LPG (until Mains gas available) or Oil?

[SteamyTea]

Bit more involved that that in reality.

Under our MCS rules, an ASHP needs to supply enough energy for space heating 99% or the time.

This is not as bad as it sounds as it is best to oversize an ASHP anyway.  There is not a direct comparison between the output of a traditional boiler say 30 kW and an ASHP oof the same size.

Others that have ASHP would be better placed to comment, but my feeling is (and a little bit of thermodynamics) you have to take into account the lower delivery temperature of an ASHP when calculating the peak power.

[ProDave]

7 minutes ago, SteamyTea said:

Bit more involved that that in reality.

Under our MCS rules, an ASHP needs to supply enough energy for space heating 99% or the time.

This is not as bad as it sounds as it is best to oversize an ASHP anyway.  There is not a direct comparison between the output of a traditional boiler say 30 kW and an ASHP oof the same size.

Others that have ASHP would be better placed to comment, but my feeling is (and a little bit of thermodynamics) you have to take into account the lower delivery temperature of an ASHP when calculating the peak power.

I found the SAP assesment particularly unhelpful. It gives me the total energy used in a year, but not the very much more useful heat input required at any particular condition.

 

For that I found @JSHarris heat loss spreadsheet far more useful.  With all the data for my house input into that, it tells me the peak heat input to the house will be a little under 2.5Kw when it is +20 inside and -10 outside.  That should comfortably be met by my 5Kw ASHP driving under floor heating and should leave it plenty of time for heating DHW as well

 

That is the figure you need to size a heat pump for a particular house.

[dpmiller]

Went through the same process using LoopCAD. Looks like around 6.5kW for us for -2c/20c.

[JohnW]

I've spoken to the company bringing mains gas to my area and they assure me that it will be available for connection at the end of 2019, approximately 1 year after our build is due to finish.

They also spent quite a bit of time talking through the options and they are suggesting a System boiler with pressurised cylinder. I know I will be able to connect PV panels to this to run an immersion heater but I forgot to ask about a back-boiler.

 

Have any of you any idea if it is feasible to connect a back-boiler onto a system like this or should I just remove the back-boiler from the equation? 

 

[SteamyTea]

If it is only a year to wait until the gas is connected, then buy 50 quids worth of fan heaters.

50 litres of hot water would cost around 50p to heat by electricity.  50 lt of 65°C water is enough for a bath.

(now there is an easy thing to remember, litre of hot water costs a penny)

[Declan52]

If it's only a year then use E7 to heat your water and a wbs with no back boiler to use when it needs to be on.

[JohnW]

It's been a while but I'd like to resurrect this thread if I may, as I now have more information and a few decisions made...

• We've ruled out ASHP due mainly to cost of install and lack of experienced engineers available to service it going forward.
• We've ruled out a wood burning stove and are now opting for a 5kW room sealed gas fire (i.e. it will have it's own external air supply so won't interfere with MVHR) as a secondary heat source.
• We've ruled out PV for the foreseeable future. 
• We're having UFH downstairs and radiators upstairs
• We will have a Gas system boiler and plan is to use mains gas when it arrives 1 year after the build is due to finish

Therefore the main decision I need help with is how to heat the UFH & DHW for the year before mains gas arrives, Economy 7, Economy 10, LPG etc... 

Our kWh requirements are shown below using both @JSHarris's excellent Fabric & Ventilation Heat Loss spreadsheet and our revised (as designed) SAP report.

 

January heat energy input for minimum OAT = 1876 kWh

 

Revised (as designed) SAP report;

• Water heating - 2,573 kWh/year 

 

• Space heating - 6,922 kWh/year

Thanks

[vfrdave]

16 minutes ago, JohnW said:

Economy 10

Is this available in NI?

[ProDave]

What is the "cost of install" that has ruled out an ASHP?  Is that the over inflated MCS install price?  They are no more complicated to install than a system boiler.

 

Have you considered a gas boiler now and get the LPG jets and run it from 47Kg propane cylinders until the mains gas is available? then put the mains gas jets back in.

 

You can get room sealed wood burning stoves so again don't let that rule them out.

[JohnW]

4 hours ago, vfrdave said:

Is this available in NI?

I noticed the Economy 10 tariff mentioned elsewhere and thought it would be perfect for my needs if we went electric for a year, but as you correctly point out, it doesn't appear to be available in the land of the "Hot Press".

