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Gravity fed heating, good but not quite right!

Lorien

By Lorien
in Boat Building & Maintenance

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Lorien Explorer

Lorien

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Hi,

We have spent the summer doing work to our boat, we had lots of clunking with the back boiler.

It has the traditional design, boiler, rise, two rads and header tank at highest point, pretty much the same as many.

We had at Torglow roomheater, great in its golden years -not so good now. It was impossible to control and would bang on request of any heat.

So out it went and in came a Squirrel - my word what a fantastic stove. Back boiler clunk has gone.

We had a loop to the front, boat is 62' stove sits roughly 20' from the bow. The front would never work and would get the kettle effect.

The front loop has now gone due to the new kitchen going in. This has made the system much more a simple affair. 45 degree fittings have been used to improve flow as much as possible.

The installation is a longstanding setup and has been drained several times firstly to cure the banging and then with the fitting of the Squirrel. Coolant has been used and there are no air locks.

 

Our only problem is that the we seem to get flow and the top pipe gets nice and hot, it works it's way right down the boat but the rads don't get warm. If you get the fire going it makes a fair bit of noise, at first I thought it was boiling but after carefully observing thing over the last month it really sounds like a slushing noise. I am almost certain it is circulation noise, or possibly the system is having trouble circulating.

 

We have tried bleeding and different fuels but it makes no difference.

 

I have studied various articles on the net and fully understand gravity systems can be a pain to get working correctly but some days with the fire ticking over the top of the rads get warm.

 

Is there any way of setting these up correctly or can anybody offer any help?

 

Many thanks,

Jim

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Tony Brooks Veteran II

Tony BrooksDonate to Canal World

Posted
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1. Does the hot water enter the top of the rads via what would be the bleeder fitting hole or the bottom?

 

2. If the latter did any antifreeze go in ready mixed or did you put it in separately?

 

3. What diameter pipes are you using for the flow and return?

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Lorien Explorer

Lorien

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Hi,

 

Sorry, should have said this first!

 

It's all 28mm

 

Yes the anti freeze was pre mixed

 

The hot water enters through a standard rad valve at the top of both rads to the left had side, opposite end has the bleed screw. It leaves both on the right had side through a rad valve at the bottom.

 

Thanks,

Jim

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Tony Brooks Veteran II

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Well to me that makes very little sense. It should work. Are those valves turned full on? I trust they are not thermostatic valves. If so you have a potential safety issue unless you provide a sufficient heat sink for the stove output.

 

Having said that my boat had the inlets and outlets on the bottom with a 28mm loop running along the side of the boat. It always worked well and caused no problems. I suspect on my boat the hotter the water in the loop became the greater the propensity for it to rise up into the rads rather than drop down against convection.

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smileypete Veteran II

smileypete

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Also I take it the top pipe rises gently and continuously toward header tank or automatic vent, and the bottom pipe rise similarly towards the radiators or back boiler.

 

To add to what Tony's said any valves on the gravity rads best be 'full bore' valves like with a lever or butterfly handle.

 

cheers, Pete.

~smpt~

Edited by smileypete
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Lorien Explorer

Lorien

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Hi,

 

Thanks for the help.

Yes, there's a rise flowing out and there's a rise flowing in so I can't see an issue there.

As far as I'm aware the valves are open all fully.

Could be stuck a little.but chances seem slim.

 

Only other clue is that the previous owner did mention that they closed the larger of the two rads to get heat up to the rear, that was on the old stove which really had seen better days!

 

We've tried turning the larger off with no difference?

 

I guess there's a run of approx 20' from boiler to first rad. The first rad is approx 5' and the rear approx 3' both are singles.

 

It's odd as Tony says, all the signs are there just no heat.

 

Frustrating.....

 

Thanks,

Jim

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smileypete Veteran II

smileypete

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28mm copper pipe at 80°C loses about 75 watts/metre, so that 20' run the first alone may lose up to about half a kW (6m x 75w).

 

I think a good way of doing it is to have an adequately sized gravity 'heat dump' rad(s) near or next to the stove, then more distant rads and/or calorifier on a pumped circuit connected by 15mm pipes, ideally lagged.

 

That way the gravity rads can be shut off and all the heat directed to the furthest rad.

 

cheers, Pete.

