LPG BOILER OPTIONS

[s2sap]

Hi Guys

 

First post on here but recognise many names from another forum – so hello!

 

In Northern Ireland at present there are NO renewable heat / energy incentives, grants, ROC payments or feed in tariff benefits etc  – NIL – NADDA – NONE.

This means that a lot of the ideas I wanted to implement like PV, Heat Pump etc are not at this stage going to be implemented. I won’t invest in a long term payback as we might only be in the new home for a few years – not sure yet.

 

We plan to have UFH downstairs and upstairs and will ensure that all plumbing etc is compatible to swap out our boiler in years to come if some Renewable incentive becomes available.

We were going to simply install an oil boiler as the most cost effective initial outlay until our future plans become more certain but have now decided ( we think ) to go with LPG.

 

There are only two LPG suppliers here and one of them is offering a 2 year contract / tie in ( LPG cost is 46p unit ) and they will offer a free boiler & flue ( details below ) or £500 towards a boiler of our choice. The tank rental is £60 p/a.  This makes this option attractive to us as

1.       There is little or no initial outlay

2.       We are only tied in for two years which means we will know our long term plans and if we are staying there may be some renewable heat incentive in place then and we can change over

 

The boilers that they are offering free are:-

• 30kw Vokera Mynute i30 Boiler with Standard Horizontal flue and LPG Conversion Kit  
• Combi 30kW Vokera Vision 30C with Standard Horizontal flue and LPG Conversion Kit

 

The house is 2600 sq feet 3 showers 2 baths, it will be well insulated and triple glazed with MVHR and just my wife and I live at home. Twice a year for a few days we have up to 10 people in the house staying.

 

Water usage is 2 showers each morning and 1 bath and 1 shower in the evening

 

We installed a gas combi boiler in my Mums house a few years ago - Worcester Bosch Greenstar  30si Condensing Combination Boiler and we found that with direct mains water supply it was a bit hit and miss getting the water to remain at a constant flow temperature.

 

The non combi version Vokera has a solar option which we are considering.

 

Are these “free” boilers worth considering for our requirements? Should we take the cash option and is there a better boiler out there?

 

Is the combi option a good steady temperature and good flow force? We have a pressurised shower at present and it is really forceful.

 

How long would it take the 30KW Vokera to heat a 250l UVC?

 

Would these boilers be sufficient for our UFH requirements?

 

Sorry for such a long post!!

 

Many Thanks

 

Simon

Edited August 15, 2017 by s2sap

[Nickfromwales]

On 8/15/2017 at 17:10, s2sap said:

First post on here but recognise many names from another forum – so hello!

 

Yes indeed ! 

 

A lot of us used to frequent Ebuild but it's owner decided to close it. We subsequently started this place and it's going strong . 

 

I'll add to this later, and welcome ?

 

[gravelld]

16 minutes ago, s2sap said:

The house is 2600 sq feet 3 showers 2 baths, it will be well insulated and triple glazed with MVHR and just my wife and I live at home. Twice a year for a few days we have up to 10 people in the house staying.

 

If it's well insulated why do you need a dinosaur bone burner? Do you take a lot of baths, i.e. do you need a lot of DHW?

[A_L]

On 8/15/2017 at 17:10, s2sap said:

Is the combi option a good steady temperature and good flow force? We have a pressurised shower at present and it is really forceful.

 

How long would it take the 30KW Vokera to heat a 250l UVC?

 

Would these boilers be sufficient for our UFH requirements?

 

First, try measuring the flow of the shower (bucket and stopwatch). To raise 15l/min by 30°C takes 31.32kW, so the boilers are going to struggle!

 

Second, to raise 250ltr of water by 50°C takes 14.5kWh of energy, so 14.5/30 or 0.483hrs, but only if the cylinder heat exchanger can transfer 30kW to allow continuous operation

 

Third, if your house as described requires more than 5 to 7.5kW of continuous input under extreme conditions I would want to know why!

[ProDave]

Why are you set on LPG? Of all the "non mains gas" options it is probably the most expensive.

 

What does the price work out at per kWh (I have no idea how much a "unit" is that you mention)?

