Boiler Recommendation

Curious as to why a thermal store should make any difference. Do Vaillant know how they work? Sounds like b*llocks.

Tim

Tell us a bit more about the store...

Is it vented or unvented? Direct or indirect?

And what do you feed from the store? (i.e. just DHW, or does it also run rads / UFH etc?)

They also will not give you the 10 yr warranty unless its an approved Vaillant Advance installer.

Intergas used to do teh same ... now they give full warranty as long as Engineer is GasSafe registered.

We have a Boilermate 2000 heat store, until very recently heated by a Potterton Suprima 50HL heat only (non-condensing, non-modulating, cast iron heat exchanger) boiler.

The Suprima has been replaced only a few weeks ago by a Worcester Bosch Greenstar 15Ri heat only boiler. It has integrated perfectly with the Boiler-mate, with no issues during the installation and commissioning processes.

At one point the fitter mentioned that a 5 wire cable was needed to connect the two, but when I looked at the circuit diagram for the BM control unit, it was obvious that the latter was controlling the pump over-run (which he was concerned about).

The WB has functioned perfectly so far, being quiet in operation and unlike the Suprima only undertaking one burn per heat cycle in contrast to the five or so burns of the old boiler.

It’s a bit hard to be accurate but so far with only DHW being demanded, savings appear to be in the region of 10%.

HTH

In this instance should not really matter, all I want is a simple boiler connection ... i.e. pumped primaries go to the store, whole content of store circulates around boiler. (as it is now)

It is pressurised to 1.5bar, and has a large expansion vessel on primary loop, tank has auto air vent. Thermostat on store sets the Heat call.

Main pressure DHW feed is through a plate heat exchanger at top half, a centre baffle and a transfer coil in lower half for UFH

I can put drawing oh heat exchanger & system on-line if you want one.

ok so that sounds fairly straight forward from the boiler's point of view, the store just looks like a normal unvented radiator primary circuit as far as it is concerned. You don't even need split temperature operation.

You ideally want a boiler intended for use with a sealed system primary. Most "heat only" boilers on the market at the moment seem to be designed for open vented operation. So you would need to either convert one to sealed operation[1], or just go for a system boiler and make the external pump redundant. (a system boiler's internal expansion vessel and overheat stat etc would work quite happily in series with the existing discrete ones without any problem).

If you are looking at the Vaillant range then you could go for a 400 series ecotec and convert it to sealed[1], or go for a 600 series system boiler and use it "out of the box". (both are easy to fit an work on)

Personally I like their system boilers. The ecotec have stainless HX, I think some of the new ecofit ones might be ali.

Considering the awful reputation that model had, you have done very well to get 18 years out of it.

I looked at Valliant site - the OV boilers have aluminium heat exchangers. (EcoTech Plus)

As I have full controls already in place, don't wnat to be bypassing teh pump and using System boiler ..... for example when you start drawing DHW the primary pump runs without firing boiler to 'stir the Thermal store, keeps HW moving over the heat exchanger.

So far choice seems to be Intergas HRE30 OV and Viessman Vitedens

The 400 series have been redesigned more recently, and the move to ali seemed to come with that. The 600 ecotec+ are still stainless.

Probably nothing stopping you have both in circuit if required...

I have no experience with either of those, so can't comment beyond the Viessman being the slightly better known brand and so possibly better supported.

Rick, Your scenario sounds virtually the same as mine! I installed NuHeat UFH about 17 years ago along with a very expensive MAN (German) boiler with radial burner and SS heat exchanger, except I didn't have a heat store so it had to be a combi. I caressed that boiler through many years of self repairs until last year the back panel with water channels rusted out and it properly died in April, so seemed like the perfect opertunity to get rid of the combi-nemesis for good and add a heat store with a new boiler.

I spoke to Veissman about wheter their OV system boiler could be used on a sealed system and their tech. said absolutely no reason why not.

I was just about to pull the trigger on a 100W(?) system boiler then stumbled across Intergas. Initially said not for me because it said Aluminium Heat exchanger BUT looking into it further, yes the heat exchanger is made from Aluminium BUT the entire water passage through the boiler is copper pipe snaking through a massive slab of aluminum. You have to watch their video to see their patented design and how aluminium isn't the pain to be avoided.

Well that was it. Reviews from "the trade" all point to intergas being a bomb-proof boiler with un-blockable heat exchanger.

Dug around and by chance a plumbers merchants in Cardiff kept Intergas boilers in stock so a quick trip across the Severn to:

Pitfalls... First, the Flue outlet is front-left of the box but the offset flue kit sorts that out so it all lined up with the original boiler position perfectly. Secondly the flow/return exit from the top but Intergas do do a back plate that allows pipes to be run down to normal bottom exit but I saved that extra £100 by routing pipes above the flue before dropping down to the thermal store.

Wiring was straight forward and it comes with weather compensation as standard from what I can tell although you have to buy the sensor but not relevant for thermal store anyway.

It's been installed by a "competent person" and has been run once into

Do you really need 28 to 30KW? My combi was 36KW (for a decent DHW water flow)but the New boiler at 15Kw heated up the thermal store extremely quickly, and I cranked open both UFH systems the original Nu-heat 4 zones (10KW output) and the additional 4 zones added in the extension (3 new rooms) AND I took off all the bedroom radiator TRV heads (6 oversized radiators) and set all thermostats to 30 degrees. Completely unrealistic scenario but everything got hot hot and the thermal store still went up to over 60 degrees and climbing while turning the house into an oven.

Anyway, there's my experiences, I've just today taken delivery of a woodburner/boiler today which I'm currently fitting that will provides

Going to be adding an Intergas combi. to replace the Valliant non-condensing boiler at work when it finally dies as it doesn't use a diverter valve, simply another copper water path through the yeat exchanger.

Hope that helps. Cheers - Pete

Not really done well, forever faulty ..... I'll try to recall ....

Those were due to intermittent lock out, eventually traced to loom earth not installed - allowing arcing across back of cards

Heat Exchanger Gas Valve x 2 Electrodes 3 or 4 then upgrade to new design and 3 of them Burner box door x 2 Burner x 3 Fan condensate trap Flue Several temperature sensors

Not much of original boiler left ... when they changed heat exchanger almost all of the boiler was in bits.

The biggest issue is lack of diagnostics ..... fault always the same, lockout with red flashing LED - not much help Fault flow charts show just about anything causes that.

Thanks ..... Intergas is certainly one of the options, I have seen the video at

Sounds like a used Vaillant 400 series would fit your requirements

They are open vented boilers - not a major problem, the can run sealed system - but will need an external filling loop and pressure gauge (if not already there), and an overpressure relief discharge valve and pipe.

Both of those in place as is an expansion vessel

Spoke to a few people, and GasSafe guy I use .....

Decision seems to be: Viessmann Vitodens 100-W ..... good boiler, excellent SS heat exchanger, thought of as high tech modern top of teh range German design. My GasSafe guy is seeing what would be needed to get the 10 yr warranty. Its only 7 years if no approved installers. He was previously approved.

Bosch Worcester Greenstar 8000 Life ..... only negative point is aluminium heat exchanger. They are expensive for what they are, but only manufacturer that offers 10 year guarantee (parts & labour) most only have a warranty, which gives a lot of exemptions.