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Discuss Thermal store for Solar PV and oil - 2 immersions? in the Renewable Energy area at PlumbersForums.net

Hi,

I'm new here and have arrived on this forum as I have a question on the above.
I'm talking to a solar PV supplier about a 4kw system with which will come and Eddi controller which can feed 2 immersion heaters.

I'm a bit lost when it comes to the cylinders/thermal stores. We currently have oil fired central heating and would like to compliment this so:

- Should I just get a large unvented cylinder with 2 immersions?
or
- Is there thermal store option that would be better - If so what are the options?
 

gmartine

Gas Engineer
Unvented as you only have one indirect heat source (oil).

Two immersions on a cylinder are never used simultaneously because of the load, the upper one will be used first to heat the smaller amount of water first then once it's up to temp the lower one is switched in if there's enough sun.
 
Unvented as you only have one indirect heat source (oil).

Two immersions on a cylinder are never used simultaneously because of the load, the upper one will be used first to heat the smaller amount of water first then once it's up to temp the lower one is switched in if there's enough sun.
Ok great - that much I understand I can see examples of such cylinders.

What about going a stage further where you incorporate a thermal store to supplement heating the rads - Or am I stretching too far?
 

gmartine

Gas Engineer
Just reconsider the last part of my last sentence..."if there is enough sun"

Considering it's size I'd settle on your array's ability to hopefully provide you with enough hot water because it will certainly decrease as Winter approaches just as your heating demand increases.
 
Just reconsider the last part of my last sentence..."if there is enough sun"

Considering it's size I'd settle on your array's ability to hopefully provide you with enough hot water because it will certainly decrease as Winter approaches just as your heating demand increases.
After some consideration of thermal storage solutions e.g. Maxipod and lack of decent case studies and testimonials I have indeed decided just to go the hot water route.

Is there such a thing as a cylinder with 2 immersions in a horizontal format? I want to go big and a loft install would really help me.
 

SimonG

Plumber
Advent Win
Try to stay away from a horizontal cylinder if possible. Fitted a couple, won't be fitting anymore.
 
Can I ask why? I'm guessing the laws of physics makes a vertical solution more efficient, heat rises etc..
That's one reason; mixing by convection is relatively ineffective in horizon cylinders so you get 'stratification', i.e a large hot-cold gradient, which needs an extra pump to stir things up. They also have a big footprint, which makes them harder to install in many situations, which means they sell fewer and prices are often higher.
 
Ok that all makes sense. Any recommendations then for vertical ones? 5 bed 3 bath house with 4 people so thinking 250 litre +
I just want to exploit as much of the solar PV as possible.
 

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