DHW flow rates - Intergas HRE 36/40

31 Aug 2016
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United Kingdom

I'm looking for a new boiler as my Alpha CB50 Combi is leaking from the DHW storage cylinder and its apparently prohibitively expensive to repair. I find the Alpha fine in terms of CH output and DHW - the manual rates it at 28 kW for both.

The guy that services my boiler recommended a W-Bosch 38 CDi Classic Combi as a replacement that would be able to match the DHW output of the Alpha without going down the route of an unvented cylinder. However, I'd read a lot of positive things about the Intergas boilers so I found an installer to quote me on one of those. He recommended the Intergas HRE 36/40, at a much lower price than the W-Bosch. However, I am a little concerned about the DHW output. As stated the Alpha I currently have has a small hot water cylinder built in so it copes pretty well with a shower and a tap running at the same time. With the Intergas I wouldn't have the thermal store so I'm wondering how it would compare? The specs on the Intergas website state 18 l/min for a rise in water temp of 25 deg C. This seems pretty decent on the face of it, but comparing it with the W-Bosch 38 CDi it doesn't look that great. The specs from each manufacturer are presented slightly differently but based on the input kW for each I calculate 13l/min for the Intergas and 16l/min for the W-Bosch for a delta T of 35 deg C. Question is, is 13l/min enough to match the output from the Alpha? If anyone is running an Intergas combi with multiple showers I'd love to hear your feedback on how it performs!

Also, the CH output of the Intergas is a lot higher than what I currently have at 40.9 kW. Seems overkill but the next model down outputs slightly lower than the Alpha at 26.6 kW so may not be enough. I live in a large 4 bed victorian terraced with a bathroom and an en-suite and the Alpha seems fine.

For the Intergas is it recommended to fit a magnetic filter? That seems to be missing from the quote.

I'm also waiting for quotes to come in from both installers for unvented cylinder options but I believe this option will be much more expensive. I'm also looking at a couple of other storage combi options, the Vailliant 938 and Viessmann 111-W.

Thanks for taking the time to read this! If you have any useful comments or advice I would much appreciate them!
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Flow rates are a matter of physics and providing your pipework and pressure are up to the task, one boiler is pretty much as good as the other on paper performance wise.
Thanks for your reply. I can see how the performance may end up being similar if the pipe work wasn't up to the task, but if it is up to the task then doesn't physics say that a larger power input will give you a larger maximum flow rate for the same temperature rise?

I see you're very experienced with Intergas products. Can you comment on why they only offer a 7yr warranty with the HRE but a 10yr with the Eco RF?
Like all long warranties it's a marketing thing. My van came with three power options. But the mechanics are the same for all three vehicles. The difference is purely software.

With the boilers, kW is kW, so you have to decide what performance you want..

The 938 is over complicated and a pita to work on. The 111 is OK, but big. Out of the two I'd go 111.

However, if I had the space, the recommendation would be an Eco RF 24 with small Unvented cylinder. Best of both worlds.
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I've just had a intergas rapid 32kw plus fitted, whilst I haven't ran the shower properly, as a boiler for heating it's very impressive, very quiet and seems very well made.
One feature of the intergas that seems good, is, it can be fitted as a combi or system boiler, you programme it how you want it.

I'm wondering if lagging all hot water pipes would make difference to the temperature of water, yes I've done this, but have nothing to benchmark it to.
Thanks for your input guys. I do have space for a cylinder, just waiting for the quotes to come.

Be interested to hear an update from you Mr Chibs once you've had the opportunity to properly test the new boiler!
Dan, I've been reading all the posts I can find on the Eco RF + Joule setup you recommended. Would any Platinum Intergas installer be able to set this up correctly with a Nest or is this a bit of a specialist setup (pin 5?)? Is worth considering ditching the Nest and going for the Intergas control offering to get the most out of this setup?
@bodneytrot tell us your nearest town and we can recommend someone who is familiar with the setup. Honeywell T6R-HW is far superior to Nest
It is easy enough to do. If they don't know then it'll take ten minutes of reading up in one of the professional forums (there's one here and the facebook installer group.

Stick with the Nest if you have one or go over to the Honeywell Lyric T6
How many rads do you have? Almost certainly if you went the combi route you'd be better with an ECO36 and not a 36/40.......
@Razor900 have you any experience with the Xtreme model? If I went the combi route wouldn't this be worth considering other the Eco RF? I appreciate the warranty is shorter but the DHW output is greater, according to the spec at least. Seems to gain from recovering waste heat from the flue gas rather than any increase in power. Not sure how well that would work in practice.
I might be wrong, but the xtreme 36 only seems to give around 1.5L per minute more hot water than the rapid, at £800 more than the rapid 32 it would have to use a lot less energy to make it worth the cash.
I'm running 9 rads and will be powering and underfloor heated room (40m2), with 10 rads you'd have no problems running from rapid or eco RF.

FWIW, I was quoted to £3800 for a complete install, from nothing to finish (if this helps)
Thanks @Mr Chibs. I have been quoted £1950 to remove the Alpha and install the HRE 36/40. £250 more if I want the Eco RF.

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