My solar PV system, produces a significant amount of unused electricity.

I have a Thermal store based heating system .... providing mains
pressure DHW off one heat exchanger and underfloor heating from the
other ... the water content of store being circulated around the boiler
when heat demand is called.

A consideration is to install a 2nd hot water cylinder, and use the
excess PV power to feed an immersion heater .... creating a large store
of heat.

Any call for DHW will result in thye incoming cold mains being
pre-heated by this store .... when store is depleted, the normal heat
exchanger function within the Thermal store would maintain DHW supply,
topped up if necessary by boiler.


I did ask a few weeks back about just using Solar PV excess direct into
Thermal store immersion, but as this is kept 'at temp' don't really see
a way to easily do that.

This pre-heat method would seem a suitable alternative ... and using the
mass of the water as an energy store.

On 03/11/2015 18:03, rick wrote:

I did ask a few weeks back about just using Solar PV excess direct into
Thermal store immersion, but as this is kept 'at temp' don't really see
a way to easily do that.

You need to reprogram it so the heat store isn't kept at full temp to
make space for the solar energy, or fit a new immersion at a lower point
so the solar energy can heat the bottom of the tank.

You could export some of the energy so others benefit.

On 03/11/2015 18:25, dennis@home wrote:
On 03/11/2015 18:03, rick wrote:

I did ask a few weeks back about just using Solar PV excess direct into
Thermal store immersion, but as this is kept 'at temp' don't really see
a way to easily do that.

You need to reprogram it so the heat store isn't kept at full temp to
make space for the solar energy, or fit a new immersion at a lower point
so the solar energy can heat the bottom of the tank.

You could export some of the energy so others benefit.


reprogram what ? ......... there is a simple standard thermostat ...
set to 60 degrees.

I could set it to 450 and immersion stat to 60 but then tank would not
get warm enough when there is no PV power

On 04/11/2015 17:59, rick wrote:
On 03/11/2015 18:25, dennis@home wrote:
On 03/11/2015 18:03, rick wrote:

I did ask a few weeks back about just using Solar PV excess direct into
Thermal store immersion, but as this is kept 'at temp' don't really see
a way to easily do that.

You need to reprogram it so the heat store isn't kept at full temp to
make space for the solar energy, or fit a new immersion at a lower point
so the solar energy can heat the bottom of the tank.

You could export some of the energy so others benefit.


reprogram what ? ......... there is a simple standard thermostat ...
set to 60 degrees.

I could set it to 450 and immersion stat to 60 but then tank would not
get warm enough when there is no PV power



No timer so you can use solar during the day and switch in other sources
when its going dark?

On 03/11/15 18:03, rick wrote:
My solar PV system, produces a significant amount of unused electricity.

Dont worry, it wont last. Winter is nearly here.



--
the biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

On 03/11/2015 19:18, The Natural Philosopher wrote:
On 03/11/15 18:03, rick wrote:
My solar PV system, produces a significant amount of unused electricity.

Dont worry, it wont last. Winter is nearly here.



today is a particularly damp, grey & gloomy day ... just looked it
produced 2.2kWh today

On Wednesday, 4 November 2015 18:02:40 UTC, rick wrote:
On 03/11/2015 19:18, The Natural Philosopher wrote:
On 03/11/15 18:03, rick wrote:
My solar PV system, produces a significant amount of unused electricity.

Dont worry, it wont last. Winter is nearly here.



today is a particularly damp, grey & gloomy day ... just looked it
produced 2.2kWh today

Yep .
Both of mine did 2.1 each.

On Tuesday, 3 November 2015 18:04:02 UTC, rick wrote:
My solar PV system, produces a significant amount of unused electricity.

I have a Thermal store based heating system .... providing mains
pressure DHW off one heat exchanger and underfloor heating from the
other ... the water content of store being circulated around the boiler
when heat demand is called.

A consideration is to install a 2nd hot water cylinder, and use the
excess PV power to feed an immersion heater .... creating a large store
of heat.

Any call for DHW will result in thye incoming cold mains being
pre-heated by this store .... when store is depleted, the normal heat
exchanger function within the Thermal store would maintain DHW supply,
topped up if necessary by boiler.


I did ask a few weeks back about just using Solar PV excess direct into
Thermal store immersion, but as this is kept 'at temp' don't really see
a way to easily do that.

This pre-heat method would seem a suitable alternative ... and using the
mass of the water as an energy store.

I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again.


NT

On 03/11/2015 22:47, wrote:

I haven't run the numbers but expect you'd be better off all round to feed

the electric heat into the existing tank. The water wil go above set point,

and not need other heat sources until the temp is back down again.


NT

Can't do that ... max temp I can have store get to is 60 degree .......
any higher and you risk damage to underfloor heating pipes.

On 04/11/2015 18:04, rick wrote:
On 03/11/2015 22:47, wrote:

I haven't run the numbers but expect you'd be better off all round to
feed

the electric heat into the existing tank. The water wil go above set point,

and not need other heat sources until the temp is back down again.


