWh of heat works out at £0.042. For an ASHP with a generous COP of 3:1, to get 3kWh of heat out, you would need to be buying electricity at less than £0.126 per kWh to match the oil cost per kWh of available heat.
And I do worry about the claimed COP values for ASHP, particularly when its cold outside, the very time you need more heat in the house.  

I agree 100% that oil is not environmentally friendly and if we could have switched to an ASHP or some other form of renewable supply for at or around the same cost, I would have done it.
I was also a little worried about the fact that the RHI grant is linked to the property, not the individual, so if we were to downsize within the 7 year grant window we would stop receiving the payments despite making the full up front commitment to the installation.  

@Iohr500, over the 10 days, the ASHP used 326 kWh at a COP of 3.16 so used 1030kWh.  I'm paying 11.6p per kWh plus 23p per day. 

A technical question if  I may please.

How do you determine that the system COP over those 10 days was 3.16?

I assume you mean the input was 326kWh giving an output of 1030kWh. Do you have heat meters for both CH water and hot water and does your system have a backup immersion? Would your measurement of input kWh include any defrosting if required?

The control unit in the house displays consumed and delivered "electrical energy" for heating and HW. I am dividing one by the other to get COP, which is different each day. It does have a backup immersion that it uses for legionella protection and that I can hook up to solar if I want to.  I don't know if the consumed kWh includes defrosting.  I also don't know how these numbers are measured and, to be honest, if they are realistic.  The consumed kWh is in the right ballpark when I compare with my electricity usage though. 

matelodave

Actually, if you calculate your COP using the power supplied to the heating system via it's own meter and the generated output as measured by the either the heatpump or a separate heat meter you must get a pretty accurate COP figure.

It will take into account all the enrgy that the system consumes which would include stuff like the defrost cycle, pumps and even the crankcase heater if you've got one. Depending on how its configured and where the power supply is measured it may even take into account any consumption by the immersion or back up heater which could aslo have an effect on the COP.

Heat meters (and I guess the internal heatpump measurement system) measure the incoming water temperature, the out going water temperature and the flow volume through the heat pump and integrate them over time to caluclate the heat output of the heatpump.