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Rethinking the layout of my unvented hot water cylinder

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Following some excellent tips and pointers from @PeterW, @AliG and others on this site, I'm starting to think that I need to reconsider the location of my unvented indirect hot water tank.

 

My question is: in an ideal world, if you have a three storey house, with the boiler on the bottom storey, the two main bathrooms on the middle storey and an extra bathroom that will only get used at weekends on the top storey, on which storey should the unvented indirect hot water tank be sited, or does it not matter? Does gravity have an impact? I guessed gravity wouldn't matter when hot water is going from the boiler to the cylinder, but that gravity would help when water is going from the cylinder to the rest of the house and on that basis, and the fact I wanted to be efficient with use of space, I planned on having the cylinder in the loft. But that is just my guesswork, as my builder is yet to introduce me to his truant heating engineer.

 

Should the cylinder actually be nearer the boiler to reduce heat loss along the journey between the two, or can that just be mitigated with pipe insulation? The boiler could probably go in the loft as well - it doesn't have to go in the ground floor.

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With heindseight I'd put it closest to the point of most frequent use. This may be to serve the kitchen/utility or a compromise of a mid point between kitchen and bathrooms. Ignore the infrequent room (use small bore pipe for faster hot water response to basin) and don't stress over the minor pressure loss due to height, it matters on a gravity system but less so on a pressurised one.

 

 

 

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I planned my tank on the first floor within feet of three bathrooms. However, it would have been 15m from my ashp. This is not a good thing my ashp installer has informed me. I am therefore re locating both buffer and heating tanks near to the ashp and running a pipe with bronze return to the bathroom location. This will be kept warm, and to save water, by a small grundfos pump which will be triggered by PIR sensors in the bathrooms. Just when I thought I had a great plan it was in an instant by the installer.

 

Lesson - tank location also depends on what method you use to heat your water

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3 hours ago, Tom's Barn said:

This is not a good thing my ashp installer has informed me. I am therefore re locating both buffer and heating tanks near to the ashp


Why..? All primary pipe work from the ASHP to the UVC and the buffer should be properly insulated and it will not matter how far it is if correctly sized. It is minimum 22mm, ideally 28mm if long distances. There are no maximums in the MIs for the ASHPs I’ve seen. 

Before you compromise your long term usage of the system, I’d ask why he thinks that first and ask for the evidence. 

 

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3 hours ago, PeterW said:


Why..? All primary pipe work from the ASHP to the UVC and the buffer should be properly insulated and it will not matter how far it is if correctly sized. It is minimum 22mm, ideally 28mm if long distances. There are no maximums in the MIs for the ASHPs I’ve seen. 

Before you compromise your long term usage of the system, I’d ask why he thinks that first and ask for the evidence. 

 

Thanks Peter. I am meeting him next week so we have this as my first agenda item. Many thanks

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Probably cause it makes the install harder for the ASHP person, like most trades unless advised otherwise they will take the path of least resistance and install what is easiest for them..  especially if there is no specification/ consultant/M&E drawings...

 

 

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Very often an ASHP comes with it's own sensor to measure the tank temperature and it is a pre made length, often 10 metres.  I think some people don't realise you can extend this which you may need to do if the tank is further away.

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On 17/01/2021 at 08:42, PeterW said:


Why..? All primary pipe work from the ASHP to the UVC and the buffer should be properly insulated and it will not matter how far it is if correctly sized. It is minimum 22mm, ideally 28mm if long distances. There are no maximums in the MIs for the ASHPs I’ve seen. 
Before you compromise your long term usage of the system, I’d ask why he thinks that first and ask for the evidence. 

+1

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