Heating needs a rethink

[Dave Thornley]

Been nosing in this forum for years but as I need advice now signed up. Bit of a long winded scenario but will try to keep it brief.
Recently moved into a 5 bed cottage with radiators on both floors. The boiler is an old oil fired job situated in an outbuilding some 20m from where the hot water pipes, 35mm, enter the property. The thing works okay but efficiency of said boiler leaves a lot to be desired. Hot water is provided by standard vented cylinder with heating and hot water tanks in loft. First thing I thought I would do is lose those and install a sealed system like I had previously when using a thermal store for the HW. We are in a very hard water area currently with a salt water softener in the system. I do not like these for various reasons. So thought out with that and in with my favoured electronic scale reducer using a thermal store as opposed to say a megaflow. As the thermal store will have the same water in from day one if treated at the outset scale is not a problem. Now though I am thinking that if I go over to a sealed system with an increased pressure in water not sure if the old heating pipes can cope with it. I cannot really replace them as the cottage is a 16c job with all the pipework hidden. So the crux of my question is can I use a thermal store with current system ie keeping tanks in the loft. The actual water pressure to the cottage is not brilliant, even though I have a massive water tower some 100m away!
Any advice gratefully received.

 

[Roger928]

As the thermal store will have the same water in from day one if treated at the outset scale is not a problem

Scale can build up on the HW coil when its cooked to 70c. As it will when static.
Then slowly but surely the hot water temp lowers. What people do then is raise the store temperature which just exacerbates the problem.

 

[Dave Thornley]

Maybe slightly but as the inside of the coil is only carrying boiler water already treated and the outside will be sitting inside the thermal store surrounded by the same water for ever which will again have been treated the problem is minimised. I had the same setup ie thermal store with an electronic scale inhibitor for over 17 years in the last place with no evidence
of scale build up whatsoever.

 

[Roger928]

The DHW is inside the coil in a thermal store. That's where it gets cooked and releases the scale deposits.
Mebbe your last place was a soft water area?
But if your confident then that's mebbe the way to go.

 

[Dave Thornley]

No the DHW passes through the heat exchanger which in turn is heated by the same volume of water in the thermal store which is put there on day one. As it only passes through the heat exchanger on usage the electronic scale inhibitor works fine. This is my reason for not wanting a system like a megastore where as the name states it stores the water before heating and using possibly rendering the electronic scale inhibitor less effective depending on hoxw long the water has bein in there. Last gaff definitely hard water area.

 

[Roger928]

No the DHW passes through the heat exchanger

Only when the hot tap is on.
When water is flowing through the coil and heating up just before coming out of the hot tap - there's no problem: there's not enough time for any deposition to occur. Trouble is when the flow stops: the water still in the coil gets to the same temperature as the heat store and any hardness in it deposits over the (several) hours before a hot tap is used again.
Especially if the store is 70c or above.

 

[Dave Thornley]

Not really sure which coil you mean. As I said before the water in the coil from the boiler, which heats the constant mass of water in the store, is irrelevant as it it the same treated water that might next time around go through a radiator. If you are talking heat exchanger bank yes some will remain in that when taps are shut off. For 99.9% of the time no worry as a hot water tap will be opened before the effects of the scale inhibitor wear off.

 

[Dan Robinson]

Electronic scale reducers are not water softeners.

They do precisely Jack schit.

 

[Roger928]

Not really sure which coil you mean.

http://heatweb.com/literature/HWA Thermal Store Specification.pdf

Some of the problems with thermals stores...
1 - Scale build up inside the DHW coil.
2 - Sludge collected in the Primary store.
3 - Hot slugs delivered to the taps.
4 - Hot water delivery limited to the heat exchange capacity of the DHW coil.
5 - Expensive to purchase

That's why plumbers avoid them and only fit them as a last resort.
They can be useful for multiple inputs from different heat sources.

 

[Dave Thornley]

Electronic scale reducers are not water softeners.

They do precisely Jack schit.

Never said they were water softeners. By your answer I presume you have never used one!

 

[Dave Thornley]

http://heatweb.com/literature/HWA Thermal Store Specification.pdf

Some of the problems with thermals stores...
1 - Scale build up inside the DHW coil.
2 - Sludge collected in the Primary store.
3 - Hot slugs delivered to the taps.
4 - Hot water delivery limited to the heat exchange capacity of the DHW coil.
5 - Expensive to purchase

That's why plumbers avoid them and only fit them as a last resort.
They can be useful for multiple inputs from different heat sources.

2 Sludge how does that get there?
3 ?
4 No limited by the heat exchanger units, if one is not enough one can fit two
5 No more expensive than megaflow units

 

[Dan Robinson]

Never said they were water softeners. By your answer I presume you have never used one!

Used what?

You'd have to be a total half wit to change a salt softener for electronic snake oil.

 

[Roger928]

2 Sludge how does that get there?
3 ?
4 No limited by the heat exchanger units, if one is not enough one can fit two
5 No more expensive than megaflow units

2 - From the heating system. The primary water in the heating system where the thermal store is heated directly is circulated into the store and the sediments separates and settles at the base causing corrosion and reduces the lifespan. That's why they get the name "sludge buckets".
3 - The DHW coil heats the water to the primary storage temperature. Usually 70c or above. When the tap is opened this scalding hot slug will be delivered to the taps unless measures are taken.
4 - Manufacturers fit one DHW coil per unit that's tested appropriately.
5 - Albion Mainsflow 180L = £1184 and a Gledhill 180L unvented = £562...Megaflow 170L indirect £759.

 

[Dan Robinson]

3 - The DHW coil heats the water to the primary storage temperature. Usually 70c or above. When the tap is opened this scalding hot slug will be delivered to the taps unless measures are taken.
4 - Manufacturers fit one DHW coil per unit that's tested appropriately.

Not if they use a plate heat exchanger.

 

[Dave Thornley]

2 - From the heating system. The primary water in the heating system where the thermal store is heated directly is circulated into the store and the sediments separates and settles at the base causing corrosion and reduces the lifespan. That's why they get the name "sludge buckets".
3 - The DHW coil heats the water to the primary storage temperature. Usually 70c or above. When the tap is opened this scalding hot slug will be delivered to the taps unless measures are taken.
4 - Manufacturers fit one DHW coil per unit that's tested appropriately.
5 - Albion Mainsflow 180L = £1184 and a Gledhill 180L unvented = £562...Megaflow 170L indirect £759.

Not sure why I posted this question answers just riddles.

4 I am talking heat exchanger not heating coil.