Sometimes - it seemed to change fairly frequently depending on what he was plugging at the time. Rianni and Reemha seemed to be favourites in later years.
So far I have been impressed with how easy the Vaillant designs are to work on as well - tightly packaged but well though out and serviceable.
Indeed - one of the many ways his "solutions" fell down!
The moral being if you need a delivery rate of more than ~15 lpm of DHW, then you need a storage system of some kind (even if its a big floor standing combi with built in cylinder)
Cold mains water flow is the vital thing. Applies both to combi and pressurised systems.
Tale of woe(ish):
House (-2) had an unvented hot water system with a system boiler. Upgrade to the plumbing was a shower pump (hot and cold) which turned out to need a bigger cold tank and a bigger hot tank to fill the spanky new extra large bath. However the pump was strong enough to service a second shower/bath when we put in a second upstairs bathroom, and would even do both at once.
House (-1) has a Baxi back boiler on the gas fire, and a vented system in the airing cupboard in the hall behind the fire. Whole thing was shagged so we replaced it with a Worcester Bosch combi of modest proportions in the loft. This filled a bath full at a good rate, and also provided a good flow rate on the shower.
Child has own house with a combi and gets a really good flow rate to the shower.
This house we have a larger Worcester Bosch sized to run two showers simultaneously but a puny cold water flow which is really irritating. However not irritating enough to take the plumbing apart to try and find out why we don't have a decent flow. Downstairs has a better flow than upstairs but it would anyway given the difference in pressure.
So before you commit to a mains pressure system double check that you get enough flow.
If in doubt go with a vented system because you can always increase pressure and flow with one or more pumps.
Cheers
Dave R
+1
These probably work best in soft water areas. A whole estate round here built in I guess the early to mid 90's was fitted with a thermal store with a cold water mains double coil running through it to extract DHW. The problem was that each coil was only about 5mm dia (good I guess for surface area to volume ratio) and although all of the houses were fitted with this type of water softener
I would say that the water here is is pretty soft.
When we had the extension added I re-routed the mains water pipe in 25mm in a straight run from the pavement to the boiler room, about 8 metre run so flow is no longer a problem. :)
In follow up to your tales of woe, my first house was "interesting" to say the least.
Coal fired Parkray back boiler in the lounge with vented H/W tank above and a single pipe central heating system with a pump under the floor in the lounge.
I added a 2nd pipe to make a proper flow/return C/H but to completely automate everything I added 3 tank/pipe thermostats, one near the bottom of the tank, one near the top and one on the 1 1/8" rising pipe from the back boiler, a 3-way zone valve and new circulation pump.
With everything connected and switched on the rising H/W from the boiler would trigger the pipe stat that switched the circulating pump on and the 3-way valve was controlled by the lower tank 'stat so HW tank was always priority before the valve switched to C/H circuit but the cylinder heated up very quickly.
The 3rd cylinder stat at the top of the tank was connected in series with the immersion heater for more accurate control of immersion.
Oh I also added a twin impeller Stuart Turner pump too for a proper "power shower" . All worked flawlessly and when gas came to the village I replaced the coal back burner with a living-flame gas fire that also had a gas back boiler and then of course added a timer. Extremely simple and very effective. :)
Pressure is around 3.5 bar so flow is pretty good especially with the upgraded water main pipe.
Cheers - Pete
If it fits the requirement, then it's not substandard. The fact that it might not fit *your* requirements matters not a jot! Price may frequently be one of the requirements.
You are conflating different things there. Heatbanks typically provide mains pressure hot water (and it indeed may be mains pressure rather than reduced to 3 - 4 bar by the typical control valve arrangements on an unvented cylinder).
Pumps are not necessarily required for a heat bank at all unless you are using one to circulate primary water to an external plate heat exchanger for DHW rather than having a purpose made tank with a DHW coil.
As would be a good heat bank. Heat banks are also good if you want to bring in solid fuel to the mix and can do split temperature outputs nice and easily with multiple tapings. So you draw heat for DHW from near the top, for rads from the middle, and for UFH from lower down.
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