New Combi running 2 showers advice!

[handypandy]

Hi all,

Due to a recent extension my 10 year old ultra reliable 17.6 K (60000 BTU) boiler cannot cope with my new heating/showerin requirements.

First of all my heating requirements alone (based on the number o radiators & sizes) come to 70000 BTU/20.6 KW) I then need a boiler t cope with 2 thermostatic showers running at the same time with goo pressure. My mains water pressure is good.

I want to get rid of my copper tank which stored hot water & the col water tank in the loft.

My questions are:-

How many KW/BTU boiler would I need? based on the "WHOLE HOUSE BOILE SIZING METHOD" I only need 19.6KW but this would only cover my heatin requirements based on my radiators

Is there a RELIABLE Combi on the market which would cater for my showers & maximum 2 hot taps running at the same time?

If some one has been successfully running the same set up as mine abov with a combi they could name It would be much appreciated.

Thanks in advance & Happy new year

-- handypandy

[meow2222]

Really? Thats a hell of a house that needs 20kW. If it really does I'd look at insulating rather than throwing even more heat at it, but more likely it doesnt need anywhere near 20kW.

want, not need.

Sure, but you'd pay a price for that with very poor HW delivery.

Not a hope in hell. For that you 'need' a bigger hot water tank.

There are some tricks you can do to extend the capacity of any given system.

1. Use a shower drain heat exchanger
2. Use a heat exchanger between hot water tank cold feed and central heating circuit. Now when you use hot water, any heat in the CH is used to add heat to the water tank, thus the hot tank supplies hot water for longer. The CH then recovers once you turn the hot shower off. Interior temp is slow responding so you would not normally notice any room temp change.

NT

[Ed Sirett]

A Vaillant Eco Tec 824 will just about do for 2 showers and the heating side is 19kW but the and 828 would give you a bit more HW water and will comfortably operate the heating at 24kW max.

Likewise and Worcester model of around 28kW would suffice.

[Dave Plowman (News)]

There's not one on the market that will give *one* decent shower with a normal domestic gas supply, let alone what you want.

[Dan delaMare-Lyon]

Define "decent" - Is that the "feels like you skin is being removed by a pressure washer with superheated steam" type shower? We seem to get quite acceptable rates out of a Baxi Platinum (24kw) for our needs.....but then - smaller house, single shower etc etc etc

Cheers Dan.

[Doctor Drivel]

The man is coming here for advise. Don't give advise on thingd you know nothing about. Just shut up, it is better that way.

[Doctor Drivel]

Take no notice of this fool, He should eff off.

[Doctor Drivel]

"handypandy" wrote in message news: [e-mail]...

Ed has given a few, but they are not the best in flow rate by a mile. Ed has a thing about Vaillants. Good but others outperform them in DHW flowrate. The CD 50 is the highest flow "wall mounted" combi. There are higher flow floor mounted combis: Viessmann, Gledhill (up to 3 bathrooms), ACV, Ideal, Powermax, Worcester-Bosch, Vokera, all two bathroom jobs.

The Gledhill has full electric backup for CH and DHW.

But, you can use a Rinnai or Andrews multi-point high flow water heater and a sied up CH system boiler. The Rinnai will do two bathrooms no problem and can be fitted outside saving space inside.

The Rinnai or Andrews costs less than an unvented cylinder and never runs out of hot water. Great for body jet showers.

Look at Rinnai and Andrews:

[John Rumm]

You can ignore the heating requirements here - it is hot water demand that will drive your choice.

Keeping it for use with one shower may be an economic option.

For water heating I would suggest 35kW or better if you want anything appoaching two decent showers. Also make sure your cold water main can supply 20 lpm or better.

My 35kW combi can *just* about cope with two showers at once in the winter - however it does reduce the performance of each in the process (partly a function of an inadequate mains feed at only 18lpm in my case). It ertainly would not cope with two showers and any hot taps at the same time.

Go with stored hot water and a pump for one shower, heated from the heating side of the combi, and the other fed from its HW side. That will give far more choice of boilers without needing to look at semi commercial kit, or big storage based combis.

[Dave Plowman (News)]

It's obvious by your mouth you never wash so no nothing about water flow.

[Doctor Drivel]

That is correct.

No. A rather silly option, when a two shower combi is available.

Or a stored water combi that beats that easily..the Alpha CD50.

An Alpha CD50 will do two showers no problem.

My God!!!! I will have to snip this tripe!!!

Great Scott!!

[Doctor Drivel]

Please eff off. It is for your own good.

[Jim Alexander]

"handypandy" wrote in message news: [e-mail]...

Why not? As regards heating *if* it cannot cope its only a few more days of the year it cannot cope assuming it was reasonably well spec'd. As regards DHW, and specifically showering while I wouldn't advocate it as a main shower, for most of the year a 10kW electric shower is IMHO adequate and crucially better than nothing on any occasion your boiler lets you down. Therefore IMHO, a 24, 28 or 35kW combi is adequate for 2 showers. The other two taps, assuming they are basin taps with intermittent delivery mainly challenge the thermostatic shower valves. All that assumes your good mains pressure translates to adequate flow.

If you want to get rid of storage fine, but you may be disappointed with a combi.

I'd keep the storage, maybe make it unvented, maybe put a combi in but only use the combi DHW for a shower and adjacent bath say.

Jim A

[handypandy]

Doctor Drivel,John Rumm,Dan delaMare-Lyon,Ed Sirett

Thanks for your comments, seems I have two options:-

As per Doctors Comments below a Stored Water Combi or A Combi linked t a unvented Cylinder.

The second option would probably be more expensive & would not sav space as i originally wanted.

I think the second option would give more hot water at pressure?

I need to do a bit more research, any more comments appreciated

-- handypandy

[Doctor Drivel]

Electric shiower. You are kidding.

A 24/28kW is not adequate for two showers at all.

Not if he get the right one. Read my posts.

Unvented cylinder? You are kidding? £60-100 a year service charge. Read my posts they give the best options.

[Matt]

Of course It can. If it's ultra reliable then there is no need to change it.

The easy solution is that although you might have two showers fitted it does not mean you have to use them simultaneously. Saves a fortune and no mess.

Copper tanks and stored hot water are, and it must be said, always have been the gold standard. Anything else is a compromise. The Japs are ripping out combi's and chucking them in the skip because they can't cope with their hot water demands. The Frog's would do the same but a 10 second lukewarm shower on the first Tuesday of each month is easily catered for by even the crappiest combi.

19.6kW is enough for more showers than you have, you need to address the storage capacity.

No

Around this time last year someone in middle England turned on the taps to fill a bath, 340.2 milliseconds later the combi boiler fired. The poor sod still hasn't got a bath of hot water. In desperation, somewhere around the end of March they tried to take a shower, the resultant skin damage will require grafts for both frostbite and scalding. Combi's are like that, nasty foreign crap, a product of French engineering, a lump of garlic and a few rubber hoses. Assembled in a slightly different order they become a Renault 4, a food mixer and a dubious sex aid.

You're welcome.

[meow2222]

OP whatever makes you think 17kW isnt enough? A huge country house with

40 bedrooms?

If your only issue is that the hw runs out too soon when showering, that can usually be fixed without installing anything.

NT

[Doctor Drivel]

My God! Loprd Hall is at it again prattling tripe. He has been on the whiskey as it's new year. I will have to snip this tripe.

[Dave Plowman (News)]

That could explain dribble's love for them and his excuse for English. He's French. He certainly doesn't know what a decent shower or bath is.

[Dave Plowman (News)]

Make sure you apply a tourniquet to your neck firmly, then.