 

Don't discount air source heat pumps just because you can't get any RHI payment. To get the RHI it has to be installed by an MCS registered installer and that seems to add a big premium to the price.  I have just bought my heat pump for a shade over £500 as an ebay bargain. I will self install it but any self respecting plumber could install it. Assuming it gives a COP of 3.5 when heating the low temperature UFH that's a price per kWh of under 4p per kWh. Not far off mains gas prices and I am sure less than LPG prices?

 

Likewise don't rule out solar PV with no FIT. I am resigned to the fact that by time I am able to fit solar PV there will be no FIT or it will be so low as not worth bothering. Again, no FIT means no need for an MCS installer and you can DIY it, or any electrician can. You need to make sure you can use most of what you generate, which means use the big appliances (washing machine etc) only in the daytime, and have a hot water tank to dump excess power into hot water.  I am also keeping an eye on battery storage for self usage but it is not "there" yet in terms of cost, particularly battery life and replacement cost.

 

Oh and welcome to the new forum.

[AliG]

I had to look up what a unit of LPG was.

 

At that price you are paying around 7p per kWh. The lowest price I got for mains gas in my area today was 2.307p per kWh plus 26.25p per day standing charge.

 

The lowest electricity prices were in the 12.5-13p area.

 

Assuming an average COP of around 4 then an ASHP will cost the equivalent of around 3p per kWh so be cheaper than buying LPG without any incentives.

 

So I would not discount an ASHP. It could save you around £500 a year depending on exact energy use and heat pump efficiency.

 

A 2600 sq foot house in the spec you suggest should have pretty low heating requirements. I would guess around 10000kwh per year and no more than 3000 at any one time so heating requirements will be low(it could well be less than this depending on exact specs). You will probably require a similar amount of energy to heat water as to heat the house. An ASHP efficiency can fall when heating water, you would perhaps need to upsize the UVC and keep more water at a lower temperature.

 

You might have to factor into your calculation the value of a free boiler versus paying for an ASHP, I have never heard of Vokera so can't comment, they seem to cost around £600 to buy.

 

When you have lots of people staying a larger UVC will be useful, you could turn up the temp so it effectively stores more hot water at that time. No matter what you do though it is difficult to heat water for 10 people if they all take showers one after the other.

[Alexphd1]

Vokera's was (ten years ago) one of our biggest money makers...... repairing them! 

 

As for the solar compatible non combi part I think that's more to do with having a solar cylinder/hot water tank with a dedicated coil for solar thermal. 

 

First step I think you should work out your heat loss as 30kW is a big boiler for a well insulated house with 3g house & mvhr.

 

[Temp]

17 hours ago, s2sap said:

We were going to simply install an oil boiler as the most cost effective initial outlay until our future plans become more certain but have now decided ( we think ) to go with LPG.

 

We opted for oil for heating with LPG in cylinders for our hob.

 

There is a running cost comparison here. See "Pence per kWh (after boiler efficiency)" in the table..

 

http://www.nottenergy.com/energy_cost_comparison

 

Electric - 18p/kWH

ASHP - 6.88p/kWH

LPG - 6.13p/kWH

Oil/Kerosene - 4.11p/kWH

 

Oil price has been up and down a lot over past 10 years but is at a low at the moment. LPG is currently 49% more expensive than oil. But if you're only going to have it for a few years then not much saving.

 

 

[Temp]

16 hours ago, A_L said:

Second, to raise 250ltr of water by 50°C takes 14.5kWh of energy, so 14.5/30 or 0.483hrs, but only if the cylinder heat exchanger can transfer 30kW to allow continuous operation

 

Go to the makers web site for that info. For example.. 

https://cdn.plumbnation.co.uk/site/worcester-greenstore-indirect-unvented-cylinders/worcester-greenstore-cylinder-brochure.pdf

"Greenstore cylinders. Within the 90-180 models, a 32kW rated coil is utilised, whilst the 210-300 models have a class-leading 39kW rated output coil."

[AliG]

1 hour ago, Temp said:

 

Electric - 18p/kWH

ASHP - 6.88p/kWH

LPG - 6.13p/kWH

Oil/Kerosene - 4.11p/kWH

 

 

Someone who has an ASHP might chime in, but that table is based on 18.5p/kwh electricty price and 270% efficiency for an ASHP.

