Gravity feed system pipe

[fudd]

Can anyone tell me what pipe is suitable for a gravity fed system please. The run is about 40' and will have 3 rads. Hopefully running a calorifier. Stove will more than likely be a Morso Squirrel or similar. Thanks.

[Tony Brooks]

I would suggest 28mm as I had on my boat. 22mm is pushing it a bit. Best it it suns uphill slightly from the stove.

[fudd]

I would suggest 28mm as I had on my boat. 22mm is pushing it a bit. Best it it suns uphill slightly from the stove.

Copper or plastic?

[Tony Brooks]

Copper for at least 1 metre to/from the boiler and then what you want, but I have never seen 28mm + high temperature plastic. I have doubts about drain type pipes and near boiling water.

[MtB]

28mm copper. Plastic is unsuitable unless you can devise a way to keep it dead straight, as otherise multiple partical airlocks reduce the effctive diameter too much.

 

A caulifower will not work a convection system unless you install it at a higher level than the stove.

 

MtB

[fudd]

28mm copper. Plastic is unsuitable unless you can devise a way to keep it dead straight, as otherise multiple partical airlocks reduce the effctive diameter too much.

 

A caulifower will not work a convection system unless you install it at a higher level than the stove.

I looked at the price of copper. It's gone up a bit since I last bought some. Thanks.

 

MtB

I was going to put a pump where I need to to divert it to the calorifier. It needn't be on all the time.

Copper for at least 1 metre to/from the boiler and then what you want, but I have never seen 28mm + high temperature plastic. I have doubts about drain type pipes and near boiling water.

 

I'll use copper then Tony. Thanks.

[Tony Brooks]

28mm copper. Plastic is unsuitable unless you can devise a way to keep it dead straight, as otherise multiple partical airlocks reduce the effctive diameter too much.

 

A caulifower will not work a convection system unless you install it at a higher level than the stove.

 

MtB

 

 

Mike

 

I hesitate to move into your domain but my Ellis gas boiler heated the radiators and the calorifier although they were both floor mounted. There was an upward path from boiler to the top calorifier coil though. I suspect much depends upon the relative heights of the stove outlet and calorifier inlet. My calorifier was only about 34" tall. It also had a two way valve T that allowed heating, water, or both and I think this must have provided some restriction.

 

I agree about the plastic. It would look horribly unsightly with all the sags. I forgot just how badly my 22mm plastic bows - and that with supports every 250 mm.

[canals are us?]

I installed my heating system using all copper 28mm 22mm & 15mm piping and have 2 rads on gravity and a pumped 15mm circuit to the 55litre calorifier under the bed. The expansion tank is a small car one off a Renault clio for £5 To heat the calorifier I turn off the full bore lever valves on the two rads and then switch on the pump. Once hot enough open the lever valves and switch pump off. The first rad red pipe goes behind the rad in my system and branches off to the rad with a full bore lever valve.

No valves or restrictions must block or impede the pipework from stove boiler to the vent or the cold feed as these are vital to the safety of the system..

 

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James

Edited September 5, 2013 by canals are us?

[fudd]

28mm copper. Plastic is unsuitable unless you can devise a way to keep it dead straight, as otherise multiple partical airlocks reduce the effctive diameter too much.

 

A caulifower will not work a convection system unless you install it at a higher level than the stove.

 

MtB

I was thinking that when I wanted hot water I could flick a switch to turn the pump on and it would maybe override the gravity system. It may work like that if I put the pump in the flow to the calorifier. Yes, no!

[DHutch]

I have to say, I would favour a 'gravity' based system any day, and if you do a search there's lots of past threads, but the design does have to reflect this heavily if your to get it work. Although once done, it will be trouble free for decades.

 

 

Daniel

[blackrose]

 

 

I agree about the plastic. It would look horribly unsightly with all the sags. I forgot just how badly my 22mm plastic bows - and that with supports every 250 mm.

 

Why would anyone even consider exposed plastic pipe? Since the pipework for a convection/gravity backboiler radiator system can't be at floor level, then unless you're extremely clever it will have to be exposed. I can't see any other way than to make a feature of it with copper pipe. 28mm for the main runs.

I was thinking that when I wanted hot water I could flick a switch to turn the pump on and it would maybe override the gravity system. It may work like that if I put the pump in the flow to the calorifier. Yes, no!

