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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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Vaillant VCW 242 - Can I preheat the incoming water
Hi all.
I have done several adaptions to my boiler including supplementing the central heating with a hot pre feed so my boiler runs 100% on the external source via a plate heat exchanger. This has worked extremely well over the winter, and the same heat source will be heating the pool ( when I set it up sometime soon ). I have been toying with the idea of linking onto this loop for a second time, that's already in place, using another plate heat exchanger to run the hot water for the house. The loop can run at anywhere from 62 degrees up to around 90 degrees c depending on my choice and I was thinking that if I can link into my cold feed in ( the same as I have linked into the CH loop to put hot water pre boiler ) I should be able to stop the boiler firing up and therefore use no gas. I have read what feels like hundreds of articles but I cannot find whether or not I can do this on my old boiler. Has anyone tried this before or can I simply not feed hot water into the boiler? Hope someone can help. Thanks David -- for full context, visit https://www.homeownershub.com/uk-diy...r-1357877-.htm |
#2
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Vaillant VCW 242 - Can I preheat the incoming water
On Tuesday, 23 April 2019 21:44:06 UTC+1, Davidcorlett wrote:
Hi all. I have done several adaptions to my boiler including supplementing the central heating with a hot pre feed so my boiler runs 100% on the external source via a plate heat exchanger. What is this 'hot prefeed'. What is this 'external source'. This has worked extremely well over the winter, and the same heat source will be heating the pool ( when I set it up sometime soon ). I have been toying with the idea of linking onto this loop for a second time, that's already in place, using another plate heat exchanger to run the hot water for the house. The loop can run at anywhere from 62 degrees up to around 90 degrees c depending on my choice and I was thinking that if I can link into my cold feed in ( the same as I have linked into the CH loop to put hot water pre boiler ) I should be able to stop the boiler firing up and therefore use no gas. I have read what feels like hundreds of articles but I cannot find whether or not I can do this on my old boiler. Has anyone tried this before or can I simply not feed hot water into the boiler? Hope someone can help. Thanks David There's no harm is having another heat source in your CH primary loop of course. As for the cold feed I don't know, can you examine/identify the materials in the relevant part of the boiler? Is there a fault code in the manual for input too hot? What will it modulate down to? How are you going to control temp for legionella safety? There are others here with much more knowledge & experience on heating systems. But the website you're using is blocked by most folk here. You can get here via google groups or a newsreader. NT |
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Vaillant VCW 242 - Can I preheat the incoming water
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Vaillant VCW 242 - Can I preheat the incoming water
replying to tabbypurr, Davidcorlett wrote:
I am running a bairan 120p waste oil burner in a camray CH boiler unit. It heats and maintains a 65-90 deg C temp. This is the loop, as it is external to the house. The loop runs up to the house where I have linked it into the CH in feed via a plated heat exchanger. I am fairly certain there are no plastic parts in these older boilers but I am not sure if I feed in water via the heat exchanger ( so the loop water will _never mix _ with the shower or tap water so no legionella problem ) will the boiler just continue to heat. Don't want super heater hot water or to destroy the boiler or worse.... Has worked really well through these last months and save me at least 60% of my last original gas bill. Just want to utilise the remaining heat for the hot water. Thanks for the reply. David -- for full context, visit https://www.homeownershub.com/uk-diy...r-1357877-.htm |
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Vaillant VCW 242 - Can I preheat the incoming water
replying to Brian Gaff, Davidcorlett wrote:
Hi Brian, I had looked into this option but the initial outlay was not going to justify the expense. It would have taken several years to recoup the costs. A roof mounted unit like those in Spain etc are really good and definitely a cheaper option but I just want to add onto what I already know works, as the main costs of the unit, burner, pipework, insulation, supports etc had already been spent. I have another 20 plate heat exchanger and it would only be integrating this new exchanger into the cold in feed. If I can get this to work, the boiler is only then a means of heat transfer and pump. Have already got back what I spent to put this together last year as I sold the oil burner which came with the boiler, that paid for most of the bits and the plate heat exchanger. Everything's sadly always on a tight, if not non existent budget -- for full context, visit https://www.homeownershub.com/uk-diy...r-1357877-.htm |
#6
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Vaillant VCW 242 - Can I preheat the incoming water
On Monday, 29 April 2019 15:14:04 UTC+1, Davidcorlett wrote:
replying to tabbypurr, Davidcorlett wrote: I am running a bairan 120p waste oil burner in a camray CH boiler unit. It heats and maintains a 65-90 deg C temp. This is the loop, as it is external to the house. The loop runs up to the house where I have linked it into the CH in feed via a plated heat exchanger. I am fairly certain there are no plastic parts in these older boilers but I am not sure if I feed in water via the heat exchanger ( so the loop water will _never mix _ with the shower or tap water so no legionella problem ) will the boiler just continue to heat. Don't want super heater hot water or to destroy the boiler or worse.... Has worked really well through these last months and save me at least 60% of my last original gas bill. Just want to utilise the remaining heat for the hot water. Thanks for the reply. David Every sane boiler has a temp detector that reuslts in it cutting heat when it reaches target temp, and has had for a long old time. It's certainly not going to overheat. The question is what the onboard software will make of the initial high temp, it might assume it's an internal error & shut down. If it does do that, perhaps you could use a thermostatic mixer valve to remedy things by having it bypass the boiler when the water's already hot, and go through the boiler when it's not. Feed your preheated feed into the TMV's output. I've not tried doing that, just an idea to consider. NT |
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Vaillant VCW 242 - Can I preheat the incoming water
replying to tabbypurr, Davidcorlett wrote:
I see what you're getting at. Am just wondering if I could do it more simply. Just get the boiler to pump when the tap is opened, but not fire up? I am guessing that the control unit would be the point of focus but after all, if the drop or flow caused by the opening of the tap causes a sensor to then run the pump and ignite the boiler, I just want to block that firing up. All manuals do the fault diagnosis and fix to create the ignition, not to stop it. Will keep thinking. Thanks for all the advice. Very much appreciated. David -- for full context, visit https://www.homeownershub.com/uk-diy...r-1357877-.htm |
#8
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Vaillant VCW 242 - Can I preheat the incoming water
On Friday, 3 May 2019 16:14:04 UTC+1, Davidcorlett wrote:
replying to tabbypurr, Davidcorlett wrote: I see what you're getting at. Am just wondering if I could do it more simply. Just get the boiler to pump when the tap is opened, but not fire up? I am guessing that the control unit would be the point of focus but after all, if the drop or flow caused by the opening of the tap causes a sensor to then run the pump and ignite the boiler, I just want to block that firing up. All manuals do the fault diagnosis and fix to create the ignition, not to stop it. Will keep thinking. Thanks for all the advice. Very much appreciated. David I doubt you can modify what it does & not have it shut down reporting a fault. You might just get away with heating its internal store externally, maybe. That way it doesn't need to do anything outside its usual routine. NT |
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