ASHP or oil boiler...

[horace]

Our oil combi boiler has reached the end of its life. No mains gas here, so we have narrowed down the options to another oil boiler or ASHP (open to other suggestions though). 

 

5 bed house (177 square metres, built 2006), 3 shower rooms, 1 bathroom. We have a large multi-fuel stove in the lounge, which (if we open all internal doors) provides most of our heating needs in the winter. 19C is warm enough for us. Our eldest is a joiner, so plenty of free scrap wood for the stove). 

We use about 1500 litres of kerosene a year. 

We also have a 4kw solar pv system (south facing) with 6.5 kwh battery. 

 

Our last EPC (about 8 years old, done prior to fitting the solar panels) gave a rating of 74 (C). Recommendations were to put in a new condensing boiler and solar panels, which would raise rating to B. 

 

The above would appear to be promising on the ASHP front (subject to the usual heat loss survey etc) and the solar panels would hopefully provide energy for DHW during the warmer months. 

 

About 3 months ago, a local ashp company gave us a rough estimate of 14k to fit ashp (likely 12 or 14kw), water cylinder and 12 new radiators. On that basis, about 9k (if we can get a BUS grant). Two quotes to replace the existing boiler (with another oil combi) suggest 5.5k plus VAT, which isn't all that much less than the ASHP would cost. That surprised me. 

 

We can survive without a boiler for now (cold showers in summer are fine, and my mother-in-law is a 5 minute walk away for when a hot shower is too much to resist) but time is a factor. 

 

My heart says ASHP, as I'd love to be free of dependency on fossil fuels. It would be good to get back the garden space occupied by the oil tank. Would also be good to maximise use of the energy generated by the solar panels. 

 

On the other hand, our relatively low kerosene consumption is also a factor, and getting an oil boiler fitted is likely to be subject to less delay than the ashp option. 

 

Grateful for any general advice. 

 

Many thanks

 

Martin

 

 

 

[nod]

There are some very efficient oil boilers 

and will work out cheaper to install and run

[horace]

25 minutes ago, nod said:

There are some very efficient oil boilers 

and will work out cheaper to install and run

Thanks. 

 

Perhaps a new oil boiler with a tank, so I can use the solar panels to contribute to the DHW needs? 

 

I do wonder what heating oil prices will look like in (say) 10 years time, and how electricity costs will compare. 

 

Anyone care to lend me their crystal ball? 

 

[Nickfromwales]

Grant do an oil hybrid ASHP, which may allow you to retain the existing rads. Would need some numbers crunched first of course, and would require the oil tank to remain. You would gain a cylinder, and a device for producing 2-3x the heat energy from 1 unit of electrical energy. 
The oil burner side of the hybrid kicks in when the heating load exceeds the max efficient operation of the ASHP side.

Have a google   

[horace]

4 minutes ago, Nickfromwales said:

Grant do an oil hybrid ASHP, which may allow you to retain the existing rads. Would need some numbers crunched first of course, and would require the oil tank to remain. You would gain a cylinder, and a device for producing 2-3x the heat energy from 1 unit of electrical energy. 
The oil burner side of the hybrid kicks in when the heating load exceeds the max efficient operation of the ASHP side.

Have a google   

Thanks - my googling hadn't got me that far. Will definitely look into it. 

 

[JohnMo]

Why so much for a replacement oil combi.  A very quick look online and they appear to be £2-3k incl vat.  So your plumbers are wanting another £2-3k to install, they are taking the (expletive deleted).  Maybe shop around.  Get a labour only job and buy yourself.

 

https://www.plumbnation.co.uk/boilers/oil-combi-boilers/?referrer=googleppc&gclid=Cj0KCQjwntCVBhDdARIsAMEwACkMWA3GBANMuO17iztLTWKeYQuCs_00LUgb-R4Xzj0McN73j4hPJxAaAl3cEALw_wcB

[horace]

18 minutes ago, JohnMo said:

Why so much for a replacement oil combi.  A very quick look online and they appear to be £2-3k incl vat.  So your plumbers are wanting another £2-3k to install, they are taking the (expletive deleted).  Maybe shop around.  Get a labour only job and buy yourself.