 

I can buy electricity for 13p and efficency of an ASHP should be nearer 4:1 so I would think an ASHP running costs is nearer 4p/kwh

 

The price @s2sap has for his LPG is 7p/kwh. However he is only locked into that for 2 years, I don't know if the price would fall after that.

 

Indeed if your energy usage is low, the £500 offer to be locked in for two years could be quite advantageous as it may be based on much higher energy usage of an older house.

 

My cost comparison was based on 15-20000kwh energy usage per year and a 3p/kwh saving

 

If @s2sap does not plan to stay in the house for more than 5 years then the yearly saving is unlikely to pay the extra cost of an ASHP.

[Nickfromwales]

2 hours ago, AliG said:

I can buy electricity for 13p and efficency of an ASHP should be nearer 4:1 so I would think an ASHP running costs is nearer 4p/kwh

Agree, but isn't that ~7p figure going to be reflecting the average with DHW prob being break even or even negative CoP ?

 

Edit to add : figures for an ashp's performance should be accompanied by a case study for the comparison to be made imo. 

Edited August 16, 2017 by Nickfromwales

[AliG]

Heating hot water to 50-55 will certainly hit the COP. It should be around 2.5 in that scenario, so you could definitely see an overall COP below 3, although I think that would be poor. I am interested to know what people with heat pumps are actually seeing.

 

However 5 minutes on Uswitch will tell you that 18p is a ridiculously high price to use for electricity and we know the price that is being quoted for LPG is higher than in the table.

 

It could be that the cost per unit comes in at around 4.5-5p including hot water, I think it is unlikely to be above this. To calculate the right figure would require a lot more information on water use vs heating use etc.

 

The other thing that affects the COP is the outside temperature. An ASHP should run more efficiently in the south of England than in the Highlands.

 

Then of course we don't know the cost of an ASHP versus the £500 the LPG people will give towards a boiler. I would guess it might cost around £2000 more.

 

So I think that there will be roughly a 5 year breakeven between an ASHP and LPG but would require a lot more information to say more exactly.

 

 

 

[Jeremy Harris]

My experience is that COP barely changes at all with outside air temperature, but it does change LOT with outdoor humidity. 

 

When the ASHP is asked to deliver a high flow temperature on a cool and damp day then the COP plummets, way below 2, primarily because of the impact of defrosting, which can reduce the time that the ASHP is producing useful heat when running by around 20% to 30% on a particularly bad day, say one where the temperature is down around 5 deg C and it's raining or misty..

 

The difference in the heat available in dry air at 15 deg C and dry air at 0 deg C is only a bit over 5%, hence the relatively small impact that outside temperature has.

[Stones]

As detailed in my recent blog entry:

 

 

ASHP: Heating CoP range between 3.5 and 4, DHW CoP 2.4 (ASHP providing all hot water)

 

I'm paying 12p per kWh for electricity, so DHW is costing 5p/kWh, Heating between 3 and 3.4p /kWh

 

My location is a very exposed, wet marine climate.

Edited August 16, 2017 by Stones
Add climate

[Alexphd1]

remember the LPG boiler has to have a gas ticket to install while a ASHP can be done DIY. Pick up deal on the ASHP and get your hands dirty then you may find there is not much difference in the installation cost.

Edited August 16, 2017 by Alexphd1

[s2sap]

OK this an interim thank you to everyone who has taken time to contribute - I think will need a plumbers dictionary to understand what you all said  !!!   Only joking - my understanding is improving the more I read.

 

The funniest thing was when my wife read @Alexphd1 suggestion that I self install an ASHP - I am the guy that takes the car to the autoparts store that fits wiper blades for you !!! Not through laziness through incomprehension of anything technical.

 

I will take time and come back with some answers and some more questions - thanks again

 

 

[Fallingditch]

Links to previous discussions on the forum in the text below - still valid 

Having been through a similar process, I can say that the key factor when sizing DHW and Heating systems is peak domestic hot water demand.

