Interesting A fairly technical question re boilers

[Jaws]

More chance of being seen here

Question is..
If a normal domestic boiler is fed with hot water at main pressure will it use less gas ?
In other words, is there a sensor that will detect the output and reduce the gas as the water will already be hot ?

I am just doodling but if yes, I have the means the the hardware to take the cold feed to a couple of solar water heater panels and feed their output in to the boiler

 

[Squag1]

I don't know in fact but if you take the hot water into the circuit it has to reduce the demand on the boiler.

I've seen mixing valves which exclude thr boiler from the circuit when it reaches a set temp. This saves the boiler.

I'm sure there is a way of doing it.

https://www.flogas.ie/residential/energy-awareness/solar-panels.html

https://www.researchgate.net/public...ar_System_in_Combined_Heating_System_of_Water

https://www.greenmatch.co.uk/blog/2015/07/combining-heat-pumps-and-solar-panel-heating


https://www.worcester-bosch.ie/products/solar

That should keep you off the street for a while

 

[johnboy]

The answer theoretically is yes, we have just taken down such a system and replaced it with a conventional combi condensing boiler, which I think speaks volumes. It's supposed to reduce the demand and therefore reduce the amount of time the boiler fires. I know we haven't yet had much demand for heat since April when we swapped over but already there is a massive difference (in a good way) of the amount of gas not used.

 

[Jaws]

The answer theoretically is yes, we have just taken down such a system and replaced it with a conventional combi condensing boiler, which I think speaks volumes. It's supposed to reduce the demand and therefore reduce the amount of time the boiler fires. I know we haven't yet had much demand for heat since April when we swapped over but already there is a massive difference (in a good way) of the amount of gas not used.

Just to get it straight, you are saying you use LESS gas by not preheating the water ?

 

[slim63]

In theory yes it could reduce the time taken to heat water as its already at a higher temperature but if doing something like filling a bath the difference will be minimal because your panels wont heat that amount of water quick enough

Also it depends on your existing boiler if its old just changing to a modern boiler will make much more difference than anything you are able to mackle up at home, modern boilers heat a small amount of water very quickly & keep doing so while there is a demand imo pre heating that water wont make any noticeable difference unless you measure it over a course of quite a few years

 

[johnboy]

Just to get it straight, you are saying you use LESS gas by not preheating the water ?

Our inherited system was two solar panels on roof into large storage tank which then fed the boiler. It was shite, in the winter when you needed more hot water it was barely warmer than mains cold coming in and in the summer it was ridiculously hot when you didn't need it, also the boiler would keep trying to maintain the cylinder temperature all day.
To be fair this was connected to an old combi boiler. All the plumbers(4) who came to quote us for just a straight condensing combi boiler said they would never have this set up as it doesn't make economic sense in this country. So yes we are now using far less gas in the same time period as last year with just a new efficient condensing combi boiler. We have also gained about a metre squared in the bathroom having the old system removed and no eyesore of heating panels on the roof.

 

[Jaws]

Boiler is 3 years old and is a current model ( very green energy rating )
We have a roof full of solar panels for the elektickery ( returns about £1800 a year )
After chatting to a local green energy professional ( he said he is not an expert as the whole scene is so young and new stuff coming almost hourly let alone daily, it was immposible to be an expert... which I quite liked ) he suggested a series of matt black 22mm copper piper with a clear makrolon sheet over them..
The cold feed has three y valves controlled by a temperature sensor
When the temp drops to 5C the y valves switch over.
Y valve 1 switches the feed from the panel to the boiler
Y valve two which is located on the output end of the solar panel to ensure the water does not back feed in to the panel
Y valve 3 is located on the bottom of the panel and just opens, letting water that is in the panel escape there by preventing any possible freezing

 

[johnboy]

Sadly our inherited PV system is facing NE so only returns about a grand each year, still free bunce in my bin! Going to relocate them to a more favourable location once the new garage is built. Your solar heating appears to be a more sophisticated version so you might well save on the gas, ours dated from 2007 and I'm not entirely convinced it was installed for optimal performance, the company went bust soon after it was installed and were investigated.

