Help with Replacement Boiler! - Oil boiler costing a fortune!

[Dazza]

Hi looking for some advice on a replacement boiler.

 

Bit of background - we have a big old farmhouse that I am slowly refurbishing. 

 

Current boiler is an oil fired boiler situated in our basement it is massive and drinks oil -see pic! looks to me more like a hospital basement than a house basement!

 

So obviously want to replace and have decided we need to do this sooner rather than later.

 

We have decided to go down the gas route rather than oil and have had a new in ground gas cylinder installed - we have also had a new 32mm water mains installed.

 

so thinking about the upgrade, there are some things I need to look at:

1. Boiler has to service the home for heating & HW (rads and place not super insulated!) - Kitchen/utility/4 beds with ensuites (showers only)/sitting room/downstairs cloakroom - around 200m2 overall over 3 floors.

2. There is a myriad of existing pipework for rads - some of it galvanised.

 

Here is where I need help!

1. Ideally, I would like a combi boiler to be man enough to supply all heating and HW, which I am sure is easily doable, but my question is, do I need a HW storage tank as if all 4 showers running at once think will run out of flow? Any good advise on what sort of system I should be looking at would be greatly appreciated. Also just to add, for HW, there will be some longish runs from gnd floor to 2nd floor if that makes any difference.

 

2. I want to get this connected up and running as soon as possible as I dont want to buy any more oil for the existing guzzler!! I know ideally I should replace all pipework to new and I will over time, but that is going to take a lot of work. I was hoping to be able to T into the existing HW and CH pipes and disconnect at the existing boiler. My concern with this is there will for sure be a lot of sludge in the CH pipes form the galv pipe and I dont want to damage a shiny new boiler by connecting up to these pipes. What is the advise here please - will it be OK? Should I get a power flush first? Or should I not do this at all - period? I am hoping to be able to do this some way as ripping all the existing pipework out will be a nightmare (there are so many pipes and I think some have been replaced over time and old ones left in situ - so my preference is to tackle it one room at a time as I am renovating the property).

 

Hopefully I will get some good advise as I am scratching my head a bit - not to mntion suffering from paying so much out for oil for the old beast of a boilerl!!

 

 

 

[SteamyTea]

What power rating is your current boiler?

And do you know how much fuel it used every year?

Does it keep the house warm, and enough hot water?

A kWh of energy is agnostic to fuel types, just as power is.

 

[dpmiller]

Not liking the look of that insulation

[Dazza]

1 hour ago, SteamyTea said:

What power rating is your current boiler?

And do you know how much fuel it used every year?

Does it keep the house warm, and enough hot water?

A kWh of energy is agnostic to fuel types, just as power is.

 

Current boiler is oversize for a domestic installation Im sure - I think it would heat a large industrial building!! Think it is 105-140kw according to rating plate (Harrier GTE 5)

[Dazza]

1 hour ago, dpmiller said:

Not liking the look of that insulation

Looks worse than it is - you are thinking asbestos? It is actually yellow rockwool insulation type stuff.

[PeterW]

That’s rigid rockwool as it’s used on process pipes and possibly here due to the size of the pipework..!

 

So where is the current hot water tank and what size is it ..? A 32mm pipe will provide volume but at what pressure ..? Ideally you want 3 bar dynamic pressure but I wonder if you will get that. 
 

I don’t think tbh you will get a combi to do that flow regardless - at full chat you’re wanting 30-40 litres / min through showers and that’s not achievable with standard domestic combi boilers. You could do some type of domino setup but you’re complicating matters and LPG is not that cheap either when you’re burning lots of it. 
 

In terms of pipework, I would possibly leave well alone as it will be a decent thick wall black iron pipe - possibly galvanised. As close to the new boiler return as possible I would put a pair of magnaclean type units that can take the crud out - get the ones with the  filters in, not just the magnets. A pair in parallel allows you to filter through one whilst you service the other and also picks up equal quantities of crud in each. 

[Dazza]

2 minutes ago, PeterW said:

That’s rigid rockwool as it’s used on process pipes and possibly here due to the size of the pipework..!

 

So where is the current hot water tank and what size is it ..? A 32mm pipe will provide volume but at what pressure ..? Ideally you want 3 bar dynamic pressure but I wonder if you will get that. 
 

I don’t think tbh you will get a combi to do that flow regardless - at full chat you’re wanting 30-40 litres / min through showers and that’s not achievable with standard domestic combi boilers. You could do some type of domino setup but you’re complicating matters and LPG is not that cheap either when you’re burning lots of it. 
 

In terms of pipework, I would possibly leave well alone as it will be a decent thick wall black iron pipe - possibly galvanised. As close to the new boiler return as possible I would put a pair of magnaclean type units that can take the crud out - get the ones with the  filters in, not just the magnets. A pair in parallel allows you to filter through one whilst you service the other and also picks up equal quantities of crud in each. 

Thanks for the reply. 

 

The current hot water tank is a vented 150l tank just behind and to the right of the boiler - although it leaks a bit and needs replacing. The current boiler is in a cellar, but the replacement cannot be in a cellar as it is gas, so new gas boiler will be on ground floor.