 

If you are willing to say that the maximum amount of hot water you will ever need is two concurrent showers, or one concurrent shower and a (slow) bath fill, then you can meet this hot water demand with a single combi LPG fired boiler and no additional storage tanks. 

 

Several people on this site have recommended Vaillant boilers because they are as the ones which seem to need fixing least.

 

A maximum capacity combination Vaillant LPG boiler can be bought for about £1,500. Even allowing for pipe install costs, boiler conversions etc, that compares favourably with the cost of air source heat pumps and storage tanks. (Important thing is to find a plumber experienced/competent in installing combi-driven underfloor heating systems - but when it comes to the design questions, you will get all the information you need on this website)

 

Because it's a combination boiler you will be going for, then it will do the underfloor heating and any radiators also. (For comparison: when you are running two concurrent showers you will need about 30 kilowatts output. When you are heating up your underfloor heating system you will need only a small proportion of that. Even if you need to run some additional radiators you are never going to be out putting the full 30 kilowatts).

 

Couple more points:

• depending upon your situation you might want to consider simply making use of 47kg propane bottles instead of a tank. That's what we use against the shed wall (although its not for everyone, I agree). Every few months a bloke drives up in a lorry and replaces two empties with two fools. Here in Essex current price is about £55 per cylinder. I cant give you accurate figures, but without heating, one bottle lasts four of us about two months. 
• finally you didn't mention cooking. If you prefer cooking with gas, say no more. Long thread about that here also :-)

 

 

 

 

Edited August 19, 2017 by Fallingditch
photo added

[s2sap]

The technical data for the Combi 30kW Vokera Vision 30C Boiler states that it delivers 12 litres per minute @ 35 degrees. Is 35 degrees a showering temperature?

 

Our current shower delivers 20 litres per minute when not using a water saving shower head ( thats my idea of a shower!! ) and 10 litres per minute with an Ecocamel shower head which I find "adequate" as I accept the lesser shower pressure as a compromise for saving heated water.

 

Would the 30kw Vokera Mynute i30 Boiler with an UVC produce a more forceful shower and at a steadier temp / flow if another DHW requirement was required at same time?

 

How would a combi boiler work with full house UFH? 

 

Please understand that I am not fully conversant with all things technical so - please go easy on me with complicated responses 

 

Thanks again guys for your patience

 

 

[Fallingditch]

46 minutes ago, s2sap said:

How would a combi boiler work with full house UFH? 

 

When a hot tap/mixer/shower is turned on, the combi boiler detects it. The combi boiler fires up and heats the water flowing through the combi boiler on its way to the hot tap/mixer/shower. If you buy a good quality combi, then they are effective at proving just the right amount of heat energy to raise the temp of the hot water to 60 (or whatever you set it to). If you have two concurrent showers, the combi boiler will run full pelt heating this 'DHW circuit'. (There;s a valve inside called a diverter valve which diverts heated water either round the DHW Circuit or the Heating circuit).

 

The rest of the time when you do not want hot water at the taps, the combi boiler is supplying hot water to that Heating circuit. Now in your scenario, the Heating circuit is not heating up radiators at (say) 75C, it is heating up a bunch of pipes in the floor at (say) 25C - 30C. Boilers are not designed to work at 25C -30C - so you will have actually two different circuits - the Heating circuit and the UFH circuit. They are joined together by something called a mixing valve which allows some of the water from the Heating circuit (at say 75C) to dribble into the UFH circuit (at say 25C - 30C). What this means is that in heating mode, the combi boiler will fire up just long enough to get the UFH circuit up to (at say 25C - 30C) - say 5 minutes. Then it shuts down for a while (say 5 minutes). Then it fires up again etc etc and that's what it spends its days doing - heating up the Heating circuit in order to maintain the UFH at (say 25 - 30). Until of course somebody opens up a hot tap at which point the combi boiler switches into heating up the DHW circuit because thats their priority. Then the tap gets turned off etc etc.

 

Hope that was the answer you were after ;-)

[ProDave]

If you have an UVC then the flow rate from the shower is a product of your water pressure, pipe sizes etc and not related to boiler output.

 

If you have a combi boiler then it's a function of how much heat the boiler can put into the water, and how cold your incoming mains water is.