 

[Jaws]

Your solar heating appears to be a more sophisticated version so you might well save on the gas,

It only exists in my head and on the bit of paper I drew it on so far !

 

[Quiney]

It only exists in my head and on the bit of paper I drew it on so far !

I blame the brain fart!

 

[ianrobbo1]

I blame the brain fart!

I blame the "old fart" All this green stuff and the wankers in charge have dropped the fit payments so much ,it's no longer worth bothering with unless you live till your 200.

 

[andyBeaker]

More chance of being seen here

Question is..
If a normal domestic boiler is fed with hot water at main pressure will it use less gas ?
In other words, is there a sensor that will detect the output and reduce the gas as the water will already be hot ?

I am just doodling but if yes, I have the means the the hardware to take the cold feed to a couple of solar water heater panels and feed their output in to the boiler

If I understand what you are saying (and that is a big 'if'!) the problem is likely to be that the panels will not be able to/efficient enough keep the supply to the boiler hot on an ongoing basis.

I think.....

 

[Jaws]

If I understand what you are saying (and that is a big 'if'!) the problem is likely to be that the panels will not be able to/efficient enough keep the supply to the boiler hot on an ongoing basis.

I think.....

Well all things considered I doubt there is any chance of that.. But when the sun is shining I want to take advantage of all that free heat..
Truth be told I really doubt it will happen. As I said in the OP, I am just doodling and want to find out whether it is a feasible thing

 

[andyBeaker]

Well all things considered I doubt there is any chance of that.. But when the sun is shining I want to take advantage of all that free heat..
Truth be told I really doubt it will happen. As I said in the OP, I am just doodling and want to find out whether it is a feasible thing

I think you have highlighted the fundamental issue - the heat is generated exactly when it isn't needed!

Funny old world....

 

[Squag1]

There was a concept of heat storage where water was stored in a huge tank under the house and heated during warm/sunny periods.

Also rock stores under the house, again heated .......

https://en.m.wikipedia.org/wiki/Thermal_energy_storage

 

[andyBeaker]

There was a concept of heat storage where water was stored in a huge tank under the house and heated during warm/sunny periods.

Also rock stores under the house, again heated .......

https://en.m.wikipedia.org/wiki/Thermal_energy_storage

If I was doing a new build (as yet unfulfilled dream) I would certainly investigate a ground source heat pump and almost certainly have a heat recovery ventilation system. Might get round to looking at the latter for the current house.

 

[Squag1]

Cousin buying new house.
Heat pump in garden no fireplace.

Another cousin put in recovery system 15 yrs ago at least with oil boiler. Seemed to be economal.
Filled wall with fibre after it was built.

 

[Jaws]

I think you have highlighted the fundamental issue - the heat is generated exactly when it isn't needed!

Funny old world....

Then again, unlike folk from th south coast, we wash and bath all year round..............

 

[Squag1]

Then again, unlike folk from th south coast, we wash and bath all year round..............

They are trying to avoid polluting French beaches

 

[richardgore]

More chance of being seen here

Question is..
If a normal domestic boiler is fed with hot water at main pressure will it use less gas ?
In other words, is there a sensor that will detect the output and reduce the gas as the water will already be hot ?

John,
I think question you're asking is whether by pre-heating the cold water entering a combi boiler, say by a solar panel, will the boiler consume less gas. The answer is, of course, yes - because the boiler will be required to put less heat in (the difference between the incoming cold water and the outgoing hot water) and therefore less energy (gas). This gives better fuel consumption in a modern boiler because of the modulating effect, rather than older style boilers which only have on/off burner control.

On conventional systems (heating boiler and cylinder) pre-heating the cold feed into the cylinder (not the boiler) will also have the same energy reduction.

But you can't just run cold water to an external solar panel unless you take account of the possibility of freezing in the winter. So either a bypass valve for when theres a possibility of freezing, or an ethylene/glycol mix, running through the external panel into a heat exchanger which will pre-heat the cold water.

Hope that answers your question.