Gravity systems

[850Rick]

Is there still alot of them about do you think.And is a semi gravity system when it has a pump in it?

 

[Dannyparty92]

Yeah there is. Semi gravity is where the heating is pumped but the hot water is circulated via gravity.

 

[Roger Welton]

DOnt see many gravity h/w and heating any more may be 2 in the last few years, loads of gravity h/m pumped heating systems around though.

 

[850Rick]

Yeah there is. Semi gravity is where the heating is pumped but the hot water is circulated via gravity.

So the pump makes it semi gravity?

 

[hammers4spanner]

fully pumped heating with gravity fed hot water was big int he 70's and 80's and to be honest its alot better imho than the combi crud you get these days .

 

[850Rick]

But does the gravity system with a pump make it semi gravity with the heating system not doing the job its self?

 

[kay-jay]

But does the gravity system with a pump make it semi gravity with the heating system not doing the job its self?

When we talk of gravity systems we mean pumped heating and gravity hw.
A fully pumped system is hw and ch both pumped.

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[kay-jay]

So the pump makes it semi gravity?

You are getting confused. On a gravity system there are 4 pipes from the boiler. The pump is on the heating and hw gravity only. Referred to as semi gravity because only half the system there(hw) is gravity

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[850Rick]

When we talk of gravity systems we mean pumped heating and gravity hw.
A fully pumped system is hw and ch both pumped.

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Im on about Gravity systems that was used in the Dinosaur age with the huge pipes hoping to be in the right place to aid heat in the Radiators or at the correct fall with it taking so long for the heat to travel round.

 

[kay-jay]

Well then there was no pump. Water moved round the system using the principles of different density between hotter and cooler water

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[850Rick]

Well then there was no pump. Water moved round the system using the principles of different density between hotter and cooler water

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Thats what i was on about rofl.If a pump was added would it be semi gravity

 

[jtsplumbing]

I think you have answer'd your own question ! if a pump has been added then its a pump'd system, convert'd for some reason from gravity, Boiler / system upgrade.

 

[Bernie2]

Another name for a pump was multiplier. In other words it multiplied the natural force of convection within a gravity system by so many times. So calling it a semi gravity system does not seem right. Its probably why they call it pumped c/h.

The full gravity domestic central heating systems where usually found in the bigger houses although you sometimes got smaller houses running a few rads if their layout allowed. The more usual set up was for a towel rail in the bathroom run off the primary supply. I suppose they figured, if you are heating water you might be going to have a bath so why not heat the bathroom as well. The problem with full gravity of course is that you have to lay your pipework like waste pipes with rises away from the boiler and falls toward the boiler or just call them falls to make it easy. To do that you need space and most houses do not have enough space to do it in. Although it is possible. A lot of modern pipework design is aimed to lay a system out so that its as close to a gravity system as possible cutting down the resistance factors in the pipework.

A good idea is to have a look at high rise building layouts. There are plenty of systems that use gravity in them to aid circulation. Many of the high rises have their boilers on the roof as it aids the pump. You could go on for ages but I figure you can find it out for yourself easier by Googling.

Incidentally getting the air out of a gravity system can be a bit challenging:sweatdrop:

 

[850Rick]

So is it a semi gravity system in simple terms lol

 

[mountainman]

No.
It's gravity hot water and pumped central heating.

 

[tamz]

No such thing as a semi gravity system. Bernie explained it quite well.
It either works on gravity (thermosyphon if you want to be pedantic) or it is pumped.
Without getting technical, on a gravity hw pumped heating system the pumped side of the system (mostly) has very little to no effect on the gravity hw circulation. Sometimes you may find upstairs rads heating when the pump is off but that is a design fault.

 

[850Rick]

No such thing as a semi gravity system. Bernie explained it quite well.
It either works on gravity (thermosyphon if you want to be pedantic) or it is pumped.
Without getting technical, on a gravity hw pumped heating system the pumped side of the system (mostly) has very little to no effect on the gravity hw circulation. Sometimes you may find upstairs rads heating when the pump is off but that is a design fault.

Thanks mate thermosyphon is a nice word lol

 

[petercj]

Thanks mate thermosyphon is a nice word lol

I'd go for the iphone if I were you - more apps!

 

[peteheat]

Another name for a pump was multiplier. In other words it multiplied the natural force of convection within a gravity system by so many times. So calling it a semi gravity system does not seem right. Its probably why they call it pumped c/h.

The full gravity domestic central heating systems where usually found in the bigger houses although you sometimes got smaller houses running a few rads if their layout allowed. The more usual set up was for a towel rail in the bathroom run off the primary supply. I suppose they figured, if you are heating water you might be going to have a bath so why not heat the bathroom as well. The problem with full gravity of course is that you have to lay your pipework like waste pipes with rises away from the boiler and falls toward the boiler or just call them falls to make it easy. To do that you need space and most houses do not have enough space to do it in. Although it is possible. A lot of modern pipework design is aimed to lay a system out so that its as close to a gravity system as possible cutting down the resistance factors in the pipework.

A good idea is to have a look at high rise building layouts. There are plenty of systems that use gravity in them to aid circulation. Many of the high rises have their boilers on the roof as it aids the pump. You could go on for ages but I figure you can find it out for yourself easier by Googling.

Incidentally getting the air out of a gravity system can be a bit challenging:sweatdrop:

I think Bernie is spot on, we didn't call them multipliers in fact we didn't call them pumps because they don't pump, they were circulators to us.

We changed the lives of many housewives (homemakers today) by fitting a tank in the attic, cylinder in the recess beside the chimney breast, pull out the fire back and fit a small boiler (not a wraparound) direct connection to the cylinder (no coil) hot water off the cylinder to the bathroom and kitchen they got the added bonus of shelves over the cylinder and a door (hot press).

Fire is lit, boiler heats up causing the warm water to rise out of the boiler to a connection at the top of the cylinder replaced by the cold water at the bottom of the cylinder, simple gravity and it worked.

When wraparound back boilers and indirect cylinders (with coils) became the norm we didn't always have room for two sets of pipes, one to the cylinder and one for the heating so we took the flow and return off one side of the boiler, depending on the size of the house we would reduce from 1" off the boiler to either 1/2" or 3/4" for the ground floor, continue in 1" to the cylinder branch off in 3/4" just before the cylinder to the upstairs rads.

When the temperature rose to around 50c the pump switched on and circulated the heat downstairs, some plumbers didn't fit a stat to switch on the pump depending on the householder to manually switch on the pump when they heard the pipes banging

The systems were fairly simple, the skills came in to play balancing the rads and making sure the system didn't "Tip" into the F&E tank in the attic.

Gravity still plays a very important part in many modern heating systems, not so much in gas because they need the pump to dissipate the heat faster or the boiler will just switch off having reached temperature, if you want a challenge link a solid fuel stove with boiler to a modern gas or oil boiler.

 

[AWheating]

you can also come across gravit hw, gravity heating upstairs and pumped heating downstairs on some old domestic systems.

 

[850Rick]

you can also come across gravit hw, gravity heating upstairs and pumped heating downstairs on some old domestic systems.

Hi mate i think after reading that this what your saying is what i meant.I new what i meant but got my words the wrong way round lol

 

[dsteves619]

There is no such thing as a semi-gravity system.
Sorry.