 

https://www.plumbnation.co.uk/boilers/oil-combi-boilers/?referrer=googleppc&gclid=Cj0KCQjwntCVBhDdARIsAMEwACkMWA3GBANMuO17iztLTWKeYQuCs_00LUgb-R4Xzj0McN73j4hPJxAaAl3cEALw_wcB

Thanks. I thought so too. The boilers they specified both cost around £3k delivered, and fitting was going to be a 2 day job. 

Even allowing for other parts needed, that's a lot of money for two days work. 

 

Am I right in thinking that a quote for 5.5k ex VAt to supply and fit a boiler means 5.5k plus 20% (ie 6.6k)?

[JohnMo]

Yep

[horace]

OK, the Grant Vortexair hybrid looks good. You can even fit the oil boiler part first and the ashp later on. But as a hybrid boiler, it looks as if it may not qualify for the BUS grant. I'll do some more research on that. 

[horace]

Shopping for a new hifi is fun. 

 

Shopping for new trainers is bearable. 

 

Shopping for a boiler is no fun at all. 

[PeterW]

I’d ditch the combi, fit an external Grant boiler and a 500 litre thermal store with an immersion and dump the solar into the TS set at 85°C. Summer the PV will keep the hot water going fine, winter the boiler will do the grunt work. No UVC to worry about and oil boilers love long burns so a TS is ideal. 

[Nickfromwales]

1 hour ago, JohnMo said:

Why so much for a replacement oil combi.  A very quick look online and they appear to be £2-3k incl vat.  So your plumbers are wanting another £2-3k to install, they are taking the (expletive deleted).  Maybe shop around.  Get a labour only job and buy yourself.

 

https://www.plumbnation.co.uk/boilers/oil-combi-boilers/?referrer=googleppc&gclid=Cj0KCQjwntCVBhDdARIsAMEwACkMWA3GBANMuO17iztLTWKeYQuCs_00LUgb-R4Xzj0McN73j4hPJxAaAl3cEALw_wcB

You can’t really say that until you’ve seen what is included in their quote??

[horace]

3 hours ago, Nickfromwales said:

You can’t really say that until you’ve seen what is included in their quote??

Fair point. So, from one of the quotes... 

Aside from fitting the new boiler:

Fitting a standard flue and flue basket.
● Fitting a new fire valve, tigerloop and associated oil pipework
● Fitting condensate pipework to drain position.
● Fitting new heating, hot and cold pipework as needed internally,
● Fitting a Worcester bosch system magnetic filter.
● Fitting 2 x HIVE phone based thermostats
● Fitting 2 x new 2 port valves
● Removal and safe disposal of old boiler

 

Not sure if all of the above is necessary, as I assume it must already be in place, but I'm no expert. There was no examination of existing pipework to establish condition, and we've had no issues other than with the boiler itself (which lasted 17 years, so no complaints). 

Edited June 24, 2022 by horace

[Marvin]

8 hours ago, horace said:

Fitting a standard flue and flue basket.
● 1 Fitting a new fire valve, tigerloop and associated oil pipework
● 2 Fitting condensate pipework to drain position.
● 3 Fitting new heating, hot and cold pipework as needed internally,
● 4 Fitting a Worcester bosch system magnetic filter.
● 5 Fitting 2 x HIVE phone based thermostats
● 6 Fitting 2 x new 2 port valves
● 7 Removal and safe disposal of old boiler

 

Hi @horace

 

To understand these items you can look them up and see if you have them.

1 A tiger loop is a piece of equipment that avoids any air in your oil getting into your boiler burner. A fire valve shuts off the oil to your boiler if the boiler gets too hot (assumes you have a fire)

2 If you don't already have a condensate boiler then you will need to drain the condensation that the new boiler will produce to a drain or a condensate soakaway.

3 Assumes that the connections to the new boiler are not in the same position as the old ones.

4 A magnetic filter collects any iron deposits washing around in the water in the central heating system. As the iron fittings (radiators for example) corrode over time this is collected in the filter.