[JohnW]

1 hour ago, ProDave said:

What is the "cost of install" that has ruled out an ASHP?  Is that the over inflated MCS install price?  They are no more complicated to install than a system boiler.

 

Have you considered a gas boiler now and get the LPG jets and run it from 47Kg propane cylinders until the mains gas is available? then put the mains gas jets back in.

 

You can get room sealed wood burning stoves so again don't let that rule them out.

When looking for cost reductions in our specification we replaced the ASHP with Oil fired heating and the build cost was reduced by £11,500....I know, I nearly fell over too!!

[vfrdave]

2 hours ago, ProDave said:

What is the "cost of install" that has ruled out an ASHP

In the glorious land of the hotpress where John and I both hail from I have found it nigh on impossible to get someone that will fit a monobloc ASHP. All of the renewable companies 'specialising' in ASHP want to install split systems and were quoting £7k for the unit alone.  Makes it very difficult to justify when pennies are tight during the build. 

 

Much in the same way as PV without grant incentive.

[ProDave]

39 minutes ago, JohnW said:

When looking for cost reductions in our specification we replaced the ASHP with Oil fired heating and the build cost was reduced by £11,500....I know, I nearly fell over too!!

You can buy a heat pump for £2K easily, a lot less if you shop around. The instalation is no harder than a system boiler.  What you met was the "MCS Premium" an over inflated price by an MCS contractor so you can claim the RHI and give most of your payment to them in the form of a much inflated install cost.

[ProDave]

16 minutes ago, vfrdave said:

In the glorious land of the hotpress where John and I both hail from I have found it nigh on impossible to get someone that will fit a monobloc ASHP. All of the renewable companies 'specialising' in ASHP want to install split systems and were quoting £7k for the unit alone.  Makes it very difficult to justify when pennies are tight during the build. 

 

Much in the same way as PV without grant incentive.

See reply above. Buy the unit yourself and just employ a plumber and an electrician who are capable of RTFM. The LAST place I would look for such a thing is a "renewables" company.

[JohnW]

10 hours ago, ProDave said:

See reply above. Buy the unit yourself and just employ a plumber and an electrician who are capable of RTFM. The LAST place I would look for such a thing is a "renewables" company. 

This sounds like a sensible approach, if you know what you're doing. However the problem would then be finding someone to service the ASHP in the future.

[PeterW]

21 minutes ago, JohnW said:

This sounds like a sensible approach, if you know what you're doing. However the problem would then be finding someone to service the ASHP in the future.

 

They are a refrigeration unit. Search for air conditioning engineers and you will find hundreds - a service is as simple as check the gas pressure, clean the evaporator and a general check over. I have 2 AC units serviced every year and they take less than an hour each - takes him longer to get the protective cages off !!

 

A quick search on Yell gave me this list... https://www.yell.com/s/air+conditioning+services-northern+ireland.html

[JohnW]

On ‎05‎/‎07‎/‎2018 at 17:27, JohnW said:

It's been a while but I'd like to resurrect this thread if I may, as I now have more information and a few decisions made...

• We've ruled out ASHP due mainly to cost of install and lack of experienced engineers available to service it going forward.
• We've ruled out a wood burning stove and are now opting for a 5kW room sealed gas fire (i.e. it will have it's own external air supply so won't interfere with MVHR) as a secondary heat source.
• We've ruled out PV for the foreseeable future. 
• We're having UFH downstairs and radiators upstairs
• We will have a Gas system boiler and plan is to use mains gas when it arrives 1 year after the build is due to finish

Therefore the main decision I need help with is how to heat the UFH & DHW for the year before mains gas arrives, Economy 7, Economy 10, LPG etc... 

Our kWh requirements are shown below using both @JSHarris's excellent Fabric & Ventilation Heat Loss spreadsheet and our revised (as designed) SAP report.

 

January heat energy input for minimum OAT = 1876 kWh

 

Revised (as designed) SAP report;

• Water heating - 2,573 kWh/year 

 

• Space heating - 6,922 kWh/year

Thanks

 

 

I must confess to not fully understanding all the results displayed above - could some kind soul please explain them to me in very simple terms?

 

e.g. Space heating requirement of 6,922 kWh/year...does this mean using average external temperatures I will need to purchase 6,922 kWh each year (from oil, gas or electric supplier) to maintain a constant internal temp of 20 degrees?