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Post by lollygagger on Nov 30, 2019 19:47:26 GMT
Very kind of you, but I think I need something more variable. Ok it was designed by a clever old friend of mine to reduce noise overnight on the pumped system on his boat, worked so well I asked for one but never got round to fitting it as I changed my boat.Β The way I figure radiator type heating systems... At one end of the spectrum is webasto with a tiny efficient heat exchanger and suitably fast pump. At the other end is a purely thermal one with no pump attached to an inefficient back boiler with slow circulation. Mine's more like the second kind - inefficient back boiler but I bought a pump that's way too fast for that. I might have to slow it to 1/4 speed or less if that's possible. I expect it would still "work" at half speed, but without slowing it down more I'd always wonder if that would be better. I've done a slab of the plumbing - hooray! Just got to finish it, fix it down, swap stoves and flue, connect to back boiler, refill, sort the electric supply and controller, connect up and light the stove. I'm doing as much as possible before I let the stove go out. Bugger, I've barely started.
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Post by Deleted on Nov 30, 2019 19:59:12 GMT
In my fairly limited experience of using pwm on brushed motors you can slow them right down until it's barely rotating.
Have not used them on pumps but I did use a Shurflo pump motor to propel a kayak with a pwm controller at one time. Since replaced with a much more powerful brushless model aircraft motor.
They do usually give a 0-99% stepless range and some of the Pwm controllers actually have a 0-99 digital readout which could prove quite useful depending on your anorakishness.
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Post by lollygagger on Nov 30, 2019 20:02:03 GMT
In my fairly limited experience of using pwm on brushed motors you can slow them right down until it's barely rotating. Have not used them on pumps but I did use a Shurflo pump motor to propel a kayak with a pwm controller. They do usually give a 0-99% stepless range and some of the Pwm controllers actually have a 0-99 digital readout which could prove quite useful depending on your anorakishness. Though I do like switches, I'm more of a gauge man myself so that does appeal. If I could get a gizmo, really not so different than a gauge, to read a thermocouple output and send it on to a 0-99% pwm controller somehow I could vary the speed according to the stove output temp. I'd be in heaven then, but this is way beyond my abilities. Perhaps Nick can sit in front of his log fire next time it's too cold to glide and design me one.
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Post by Jim on Nov 30, 2019 20:06:58 GMT
Phwoar!
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Post by Deleted on Nov 30, 2019 20:11:18 GMT
In my fairly limited experience of using pwm on brushed motors you can slow them right down until it's barely rotating. Have not used them on pumps but I did use a Shurflo pump motor to propel a kayak with a pwm controller. They do usually give a 0-99% stepless range and some of the Pwm controllers actually have a 0-99 digital readout which could prove quite useful depending on your anorakishness. Though I do like switches, I'm more of a gauge man myself so that does appeal. If I could get a gizmo, really not so different than a gauge, to read a thermocouple output and send it on to a 0-99% pwm controller somehow I could vary the speed according to the stove output temp. I'd be in heaven then, but this is way beyond my abilities. Perhaps Nick can sit in front of his log fire next time it's too cold to glide and design me one. Not looked into it but I think there might be a device on the market for that already.
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Post by Deleted on Nov 30, 2019 20:16:13 GMT
I wonder if you could use a temperature sensing pwm fan speed controller but fit it to a pump and work out where to put the temp sensor by error and trial.
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Post by Deleted on Nov 30, 2019 21:13:51 GMT
Very kind of you, but I think I need something more variable. Ok it was designed by a clever old friend of mine to reduce noise overnight on the pumped system on his boat, worked so well I asked for one but never got round to fitting it as I changed my boat. I have just been out to find the device and I will have to retract part of the above! The application was designed by JW but it uses a standard RS components pc board 434 071 to drive the relay controlling the pump. The way it works is to switch the pump on for periods of time set by an internal trim pot, so variable but not in the way I think you want. It falls into those devices that are KISS which is what John was about. Right time to put the lid back on and return it to the void that is my junk collection.
