Heatbank wiki and PING John Stumbles

[Tim S]

Hi,

Just looking at this:

stupid question: the G1 3/4" BSP connections on the plate exchanger: are they parallel or taper joints? ie would one use PTFE or expect to use a

22mm adaptor with a washer in? I'm not familiar with this "G1" nomenclature and my knowledge of BSP joints is sketchy at best.

Second stupid question: I notice that the specs say the the return primary water is 63C and the output secondary (DHW) is 60C. If the plate is capable of nearly equalising return primary with soutput secondary, then why don't people achieve regulation by using a 3 port mixer in the primary circuit?

This would minimise stratification of the store, 3 port mixers are ubiquitous and AFAICS, the regulation of the DHW would be to within a few degress celcius which is more than good enough. Obviously one still has the flow switch to run the primary side pump.

Third question:

If the BP12M 20 plate model is good for 50kW transfer in a particular setup, would it be reasonable to assume that teh 40 plate version is good for

100kW?

Cheers

Tim

[YAPH]

Pretty sure they were parallel and I used a BSP Female (x compression) fitting with a fibre washer to connect to it.

You mean like a 3-port version of a TRV with a remote sensor? I think you could, but they're anout £200 all up whereas a TMV is £50. If I were doing it again I'd prolly try the 3-port valve though.

only one or 2 mfrs I know of - or are you thinking of a TMV in some configuration I'm not thinking of?

I'd guess so. I'd use a 100kW model if I were doing it again: at full flow from the bath tap the water ran cool with the 50K one.

[Tim S]

YAPH coughed up some electrons that declared:

OK - now that I know, it's easy... Ta!

Scrub that - I misread your PlateX specification table... For some reason I assumed DHW output would be within a few degrees of primary flow. It's not, is it... PlateX are good, but not *that* good. Unfortunately I fell asleep in all the lectures to do with fluids and thermodynamics ;->

I was thinking to regulate the primary supply to the PlateX, thinking DHW output was always within a few degrees of primary input - but as that probably not true, then my idea collapses in the heap of senility inspired shame that it is :(

In that case, Danfoss RAVK valve it is (with the remote sensor as you suggest).

The BP12M-40-G1G1 should be close enough then. I rang up for a quote, spoke to a swedish bloke (via the UK tel number after being transferred twice) and they haven't got back to me. They muttered something about going to a wholesaler... Did you buy yours direct for the address in the Wiki?

On an aside, I think I'll be using Grunfos Alpha+ pumps for most of it - nice ability to set speed 1-3 or modulation level on one knob and the price isn't bad, unlike the Alpha 2's. Maybe just a basic 3 speed circulation pump for the boiler circuit.

Cheers

Tim

[Doctor Drivel]

There is the Drayton tap stat, which is under £100, but only in 28mm two=port and three ports is only;only in 15mm. The temp sensor is for slapping on the side of a copper cylinder and I doubt fast enough reacting for DHW sensing a pipe.

> If the BP12M 20 plate model is good for 50kW transfer in a particular

Use a 150kW plate as the water returning from the plate always cool as it extracts so much heat from the stored water.

[Doctor Drivel]

An oversized plate heat exchanger can work at 5C difference. That is 55C store temperature and 50C DHW outlet temp.

If you are using an Alpha+ for the DHW plate it mat fight against the TMV control or RAVK control. An Alpha+ when using a two-port RAVK may work. It may need some tweaking to get it stable.

[Tim S]

Doctor Drivel coughed up some electrons that declared:

Hi

How oversized do you reckon? I'm working at a store temp of 75-80C, hence the original idea of regulating that down to 60-65 for the PlateX primary.

An uncertainty of 5C on teh DHW is perfectly fine - obviously with a low tap flow, the DHW will more or less equalise with the primary input.

That's the good thing about Alpha+ pumps - the knob can select fixed speeds

1,2 or 3 or it can select modulating on a sliding scale (of pressure I guess). Best of both worlds then - can play around to see what works. I'd rather have 4 of the same pump if possible for my sanity.

Cheers

Tim

[mark]

Think you will find that it is G one and three quarter inches.There is not a G1 standard,it is G for parallel BSP threads and should be written as G1.3/4" BSP

[Doctor Drivel]

50% more in kW.

