central heating installation

[Fred]

I think I'm quite happy with the gravity fed system, though I've never known anything else. Why is it noisy and inconvenient to have mains pressure HW?

[Calvin]

Your're right, there is a requirement to have a wall if the tank is less than (IIRC) 1.8m from a boundary. It's fine to do the installation yourself so long as you do it to the regs, and yes, they do tell you what pipe to use for the oil, how deep it must be laid, how to line the trench and how to mark it so that some numpty doesn't dig it up later.

You're also right about how the pipe sizing works. For the section of pipe after those 2 have joined you need to handle 4kW etc.

[Dave Plowman (News)]

Mains pressure means the water moves faster in the pipes - so makes more noise. It's *very* inconvenient if you have a water cut - with a header tank you still have water for washing etc.

[Fred]

I had a look at the plumb merchant URL that was mentioned. The Worcester boilers all weighed in about £1000. I haven't looked at the other makes yet. Is that a reasonable price for an oil fired boiler?

I thought the accessories: thermostats, pumps, etc. were more expensive than Screwfix though.

Neither site seems to sell 15x10x15 reducing tees though. Where can I get these, preferably in brass? SF do sell some plastic push fit ones are these any good/suitable for CH?

I had a look on the direct.gov.uk site and searched for building regs. I was hoping to find a regs.pdf to download! I eventually found:

this the right page?

Do I need to download each part individually?

Thanks.

[Tony Bryer]

Now every year -

- It used to take the whole of the NEC but is now a shadow of its former self: for example all the boiler firms would be there, this year just Viessman. No Catnic lintels, Redland roof tiles or many of the other big names.

I think the pitch has been changed to building tradesman as there were loads of power tools (with some very good stand offers) and white vans of all makes. There's also a move to smaller more focussed shows like PHEX for plumbing and heating later this month and one for electricians in December at Kempton.

[The Natural Philosopher]

Its not noisy and inconvenient, and most places do have good water pressure.

Its highly convenient, since the tank can be located anywhere, It gives a terrific rate of how water delivery, without the use of noisy pumps, and it avoids a lot of pumps an water tanks, and if you DO want showers, ends up cheaper and quieter. It means you do not need a boiler with a massive peak output that will be larger and less efficient when just idling way short cycling doing central heating.

It is not suitable for small houses..its far more suitable for large ones, as it is capable of feeding more than one shower or bath or basin or sink at a time.

There are three classic ways of dong hot water.

- Combi or 'heat on demand'. Very compact, runs at mains pressure, but the combi needs to be large enough to heat the water as fast as it is required. So needs a bigger boiler. Suitable for small properties as its very compact wih NO tanks AT ALL. Some combi fanatics add heat banks but e result is the worst of all possible worlds IMHO..it iessinally is a pressrised HW system using a more xepenive boler.

- Stored hot water at low pressure - pressure is limited to the highest point you can put the storage tank(s) - typically the loft. That means that shower flow rates - especially in the upper stories - are limited unless you use extremely large bore pipes and even than that means wasted hot water in them, nad gush rather than a spray. I addition there is an open tank on te roof, where it can collect bacteria dirt and dead things, block up, overflow and freeze up. In addition you need an electric pump - very noisy - to feed showers etc. Unless you DO have intermittent water supply, it is the worst of all solutions. In order to pump the water TO the header tank the mains pressure MUST be at LEAST as high as the pressure you will get OUT of the tank. So its axiomatic that mains pressure systems will always be of higher pressure than a gravity fed system can ever manage without pumping it.

- fully sealed mains pressure systems. Medium compact..between combi and gravity. You need a tank of hot water - or a heat bank if thats the way you want ot go. However water pressure is uniformly high, and there are no issues mixing high and low pressure water in e.g. shower heads and mixer taps. The boiler can be sized for efficiency under central heating loads..typically the HW is only a small part of what it does. herfire typically smaller than a combi. Its a shade more expensive than the others to install - although if you look at what a gravity system costs with shower pumps, thats not always the case. Pipework apart from showers can be smaller bore, minimising wastage of heat in them. The tank can be sited anywhere in the building.

I loked at combi + heatbank and could see no cost or performance advantages over PHW, so despite drivels drivelling, if you want more than one shower or bathroom, go for PHW. Unless you live somewhere where the water supply is SO bad that you cannot bear to be without it for an hour or so, do not ever consider a gravity system: They are totally old fashioned and relatively useless. The idea goes back to the days before the water mains existed.

[The Natural Philosopher]

Only when it IS moving. Having grown up UNDER the tank in the loft and been woken up by its hissing and gurgling as it took minute to refll after someone had flushed the loo, I would say its noiseir.

Frankly for the same flow rate in the same pipe the speed is the same, so if you want the pathetic trickle your gravity system gives you, just don't turn the taps on so hard.

AND if you want a shower you WILL need a pump, and NOTHING is noiser than a shower pump bolted to a wooden floor structire.