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Post by lollygagger on Dec 14, 2019 9:54:29 GMT
Back to this --ing back boiler system. PMR thing works a treat. Plumber fixed my leaks for me. Flue welded and fitted. First impressions of the actual stove are good, it's no Morso Squirrel but it pumps out more heat than the one it replaced. Now the problem. It's utterly shite. After about 6 hours, the rad we particularly want to work got warm...the top half anyway. It's a way from the stove -10m or so. 3m 22mm pipe hold 1 liter so it's only 3 litres away or so. The return pipe wasn't even luke warm. All the other rads and calorifier were turned off at this point. It seems to work best with the pump turned up bit the basic problem persists - the stove is cooking the lounge occupants and the rad(s) are nowhere near hot enough. I'll play some more today. I note the Squirrel back boiler replaces the baffle plate whereas mine os the more common back wall type. Also note someone had painted it with gloss black heat resistant paint inside the stove. Other than that surely the ---ing thing should be able to heat one ---ing radiator? What now?
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Post by Jim on Dec 14, 2019 10:00:56 GMT
Slow down the pump? So the water gets hotter while it's in the fire. Put more coal on? I made a copper backboiler for a little cast iron range I used to have in my house, about 3x6 x 8 inch, it heated a couple of radiators, no pump needed cos it was in a house and radiators were upstairs.
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Post by peterboat on Dec 14, 2019 10:30:58 GMT
Pipework to large? or backboiler to small? The backboiler in my rayburn was to small so I changed it for a bigger one which has made a huge difference
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Post by lollygagger on Dec 14, 2019 10:39:22 GMT
I did measure mine but I can't find it. It's _30mm thick, the width of the fire between the bricks and height from grate to baffle plate.
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Post by Deleted on Dec 14, 2019 11:21:41 GMT
I would fit a 28mm flow pipe and take it from the boiler fitting to ceiling height vertically. Put a tee in and lead it through the cabin top. That's one vent in the system where any air can leave the system and boiling problem is taken care of outdoors. On the other leg of the tee add your continuing flow pipe with a slight downward slope. If the boat tends to be higher at the front than the back (spirit level on ceiling) that would probably be enough downward to let air get out.
Once you get the thermosyphon working it has no option but to do it.
It's a bit untidy but it really works well or at least did on my Rayburn which admittedly had a much larger back boiler. Any odd pipes in silly places can be used to hang clothes and towels on.
Depends on fire location mine was central and I was able to use the ceiling for the flow pipe back to the engine room as boat was always up a little at the front anyway. So the pipe was simply clipped to ceiling lining.
I put the header tank directly against the cabin top by cutting out lining and insulation, again with a bulkead fitting to outside to take care of boiling problems, condensation and filling it. That way header tank was higher than the elbow/tee at the top of the flow pipe. Obvious requirement.
Header tank plumbed into the return pipe which was on the floor, using a vertical 15mm pipe to a reducer tee. Rads connected across flow and return with a decent temperature differential and they got hot fast including the one in the engine room which was about 7 metres away.
But that Rayburn had a huge boiler so this could all be no use anyway.
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Post by Andyberg on Dec 14, 2019 11:44:34 GMT
Have you isolated your webasto from the other end of your rad circuit? If not, your webasto waterpump will be preventing flow and causing exactly the symptoms youβre describing When I run my webasto I have webasto taps open and red tap closed as in this pic, so flow is going thro right hand pipe to rads / colorifier / underfloor heating then returning to webasto via left hand pipe. With Bubble stove running I shut the webasto taps and open the red tap in the middle to let flow straight thro along top pipe and back round via the return pipe below. 28mm pipe is far better for the job too!
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Post by lollygagger on Dec 14, 2019 11:55:30 GMT
Thanks Andy, yes I've isolated the webasto and it's flow through header tank. The coolant has to go through any rads or the calorifier that are on to get back to the return pipe. I am not going to change from 22mm to 28mm. The back boiler is supposed to be 2kw, not massive but it should manage one radiator!
Now trying a small rad near the stove with the pump speed really slow just for a test. Not good.
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Post by peterboat on Dec 14, 2019 15:09:31 GMT
Thanks Andy, yes I've isolated the webasto and it's flow through header tank. The coolant has to go through any rads or the calorifier that are on to get back to the return pipe. I am not going to change from 22mm to 28mm. The back boiler is supposed to be 2kw, not massive but it should manage one radiator! Now trying a small rad near the stove with the pump speed really slow just for a test. Not good. Has the stove got a baffle plate in it? and that 2 KW backboiler is with the stove on full bore like my old rayburn backboiler. It maybe that all your heat is going straight out of the flue my rayburn has a flue box wih a closing baffle plate so it restricts the heat going up the flue and really makes a difference with heating up the backboiler and hence giving hotter rads and hotter oven. Where are you based at the moment mate?
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