Gas vs.Oil AND how many Btu?

I am just about to exchange contracts on a run down old house - 1830

near Chard. Everything is ancient and needs replacing from scratch. Th oil fired AGA will be the only thing that stays. It does heat a corne of the house.

Although there's only 5 of us living there the house when it's al waterproof will be 7,000 sq ft, hopefully including a summer holida let. We'll never want to heat the whole house. I don't know where t pitch the boiler size, possibly 220,000 btu?

I'd like to get a decent qualuity boiler. Am considering Potterto Osprey 2 CF 220 for £1660 odd inc. vat. Have you had good results wit Potterton? Is there a lower cost supplier?

It's connected to mains gas and am assuming this will be cheaper tha oil.

I'll be doing several zones to keep the running costs down. In my las house I fitted 7 zones using motorised valves and various programmabl timeswitches. The know-it-all who bought the house laughed saying he' never seen motorised valves used for zoning before. Should I have use something else

-- peterd

Reply to
peterd
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How long is a piece of string! It's impossible to specify boiler size without first having calculated the heat losses - for which you will have to specify the size and construction of each room. Several radiator suppliers have free programs which you can download to help you do the calculations. There is a *big* difference depending on the level of wall, floor and roof insulation and the type of glazing.

Since you want to zone it anyway, have you considered having two or more smaller systems - each heating just part of the house?

I think that is currently true - whether it will remain so with the escalating price of gas, I don't know. Probably though, 'cos oil is escalating too.

Assuming you wired it in an S-Plan-Plus configuration, what you did was exactly right.

Reply to
Set Square

Boiler size needs to be calculated taking into consideration room sizes, wall materials and insulation levels. There are programs about that do this for you, ISTR that they are available from the major radiator makers web sites.

ATM, see previous post about current oil prices at around 35p + 5% VAT per litre which works out at around 3.5p per kWhr. Oil prices will rise when the winter demand kicks in. Over the longer term unless something radical happens in relation to supply and demand I can't see the price falling to the levels it was 5 years ago (17p/l)...

I can't think what else unless you do it manually... Solenoid valves (as found in the back of washing machines) generally don't have the seperate "valve open" switching that you really need for zoning.

Reply to
Dave Liquorice

How many bathrooms? Is the holiday let a true self contained flat? If so have a separate combi, water main, electricity and gas meters just for that.

Keep to gas, cheaper all around. I would consider using a thermal store/heat bank. How is the water mains pressure?. It is worth upping the water main to 32mm and going mains pressure throughout. Have two smaller boilers heating the store "directly", not via a manifold. You then have backup, and rapid re-heat too. Also two smaller boilers may be cheaper than one large boiler, which may be a commercial product for this size of house.

The zones. Have say, two major zones, say upstairs and downstairs. Have these off the store "directly" using a Grundfoss Alpha auto variable speed pump for each zone, then no auto by-pass valve and all rads can have TRVs fitted with no central room stats to switch off the zone when maybe heat is wanted elsewhere in the zone. Off each zone you may want to sub this to further zones. Have one time clock for each major zone and maybe manual switches for each sub zone. So, say the upper major zone is subbed into 3, then you may have just two sub zones on, or whatever. Divide and rule and gives you flexibility.

On another point insulate the hell out of the place and make sure it is air-tight if major works is to be undertaken.

Nothing wrong zoning off using "zone" valves.

I hope this helps.

Reply to
Doctor Drivel

The Aga can be converted to gas (recommended), and it can also heat the thermal store along with the boilers too.

Reply to
Doctor Drivel

We have 2 boilers each heating part of the house (and an Aga) and it is a real pain - if you want to heat one room then sometimes you need to switch on a 110,000 btu boiler for one radiator! Plus double the servicing costs and so on. By the time they have been installed I can't believe it is cheaper to have two. We are looking at going the other way and putting in one large boiler. If your Aga does not heat the water then you need to think about this too. If you are going to heat the water with it then be aware that it is relatively slow and a sudden large demand for hot water can cause the Aga temperature to drop - a pain if using it for cooking.

The only sensible split based on your description would be to have a separate system for the holiday let so guests can control things for themselves.

We use oil. I cannot comment upon the advantages of gas over oil other than for a long time oil has been cheaper although this may not be the case now. LPG has been popular but I believe it to be rather expensive.

HTH

Reply to
Hzatph

Move the Aga well out of the way into an airing cupboard which will then leave lots of space to fill. In the kitchen install four Alpha DVD50's feeding a stainless steel heatbank and eight Grundfos Beta constant leak pumps. Pipe in plastic as its the future using a hacksaw, duct tape and B&Q orange buckets where necessary. Fit dual exhaust TVR's on each radiator, preferably the 5 litres ones and always ensure you have a bypass in case things get snarled up in the middle of town. Fit zone valves in a convenient place somewhere near the time zone but ahead of the reverse suction flow splitter. A gas supply with diversity fed with a 400mm main will prove useful as will water supply that will deliver 700 litres a second at 200 bar. You might question why but you can never have too much water and planning now will ensure you are not left behind by future developments in shower technology.

I hope this helps. I am expert in many fields, some of them very damp ;-)

Nurse, bring me my medicine NOW.

Reply to
Doctor Evil

There is no point in doing this if there is already another means of heating the water using the same fuel.

The heat input to an Aga is only around 5kW max.

Reply to
Andy Hall

Not really, as a commercial sized boiler is commercial servicing rates. Two domestic boilers side by side can be quite cheap to service. Usually not x

  1. > By the time they have been installed I can't believe it is

Heating a thermal store it is. If you wanted just one room to be heated the two boilers will heat up the store in rapid time and then stay off until the radiator has exhausted the heat from the hot water in the store, which may be quite a time. That is beauty of a thermal store. Having large boiler heating only one rad may result in great inefficiencies and excessive boiler cycling, as you have noticed. Also with two boilers you can keep one boiler off in summer, spring and autumn, and only bring in the two. If one boiler can do both CH and DHW all year, then you can alternate the operation year by year and only have each boiler serviced every other year, so only one service cost each year. The run time of each boiler is less than for one, so less wear on each.

