Is there any regulatory or other obvious reason to locate CH sealed system components physically close together as is achieved with a sealed system kit, or is it acceptable to separate them?
e.g. expansion vessel located remotely from other components.
Obviously the pressure gauge ought to be visible from the filling loop valve position.
ISTR that when I was wading through lots of boiler installation instructions when choosing a boiler, a number of them required the expansion vessel in the return near the boiler. I doubt that's a regulatory issue -- probably something more like ensuring there was no momentary pressure drop in the boiler when pump started that might otherwise trip a lockout due to low system pressure.
When we had our Vaillant fitted a few years ago, I'm fairly sure the installation instructions permitted/suggested the expansion vessel to be sited near the boiler downstairs, as opposed to the tank upstairs (which is where we wanted it, and where it went).
If you don't get a definitive answer here I'll have a root around and see if I can dig them out.
David
On Sat, 15 Jul 2006 01:59:01 +0100, Andrew Gabriel wrote (in article ):
I looked as well and couldn't find anything. The items to make a system are available separately.
The relief valve needs to have a suitable exit but I couldn't see a reason that it needs to be next to the expansion vessel. I also couldn't see a reason why the filling loop has to be near either apart from the point about seeing the gauge when filling. Obviously the filling loop has to be a proper one with check valve etc.
On Sat, 15 Jul 2006 10:30:15 +0100, Lobster wrote (in article ):
Thanks David
I am pretty sure that that isn't' an issue, although note Andrew's point.
I was thinking about separation of the individual components such as the expansion vessel, the filling point, the pressure gauge and the relief valve. These often come as a kit, but I can't ind anything that says that they have to be co-located. The components are available separately as well.
The source of expansion is the heat source, the boiler. The relief valve has to be where the highest pressure point would be, the flow right on the boiler. The expansion vessel has to be where the expansion would be greatest, the boiler. Before system boilers came along, and all kit was loose, the expansion was always on the flow. On the return, keeps it cooler and Andrew hit on one the points it goes near the boiler. The expansion vessel can add pressure when a negative pressure is around it. On the suction side of the pump, when pressure drops compared to the pressure side, it will expand back into the system equalising the pressure difference around the pump somewhat. On an open vented system there may be sharp differences in pressure from the highest to the lowest pressure around the system as the expansion rise up the expansion pipe and nothing comes down to compensate. The expansion vessel compensates to reduce negative pressure.
On an open vented system with a low head cavitation may occur in some pump models. Having the charge pressure as high as possible in a sealed system prevents pump cavitation (also this reduces as oxygen is eliminated from the system), and also the higher pressure makes the boiler quieter as it raises the boiling point. In some small capacity boilers there is local boiling of the water in the heat exchanger giving the hiss sound. A higher pressure prevents the boiler hissing.
Inhibitor can also cause system noise too. It may be wroth eliminating inhibitor with a sealed system. The inhibitor swells joint seals and over time causes leaks. In some Continental countries it is used infrequently.
I don't think I've seen any such claim, but I would put it close to the boiler exit (about 3" away in the case of the one I fitted).
Whilst sitting at some traffic lights, I was looking at the row of terraced houses along the road. On one, there was the classic pattern of gas pipe, flue, and pressure relief exit pipe indicative of a sealed system boiler on the inside. However, what caused me to do a double- take was that the pressure relief exit pipe was pushfit plastic with a pushfit elbow and an extra 6" of pushfit pipe pointing it downwards (and with no bracket holding it in place). The house wall only about a foot back from the pavement edge.
Then I got to thinking. I suppose there's no point in a metal pressure relief pipe if the system itself is all pushfit indoors, although I don't think I've ever seen a plastic pressure relief pipe before.
It has to be metal, no need for sleeving through a wall, and terminate at floor level with the pipe turned towards the wall (an elbow). It can terminate at high level like at the eves when a boiler is fitted in the loft, but must turn in on itself. and it must not be over a used pathway. It can be terminated onto a flat roof too without turning into the wall.
The HSE should be called in to this house. If it blows it could scald people in the street below.
Oh dear -- every single statement incorrect.