[YAPH]

Yes, spoke (on separate occasions) to a couple of guys - pretty sure they were in the UK (certainly didn't sound Swedish)

[Tim S]

YAPH coughed up some electrons that declared:

I'll phone them again...

Ta

[Tim S]

John Stumbles coughed up some electrons that declared:

Hehe :)

BTW - I did get someone more useful this time. BP12M-40-G1G1 is £175+VAT (hopefully english VAT and not swedish VAT!)

I added up all the parts for my design, and it's getting rather expensive :( Almost as expensive as DPS. So I might be persuaded to use a prebuilt one to save time...

We'll see...

Cheers

Tim

[Doctor Drivel]

With an oversized plate heat exchanger the temp difference between the stored water temp and the DHW draw-off temp can be approx 5C, the plate is so efficient at extracting heat.

Having a blending valve with its hot inlet from the hot top of the cylinder and the cold inlet from one third up from the bottom of the cylinder. Then the outlet set to approx 5C above the DHW setpoint into the plate. This will ensure stratification will not be affected. When small draw-offs the bulk of the heat from the store will come from the bottom section of the store. Say the blending valve is set to approx 55C to give a 50C draw-off temp and store temp is approx 55C 2/3 down, all the water come from the bottom section, leaving the hot top section undisturbed. When larger draw-offs the blending valve opens up to take hot water from top of the store.

Also have a blending valve as per usual on the DHW draw-off. Two blending valves and one single speed pump is a lot cheaper than an Alpha pump and RAKV valve.

The blending valve temp setting will need to be set up on the higher flow draw-offs.

[Tim S]

Quick follow up...

I designed and priced up a heatbank based on this Wiki and other ideas.

Came to £1450 for a 250l unit with 4 pumps and some mixers and a 80 plate heat exchanger.

Cylinder was £610 from Newark Plate exchanger £200 from GEA Ecoflex

3 modulating pumps at £80 from Screwfix 1 simple 3 speed pump at £45

The rest of the cost were mixers, flow switch, immersions and random fittings - which bumped the price up rather a lot.

So I concluded I was getting quite close (within £300) of an old DPS quote for a similar unit. £300 extra to not bother with drawings and wibbling is worth it.

So I went to see them and had a most informative talk. Unfortunately they've had a price increase this year which means their version is now about 700 quid more than my version!!!

I'll sit on it for a week and have a think. Had a look in their workshop at Epsom and I do agree, DPS seem to make nice units. But at the end of the day, it's a tank. The only thing against a homebrew is time - if this were an isolated project it would be fun, but lobbing in a mostly ready to go unit, adding header tank and cold mains and electrical feed means hot water and a couple of rads working straight away, even without a boiler, all of which is quite attractive.

Well, only I can decide, but someone might be interested in the musings(!)

SWMBO likes the ready made unit, because, well, it will work quicker, but does accept the cost element is non trivial.

Cheers

Tim

[Doctor Drivel]

£700 extra? Heafty. It will take no more than a day, if that, to assemble the home made unit. £700 can pay for more insulation in the loft. Also your unit apears to be better specced and bang on to what you need/want.

[Tim S]

Doctor Drivel coughed up some electrons that declared:

Yeah :(

I could live with +300 quid, based on their last quote. But +700 is hurting.

And a day to get the cylinder drawings right so that stuff fits. And a day to check the drawings when the come back and find the stupid mistake missed by the first day. And a day to chase round sourcing all the bits.

Possibly. At least, I'd build a little scope to reconfigure into mine, so if it became clear it wasn't working well, I have the option of moving a connection to a different tapping.

As it happens DPS can also tweak stuff too - I might get them to remove one or two bits that I'm not convinced are necessary. The bloke I saw very much had the philosophy that the store should run in a mode where reheat of the top portion is fast, involving, for example another 100 quid's worth of

28mm mixer on the boiler circuit.

My philosophy is more inclined towards keeping the unit charged (perhaps in summer with the option of only charging the top half - easily done with an extra stat).

This is why I didn't get my card out on the spot!

Cheers

Tim