It is far better to have two small boilers than one large boiler, especially in such a large house. You have backup for a start. The benefits outweigh the cons. But you have to know how to connect them.

I would advise you to read what I write and take note. Consider a thermal store

That was along time ago and only briefly, and in summer.

Expensive to run, not to install. Natural gas is by far superior overall to oil and LPG.

Reply to
Doctor Drivel

Matt please tell beforehand when the funnies come in. Then we will know when to laugh.

Reply to
Doctor Drivel

I'd recommend talking to folk here about the house overall, and the things you plan to do:

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's lots of expertise on these old properties there. Heating plumbing is probably the one thing they wont help with.

Lol! too funny.

NT

Reply to
meow2222

Thant was funny? Gosh.

Reply to
Doctor Drivel

My guess is that you are looking at a 'commercial' sized installation here, and the specialist installers will be able to help - at a cost.

An alternative approach is to have at least one more domestic sized gas supply installed and then divide the problem up into a couple or three domestic installations. This could be really useful for dividing up cost as well.

The Osprey sounds like a huge commercial gas guzzler the CF means 'conventional flue' the whole thing is not likely to meet current (domestic) standards.

Reply to
Ed Sirett

My house is not too dissimilar in size (4000sq roughly) , and with modern insulation standards peak requirments came to about 10Kw. Of which the AGA supplies about 1KW.

I have a simple oil system boiler.

Now I appreciate that aan old house might leak ten times as much heat...but with oil the price it is - I am on current prices up around £2k per year - I would seriously consider the cost benefit of a complete insulation program. Walls especially. If you have a house that takes £20k of oil a year to heat because its un-insulated and draughty, thats a huge incentive to sort that out as second priority after waterproofing.

In my case, having to actually meet standards for a new build, and wanting single glazing, I paid about £200 for a complete energy calculation by a team of specialists. This not only satisfied the BCO, but it enabled me to size the boiler adequately.

ISTR teh boiler was about 800 quid and the mains pressure HW tank similar...installation was a lot more as there were a LOT of poipes to run. Water softener keeps the DHW circuits free of scale, and its certainly possible to get several decent baths and a lot of showers out of one tankful and unbelieveable flow rates (use big bore pipe).

I am on a three zone controller, but frankly I should have used more. If you are cunning in your electrical knowledge and a complete rewire is happening anyway, route as many zones as possible back to the main boiler area and use multiple zones and maybe two or more controllers.

Or there is an argument frankly for an electrical thermostat in every room, and a motorized valve as well, so that you can set every rooom up without using TRV's to a sensible temperature - frost settings for unused areas, cool temps for utility areas and bedrooms, and full blast for living ares in constant use and bathrooms.

Just take the motorized valve switch outputs back to central and common them up and use them to control the boiler via a timer zone.

Forget an OVERALL thermostat. With this arrenagment any zone that needs heat will fire up the boiler and pump and it will cut off when ALL zones are up to temp.

Yes, its expensive, but so is oil...

Insulation first - try and get to modern standards as best you can, and usie thermally lined curtains if the windows are single galzed. First step is total draughtproofing, then roof insulation, then walls.

If you are ripping up ground floors, insulate them as well. Or use thick fitted carpets and deep underlay.

Then pipework. CH pipework canb be carried to each room as per normal, into a motorized valve controlled by a thermostat on a switched fused spur off the local ring main in the room. Run the switch outputs back to the main boiler area, and use plenty of rads (or UFH or towel rails or indeed as I did hot air blowers fed from CH water) in each room as per normal heatloss calculations for the room.

Use large bore for all showers and baths going back to the cylinder if you want top flow rates, and large bore for all main CH runs.

Use a timer with at least three master zones. You probably want one for hot water - ours runs pretty much all day for water - one for daytime areas and one for bedrooms.

In practice I seem to set my stats for 22-23C in living areas, 25C or more in bathrroms and about 20C in bedrooms. Unused areas range from frost stat to around 10C. Depending on how 'unused' they are.

Its up to you whether you use one boiler overall, or maybe two boilers - one for living areas and one for bedrooms etc.

I'd say you would need around about 5-10k liter sized oil tank.

Reply to
The Natural Philosopher

Flippin heck I'd melt at those temperatures! Living room is set at

18.5C rising to 20C during the evening. No we don't compensate with jumpers either well not until it gets windy (>F5) and cold ( I'd say you would need around about 5-10k liter sized oil tank.

Thats a *very* big tank we have a 2500l one and even with our big boiler (38kW burns 7l/hr) and poor insulation and drafty windows we only need to fill it with 2000l twice a year. Thats around =A31500/year =

at current prices and yes that bill is an incentive to sort the windows, insulation and solar HW heating. Pity that there is a cash flow problem. Too much flow, not enough cash. B-(

Reply to
Dave Liquorice

His is near twice the size at 7000.

Very sensible.

Reply to
Doctor Drivel

No guarantee on thermo accuracy, but that's what I set em to :-)

I have a 2500l one, but his house is nearly twice as big as mine, and I use three tankfuls a year on good insulation levels.

Reply to
The Natural Philosopher

-- peterd

Reply to
peterd

B-) Most mordern electronic rather than mechanical ones are pretty damn close.

Ouch, mind if we heated the barn part (3 more double beds, bathroom and large living room) to comfort levels rather than 10C I'd expect to see a rather large increase in oil consumption...

Reply to
Dave Liquorice

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