high output DHW condensing combi

[jayjay]

Hi there

I'm replacing my existing boiler and am planning on getting a natural gas condensing combi. I want to run two showers at the same time (also detached 4 bed house) and therefore need high power. I think a worcester HE40 (or I hear a Vaillant Ecomax 35E is quite good) will probably do it, but was considering some other less well known makes, but wondered if anyone had any experience of them:
1) mikrofill ethos 36 and 46, on paper looks good, but does not come with expansion vessel, filling loop and sefetly valve - then need to be installed separately. The bumf says 46 modulates from 6 - 46 kw which is a much wider range than most domestic boilers, is this an advantage? Only a 12 month guarentee.
2) Beeston S-HR 35 and 51, 2 year guarentee.
3) Viessman
4) Atag

Finally, should any decent independent heating engineer be capable of installing on, or should I try and source the right person (experience in the chosen boiler) to do the job?

One last thing, will the person that installs the boiler be able to flush the existing radiator network?

Thanks
jayjay

 

[ChrisR]

last question - I should darned well hope so!

Which boiler - dunno mate, all a bit off the beaten. If you're having something like a Viessmann I would try to get a V recommended engineer to fit it.

 

[jayjay]

Thanks

I take it from your reply that flushing the old system should really be done as a matter of course?

Anyone else got any opinions on the boilers?

 

[blahblah]

Most 'experts' will tell you that muck in the system is the quickest way to knock out the heat exchanger. The majority will endorse powerflush but many still argue the case for a chemical cleanser being sufficient provided that the system is circulating properly. £15 chemical additive against £300 flush. The choice is yours. (Personally I'd have the flush for peace of mind and bomb proof warranty).
I love combis but doubt I'd recommend one for a house with your usage. Two showers at the same time, maybe a washing machine on the go, someone flushes a toilet. That's a big ask- even of the best, and you may not get the performance you hoped for. Have you tested the mains pressure and flow rate?
If your mind is made up then you won't go wrong with the Vaillant. If you're concerned, find one who has done a day course on the boiler you choose.
Mention where you are- you may strike lucky on here.

 

[jayjay]

Thanks

I've pretty much made up my mind on a combi - I had a worcester 24cdi installed in the flat I lived in before and it was great, only probelm I had was a burnt out PCB when the entire block was hit by a power surge (neighbour downstairs had smoke coming out of their video!). Scottish Power sorted it (and so they bl**dy should).

I agree that sometimes it can be a bit of a bind that the DHW flow rate is limited, but on the whole I think the benfits outweigh the disadvantages.

I've checked my mains inlet pressure and it's not a problem.

 

[Noisemaker]

Thanks

I've pretty much made up my mind on a combi - I had a worcester 24cdi installed in the flat I lived in before and it was great, only probelm I had was a burnt out PCB when the entire block was hit by a power surge (neighbour downstairs had smoke coming out of their video!). Scottish Power sorted it (and so they bl**dy should).

I agree that sometimes it can be a bit of a bind that the DHW flow rate is limited, but on the whole I think the benfits outweigh the disadvantages.

I've checked my mains inlet pressure and it's not a problem.

Hi "jayjay"

I have 18 month old vaillant Ecomax 828E condensing boiler. It had a slight problem when it was comissioned. Then a second problem was the dude who fitted it didn't flush system. (I had the heat exchanger out in less then 10 minutes and fitted it back in about same time). Otherwise its a pretty good boiler. Hotwater delivery is plentifull considering having a teenage family.

The make I have recently heard of viessman boilers. Apparently a Rolls Royce of boilers but I guess they will be expensive.

Hope I have been of some help.

Noisemaker

 

[jayjay]

Thanks noisemaker, I've pretty much decided on the Vaillant, and plan to replace all the radiators now - they are ancient. Basically the cost is going up, but I figure if you're doing a job... Also, just for completeness of info, I've decided to go for cast aluminium rads - for just a little extra cost, them seem to way out perform the pressed steel ones.

Jayjay

 

[ChrisR]

I've checked my mains inlet pressure and it's not a problem.

HOW did you check it? It matters! Less than 30 litres/minute, and you'll notice it. At what pressure? What flow at say 1 bar? No point measuring one without the other.

I like ally rads but you often get dirty stains from the convected air, above the tall ones.

 

[jayjay]

Okay - you got me - I didn't check the mains inlet pressure, I ran the kitchen tap on full for a minute and checked the flow rate, can't remember what it was just now, but it was good and it comes out with the ferocity of a sand blaster - you could blow a hole in your hand if you're not careful!

On the alloy rads - I noticed that for a little extra you can go for a convection profile that deflects the warm air away from the wall a bit, the fins kind of bend forward at the last minute - it does change the look of the radiator though.

jayjay

 

[PTH]

I wouldn't be choosing a combi for your intended use but it seems that you have made your mind up. You'll find plenty of discussion here about the gas pipework sizing to make the larger ones work properly.

Veissmann boilers are generally very good (at least their commercial/industrial ones are) and the price reflects.

With reference to your choice of aluminium rads - be careful to use the right inhibitor and, in the future any chemical cleaners - not all will be compatible with the combination of copper, aluminium and the chrome content of the stainless steel heat exchanger in the boiler - if that's what it has. They also have a tendency to 'ping' when warming and cooling, follow the installation instructions for the mounting brackets very carefully.

 

[jayjay]

Thanks again for your feedback.

On the combi/conventional boiler question - Yes, I've made my mind up, but totally understand people's reservations with this. I have weighed up the pros and cons and have come to the conclusion that the benefits outweigh the cons. Also I lived with a combi for 7 years and having just bought a house with a conventional boiler and open vented system, can't wait to get a combi installed and get rid of all the tanks, pumps, pipes, immersion, inefficiency of storing hot water, running hot water through umpteen meters of pipe to and from the boiler to the tank to the tap etc. Hot water on demand is the future, end of story.