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Post by lollygagger on Oct 20, 2019 9:25:33 GMT
Could anyone recommend a reliable reasonably quiet 12V heating pump for a solid fuel back boiler?
I already have a Webasto radiator and hot water system, I thought I'd add a bypass with a manual valve at that end of the system where there is also an expansion tank (the water appears to pass through this rather than T'd off).
Am I right thinking I should control the pump with a thermostat? Attached to the outside of the back boiler?
The expansion tank is 40ft away from the back boiler. Is that safe? Should I have some kind of emergency blow off valve close to the boiler?
Any other tips or safety advice?
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Post by lollygagger on Oct 20, 2019 9:28:46 GMT
One more thing - what temp for the pump control thermostat?
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Post by Jim on Oct 20, 2019 9:57:47 GMT
Could anyone recommend a reliable reasonably quiet 12V heating pump for a solid fuel back boiler? I already have a Webasto radiator and hot water system, I thought I'd add a bypass with a manual valve at that end of the system where there is also an expansion tank (the water appears to pass through this rather than T'd off). Am I right thinking I should control the pump with a thermostat? Attached to the outside of the back boiler? The expansion tank is 40ft away from the back boiler. Is that safe? Should I have some kind of emergency blow off valve close to the boiler? Any other tips or safety advice? There is a thread dedicated to emergency blow offs thunderboat.boards.net/thread/5534/acceptable-women-fart-bed
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Post by peterboat on Oct 20, 2019 11:09:13 GMT
Cars have them for heating systems now days so look on line for one, they are reliable and cheap normaly 5/8ths outlets which is a good size, remember to put it pushing in to the boiler so it runs cooler
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Post by Telemachus on Oct 20, 2019 12:13:56 GMT
I recommend these for “cheap and cheerful” but quite effective. We have one running our engine to central heating heat exchanger system. Been working fine for about 6 years, but it only gets intermittent usage of course: shop.solarproject.co.uk/catalog/product_info.php?products_id=10&osCsid=3e1e5077941aca77bafd009f56cb5bd4Personally I wouldn’t want just one pump running from one power supply to stop a back boiler from boiling though. And if your header tank is 40’ away, that is a lot of hot antifreeze mix /steam to be sprayed out all over the boat
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Post by lollygagger on Oct 20, 2019 12:29:15 GMT
I recommend these for “cheap and cheerful” but quite effective. We have one running our engine to central heating heat exchanger system. Been working fine for about 6 years, but it only gets intermittent usage of course: shop.solarproject.co.uk/catalog/product_info.php?products_id=10&osCsid=3e1e5077941aca77bafd009f56cb5bd4Personally I wouldn’t want just one pump running from one power supply to stop a back boiler from boiling though. And if your header tank is 40’ away, that is a lot of hot antifreeze mix /steam to be sprayed out all over the boat Yes it's a worry, both those points. Two parallel motors maybe and hence my emergency blow-off valve question, I don't really want a header tank in the lounge!
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Post by Telemachus on Oct 20, 2019 13:28:30 GMT
I recommend these for “cheap and cheerful” but quite effective. We have one running our engine to central heating heat exchanger system. Been working fine for about 6 years, but it only gets intermittent usage of course: shop.solarproject.co.uk/catalog/product_info.php?products_id=10&osCsid=3e1e5077941aca77bafd009f56cb5bd4Personally I wouldn’t want just one pump running from one power supply to stop a back boiler from boiling though. And if your header tank is 40’ away, that is a lot of hot antifreeze mix /steam to be sprayed out all over the boat Yes it's a worry, both those points. Two parallel motors maybe and hence my emergency blow-off valve question, I don't really want a header tank in the lounge! I don’t think there is much point in having parallel pumps without some means to know that one pump has gone faulty - otherwise you just end up running on 1 pump for a few years of blissful ignorance before that too fails and then you have boiling anti-freeze all over the boat. And especially if you have a single electrical supply. You can’t really have a “blow off” valve that relies on much pressure build up, since the pressure will seek the easiest route which is via the header tank. You would need some other point of escape for the coolant, that is vertically between the water level in the header tank, and the top of the header tank. Tricky! Or you could go for a sealed system with a couple of pressure relief mechanisms, but I don’t really like the idea of that. Ive vaguely thought of doing this with our stove: One pump with a normal electrical supply, controlled by a temperature switch on the boiler, maybe set at around 50-60C. And another pump in parallel controlled by a switch set to say 90C, powered from a small gel cell (7AH or whatever), with a buzzer in parallel so you know if it has activated. And a push button to manually power the backup pump so you can test it works from time to time. And a means to keep the little battery trickle charged. When you parallel the pumps you need to include non-return valves to stop the one pump “short circuiting” the other. I’ve used these low activation pressure non-return valves, also from Solarproject, to allow my radiators to be either fed from the Mikuni, or from my pump heat exchanger system, without any back flow through the non-active heat source and without needing to operate any valves. They seem to work well: shop.solarproject.co.uk/catalog/product_info.php?cPath=8&products_id=17
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Post by Gone on Oct 20, 2019 14:01:23 GMT
Yes it's a worry, both those points. Two parallel motors maybe and hence my emergency blow-off valve question, I don't really want a header tank in the lounge! .......................When you parallel the pumps you need to include non-return valves to stop the one pump “short circuiting” the other. I’ve used these low activation pressure non-return valves, also from Solarproject, to allow my radiators to be either fed from the Mikuni, or from my pump heat exchanger system, without any back flow through the non-active heat source and without needing to operate any valves. They seem to work well: shop.solarproject.co.uk/catalog/product_info.php?cPath=8&products_id=17If they are centrifugal pumps then I don’t see why you would not put them in series as the water will flow through the non spinning pump without too much loss. If loss is a worry, make the pump that is normally off a bit on the big side so it has little restriction, if/when it does run it will take slightly more power but as it is an emergency back-up I don’t see that as a problem.
