Thermocycling questions

[canals are us?]

Hello James. I've managed to get the out put to nearly 6000 BTU without the pumped circuit.

Doubles would be too deep. I've managed to get a double in the engine room and two more 300x800 singles in the corridor and bathroom.

 

I think you will be fine at that as 2,000btu equates to around a 500mm x 500mm single rad. You will have heatloss from the pipes too and will be switching the pump on to heat the water anyway. You will turn the rad(s) off to divert the heat to the calorifier as the boiler won't heat all the rads and calorifier as the rads alone roughly equate to the boiler output.

 

I turn the pump on to my calorifier circuit and then turn the rads off at the full bore lever valves entering the rads. Then when the calorifier has heated turn the rads on and switch the pump off.

The main critical thing is to have no restrictions or valves in the pipework from the stove to the expansion tank and cold feed path. This should be unobstructed for safety.

 

James

Edited September 20, 2013 by canals are us?

[MtB]

Solder is ok for water but not for gas or fuel. because solder joints may crack with viberation.

 

That isn't the reason for soldered joints being banned on gas pipes. In a fire, the solder can melt leading to the joint coming apart and neat gas gushing out which will obviously keep the fire going until the fire brigade arrive...

 

For a thermosyphon system you HAVE to use copper. Plastic goes all wavy when it gets hot due to it's phenomenal coefficient of expansion. The bends which appear when hot then trap air and air locks prevent circulation. If you fit a pump, this no longer matters as the pump will push the water along and air pockets will get distributed back into the rads or back boiler.

 

MtB.

[fudd]

Getting back to the pump part of the system, if I treated the calorifier as the first radiator(although its on the other side of the boat and I would have to take the flow and return below the floor) could I not put a pump somewhere in the system to make it flow to the calorifier and the main gravity fed part?

That way the whole system would be treated as a pumped circuit and when the water is hot I could just turn the pump off and revert back to the thermocycling effect? If that makes sense.

[blackrose]

I don't know how people who say they use plastic pipes for themocycling manage to box them in given their rise and fall. Much better to make them part of the exposed radiating system in my opinion.

[fudd]

I don't know how people who say they use plastic pipes for themocycling manage to box them in given their rise and fall. Much better to make them part of the exposed radiating system in my opinion.

Well, I'm using copper and I'm going to box it in. I don't fancy seeing the pipes running down the length of the boat. It's a lot of work but it will look better, in my opinion.

[blackrose]

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James

 

That looks like a good system. The only thing I don't like about it is that I think the rise on the main run goes on for far too long. If you think about it hot water begins to cool shortly after it leaves the backboiler, so really there should be a steep rise for a couple of feet and then it should level out and even have a shallow fall on the top run. Avoid 90 deg bends - use 2 x 135 deg bends instead as this facilitates flow through the 28mm dia main run. I prefer to have the last rad fully plumbed in on all 4 ports.

Edited September 20, 2013 by blackrose

[fudd]

 

That looks like a good system. The only thing I don't like about it is that I think the rise on the main run goes on for far too long. If you think about it hot water begins to cool shortly after it leaves the backboiler, so really there should be a steep rise for a couple of feet and then it should level out and even have a shallow fall on the top run. Avoid 90 deg bends - use 2 x 135 deg bends instead as this facilitates flow through the 28mm dia main run. I prefer to have the last rad fully plumbed in on all 4 ports.

On your advice Mike, I'm using all 4 ports on all the rads. I can't believe how much the fittings cost though. The two 90 degree bends that come out of the boiler cost £30. Three rads and most of the rest of the fittings came to £250 and I ain't nowhere near finished.

[canals are us?]

g

 

That looks like a good system. The only thing I don't like about it is that I think the rise on the main run goes on for far too long. If you think about it hot water begins to cool shortly after it leaves the backboiler, so really there should be a steep rise for a couple of feet and then it should level out and even have a shallow fall on the top run. Avoid 90 deg bends - use 2 x 135 deg bends instead as this facilitates flow through the 28mm dia main run. I prefer to have the last rad fully plumbed in on all 4 ports.

Using the 4 ports on the last rad is a good idea.

If you had a sharp rise, and then further along a slight fall, I would of thought it would trap air and the fall would reduce gravity circulation. When I did my City & Guilds/NVQ Level 1,2,3 we were taught that the gravity circulation flow pipe should constantly rise and that the return pipe should gradually fall to the boiler.

On my run the pipework runs in 28mm to the first rad 4.6m away then I reduced it to 22mm to the 2nd rad 3m further on to save money!!

28mm should work even better over a longer distance.

 

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On your advice Mike, I'm using all 4 ports on all the rads. I can't believe how much the fittings cost though. The two 90 degree bends that come out of the boiler cost £30. Three rads and most of the rest of the fittings came to £250 and I ain't nowhere near finished.

 

I know the feeling!! My heating materials came to £350 and done in copper. and too boot the stove heats my 50ft trad boat perfectly by itself before I plumbed in the back boiler for the hot water. Needed the rads to dissipate the heat in the event the hot water cylinder is heated or the pump is off.

The heat in the back boiler has to go somewhere.

 

James

Edited September 20, 2013 by canals are us?

[MtB]

On your advice Mike, I'm using all 4 ports on all the rads. I can't believe how much the fittings cost though. The two 90 degree bends that come out of the boiler cost £30. Three rads and most of the rest of the fittings came to £250 and I ain't nowhere near finished.

 

I think you are buying from the wrong place then. Try www.bes.ltd.uk

 

MtB

[smileypete]

BES also do galv. 'malleable iron' fittings that are a good deal cheaper than brass, and include swept elbows.

 

Not a bad idea to have a gravity 'heat dump' rad nearby the stove in the saloon, then all the other rads pumped which makes pipework cheaper.

 

cheers, Pete.

~smpt~