5 wireless wall thermostatic timed controller that can be controlled manually of via a phone. ( no need to run lots of wires about the house)

6  Two new port valves. used to control the flow of water to the heating, hot water or both.

7 Speaks for itself

 

As they list some items prudent to replace/install whilst having the boiler replaced, I assume that inhibitor will be added to the water to inhibit the corrosion and protect the system and that if the existing water has not been replaced for a long time, that if it is black or has gunge in it the whole system will be flushed through before refilling?

 

IMHO:

we converted from a gas boiler to an ASHP and have 5.12kW PV installed.  When available we use the PV to heat the house and water, something I could not do with our old gas boiler and you cannot do with an oil boiler unless as @Nickfromwales says you install a special one.

 

4kW PV will easily give you the majority of your hot water for 6 months of the year, and partially for the other 6 months(simplified explanation), but you would need a 200-300 litre tank and thermostatic valves on the water outlets so you can store enough hot water from a sunny day to hold over for use on a cloudy day/days.

 

So you can relate your home to our position, here are some figures:

100m2 floor timber framed 1970's bungalow on the isle of wight, 2 people. 205 litre tank. ASHP: air to water.

Installed are all of the AIM and APE elements: That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery, and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

We have no other sources of energy production at present.

 

Recent results excluding  energy used for the EV (metered separately):

 

Recent daily PURCHASED electrical consumption for heating, hot water, lighting, cooking and all electrical equipment: about 4kWh a day. ( longest day 2 days ago)

5 month record 1202kWh ( more in winter)

Estimated 12 month outcome 3000kWh

 

Personally we like the ASHP option.

 

Good luck

 

M

 

 

 

 

 

 

[horace]

1 hour ago, Marvin said:

Hi @horace

 

To understand these items you can look them up and see if you have them.

1 A tiger loop is a piece of equipment that avoids any air in your oil getting into your boiler burner. A fire valve shuts off the oil to your boiler if the boiler gets too hot (assumes you have a fire)

2 If you don't already have a condensate boiler then you will need to drain the condensation that the new boiler will produce to a drain or a condensate soakaway.

3 Assumes that the connections to the new boiler are not in the same position as the old ones.

4 A magnetic filter collects any iron deposits washing around in the water in the central heating system. As the iron fittings (radiators for example) corrode over time this is collected in the filter.

5 wireless wall thermostatic timed controller that can be controlled manually of via a phone. ( no need to run lots of wires about the house)

6  Two new port valves. used to control the flow of water to the heating, hot water or both.

7 Speaks for itself

 

As they list some items prudent to replace/install whilst having the boiler replaced, I assume that inhibitor will be added to the water to inhibit the corrosion and protect the system and that if the existing water has not been replaced for a long time, that if it is black or has gunge in it the whole system will be flushed through before refilling?

 

IMHO:

we converted from a gas boiler to an ASHP and have 5.12kW PV installed.  When available we use the PV to heat the house and water, something I could not do with our old gas boiler and you cannot do with an oil boiler unless as @Nickfromwales says you install a special one.

 

4kW PV will easily give you the majority of your hot water for 6 months of the year, and partially for the other 6 months(simplified explanation), but you would need a 200-300 litre tank and thermostatic valves on the water outlets so you can store enough hot water from a sunny day to hold over for use on a cloudy day/days.

 

So you can relate your home to our position, here are some figures:

100m2 floor timber framed 1970's bungalow on the isle of wight, 2 people. 205 litre tank. ASHP: air to water.

Installed are all of the AIM and APE elements: That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery, and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

We have no other sources of energy production at present.

 

Recent results excluding  energy used for the EV (metered separately):

 

Recent daily PURCHASED electrical consumption for heating, hot water, lighting, cooking and all electrical equipment: about 4kWh a day. ( longest day 2 days ago)

5 month record 1202kWh ( more in winter)

Estimated 12 month outcome 3000kWh

 

Personally we like the ASHP option.

 

Good luck

 

M

 

 

 

 

 

 

Thanks - that's very helpful. 