 

A combi gives priority to HW, so while showering it temporarily stops feeding the space heating.

[Jeremy Harris]

As a rough rule of thumb, 10 kW will raise the temperature of an incoming flow of water at 10 litres/min (pretty typical decent shower flow rate) by about 13 deg C.  So a 30 kW combi will increase the temperature of a flow at 10 litres/minute by around 39 deg C.  Incoming mains water is typically around 6 deg C to 8 deg C, and a shower will usually be between 38 deg C and 42 deg C.  So a 30 kW combi should be able to deliver DHW at around 45 deg C at 10 litres/minute.  Our Vaillaint combi can deliver around 28 kW, and we find that's fine for a decent shower (a bit over 10 litres/minute) at around 38 deg C.

[Nickfromwales]

Bigger combi = more DHW output. I fit Vaillant 937's ( now 938 erp ) when the remit is lots of hot water but nowhere to put a cylinder, or simply fitting an uvc is wasteful / overkill. 

The 938 ( 38kw ) is a heatstore combi which blends a small amount of stored water into the DHW output side to reinforce its DHW delivery. These are really good if you don't want / actually need a cylinder, and will still modulate down to 9kw when your heating demand is low. 

As prodave says above, the DHW coming out is only as good as the cold mains pushing it out of your outlets, so a survey is critical before actually deciding on an end solution.  

[Nickfromwales]

@s2sap

Something I've not added yet, but the Vokera is considered a very budget boiler. I don't ever fit them, and haven't even seen one for a few years . I'd put them in the same category as Biasi, HeatLine, Halstead and Ariston, as in I'd only ever suggest fitting one of these if someone was broke, basically. I wouldn't even recommend any of the former for rental properties as the reliability and longevity just isn't there. 

Ideal are a great entry level boiler with Glow-worm next in line, but those are again only for where the budget is tight. Worcester Bosch seem to have finally got their act together, but I'm still a Vaillant man. Baxi have dropped down a bit with their latest offerings so I'd place them at the Ford Focus end of the scale, with WB next, then Vaillant and Veissmann up top. Veissmann are a LOT of money for what they are, and I can't see how they justify it tbh. 

[s2sap]

Ok I,m back with more questions - I hope you guys are patient!!

 

As I said at the start I cant be sure we will be in this new house long term - we might be there till our dying day ( which might be quite soon with the stress of this ) or we might be out in 2-5 years. I wont compromise on insulation and windows etc as this is something we cant change if we end up staying but the idea of LPG gas CH was that it gets us in with little or no capital outlay and a tie in to buy their gas for only 2 years. So if we move on its been cost effective and if we are to stay we could change the boiler to perhaps ASHP in a few years - more specific questions about that now.

 

(1)  If we install a non combi gas boiler with UVC and UFH both upstairs and down and then change the boiler to perhaps ASHP / GSHP / even oil boiler am I right in thinking that all the plumbing will still work i.e all the inside of the house plumbing circuits and it would just be the plumbing at the boiler would need to be changed ?

 

(2)  Am I right in saying that the UFH pipes should be 150mm spacing for heat pumps, and gas or oil heating etc should be 200mm spacing? If that is the case can I install 150mm spacing and use it with gas ( in case I change to heat pump later )  - surely the additional cost of the pipe and work wouldn't be THAT much more?

 

(3)  @Nickfromwales You are a fan of Valiant boilers and if I dont want the Vokera boiler the gas company will give me an allowance towards any boiler of my choice - which one would you recommend and roughly what cost would it be? Also how much would a suitable 250L UVC be roughly? I wouldn't need  a buffer tank for the UFH would I?