NT

Can't do that ... max temp I can have store get to is 60 degree .......
any higher and you risk damage to underfloor heating pipes.

They should have a mixing valve to prevent the floors getting too hot.

On 04/11/2015 19:48, dennis@home wrote:
On 04/11/2015 18:04, rick wrote:
On 03/11/2015 22:47, wrote:

I haven't run the numbers but expect you'd be better off all round to
feed

the electric heat into the existing tank. The water wil go above set
point,

and not need other heat sources until the temp is back down again.


NT

Can't do that ... max temp I can have store get to is 60 degree .......
any higher and you risk damage to underfloor heating pipes.

They should have a mixing valve to prevent the floors getting too hot.


No the design has a mixing valve on the DHW take off, but the main feeds
off for the UFH loop is not via a mixing valve ... the main tank stat
prevents it going over 60 degree.

On 04/11/2015 21:35, rick wrote:
On 04/11/2015 19:48, dennis@home wrote:
On 04/11/2015 18:04, rick wrote:
On 03/11/2015 22:47, wrote:

I haven't run the numbers but expect you'd be better off all round to
feed

the electric heat into the existing tank. The water wil go above set
point,

and not need other heat sources until the temp is back down again.


NT

Can't do that ... max temp I can have store get to is 60 degree .......
any higher and you risk damage to underfloor heating pipes.

They should have a mixing valve to prevent the floors getting too hot.


No the design has a mixing valve on the DHW take off, but the main feeds
off for the UFH loop is not via a mixing valve ... the main tank stat
prevents it going over 60 degree.



60c is too high for underfloor heating IMO.
If someone collapsed on a floor that could get that hot they could die.
If it had a mixer then that would limit the temperature and allow more
heat to be stored by allowing a higher temp in the thermal store.

On Wednesday, 4 November 2015 21:35:08 UTC, rick wrote:
On 04/11/2015 19:48, dennis@home wrote:
On 04/11/2015 18:04, rick wrote:
On 03/11/2015 22:47, nt wrote:

I haven't run the numbers but expect you'd be better off all round to
feed
the electric heat into the existing tank. The water wil go above set
point,
and not need other heat sources until the temp is back down again.

Can't do that ... max temp I can have store get to is 60 degree ........
any higher and you risk damage to underfloor heating pipes.

They should have a mixing valve to prevent the floors getting too hot.

No the design has a mixing valve on the DHW take off, but the main feeds
off for the UFH loop is not via a mixing valve ... the main tank stat
prevents it going over 60 degree.

This extra electricity comes at times of high sun output, ie when ufh is not usually being used. So in principle you could add a stat that stops the ufh pump coming on when the cyl is too hot for it. Then you get the benefit of your extra leccy without a bunch of extra costs.


NT

On Wed, 4 Nov 2015 21:35:01 +0000, rick wrote:

Can't do that ... max temp I can have store get to is 60 degree
any higher and you risk damage to underfloor heating pipes.

They should have a mixing valve to prevent the floors getting too
hot.

No the design has a mixing valve on the DHW take off, but the main feeds
off for the UFH loop is not via a mixing valve ... the main tank stat
prevents it going over 60 degree.

Strikes me as bad design then. Can't you fit a mixing valve between
the flow and return of the floor loop such that the pump circulates
via the valve when the temp approaches 60 C.

--
Cheers
Dave.

On 04/11/2015 21:35, rick wrote:
On 04/11/2015 19:48, dennis@home wrote:
On 04/11/2015 18:04, rick wrote:
On 03/11/2015 22:47, wrote:

I haven't run the numbers but expect you'd be better off all round to
feed

the electric heat into the existing tank. The water wil go above set
point,

and not need other heat sources until the temp is back down again.


NT

Can't do that ... max temp I can have store get to is 60 degree .......
any higher and you risk damage to underfloor heating pipes.

They should have a mixing valve to prevent the floors getting too hot.


No the design has a mixing valve on the DHW take off, but the main feeds
off for the UFH loop is not via a mixing valve ... the main tank stat
prevents it going over 60 degree.

They normally use tall cylinders for these applications so that you can
rely on stratification to deliver lower temperatures to the UFH using
lower tappings on the cylinder. That does not stop you having the upper
section hotter than the UFH temperature.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Wednesday, 4 November 2015 18:04:32 UTC, rick wrote:
On 03/11/2015 22:47, nt wrote:

I haven't run the numbers but expect you'd be better off all round to feed
the electric heat into the existing tank. The water wil go above set point,
and not need other heat sources until the temp is back down again.

Can't do that ... max temp I can have store get to is 60 degree .......
any higher and you risk damage to underfloor heating pipes.

If your ufh runs off a bottom coil you can normally heat the water above it to over 60. Otherwise as you say it's a preheat tank. But a preheat tank brings a few issues:
1. water staying in the unsafe temp zone - ok for most things but not ideal for showers
2. Lots more area for heat loss, but in fairness a foot or 2 of insulation is pretty cheap.
3. Upfront costs that arent there with feeding the power into the main HW cyl.


