Flow Rate Reqd for Thermal Store/Heat Store

[baggy99]

'm planning on installing a thermal store/heat store and I understand I should have 20 litres/min incoming mains flow rate min, BUT what's the effect if my flow rate is lower?

I can't check it till the weekend. If it comes in at less than 20 l/m does this affect the function of the store, or is it just a bit dodgy for thermostatic showers (which I don't have)? All I am trying to acheive is improved hot pressure at the upstairs taps and more effciency for the boiler.

Any advice appreciated. Thanks.

 

[Agile]

Most thermal stores are still designed for a store temp of 80°C which is not efficient for a condensing boiler!

Your hot water flow will always depend on the incoming mains supply.

Unless thats very good then you would be better using a pump on a storage system.

If converting from storage to direct supply then remember the cold using devices like WCs all have to come off the same supply and can reduce shower flow.

Tony

 

[baxpoti]

All I am trying to acheive is improved hot pressure at the upstairs taps .

You cannot improve the 'pressure' simply by installing a thermal store,
do you mean flow rate?

 

[Doctor Drivel]

Most thermal stores are still designed for a store temp of 80°C which is not efficient for a condensing boiler!

Tony

Most do not at all. A condensing boiler heating a thermal store direct and using a plate heat exchanger can easily operate at 70C or below. With 20C boiler delta T, or more, that gives a return temp of far less than condensing dew point. Plate heat exchangers are so efficient they send water back to the cylinder at not much more than the mains cold water temperature, extracting an amazing amount of heat from the hot water. I have seen thermal stores operate very effectively at 60 to 65C store temperatures, really producing condensing efficiency.

They also have one long efficient boiler burn. The equivalent of a normal car running at a constant speed on a motorway or crawling through a town doing stop-start, as is boiler cycling..

 

[baggy99]

Thanks all, but I'm still not clear on the real world effect it will have if my flow rate comes in lower than 20 l/m. As I said, I don't have showers attached to the dhw, so its only the tap flow rates I am concerned with (yes baxpoti - I should have said flow rate, although surely if the dhw is now being fed from the main b4 going through the TS it will also increase pressure?)
Am I right in thinking my dhw will come out of the taps at the same rate as the mains cold? If so, why all the fuss over 20 l/m min?

 

[gas4you]

20 l/m is a text book ideal recomendation for you to get the best results from your investment. The lower the figure then the more money you have wasted in terms of you not getting the full benefit from it.

 

[Paul Barker]

If you only get 20 ltr / min don't bother with a mains hot water system. Just put a pump on the gravity hot water system.

You can maybe have a thermal store with pumped gravity (break tank) water through the dhw plate heat exchanger.

I have a few customers with Gledhil 2000's and they really like the fact that when they get in there is such a good reservoire of stored heat that the heating can be turned on when they get in and the house is warm in 15 minutes. There is lashings of hot water on demand. The boiler is not overworked like a combi. If you have ever stood in the room where a combi is in the morning of a busy house you will be amaised (knowing anything at all about physics) that they don't break down more frequently than they already do.

Combis are for people who like laminated flooring and watch too many makeover programs, and know nothing about physics.

 

[Balenza]

20 L/min is fine for what the OP is suggesting.

Just because you have stored water doesn't mean the mains supply will not be drawn upon.

 

[Agile]

Most thermal stores are still designed for a store temp of 80°C which is not efficient for a condensing boiler!
Tony

Most do not at all.

Can you quote a link to the web site of a manufacturer who does NOT quote a recommended store temp of 80°C ?

Tony

 

[Doctor Drivel]

Most thermal stores are still designed for a store temp of 80°C which is not efficient for a condensing boiler!
Tony

Most do not at all.

Can you quote a link to the web site of a manufacturer who does NOT quote a recommended store temp of 80°C ?

Tony

Http://www.heatweb.com Give them a ring. Anyone who know about heating systems would figure out what I wrote.

 

[baggy99]

Thanks again all. I'll check the flow rate tomorrow, but even if the flow rate's down it looks like I should still see a benefit over the current gravity fed dhw AND I will get the benefits of the TS (instant heat & better boiler effeciency.)

I'm still torn over a conventional thermal store or a heat store with external heat x. I haven't checked out the price difference yet, but I presume the latter is going to cost a fair bit more? Is the external heat x worth the extra money do you think?

 

[Doctor Drivel]

Thanks again all. I'll check the flow rate tomorrow, but even if the flow rate's down it looks like I should still see a benefit over the current gravity fed dhw AND I will get the benefits of the TS (instant heat & better boiler effeciency.)

I'm still torn over a conventional thermal store or a heat store with external heat x. I haven't checked out the price difference yet, but I presume the latter is going to cost a fair bit more? Is the external heat x worth the extra money do you think?

I don't think thee is much in the price between them.

 

[baggy99]

>> I don't think thee is much in the price between them.

Hope you're right. Def a heat store if that's the case! Cheers.

 

[Agile]

Http://www.heatweb.com Give them a ring.

I have found nothing on that site within three minutes which gives any recommended store operating temperatures.

If its really there then please give me the link to the actual page.

Tony

 

[simond]

He likes heat stores.

I'd put in an unvented and if there are any issues at all about flow rates, add an accumulator, job done. If you have to have a heat store (don't understand why unless you want to fit it yourself) you can bung an accumulator on the front of that.

It will be a good test for the HS specs because you can reach the max flow rate easily.....assuming you have enough taps?