 

As already stated I have no building or technical knowledge so I would be paying the contractor to do this work. I would also not be in a knowledgeable position to buy a heat pump without local guidance. With this in mind I approached two local companies to give me an estimate for ASHP. I apologise for the detail below but I dont know what bits are relevent so I have copied both quotes into this post for your perusal and comments - see below

 

Quote Company 1

 

Hitachi Yutaki - M Monobloc Air Source Heat Pump 11kW Single Phase £6790 ( to include )

1 x Hitachi Yutaki - M Monobloc Air Source Heat Pump rated at 11kW Single Phase

1 x 3 port diverting valve to switch system between heating and hot water

1 x LCD Hitachi Integrated Timeclock/Temperature Control for Heating/Cooling and Hot Water

System with Weather Compensation

1 x Hitachi Wireless Intelligent Stat

1 x Hot Water Sensor

1 x Heating Strainer

1 x Set of Flexible Braided Hoses

1 x Installation visit

1 x Commissioning Visit

1 x 7 year warranty on heat pump

 

250L Hot Water Cylinder £1440 ( to include )

Heat Pump Hot Water Cylinder:

1 x 250L Unvented Stainless Steel Heat Pump Rated Cylinder

1 x Coil in Tank min. 2.2m2 surface area to suit heat pump system

1 x Delivery of Cylinder to site (Plumbing of cylinder by others)

 

Heating Distribution Pipe Work £1380 ( to include )

Heating Distribution Pipework:

16m x 28mm Copper Pipework at Heat Pump and to Underfloor manifolds/ Radiators

3m x 28mm Copper Pipework to Hot Water Cylinder

1 x 25mm Coils of 28mm HEP Pipe in Pipe in Floor

1 x Selection of Copper Mapress Fittings for Leak Free Installation

1 x 19mm Armaflex Insulation on Heating Pipes in Unheated Space

6 x 28mm Wheelhead Gate Valves

2 x Automatic Air Vents at Cylinder and UFH Manifolds

1 x 25L Expansion Vessel & Quick Fill Loop

1 x Corrosion Inhibitor & Antifreeze Protection Added to System

1 x Labour for piping the above and filling and testing complete heating system

 

Quote Company 2

 

Daikin Altherma 8kw LT split c/w integral 260litre cylinder £5500 ( to include )

Supplied, installed & commissioned

DAIK003 Daikin Altherma LT 8kw outdoor unit

Altherma LT 6/8kw 260L Integrated Hydrobox With 260L DHW Tank

G3 Kit for 260L Floor Standing Indoor Unit

Daikin Altherma LT Controller

Installation of LT Indoor & Outdoor Units.Supply & connection of 10m's of refigerant pipework, insulation FGAS certified.

Daikin Altherma Commissioning

 

This installer adds:-

The air source heat pump is supplied in two components with an outdoor condenser positioned on an external  wall connected to the integral cylinder/floor standing unit in the hotpress.  Refrigerant pipework is connected between the two.

Based on heat demand of 35 W's per m2 the heat pump would provide 100% of your heating & hot water.  There is no requirement for any of the below which you need to consider when pricing against oil -

- oil boiler.

- oil tank.

- external interconnecting pipework, pumps, valves etc.

- flue pipe.

- hot water cylinder.

- time controls, motorised valves etc

- labour for above.

The system offers a very efficient, comfortable and reliable heat which is very important for a highly insulated house. The heat pump can offer efficiencies of 430% with the underfloor heating. It  would be designed to operate @ 35C flow temperature when -3c outside.

 

Final question then

 

(4)   I asked both companies to quote based on our drawings and that's what they suggested ..... over £4000 apart!!!!  Why? I can see that one is supplying an additional UVC and the cheaper quote has one inbuilt. The dearer quote also has a lot of Heating Distribution Pipework - will I not need that for the cheaper quote?

 

Guys thank you all again for the time and effort you put into this - and as usual plain simple English talk is required for my comprehension  

 

[AliG]

The second quote does look much better value. It would still need most of what is in the first quote for heating/distribution pipework. Googling it the Hitachi ASHP looks to be very expensive, not clear why.

 

I would probably get a quote for a LPG boiler and UVC also. I would guess it will come in at around £4000 including connecting the boiler to the UVC etc. There will still be the cost to connect it to the UFH as in quote 1.

 

Then you can compare capital costs vs running costs. If your house is very well insulated and has low heating requirements then the premium for LPG will become less of an issue as you won't be using as much gas.

 

One thing to note is that the ASHP will take a lot longer to heat up hot water than a boiler. Now when you get up in the morning with a full hot water tank that isn't an issue, but if you do have a lot of people staying and a few people have showers it will take a long time to reheat the tank with an ASHP.