~smpt~

Edited by smileypete
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MtB Veteran II

MtBDonate to Canal World

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I too would be removing the ordinary rad valves and fittin full bore ball/butterfly type isolating valves. the motive force with a natural convection system is microscopic, which is why 28mm pipes are used. This is totally compromised by the use of ordinary rad valves designed for use with pumped systems as they only have a really tiny waterway even when fully open. Inspect one and compare the gap inside with a 28mm pipe!

 

MtB

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Lorien Explorer

Lorien

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Guys,

 

Really, thanks for helping me.

 

Went boating this afternoon, whilst mulling over your posts.

 

Got in tonight and it dropped quite cold, by pure chance I put fuel in the fire, then the good lady without realising put more in! However, despite sweating we noticed no swooshing noise. Actually quite odd, very quiet....so we've maintained this all evening.

 

First problem may be not enough in the fire, but we have only had a really nice boatman stove before the Torglow. Good fire but quite small in retrospect to the Squirrel.

 

I noticed the rads have got more heat in them, small one quite a bit about 3 inches from the top. I know it sounds daft but that's the best yet. And the larger is only an inch but it's all the way along.

 

Embarassingly as I write it's really hot in here, with no noise. I really think you're ideas about valves could well be in the right direction. I'm guessing but surely with this result we have a good flow going round!!

 

Without sounding daft could you point me in the right direction of full bore valves?

 

Thanks again for all the help :-)

 

Jim

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smileypete Veteran II

smileypete

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http://www.ebay.co.uk/itm/Full-Bore-Heavy-Duty-Ball-Lever-Valves-Blue-or-Red-Handle-15mm-or-22mm-Brand-New-/251281326646

 

http://www.ebay.co.uk/itm/Full-Bore-Heavy-Duty-BUTTERFLY-LEVER-Ball-Valves-Blue-or-Red-Handle-15-22mm-/251293927598

 

http://www.toolstation.com/shop/Plumbing/Valves/Lever+Ball+Valve+15mm+Blue/d20/sd2696/p14624

 

The lever ones are easier to turn than the butterfly ones, but the handles stick out more.

 

cheers, Pete.

~smpt~

Edited by smileypete
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nb Innisfree Veteran II

nb InnisfreeDonate to Canal World

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Some valves look identical but are not full bore, they reduce in diameter halfway along, should be full bore along the entire length. I bought some valves from a plumbers merchant, was told they were full bore, when I returned them the assistant didn't know the difference and thought all valves were full bore!

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smileypete Veteran II

smileypete

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How did you connect the 15mm pipe at the end of the rad without the valve? If the tapping is the same at top and bottom probably just use the same fitting.

 

The tappings could be 3/8 or 1/2 or 3/4 BSP, just match up the approx diameter with the 'major diameter' in the table on this link:

 

http://en.wikipedia.org/wiki/British_Standard_Pipe

 

cheers, Pete.

~smpt~

Edited by smileypete
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Bee Veteran

Bee

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Personally I have always put rad inlet and outlet on diagonally opposite ends to stop the water taking the shortest route through the rad. and had no probs. Whooshing noise. Is the pipe to the header tank tee`d off from the highest point in the circuit and open to the air? I did a system where I tee`d it from the highest point on the return pipe thinking that it really couldn`t make any difference but it did, the water tried to go up the return pipe and made some odd noises where it `stuck` then suddenly `whooshed` as it moved, When you've got it right it will be very reliable.

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Tony Brooks Veteran II

Tony BrooksDonate to Canal World

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in my view it is far better to feed the header tank into the lowest point in the system and then fit a (Say) 3/8" permanent air vent tube to the highest point. Just make sure the top of the vent pipe is higher than the top of the header tank. MY boiler and tank were at the back of the boat and the vent pipe at the front venting through the forward bulkhead. If by some chance one of the pipes became blocked there is still a pressure release path and it makes the system with top inlet rads virtually self bleeding.

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David Schweizer Veteran II

David Schweizer

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The tails for the valves on our radiators have 15mm pipe ends, surely a standard butterfly ball valve will screw onto these, as long as the original olive is removed without damaging the tail.

 

The main problem with conversion from standard valves is that the ball valves require a lot more room and are not angled at 90 degrees, so some pipework modification is also needed.

Edited by David Schweizer
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Lorien Explorer

Lorien

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Hi,

 

I'll try and change the valves when I can, it'll take some adjustments as the valves will take up more room.

 

I'd like to make as tidy job as poss, so I like the screw in fittings and could solder some tidy pipe work, it'll be tight though and I could do with minimal downtime.

 

I'm really hoping the valves work, it'll warm the place up a treat if successful.

 

Thanks,

Jim

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