 

I was hoping to get away with a combi because it makes installation so much simpler, but it seems that is not likely. If I have to have a HW tank it does add a  lot more complexity as I was hoping to be able to effectively bypass all the current installation and allow me time to rip it all out, but if I had to add a new HW cylinder with new boiler I would probably need to instal it temporarily and then move it later - but if thats what I need to do, then so be it.

 

Thanks for the advice on the maglclean thing - never heard of them - will look into it! At least that will save me some hassle up front and allow me the time to gradually replace the pipework as I work through the place!

[Temp]

Personally I doubt switching to a new LPG boiler will save a lot. Think I would spend money on insulation.

 

[SteamyTea]

1 hour ago, Dazza said:

Current boiler is oversize for a domestic installation Im sure - I think it would heat a large industrial building!! Think it is 105-140kw according to rating plate (Harrier GTE 5)

Have you done a basic heat loss calculation on your place?

 

100 kW (not kw) is pretty big, but not ridiculous if you need a lot of hot water.

Does it heat a cylinder up, what size it that?

[SteamyTea]

2 minutes ago, Temp said:

Personally I doubt switching to a new LPG boiler will save a lot. Think I would spend money on insulation.

LPG is generally the most expensive, and you can easily get locked into a single supplier.

 

Reducing losses is always the best thing to do.

[PeterW]

How close to the tank (vertically) can you get the boiler ..? Wall hung 45kW gas system boiler would keep a 400 litre horizontal UVC happy and give you plenty of water. Just re-route the supply pipes to the oil boiler connections and use the same bits.

Any reason to remove the pipework etc ..? That circ pump is a beast and you’ll need to replace all of the pipework before that goes as a standard pump won’t cope with 1 1/4" steel pipework volumes. 

[SteamyTea]

Just thought I would see what the energy content of LPG was, ~7 kWh/litre.

So a 45 kW boiler would burn around 8 litres of fuel (allowing for some efficiency losses, actually 6.43 litres).

A quick google and the price seems to be about 45p.litre, so to run a 45 kW boiler for an hour would be £3.6.

 

Get insulating and fix those air leaks.

[Ferdinand]

 @Dazza

 

TBH it doesn't sound *that* big for an old farmhouse.

 

I'd endorse a coupe of suggestions above - do a heat model to work out what your demand would actually be. Should be doable in an evening. The forum has a sprreadsheet available here:

 

And do some planning work on your insulation scheme. There's no problem making it long term - the most important thing is not to do anything on top before you do the insulation underneath, 'cos then you'll never get a round tuit. And evrybody needs a round tuit. 

 

How much can you reduce those heat losses by? Then you can get to what size boiler you actually need. Bosch seem now to have some big ones on their list.

 

One other thought (which others really need to comment on) - is this a good application for a Sunamp in series with a not-quite-that-huge boiler, as it would heat the water first from its stored solar or offpeak electricity energy, and therefore reduce the highest demand item?

Ferdinand

[SteamyTea]

14 minutes ago, Ferdinand said:

is this a good application for a Sunamp in series with a not-quite-that-huge boiler

Not really, they are limited capacity and a lot more expensive than a water cylinder.  Heat losses from a cylinder, though higher, are not much of a problem in a large old house.  Most old places like this only have 2 months of the year when they are not heated.  And that is in Cornwall, no idea where the OP is located, may be NE, or worse.

[Temp]

1 hour ago, SteamyTea said:

Just thought I would see what the energy content of LPG was, ~7 kWh/litre.

So a 45 kW boiler would burn around 8 litres of fuel (allowing for some efficiency losses, actually 6.43 litres).

A quick google and the price seems to be about 45p.litre, so to run a 45 kW boiler for an hour would be £3.6.

 

Get insulating and fix those air leaks.

+1

 

I was looking at the figures here..

https://nottenergy.com/resources/energy-cost-comparison/

Kerosene 4.59 p/kWh

LPG 7.55p p/kWh 

 

If they are correct a £1000 Oil bill becomes an LPG bill of £1644 not allowing for improvement in boiler efficiency. 

 

 

 

 

 

[Dazza]

11 hours ago, SteamyTea said:

Have you done a basic heat loss calculation on your place?

 

100 kW (not kw) is pretty big, but not ridiculous if you need a lot of hot water.

Does it heat a cylinder up, what size it that?

Havent done heat loss calcs but will give it a go - yes it heats the 150L HW cylinder easily!

[Dazza]

10 hours ago, PeterW said:

How close to the tank (vertically) can you get the boiler ..? Wall hung 45kW gas system boiler would keep a 400 litre horizontal UVC happy and give you plenty of water. Just re-route the supply pipes to the oil boiler connections and use the same bits.

Any reason to remove the pipework etc ..? That circ pump is a beast and you’ll need to replace all of the pipework before that goes as a standard pump won’t cope with 1 1/4" steel pipework volumes. 

I can get the tank vertically within about 2m, but horizontally it would be about 10m.

