Horizontal UVC vs vertical UVC

[Adsibob]

I'm sure this has been covered before, but after various searches I couldn't find a post on it, other than the odd comment from @Nickfromwales about how horizontal cylinders are okay.

I was about to order a horizontal UVC from Cylinders2Go. Spoke to Trevor who was very nice and he asked me why I wasn't getting a vertical one. I explained my space issues and he said if I can squeeze in a vertical one somehow I will have a more efficient system. Now that is a truism, I'm sure. But my question is how much more efficient will the system be? Say with a 400L tank, both the horizontal and vertical one made by Telford is the same dimension and so has the same heat loss of 2.58kW per 24. I get that hot water is lighter than cold and so rises, giving better stratification, but how much is this going to make a difference in practice? I'm sure it means the boiler needs to run more, but how much more?

 

Other option I'm considering is a vertical 380L which is taller and slimmer than the 400L.

 

It would be a real compromise to our house if we have it vertical, but I'm concerned about getting massive gas bills! (Changing to a different energy source isn't an option unfortunately.)

[Adsibob]

Or is it just a case of adding a pump to the cylinder to mix the water and accept that there won't be any stratification.

[Nickfromwales]

Depends if you have PV and want to ‘stir’ the tank when diversion is happening, as, tbh, that’s when I’d recommend fitting the pump to aid stratification. 
HRC pump will sort that if not  ?

 

[Adsibob]

4 hours ago, Nickfromwales said:

Depends if you have PV and want to ‘stir’ the tank when diversion is happening, as, tbh, that’s when I’d recommend fitting the pump to aid stratification. 
HRC pump will sort that if not  ?

 

No PV, just a gas boiler system. Not sure how a Hot return circuit pump would fix the issue. Does it just mix the water in the tank so that it is all hot when heated? 

Edited September 20, 2021 by Adsibob

[Nickfromwales]

4 hours ago, Adsibob said:

No PV, just a gas boiler system. Not sure how a Hot return circuit pump would fix the issue. Does it just mix the water in the tank so that it is all hot when heated? 

In a nutshell, yes. The only issue with an HRC is that any serviced DHW runs, plus the HRC return pipework, need to be super well insulated to stave off heat loss in the connective pipework.

 

With a modern, well insulated UVC you should not really have to worry about the extra bit of heating input from the boiler when using any pump to stratify, as these lose very little heat per 24hrs tbh. They are designed to be 'fully' heated during normal ( vertical ) service plus when 'stirred', the horizontal units will give much closer to their stated useful DHW capacity. See page 18 HERE

 

If you don't want to install a full HRC, then just fit the stratification pump and power it off the switched live of the DHW zone valve ( so that only runs during a reheat cycle thus filling the UVC to the max with heat energy ). Just remember to insulate the pump and pipework as much / best as possible. There are EPS pump body jackets available to make that easier / more practical.

[Adsibob]

On 21/09/2021 at 07:37, Nickfromwales said:

With a modern, well insulated UVC you should not really have to worry about the extra bit of heating input from the boiler when using any pump to stratify, as these lose very little heat per 24hrs tbh. They are designed to be 'fully' heated during normal ( vertical ) service plus when 'stirred', the horizontal units will give much closer to their stated useful DHW capacity. See page 18 HERE

Thanks @Nickfromwales but unfortunately that link doesn't seem to work. My pipes will mainly be plastic with decent insulation.

Are you saying that a horizontal cylinder will actually hold more hot water than a vertical one?

[Nickfromwales]

15 hours ago, Adsibob said:

Thanks @Nickfromwales but unfortunately that link doesn't seem to work. My pipes will mainly be plastic with decent insulation.

Are you saying that a horizontal cylinder will actually hold more hot water than a vertical one?

https://www.installershub.co.uk/wp-content/uploads/Telford-Cylinder-Installation-Guide.pdf

 

If the pump is used to ‘stir’ the tank then possibly yes, but in regular service I would upsize by at least 50L to mitigate.
 

For the last one I did I assumed 180L would suffice but I fitted a 250L, but that was also driven by the PV array that was south facing and so gave them some extra room to absorb the excess via the diversion controller. I treat each instance as unique and size to the application / circumstances, but with a minimum threshold that the dwelling requires to get through a 24hr period. 

Edited September 29, 2021 by Nickfromwales