Thermal store advice

[ianmcd]

and it does not require fiddly balancing

Your Rad system will still require balancing

 

[sirocosm]

Your Rad system will still require balancing

With TRVs all round you can run with the locksheilds all wide open, so it does not really "require" balancing as a standard system would, the TRVs will do that for you.

Of course if you are starting the system from cold, then the rads nearest the store will heat first, but once the heating is left on for some time the rads will all reach their equilibrium temperature for the heat loss in that room and stay at that temperature. The rads do not get hot and cold as the boiler cuts in and out, but rather maintain an even temperature.

 

[ianmcd]

With TRVs all round you can run with the locksheilds all wide open, so it does not really "require" balancing as a standard system would, the TRVs will do that for you.

Of course if you are starting the system from cold, then the rads nearest the store will heat first, but once the heating is left on for some time the rads will all reach their equilibrium temperature for the heat loss in that room and stay at that temperature. The rads do not get hot and cold as the boiler cuts in and out, but rather maintain an even temperature.

Not correct, you are assuming that all TRVs will close, never seen that happening, in theory yes, but in reality you will have to balance the system

 

[sirocosm]

Not correct, you are assuming that all TRVs will close, never seen that happening, in theory yes, but in reality you will have to balance the system

If your TRVs don't close, you should replace them. The setup I have described works fine, I had it in my previous house and it is very common in thermal store setups. It is more comfortable, as larger rooms with windows are not heating up and cooling down all the time, the system maintains a much more even temperature than unbuffered systems as the rads are always on. It is also much easier to control the temperature precisely in individual rooms.

The "standard" heating system works like a yo-yo. The house stat calls for heat, and then all the rads get hot, hopefully all at the same time if it is perfectly balanced (not possible). Then when the set point temperature is reached the heat to the rads is cut, and they all get cold until the house temperature drop a couple degrees and the cycle starts again. Al large stat differential makes this more noticeable, and a small one causes boiler cycling. How is this a better setup?

 

[Ryler]

All the same sircosm I think the unvented cylinder will give you more hot water for an equivalent volume that a TS holds.
Putting the buffer section aside.

 

[sirocosm]

All the same sircosm I think the unvented cylinder will give you more hot water for an equivalent volume that a TS holds.
Putting the buffer section aside.

I would agree with that, although I am not sure how much more, I would guesstimate up to 2x bigger if you have a small boiler.

With a thermal store, you can put in a boiler large enough to have infinite hot water if you want/require it, with an unvented you are limited by the size of its primary coil.

 

[John D v2.0]

Re balancing it's not just to keep the return to the boiler cool enough, it's also to provide the most responsive heating system for the energy used by the pump. If you have an unbalanced system the further radiators will be slow to heat up and will have lower output.
Also the benefits you descbee about not yoyo, you can just use a weather compensating system which will keep the flow temperature low.
Yes boilers have minimum cycle time but if you configure the pump to stay on, the water in the system will provide the buffer. With your thermal store you'd have to have a pump running all the time anyway.

 

[sirocosm]

Re balancing it's not just to keep the return to the boiler cool enough, it's also to provide the most responsive heating system for the energy used by the pump. If you have an unbalanced system the further radiators will be slow to heat up and will have lower output.
Also the benefits you descbee about not yoyo, you can just use a weather compensating system which will keep the flow temperature low.
Yes boilers have minimum cycle time but if you configure the pump to stay on, the water in the system will provide the buffer. With your thermal store you'd have to have a pump running all the time anyway.

With the thermal store and TRVs all round balancing is not really an issue, as the system never has to "heat up", it is always warm. It is true that a second pump is required, but my Grunfos alpha 2 typically ran at 6-10W, so about the same as a single LED light bulb. It somewhat amazes me all the effort put into boiler design, modulation, weather compensation, etc, when a much simpler solution exists, buffering. I guess for many it is a space issue.

 

[John D v2.0]

sounds like you already made your mind up and I can see your message about adapting the world to yourself!
But the reality of the world is given the cost conscious customers, simple is whack a (cheap in many cases) one box combi on the wall, get paid, on to the next job. With the cost of labour piping up cylinders and stores is not an easy choice for the vast majority of people and their wallet. You think permanently on system and running rads at 60c with TRVs is simpler, weather compensation thinks that running the rads at the minimum temperature for the heatloss is more efficient. A lot of people think wood burners are simpler. Each to their own.
But if you're doing it yourself you can go all in, and make whatever you feel is most effective.

 

[Ryler]

The reasonable man adapts himself to the world:

Be reasonable sirocosm and embrace unvented cylinders.

 

[sirocosm]

The reasonable man adapts himself to the world:

Be reasonable sirocosm and embrace unvented cylinders.

Why? When I know I can install something better?

 

[sirocosm]

sounds like you already made your mind up and I can see your message about adapting the world to yourself!
But the reality of the world is given the cost conscious customers, simple is whack a (cheap in many cases) one box combi on the wall, get paid, on to the next job. With the cost of labour piping up cylinders and stores is not an easy choice for the vast majority of people and their wallet. You think permanently on system and running rads at 60c with TRVs is simpler, weather compensation thinks that running the rads at the minimum temperature for the heatloss is more efficient. A lot of people think wood burners are simpler. Each to their own.
But if you're doing it yourself you can go all in, and make whatever you feel is most effective.

I suppose if you don't have the space, a combi might be the way to go. It is funny how they are cheaper then plain boilers, even though they are more complicated and more expensive to manufacture. It is the same with cylinders. An indirect unvented is cheaper than a plain buffer tank, even though it is more expensive to build, again because of demand I suppose. As soon as you put the words "thermal store" on it, the price goes through the roof.

 

[John D v2.0]

Top tip for those not in the know, if you're aware your opinion is at odds with most other people's, it might be worth prefixing your posts with "In my personal opinion" to avoid rubbishing everyone else's views

 

[sirocosm]

Top tip for those not in the know, if you're aware your opinion is at odds with most other people's, it might be worth prefixing your posts with "In my personal opinion" to avoid rubbishing everyone else's views

If you think an unvented is better than a thermal store, then maybe present some arguments as to why, if you can.

 

[Ryler]

If you think an unvented is better than a thermal store,

If you have 210 liters in an unvented cylinder heated to 60c and dump the entire contents (until empty and full of air) into a bath you have 210 liters of hot water @ 60c. Or just about.
If 10 bathers are lined up for a bath the final person should still have a hot bath.

If you have the same in a thermal store you cannot dump it into a bath because it is primary water, full of additives.
So you have to transfer the heat energy through a heat exchanger via a separate cold supply. Usually a cold water tap.
And the bath won't have anything close to 210 liters of 60c hot water when you go through that inefficient process.

The maximum temp you might get is 55c.
As for the volume @55c that's anyone's guess. Mebbe 130 liters tops.
Then another 80 liters tailing off at a much lower temp. Further diluting the final bath temp.
If your lucky you might might end up with a final 210l bath temp of 40c.
Do you see the cunundrum here for the 10 bathers? Last person will need skin like an elephant seal or have cold water shock survival skills..