[The Natural Philosopher]

ISTR mine was about £750 for a 12KW unit.

PHW tank was another £650.

Pretty sure you can get an old fired boilerhouse boiler for aroind £600-£700 still.

[John Rumm]

I find it much cheaper to just use a equal tee with a fitting reducer. See BES part number 6787. Works out at pennies a joint that way. Unequal tees can cost silly money.

Its the start page for the building regs yes.

Yup, although you probably don't need all of them.

[Martin Bonner]

Oil burns, gas explodes; that's why the rules on oil work aren't so fierce.

[Dave Plowman (News)]

Now lets just see. Just what is that tank filled from? The mains, isn't it? So if it's taking longer to fill than the toilet cistern from the mains does there's something not quite right...

Thanks for confirming the system you had was more than 'not quite right'.

Total bollocks. With careful planning, decent pipework and the header tank correctly positioned you can get an excellent shower - provided you pay for one designed for low pressure.

[David Hansen]

On Tue, 06 Nov 2007 08:55:48 -0800 someone who may be Martin Bonner wrote this:-

That rather depends on the conditions. Gas burns quite happily in a boiler for example and many types of oil can be made to explode fairly easily.

[geoff]

gas is explosive only in concentrations between 5% and 15%, outside that concentration window, gas burns (as it does in a boiler, for example

Oil as fine droplets can make a fair attempt at exploding

[The Natural Philosopher]

Not leaking out of a storage tank.

Its pretty much impossible to get kerosene to explode unless there is a fierce fire already going, or a way to atomise it.

Propane explosions are very common in boats and caravans though. As a gas at normal temperature an explosive mix is not that hard to achieve.

All of which is merely the reasons WHY the regulations for oil tanks and propane tanks are considerably different: kerosene is more a problem in terms of ground contamination, than explosion risk. Exactly the reverse is true of gas.

>

[The Natural Philosopher]

Well with a gas leak you get a nice range of conncetrations from 0% at infinity to 100% at the leak (in free air).So EVERY leak has at least ONE plane or surface that is at of any concentration between the two. Including a large volume of gas at the perfect concentrations for a big bang.

Ergo every gas leak has a part where if ignited, there will be a lesser or greater explosion. Every single one. *By your arguments*.

But oil leaks tend to drip harmlessly into the ground.

[Dave]

I'll vouch for that.

Several years ago I was doing some fuel checks on a jet aircraft, along with two other men. We were looking at the ground fuel control panel when our boss arrived with the usual cigarette in the corner of his mouth. He asked us what the problem was and promptly threw the cigarette into the tun dish that was below the refuelling line that had a steady stream of fuel getting past the seals.

Bum tightened instantly until I saw the ciggy go out as soon as it hit the jet fuel.

Dave

[Dave]

Not all the time.

It became my job to fit an anti spin system to an aircraft. What this does is to provide a way of flying the aircraft if both engines flame out. This happens when the air from the front of the engine is replaced (by the flight direction) by air coming in from the back. This tends to blow out the flame in the engine. This emergency system consists of a chemical battery that drives an emergency hydraulic pump. On the development aircraft, all the hydraulics were put in the rear cockpit. Once the aircraft is flying nose first, then the engines can be fanned up to running speed by the flow of air through them.

In an oxygen rich atmosphere of a pressurized cockpit, it was decided to wrap each pipe joint with self amalgamating tape, to force any leaks into drips instead of a volatile spray that could have ignited.

Dave

[Fred]

Actually, that's the situation with the pipe in our current house: the

15mm copper is just under the floorboard and cannot be insulated. I know someone said it would heat the house, but I don't really want under the floorboards heated, I'd rather the heat waited until it was in the room before radiating out. Is there any way around this?

Looking at the plastic pipe, I see Screw fix sell two types PE-X and polybutylene. Is there any difference between the two or do I just use whichever is the cheapest or available? 22mm is only available in polybut. in SF as far as I could see - yes, I know I should go to a proper plumbers merchant ;)

[Steve]

Yes, partly because of this consideration and mainly because I did not want to notch joists or drill them, I have decided to take the pipe under where they cross the joists and then along to the radiators over the top of the sleeper walls. The radiators are thus supplied (by 15mm) from a central 22mm pipe run that is below the level of all the other pipes in the system and would then become a sump to collect debris and sludge. After some good advice on this newsgroup (see thread: "New lowest point in CH", recently), I was convinced that, in my case, drain points outside near to the ground were needed. This is a small price to pay, IMO for avoiding drilling or notching joists and will provide a better method of draining in the future. YMMV.

I don't know enough about plastic, but I have decided to stick with copper here as access will be difficult in the future and I do have worries that any joints other than End-feed/Yorkskire soldered joints could potentially fail. Plastic pipe is attractive but I do not think that there are solvent-weld joints or pipe available that could match the reliability of a soldered joint in an inaccessible place.

HTH

Steve