Combi-boiler or stored?

[VisionSet]

Perhaps, but that is purely subjective and I only said noticeable, and I qualified it.

Back on topic - I am interested in your set up - on a cursory glance over the possibilities, the WB 28HE & the Pandorra seems a good solution. I'm not sure about the zone valves yet - I'll have to study the heatweb site further. I thought it the heat bank was simpler - just a loop to the heat exchanger otherwise a closed system supplied by another closed system from the boiler.

About the boiler - the loop to and from boiler and heatbank - does that supply the radiators - is that where the zone valves come in? Is that a truly closed system - in my ancient system that would get a top up from a tank in the loft - how is that system filled?

-- Mike W

[Huge]

I couldn't disagree more. I *hate* having a hole drilled in the top of my head by a shower that thinks it's a pressure washer.

What I want is huge volumes of water at low pressure - we have one of those "soup plate" shower heads about a foot across.

Your point still stands, though. You still have to flow large amounts of water.

[Dave Plowman (News)]

Consider this. If you pour a bucket of water over your head, would you consider the velocity inadequate?

Same with a shower.

A low pressure type with decent pipework can provide a very satisfactory shower even with far less than one bar pressure, and under marginal conditions an extra foot of head can make a difference. But of course with a conventional house with the normal roof void getting enough head isn't usually a problem.

I prefer a high flow shower to a low flow one at high pressure. You're washing skin - not a patio.

[Dave Plowman (News)]

Some use a shower to wash themselves. As one does with a bath. I prefer my sensations elsewhere.

[Christian McArdle]

I'm not quite sure what you're getting at here. The heat bank is about as simple to plumb in and wire up as it could be made to be. Note that we're talking about an indirect coil version here.

If you opt not to have the mounted controls, you have:

1. Cold mains in
2. Hot water out
3. primary flow in
4. primary flow out
5. immersion connection
6. power connection
7. cylinder thermostat.

These connections are wired/plumbed up to the central heating system in the normal way, just like a conventional indirect cylinder. Obviously, a zone valve arrangement and boiler interlock using the cylinder thermostat is required, but this is completely normal and would be required for any indirect cylinder.

The heat bank is also available with zone valves and control logic ready attached, so you only need to connect up the boiler power and water connections and attach radiators.

Christian.

[IMM]

Those figures look impressive. the stark reality is that 4 or 3 foot make little difference to the user.

[IMM]

If you are going for a heat bank. Preferable is an "integrated", "direct" one. Direct is that there is no coil between boiler and cylinder and integrated means the CH is run from the cylinder too.

Range do the Flowmax and DPS do the GVX (?), which I believe is cheaper than the Pandora. The Flowmax is well priced.

[VisionSet]

My original comment was soley in response to this by another mike:

!> Re-siting the header tank to give more head is often possible for little !> cost on a DIY basis. !>

! I already did that with no noticeable difference, but the Grunfos booster ! I've just fitted is not audible, and works a treat

I stand by the comment that even 1ft should be noticeable.

[IMM]

You must be very sensitive. ;)

Many moons ago, To get a better head on a gravity shower I installed at the loft apex (this loft was huge with a tall pointed roof being 15 foot from floor to apex) a small 20 gallon cold water tank. It had to be small to get right into the apex. I then fitted a 3/4" ballcock and a 22mm cold mains water supply to it. The tank acted as a break tank with the mains so good it would fill up as fast, or faster, than what was being drawn off, even when running a bath.

Worked a treat. The extra 15 foot (0.5 bar) made a noticeable difference.

[VisionSet]

Yes that's right, so sensitive I can detect a 33% change. Very few humans are can detect such infinitesimal changes.

-- Mike W

[Andy Hall]

That's horrible. It's like bombarding yourself with one of those needle jet things.

A very unpleasnt experience.

.andy

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[Christian McArdle]

I should add, given that you are considering such a system, that mine has now been installed for about a year and it has given me absolutely trouble free service. I haven't topped up the heat bank, even once, so the manual fill system works as advertised and gives peace of mind against unlimited leakage. The anti-evaporation system clearly works.

The hot water still gushes out at the rate and temperature I would like, although for how much longer I don't know, because my planned water softener has not yet been installed. The boiler hasn't had a single issue with it. It ignites first time, every time. What more could you ask?

My only problem so far has been a dodgy valve I installed, which dumped some water on the floor. The valve was clearly faulty and not part of either the boiler or heat bank.

Christian.

[Andy Hall]

Amen.

.andy

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[Andy Hall]

boiler does not modulate down to its more efficient low burn and low temperature ranges.

If you look at the behaviour of a condensing boiler with a CH system in spring and autumn it comes on at low level and works at low and very efficient temperatures using long burns with an occasional off at the set point. This is purely an issue of matching heat requirement with boiler output. Once you reach the point where the heat requirement equals the bottom end of modulation for the boiler, it will run continuously at that low level rather than cycling at higher level. This is the intent of the boiler manufacturer's design.

If you put a heat bank in the middle to run radiators it has the effect of causing the boiler to burn at high output periodically to replenish the heatbank. It will never run at low output and therefore not in its most efficient range.

An indirect heatbank just for the DHW makes a lot of sense, because it is recharged at high boiler output for a short time. The requirements for the DHW system are totally different to space heating and the boiler can quite easily drive both optimally by having the boiler drive the heatbank and CH separately.

.andy

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[Andy Hall]

In fact it's far more likely to be able to drop in in place of the existing cylinder if one wanted to do that, or easily in the loft position, simply because the boiler is typically in the kitchen, the cylinder on the first floor and tank (space) in the loft.

.andy

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[Dave Plowman (News)]

Same here. As with everything, tastes vary. Which is why the IMM one answer to everything is so stupid.

Yup.

Which can be done with little pressure - it's down to the pipe size and runs. Within reason, of course.

[IMM]

Depends on the boiler. Most condensing boiler "modulate" on marinating a setpoint flow temp. Only the up market boilers modulate on load compensation.

The Gledhill Systemate heat bank has two pumps and has the boiler heating the rads direct. This would be good with a load compensating condensing boiler.

If the CH is on it would be lowering the water temp at the bottom of the store. This returns to the boiler at a low efficient temperature. Many stores have the cycl stat low on the cylinder and set low, as they calulate that stratification would keep the top at approx 75-80C and the bottom very much lower.

A DHW only heat bank is best as one layer of heat interchange is removed. The return temp from the store would be low in usage promoting condensing efficiency.

[IMM]

Who wants a boiler in the kitchen? Why not have the dishwasher in the bathroom as well.

[Huge]

The best shower I ever had was supplied by a "Tanganyka Boiler" in the middle of the Masai Mara. A 40 gallon oil drum on it's side is filled with water, the shower connected to one port and a vertical pipe connected to the other, to provide the head. Light a large bonfire under the oil drum, et voila, large quantities of hot water at low pressure.

[Tim]

I'd have to second that. I worked in a new building once that had staff showers on the ground floor. They managed somehow to deliver mentally high pressure and flow rates to the said showers building was only two storey so I assume it was mains or pumped and not gravity fed.

On the good side, you could get clean in about 30 seconds (pre-soap, blast off). The downside was - aim the shower head the wrong way and you nearly got you n*ts blown off. Bl**dy hurt too.

Makes my eyes water just thinking about it...

Timbo