Heating system design

jonny-b-

Hi everyone,
We are currently at the stage of deciding what heating system to install in our self build. The house is 2300sq ft and will be very well insulated with MHRV installed also.

The plan was to install a 16.5kw stove (11.5kw to the back boiler), 50 solar tubes and as we have a dual fuel cooker in the kitchen a gas boiler to top up the tank on days when we don't feel like lighting the stove or we are away during the winter.
I was hoping to use a thermal store, possibly a 500 litre akvaterm solar plus tank with the stove and gas connected directly to the store and the solar using 2 coils (upper and lower)
DHW would be drawn off through 2 coils also, the bottom coil preheating the DHW and the top coil heating it fully.

I have had two plumbers around to look at the house and they both preferred using a 300 litre triple coil tank, with gas on top, stove in the middle and solar at the bottom.

This got me wondering which system would be best? With the thermal store it soaks up any solar energy over the winter, even raising the tank by a few degrees makes the stoves job easier heating the house (don't get my wrong I know it won't provide much to the winter heating demand).
The plumber was concerned about the recovery rate of the DHW coil in the thermal store.

Any help on this would be great.

J

JohnnieK

this sounds like a good suggestion to me. It will also depends on what your heating your house with. If it's standard rads then the pull on the thermal store will be high especially during the winter.
It would work best with low output heating like underfloor or low temp rads. If you are using standard rads you could be looking at something in the region of 1000l thermal store so the impact of the rads pulling off it in the winter will not affect your domestic hot water.

Why were they concerned about the coil?

jonny-b-

We would be using low temp radiators.
The reason the plumbers were concerned about the coil was the same as you mentioned, the heating drawing off most of the water from the tank leaving the DHW coil short.

JohnnieK

jonny-b- wrote: »

We would be using low temp radiators.
The reason the plumbers were concerned about the coil was the same as you mentioned, the heating drawing off most of the water from the tank leaving the DHW coil short.

The DHW would be from the store it's self not a coil. There are ways of sizing these things correctly so no effects would be felt. Are they making this up as they go along or are they doing the maths? It is important this is done right now so you will have a system that ticks along hassle free.
Where i get my cylinders from i sit down with the engineer and with the engineer and with the necessary calculations come up with a plan.
Hope this helps.

jonny-b-

Thanks for the info JohnnieK, in this particular thermal store the DHW is drawn from a coil, pre heated at the bottom and then topped up by the upper coil therefore providing Hygienic DHW and aiding stratification of the store . I presume they are doing the maths for my system.

Outkast_IRE

I would agree with JohnnieK here i would use a thermal store but 500 ltr size would be too little imo , you should be talking about a 1000 ltr plus, just ensure it is being sized correctly, nothing worse than spending good money on this systems and finding out something is sized incorrrectly.

EHP

jonny-b- wrote: »

Hi everyone,
We are currently at the stage of deciding what heating system to install in our self build. The house is 2300sq ft and will be very well insulated with MHRV installed also.

The plan was to install a 16.5kw stove (11.5kw to the back boiler), 50 solar tubes and as we have a dual fuel cooker in the kitchen a gas boiler to top up the tank on days when we don't feel like lighting the stove or we are away during the winter.
I was hoping to use a thermal store, possibly a 500 litre akvaterm solar plus tank with the stove and gas connected directly to the store and the solar using 2 coils (upper and lower)
DHW would be drawn off through 2 coils also, the bottom coil preheating the DHW and the top coil heating it fully.

I have had two plumbers around to look at the house and they both preferred using a 300 litre triple coil tank, with gas on top, stove in the middle and solar at the bottom.

This got me wondering which system would be best? With the thermal store it soaks up any solar energy over the winter, even raising the tank by a few degrees makes the stoves job easier heating the house (don't get my wrong I know it won't provide much to the winter heating demand).
The plumber was concerned about the recovery rate of the DHW coil in the thermal store.

Any help on this would be great.

J

Go with the thermal store. I have fitted a number of systems this way and you will have no issue with the recovery of the DHW coil. The smallest tank I have used though is an 800ltr, but this is supplying enough hot water for a hairdressers and a family home with 5 living in it. This system will also make your stove more efficient and often times the stored excess heat from the stove will provide you with your heating in the mornings before lighting the stove again, the most important thing with this type of installation is the controls and also fit a mixing valve to the heating system so if the thermal store is at a high temperature like 80deg you can reduce the temp to your heating system and prolong the use of your stored heat. Make sure the stove is not controlled by a pipe stat as this will cause your tank to be cooled, Id recommend a temperature difference controller there is ones that are specific for this.

JD6910

hi folks,

who would usually do the sizing of the thermal store - the plumber or the thermal store supplier???

will the system work as a high temp system if you keep the DHW in a seperate 300L tank and therefore keep the thermal store seperate. the solar and stove do as much of the hard work as they can and the gas tops up the thermal store the remaining few degrees.

how about 300L DHW tank, 500L thermal store and 80 tubes of solar???