 

Reason for removing the pipe work is that want to use the area where it is currently as a habitable space and the pipe work goes everywhere in the basement making it pretty unusable at the moment.

There some even bigger pipework - some of the pipe work is about 4"!! So I guess for the heating, I would need to get all the bigger stuff out and bring it down to 15mm which might be achievable?

[Dazza]

10 hours ago, Ferdinand said:

 @Dazza

 

TBH it doesn't sound *that* big for an old farmhouse.

 

I'd endorse a coupe of suggestions above - do a heat model to work out what your demand would actually be. Should be doable in an evening. The forum has a sprreadsheet available here:

 

And do some planning work on your insulation scheme. There's no problem making it long term - the most important thing is not to do anything on top before you do the insulation underneath, 'cos then you'll never get a round tuit. And evrybody needs a round tuit. 

 

How much can you reduce those heat losses by? Then you can get to what size boiler you actually need. Bosch seem now to have some big ones on their list.

 

One other thought (which others really need to comment on) - is this a good application for a Sunamp in series with a not-quite-that-huge boiler, as it would heat the water first from its stored solar or offpeak electricity energy, and therefore reduce the highest demand item?

Ferdinand

Thanks for the spreadsheet - I will give it a go and then we can see where we are. I was reticent to insulate the house as it is quite large and to insulate all the walls floors/ceiling will cause a lot of disruption and cos, but I will have a go at the spreadsheet and see what I find.

[Dazza]

8 hours ago, Temp said:

+1

 

I was looking at the figures here..

https://nottenergy.com/resources/energy-cost-comparison/

Kerosene 4.59 p/kWh

LPG 7.55p p/kWh 

 

If they are correct a £1000 Oil bill becomes an LPG bill of £1644 not allowing for improvement in boiler efficiency. 

 

 

 

 

 

For a variety of reasons we wanted to move away from oil, hence we went to LPG. We did the numbers on it and actually it worked out pretty close as a cost comparison - but we also got the in ground tank tank supplied and fitted FOC!

[ProDave]

I suspect this house is a money pit in so many ways.  It reminds me of a large country house I used to do work for which was operating as a care home at the time.  That was heated by a big LPG fired boiler and speaking to them the annual heating bill was in the order of £10K

 

I doubt you will lower the heating bill much just by fitting a better boiler. The pipes are large for a reason, if you think you can heat a house of that demand with all 15mm pipe work you may find the results disappointing.

 

LPG with an in ground tank has tied you to one supplier so no chance to compare prices and shop around each time like oil, and no chance to buy all your years heating oil in the middle of the summer when prices are usually lower like you can with oil.

 

 

[PeterW]

2 hours ago, Dazza said:

There some even bigger pipework - some of the pipe work is about 4"!! So I guess for the heating, I would need to get all the bigger stuff out and bring it down to 15mm which might be achievable?

You will probably be on a mix of 28/22/15 depending on the routing etc. 4” sounds odd, sure it’s not a support column ..??!

[Carrerahill]

16 hours ago, Dazza said:

Current boiler is an oil fired boiler situated in our basement it is massive and drinks oil -see pic! looks to me more like a hospital basement than a house basement!

 

So obviously want to replace and have decided we need to do this sooner rather than later.

 

We have decided to go down the gas route rather than oil and have had a new in ground gas cylinder installed - we have also had a new 32mm water mains installed.

I am not sure this is going to work like you intend, using LPG is going to cost far more than oil. 

 

These LPG distribution firms are crooks. 

 

 

 

 

[Carrerahill]

14 hours ago, Dazza said:

Current boiler is oversize for a domestic installation Im sure - I think it would heat a large industrial building!! Think it is 105-140kw according to rating plate (Harrier GTE 5)

You clearly have not been in many large industrial buildings, try the size of a Minibus for them and pumps that sit on concrete plinths... to be honest that boiler looks about right for a large house given it's age, floor standing and oil. 

Edited June 29, 2021 by Carrerahill

[scottishjohn]

my two pence worth 

seriously consider major insulation in your refurbishments as priority 

 getting heat loss down should be first thing to do -then look at how you make the heat next 

I,m guessing walls are solid + no dpc +no cavity so normal practise would be to make a new walls full of insulation 140mm? with a gap between them and outside 

bit like building a   modern TF house inside what you got 

at same time as doing that look at electrics and water system -- all can be hidden behind walls and maybe just ignore old systems -cover them up and swop over  when you are done 

 you can carry on living there while you do -so time will not be a problem to complete the right job 

 high insulation cannot be over stressed when it comes to modernising and running costs

[Dazza]

Thanks for all the replies and advice guys.

 

We are definitely going with the LPG (obviously as it is installed!), but I guess now it is a matter of what size boiler we require etc.

 

The property is old and has triple brick walls (so over 300mm thick) but does have double glazing - there is also no insulation between floors.

 

As has been suggested, it does seem like a good idea to get an idea of the heat losses from the property, so Im going to go away and work on that.

 

Can anyone suggest a good place to find U values for the various elements - external walls/internal walls floor etc?