The point was that in the initial fraction of a second when the pump starts and there's not yet any flow, you will get a significant momentary pressure drop (which in turn is responsible for starting the flow round the system). This is not of any consequence as it lasts only a fraction of a second, except it could trip an under pressure sensor, and cause a lockout. The pressure vessel will significantly reduce this pressure drop if there's a short path between it and the pressure sensor. For this purpose, it's probably more important to have it near the under-pressure sensore than the pump. You might get similar effects as zone valves open/close when the pump is running.
That paragraph is rubbish, and there is no expansion vessel in open vented systems (the header tank performs that function).
Gosh, that's actually right (but largely irrelevant).
This voids pretty well all boiler guarantees.
I thought the regulations were to have metal pipe within a metre of the boiler, and similar for /all/ the releif valve piping.
On Sat, 15 Jul 2006 13:27:20 +0100, Doctor Drivel wrote (in article ):
Do you have a reference?
Unfortunately for you, every one right. Lets go into it again as you are bit hard of thinking:
It is.
It does.
It has to.
There that is better you.
Read it again.
It is right, and it isn't.
Tell the Dutch and Germans that. In soft water areas of the UK, 30 years ago few put in inhibitor. Well few put in it full stop, anywhere. In many cases it made hissing and gurgling noises - inhibitor is better these days.
From Alpha CD50 instructions: "If a cleaning agent and inhibitor are used, they must be applied in accordance with their manufacturers instructions."
Note the first word "If".
Matt, look in Two-Jags site.
Plastic pipe can go right to a boiler if it connects outside the casing. See makers blurb. The relief pipe "has" to be metal and metal fittings.
In article , Doctor Drivel writes
In other words, you don't have a reference.
On Sat, 15 Jul 2006 14:45:04 +0100, Doctor Drivel wrote (in article ):
That would be reasonable, and one might expect to find it in the Approved Documents to the Building Regulations, ether in Part J or possibly Part G.
Presumably that's what you meant.
Part G3 appears to refer to pressurised stored hot water systems, where indeed there is mention of discharge pipe arrangements, metal being required. In section 3.9 it talks about different arrangements including terminating the pipe below a grid in a gully. However, it does not mention elbows pointed at the wall, only keeping the pipe less than 100mm from the external surface but rather a guard where there is a possibility of children playing.
However...... there are specific exemptions if the storage vessel has a capacity of 15 litres or less or the system is for space heating.
I can't see any reference to water discharge arrangements in part J at all - it is about ventilation, flue arrangements and fuel storage.
Did you have the Building Regulations in mind, or something else?
This is not to say that it isn't sensible to make careful arrangements for the discharge of water from a sealed primary circuit going faulty, but I can't see where there is a regulatory requirement so to do.
Do your own looking. Cheeky sod.
Exactly that is what it covers, not boilers
And if the vessel uses a plate heat exchanger then the G3 does not apply. No approved unvented ticket installer or annual service required and only one pressure relief valve is needed.
The W-B Highflow has an unvented pressurised vessel of over 15 litres yet no BBA approval and annual service. It can be DIYed. A Powermax has a secondary water unvented pressurised cylinder and needs a BBA approved installer. If the pressurised vessel has a coil inside (thermal store) it comes under G3, use a plate, inside or outside the vessel, and it doesn't. An unvented cylinder requires three mechanical safety stages while a pressurised vessel of the same size using a plate needs only one.
I would put two pressure relief valves on, in case.
So, anyone can buy a cylinder, put on a plate for DHW, one relief valve, have the boiler direct, the CH direct and have one ~24 litre pressure expansion vessel for the lot. Or buy a pressurised Heat Bank complete and do it yourself.
The W-B HIghFlow 440 clearly states what I stated in the manual, with a little piccie too.
Try BS 6798. Installation of gas fired boilers.
On Sat, 15 Jul 2006 17:14:47 +0100, Doctor Drivel wrote (in article ):
Because the vessel is on the primary circuit, presumably, and hence not directly part of HW production....??
That's all nice, but wasn't really the question.
Do you *know* that it's in this document?
No. They wrote it before plate heat exchangers came along. A pressurised thermal store with a coil is G3, one with a plate is not.
They have taken it from the BS.
Last time I looked, the 200 vsn, I'm pretty sure. Available from the Corgi Sharks for £88. Buy two.
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