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Post by lollygagger on Oct 20, 2019 14:42:46 GMT
Part of my nervousness is that the existing heating circuit is 100% plastic push fit. I'll be doing everything up to the existing flow and return pipes in copper to have some sort of chance of isolating the pump/boiler loop.
If I could detect no flow in that loop and isolate it with solenoid valves then have a PRV to let the steam out would that work? Or am I over thinking this.
Hmm crap idea, it would be impossible to start it pumping to get the flow to open the valves.
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Post by Telemachus on Oct 20, 2019 14:47:01 GMT
.......................When you parallel the pumps you need to include non-return valves to stop the one pump “short circuiting” the other. I’ve used these low activation pressure non-return valves, also from Solarproject, to allow my radiators to be either fed from the Mikuni, or from my pump heat exchanger system, without any back flow through the non-active heat source and without needing to operate any valves. They seem to work well: shop.solarproject.co.uk/catalog/product_info.php?cPath=8&products_id=17If they are centrifugal pumps then I don’t see why you would not put them in series as the water will flow through the non spinning pump without too much loss. If loss is a worry, make the pump that is normally off a bit on the big side so it has little restriction, if/when it does run it will take slightly more power but as it is an emergency back-up I don’t see that as a problem. Yes you could put them in series I suppose, but there would be some flow restriction and they are not particularly powerful. I would suggest that series installation intrinsically increases power consumption and probably noise (pump is working harder) but whether by a significant amount, I don't know. Those low opening pressure non-return valves seem to work pretty well.
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Post by Telemachus on Oct 20, 2019 14:49:35 GMT
Part of my nervousness is that the existing heating circuit is 100% plastic push fit. I'll be doing everything up to the existing flow and return pipes in copper to have some sort of chance of isolating the pump/boiler loop. If I could detect no flow in that loop and isolate it with solenoid valves then have a PRV to let the steam out would that work? Or am I over thinking this. Hmm crap idea, it would be impossible to start it pumping to get the flow to open the valves. I think anything deliberately designed to increase the pressure is probably a bad thing. I suggest there are two design approaches, one is to make the system tolerant of pump failure by venting the boiling coolant in a non-catastrophic way. The other is to have redundancy so as to assure that the probability of circulation failure is vanishingly small. I prefer the latter tactic.
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Post by lollygagger on Oct 20, 2019 14:52:51 GMT
Belt and braces, however vanishingly small the possibility of failure, it's still there. Would a simple vent pipe from the highest boiler pipe work? Onto the roof perhaps? I wonder it that would be high enough to stop the pump emptying the system onto the roof.
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Post by Gone on Oct 20, 2019 14:55:56 GMT
Part of my nervousness is that the existing heating circuit is 100% plastic push fit. I'll be doing everything up to the existing flow and return pipes in copper to have some sort of chance of isolating the pump/boiler loop. If I could detect no flow in that loop and isolate it with solenoid valves then have a PRV to let the steam out would that work? Or am I over thinking this. If the pump fails the water in the boiler will get hotter until it turns into steam, there is a massive volume expansion which will create enough pressure to blast any coolant out of the way. The further the distance to the prv the greater the volume of very hot coolant that will be released. The prv will probably not provide enough release to avoid having lots of coolant pushed back into the header tank, which may or may not overflow. However if you seal the system in an over heat situation you need to be confident that the prv can release the pressure fast enough otherwise the pressure could cause a weak joint to burst. I would keep it simple and just go with a big header tank kept fairly empty to allow space for expelled fluid.
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Post by lollygagger on Oct 20, 2019 15:28:55 GMT
The solution appears to be add a header tank close to the boiler, connected to the upper boiler pipe. It'll have to go on the kitchen wall, I can hide it with a faux cupboard.
Then connect the flow and return at the webasto end, cutting out the Webasto and the existing flow-through header tank. If I do that with isolating valves I can revert to Webasto heating.
So I can revert to Webasto, I guess I'd have to site my new expansion tank so the bottom was approximately level with the coolant level in the existing flow-through one that likes to be at least 1/2 full.
Belt and braces would be parallel pumps so at least if we're about, which someone usually is, we can switch pumps. If not it'll gravity feed/boil itself because the most of each radiator is higher than the back boiler - If I loop the the boiler pump pipes higher than the top of the radiators that might stop that?
What you reckon?
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Post by lollygagger on Oct 22, 2019 17:05:56 GMT
This is probably a silly question, but could someone please describe the electrical circuit for a thermostatically controlled pump. Ta. The one I ordered probably goes a bit fast. Can I slow it with a cheap pulse width type control?
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