 

I've modified my system to do that this year, so we shall see if it works this winter. I have a feeling that the pump will disrupt the thermocycling to the rads, but you'll still get the heat from the stove of course.

Edited September 7, 2013 by blackrose

[fudd]

 

Why would anyone even consider exposed plastic pipe? Since the pipework for a convection/gravity backboiler radiator system can't be at floor level, then unless you're extremely clever it will have to be exposed. I can't see any other way than to make a feature of it with copper pipe. 28mm for the main runs.

I'm going to cover it up with panelling. I have 75mm under the gunwales so I won't miss 30mm.

[MtB]

 

 

Mike

 

I hesitate to move into your domain but my Ellis gas boiler heated the radiators and the calorifier although they were both floor mounted. There was an upward path from boiler to the top calorifier coil though. I suspect much depends upon the relative heights of the stove outlet and calorifier inlet. My calorifier was only about 34" tall. It also had a two way valve T that allowed heating, water, or both and I think this must have provided some restriction.

 

I agree about the plastic. It would look horribly unsightly with all the sags. I forgot just how badly my 22mm plastic bows - and that with supports every 250 mm.

 

Tony, the Ellis presumably had no pump so the circulation to the calorifier must have been feeble. People's expectations vary enormously and convection system won't heat a tank of water in 15 mins like in a house as some peeps expect! The water in the calorifier would eventually achieve the same vertical temperature gradient as in the Ellis after an hour or three, and I'd suggest if you checked the bottom of your vertical calorifier it will remain cold at heights lower than the bottom of the Ellis heat exchanger. (In the world of plumbing a calorifier is a horizontal hot water cylinder and I keep forgetting peeps have vertical ones too on boats and these perform better with convection circulation.)

 

Once a pump is added as intended by the OP then everything changes and a whole load of different problems are potentially introduced as I'm sure you know! (Just saying this stuff for the benefit of future readers to the thread.)

 

The reason your 22mm plastic sags and bends is the coefficient of expansion is massive compared to metal. Each 3m length grows by something like 8mm when you heat it from 20 to 75 degrees C, IIRC and all that extra length causes the kinks and waviness to appear when hot.

 

MtB

[Tony Brooks]

continuing as a matter of interest.

 

The calorifier coil input side heated up as fast as the radiator circuit (the feed from the stove T'd in the valve to feed the two circuits) and got as hot. There was no other form of water heating on the boat and it worked well. The calorifier did have a 22mm/three quarter coil, unlike the crimped 15mm we seem to get nowadays, and there was a rise of maybe 9" from boiler to calorifier which was beside the boiler. I think gravity will heat a calorifier satisfactorily providing there is sufficient rise form boiler to calorifier and they are close enough together. I accept there is no way a stove will heat a horizontal calorifier several yards away simply by gravity circulation.

[smileypete]

Can anyone tell me what pipe is suitable for a gravity fed system please. The run is about 40' and will have 3 rads. Hopefully running a calorifier. Stove will more than likely be a Morso Squirrel or similar. Thanks.

 

28mm copper is the safest bet, but 80' of it won't come cheap!

 

Maybe have one or two adequately size gravity rads near the stove as a heat dump, then the more distant rad(s) and cauliflower on a pumped circuit.

 

28mm plastic is OK in places if you can overcome the problems of expansion, sagging, appearance etc...

 

cheers, Pete.

~smpt~

Edited September 7, 2013 by smileypete

[fudd]

 

Why would anyone even consider exposed plastic pipe? Since the pipework for a convection/gravity backboiler radiator system can't be at floor level, then unless you're extremely clever it will have to be exposed. I can't see any other way than to make a feature of it with copper pipe. 28mm for the main runs.

 

 

I've modified my system to do that this year, so we shall see if it works this winter. I have a feeling that the pump will disrupt the thermocycling to the rads, but you'll still get the heat from the stove of course.

I would have thought that pump would just take over the whole system when it was turned on. It wouldn't matter if the thermocycling was interrupted. It would only be needed when you wanted hot water. I think.

[smileypete]

Ideally tee in the pumped circuit quite near to the back boiler.

 

Having said that a lot of people tee the pumped circuit in somewhere further away like just before the first gravity rad, and this seems to work OK.

 

cheers, Pete.

~smpt~

Edited September 8, 2013 by smileypete