NT

On Tuesday, 3 November 2015 18:04:02 UTC, rick wrote:
My solar PV system, produces a significant amount of unused electricity.

I have a Thermal store based heating system .... providing mains
pressure DHW off one heat exchanger and underfloor heating from the
other ... the water content of store being circulated around the boiler
when heat demand is called.

A consideration is to install a 2nd hot water cylinder, and use the
excess PV power to feed an immersion heater .... creating a large store
of heat.

Any call for DHW will result in thye incoming cold mains being
pre-heated by this store .... when store is depleted, the normal heat
exchanger function within the Thermal store would maintain DHW supply,
topped up if necessary by boiler.


I did ask a few weeks back about just using Solar PV excess direct into
Thermal store immersion, but as this is kept 'at temp' don't really see
a way to easily do that.

This pre-heat method would seem a suitable alternative ... and using the
mass of the water as an energy store.

Not worth bothering about.
There will be no heat when you need it most.
Also heat leaks away from small heat stores before you can use it.
Small thermal heat stores are a complete waste of space/money.

A typical sub 4kw domestic array will only be generating a few kwh units each day during the winter months so economically a pointless waste of time, money and effort. You will be better doing your cooking or washing during the daytime, maybe with a slow cooker and timer.

In article , wrote:
A typical sub 4kw domestic array will only be generating a few kwh units each day during the winter months

He could be planning it now to use next summer.

I've considered doing something similar. My thermal store is two cylinders
in parallel, with both DHW and UFH being heated by them. But the remaining
failed old Nu-Heat UFH is being replaced by radiators (upstairs was done
a while ago), so my half-plan was change the stores to series, and make the
lower heat exchanger on the first one a heating coil connected to
(hypothetical) thermal solar panels.
Or, with all the UFH now gone, both lower coils could be repurposed as solar,
but in conditions when the boiler will be needed anyway, having one cylinder
as lower temperature preheat seems to make sense for the same reasons as the
OP.

(The stores do have immersion heaters as backups, so PV panels could
also be used in the same way as the OP.)

On 04/11/2015 17:13, Alan Braggins wrote:


I've considered doing something similar. My thermal store is two cylinders
in parallel, with both DHW and UFH being heated by them. But the remaining
failed old Nu-Heat UFH is being replaced by radiators


How did your Nu-Heat fail ? ............ mine is Nu-Heat and runs really
well.
Although I went wit the pex system not their earlier triple pipe rubber
system.

In article , rick wrote:
On 04/11/2015 17:13, Alan Braggins wrote:


I've considered doing something similar. My thermal store is two cylinders
in parallel, with both DHW and UFH being heated by them. But the remaining
failed old Nu-Heat UFH is being replaced by radiators

How did your Nu-Heat fail ? ............ mine is Nu-Heat and runs really
well.
Although I went wit the pex system not their earlier triple pipe rubber
system.

Mine was the earlier double rubber pipe system. (Which apparently they
sold briefly after the triple, but before moving to PEX.) Failures of the
double and triple systems seem to be similar, and common.

Mostly it's perished near the manifolds, one zone leaked somewhere I
couldn't find it, and one zone (the last failure) isn't leaking, but the
rubber is gunked up and hardly any water circulates. Possibly because,
although it's had inhibitor in it, it's been repeatedly refilled because
of all the leaks.

On Wednesday, 4 November 2015 17:13:53 UTC, Alan Braggins wrote:
In article , wrote:
A typical sub 4kw domestic array will only be generating a few kwh units each day during the winter months

He could be planning it now to use next summer.


Tch.
You don't need any heat in Summer

In article , harry wrote:
On Wednesday, 4 November 2015 17:13:53 UTC, Alan Braggins wrote:
In article , wrote:
A typical sub 4kw domestic array will only be generating a few kwh units each day during the winter months

He could be planning it now to use next summer.

Tch. You don't need any heat in Summer

Some of us like to wash in hot water in the summer, even when the heating
is off. Also, not all of the summer is warm enough to swim comfortably in
my swimming pool without heating. (It used to be better, but more of it is
shaded by trees now.)

On 04/11/2015 07:52, wrote:
A typical sub 4kw domestic array will only be generating a few kwh
units each day during the winter months so economically a pointless
waste of time, money and effort. You will be better doing your
cooking or washing during the daytime, maybe with a slow cooker and
timer.



trying to educate the wife on this .... limited success so far.

Needs to have a large display giving count of free power ... maybe she
would use it then.

On Tue, 3 Nov 2015 18:03:55 +0000, rick
wrote:


This pre-heat method would seem a suitable alternative ... and using the
mass of the water as an energy store.

I had a similar installation many years ago but using solar water as
the pre-heating. The solar tubes warmed a heavily insulated cylinder
in the attic. Incoming mains water went first to the solar cylinder
and then to the second cylinder heated by a gas boiler. It was
interesting to play with but didn't achieve much. In the summer it
provided most of the hot water, in the winter sod all.