 

The ashp company I spoke to a few months ago are coming on Thursday to do a full heat loss survey etc, so we'll see what happens from there. They could fit the pump in about 4 weeks time. 

[horace]

Just a thought, but if we do go down the ashp route, we'll need to dispose of a 1200 litre tank (which still has about 300 litres of kerosene in it). It's in the back garden, and I haven't a clue how we'd get it out...

 

[HughF]

2 hours ago, horace said:

Just a thought, but if we do go down the ashp route, we'll need to dispose of a 1200 litre tank (which still has about 300 litres of kerosene in it). It's in the back garden, and I haven't a clue how we'd get it out...

 

Advertise it on marketplace  If no-one takes it then empty it into 25ltr drums and flog those then chop it up with a chainsaw (assume it's green plastic) and take it to the tip.

[horace]

19 minutes ago, HughF said:

Advertise it on marketplace  If no-one takes it then empty it into 25ltr drums and flog those then chop it up with a chainsaw (assume it's green plastic) and take it to the tip.

I like your thinking. I'm sure the contents will be easy to move on. 

 

The tank is indeed of the green plastic variety. Once empty, we might even be able to man-handle it (probably has the weight written on it somewhere). 

[Marvin]

Hi @horace

 

Further thoughts on the ASHP side:

 

We had an existing bottled gas boiler serving the central heating and hot water system before we installed the ASHP. 

 

The ASHP is most efficient when the temperature difference between the outside air and the temperature to be achieved in the water coming out of the ASHP have the smallest difference.

 

This seems odd because you would assume energy in equals energy out but this is not so with an ASHP!  With 1kW of power you can produce anywhere between 1.5 and 5 times the heat that you would with a 1kW electric fire.

 

With the above in mind you can see there is a great saving to be made, if you can run the central heating water temperature, as close to the  outside temperature as possible.

 

We tested the ASHP setup for our home over the last winter and found for us we are better heating 24 hours a day. We turn down the temp about 3  degrees over night.

 

The outside temperature seems usually coldest just before the dawn so we do not heat the hot water then.

 

However, the lower the temperature of the water in your radiator, the less heat the radiator emits.

 

So to produce the same amount of heat required in any given space, if the radiator usually runs at full blast on a traditional boiler ouput temperature of say 60C, to make an ASHP the most economical you may need a larger radiator.

 

The calculating of the radiator sizes is usually carried out during the heat loss survey.

 

When renovating our home I did not believe that the MVHR would save as much heat in the winter as it actually does and so all our radiators were already 50% bigger than required.

 

Good luck

 

M

[Iceverge]

Can the existing boiler be fixed? 

 

My parents have an oil boiler that's about 25 years old. It died a couple of years ago but from memory €20 or so of parts got it running again. 

[Gone West]

On 23/06/2022 at 20:54, PeterW said:

I’d ditch the combi, fit an external Grant boiler and a 500 litre thermal store with an immersion and dump the solar into the TS set at 85°C

I'm hoping to do as you suggest but I was wondering about the oil boiler not being in condensing mode if the thermal store is heated to more than 70C. Does it matter?

[JohnMo]

You could install a slightly larger store and run at a lower temperature. You would need an oversized heat exchanger for DHW and an oversized coil for heating or heat direct.

 

I think an oil boilers needs a return temp below about 46 degC to drop into condensing mode.

[PeterW]

36 minutes ago, Gone West said:

I'm hoping to do as you suggest but I was wondering about the oil boiler not being in condensing mode if the thermal store is heated to more than 70C. Does it matter?

A 500 litre tank sorts that - you take the oil flow temp to 70°C then let the solar do the rest. 

[Gone West]

47 minutes ago, JohnMo said:

I think an oil boilers needs a return temp below about 46 degC to drop into condensing mode.

I think Grant recommend a return temperature of not less than 50C to stop corrosion. I'll have to check that.

[Gone West]

31 minutes ago, PeterW said:

A 500 litre tank sorts that - you take the oil flow temp to 70°C then let the solar do the rest. 

OK thanks, so as large tank as possible running at 70C in winter.