DPS thermal store DHW performance

[silverback]

A CH pump in the cool bottom section of the cylinder. It will remain cool with a more even temperature over the pump. Heat from the pump is captured. Immersed pumps are common. There is no reason why they cannot be immersed in heating and water systems.

Here you go, you said about a CH pump immeresed in the bottom of the cylinder, I am just asking for you to give me details of a CH pump that does this, as far as I am aware they do not exist

 

[kevplumb]

A CH pump in the cool bottom section of the cylinder. It will remain cool with a more even temperature over the pump. Heat from the pump is captured. Immersed pumps are common. There is no reason why they cannot be immersed in heating and water systems.

Here you go, you said about a CH pump immeresed in the bottom of the cylinder, I am just asking for you to give me details of a CH pump that does this, as far as I am aware they do not exist

they do in walters vivid imagination

bit like he thinks he knows what he is talking about
cos it says so in the glossy paper thing

 

[mysteryman]

Guys

"Since returning home, I have turned up the boiler stat to Max, this has resulted in the production of a greater volume of available water, that is continously available - bath after bath."

This is the problem with thermal stores - they have to be kept extremely hot just to get a good dhw performance. So hot that the boiler can't condense.

Is there such a thing as an immersed circ pump - I've never seen one, nor a cyl with a plate heat ex inside it?

 

[SimonH2]

"Since returning home, I have turned up the boiler stat to Max, this has resulted in the production of a greater volume of available water, that is continously available - bath after bath."

This is the problem with thermal stores - they have to be kept extremely hot just to get a good dhw performance. So hot that the boiler can't condense.

That may be true in some cases, in exactly the same way that the statement "boilers running radiator systems can't condense". It depends very much on the setup, and in mine I have a TMV to artificially raise the boiler return temp to avoid it condensing (it's an old non-condensing boiler). Without the mixing valve, the boiler return temp would be under 40˚C pretty well all the time, possibly under 20˚C some of the time.

When the boiler gets replaced, the plan will be to remove the TMV and control the flow rate to get the right boiler outlet temperature - but that's a future design project.

All it needs is for the system to be designed correctly.

 

[mysteryman]

Yes, but why?

Just supply the rads directly from a condensing boiler with weather comp, and keep it all understandable, controllable, effective, economical, and above all - SIMPLE!

 

[SimonH2]

Yes, but why?

Just supply the rads directly from a condensing boiler with weather comp, and keep it all understandable, controllable, effective, economical, and above all - SIMPLE!

"understandable, controllable, effective, economical, and above all - SIMPLE!" that exactly describes my setup once I've got rid of the combi and replaced it with a heat-only boiler.

understandable - yup. If you can understand a combi then you can understand this setup. If you can't understand a simple thermal store then ...

controllable - yup. How controllable do you want it ? TRV sets the temperature in each room, fully modulating pump controls flow rate to match demand. No compromises to deal with minimum flow rate sin boilers and all that crap.

effective - it works very nicely thank you.

economical - standing losses for the store were measured at around 80W average. Standing "losses" for the RD532 in the house when in "keep firing up to give some semblance of DHW on demand" mode were measured at about 160W. The 80W was measured on electric using the immersion heater, the 160W was measured on gas - so allowing for a gas-heat conversion, the combi still has considerably higher losses*. Even if I were to get the newest and best combi instead of the store, I still doubt it could be both big enough to provide decent DHW and still modulate low enough for heating (and remain economical when doing so).

simple - yup. Less moving parts than a combi, easier to diagnose than a broken down combi, etc, etc.


But you missed off one key feature - reliable. Whenever I've mentioned the number of breakdowns I've had with boilers (my parents Ideal has now broken down more than once every 2 years average, the Vokera in the flat has a similar track record), comments come back along the lines of "think yourself lucky" ! Given that condensing boilers, and especially combi condensing boilers, are expected to break down regularly then I'll take the store with it's backup immersion heater thank you very much. Have you any idea how a tenant moans when she's got no hot water or heating for 10 days ? At least at home we have an "old fashioned" OV cylinder with immersion heater for hot water, and a gas fire in the living room for heat.

* Yes, I know it's only one data set, and only one not very new boiler - but that's the data I have.

 

[SimonH2]

Yes, but why?

Just supply the rads directly from a condensing boiler with weather comp, and keep it all understandable, controllable, effective, economical, and above all - SIMPLE!

"understandable, controllable, effective, economical, and above all - SIMPLE!" that exactly describes my setup once I've got rid of the combi and replaced it with a heat-only boiler.

understandable - yup. If you can understand a combi then you can understand this setup. If you can't understand a simple thermal store then ...

controllable - yup. How controllable do you want it ? TRV sets the temperature in each room, fully modulating pump controls flow rate to match demand. No compromises to deal with minimum flow rate sin boilers and all that crap.

effective - it works very nicely thank you.

economical - standing losses for the store were measured at around 80W average. Standing "losses" for the RD532 in the house when in "keep firing up to give some semblance of DHW on demand" mode were measured at about 160W. The 80W was measured on electric using the immersion heater, the 160W was measured on gas - so allowing for a gas-heat conversion, the combi still has considerably higher losses*. Even if I were to get the newest and best combi instead of the store, I still doubt it could be both big enough to provide decent DHW and still modulate low enough for heating (and remain economical when doing so).

simple - yup. Less moving parts than a combi, easier to diagnose than a broken down combi, etc, etc.


But you missed off one key feature - reliable. Whenever I've mentioned the number of breakdowns I've had with boilers (my parents Ideal has now broken down more than once every 2 years average, the Vokera in the flat has a similar track record), comments come back along the lines of "think yourself lucky" ! Given that condensing boilers, and especially combi condensing boilers, are expected to break down regularly then I'll take the store with it's backup immersion heater thank you very much. Have you any idea how a tenant moans when she's got no hot water or heating for 10 days ? At least at home we have an "old fashioned" OV cylinder with immersion heater for hot water, and a gas fire in the living room for heat.

* Yes, I know it's only one data set, and only one not very new boiler - but that's the data I have.