Combi question.

[Paul]

I have to replace my old boiler so and going for a combi i live in a 2 bed bungalow and have an electric shower. After searching the net I have come up with two options. Any thoughts for or against each one.

Biasi Rive compact HE £468.83 inc vat, flue and timer

or

Ideal Isar 24 HE £688.64 inc vat and flue

I plan to run my dishwaser and washing machine just of the cold supply so they need not enter the equation and a rough calc of BTU requirements for rads is 26000.

I do plan to hopefully loft convert at some point so that would mean possible 3-4 more rads and another basin.

Thanks for you help

Paul

[Doctor Drivel]

Give this a miss. The condensing boiler has a secondary heat exchanger. Bad news.

Much better. 2 yr guarantee, one piece heat exchanger, pre-mix downwards firing burner.

The boiler is big enough to heat your house, with more capacity to spare, unless it is "very" big. Combi's are high rated burners for the DHW side, so lots of oomph for CH. It will not fill the bath quickly at all. It will give very good showers. If you don't mind slow bath fills or shower most of the time, then it is fine.

If you want fast bath fill then you will require a high flowrate combi, which are more expensive.

Try these for cheap combi's. They are the cheapest. Give them a ring:

Go for in this order:

- Glow-Worm 38CXI @ £719.19

- Worcester Greenstar 35HE Plus @ £832.30

- Isar 35HE @ £685.00

[Paul]

Snip

How quickly on bath filling is not very quickly? I can afford the glow worm 30CXI or the Ideal HE30 which would you pick? The glow worm has a stainless steel heat exchanger is this better?

I have just had to replace the control pack on my old CH system will i be able to use that on my combi to save buying another?

Cheers for you help someone who makes sense( there seems to be a shortage)

Paul

[Matt]

Has someone put something in his tea?

[Andy Hall]

I would suggest checking on the track record of Dr Drivel/IMM before forming an opinion.

The Glow Worm (highest power of these) manages 15 litres/minute for a temperature increase of 35 degrees. Assuming that the water supply can deliver this rate (you should check that), then in the winter, when the cold water temperature is around 5-8 degrees, it means that in effect this will be the *total* rate supplied to a bath or shower at 40 or so degrees.

In the context of a bath, which requires 150 litres to be at all reasonable, it would take around 10 minutes to fill. You may be OK with that, or you may not.

You could use your existing controller with any of these boilers although some have one built in.

A stainless steel heat exchanger is a good idea.

[Doctor Drivel]

8 to 10 minutes, depending on bath size and temperature of in the incoming cold mains water. A very large bath will be irritating to fill. A modern 100 litres bath is not that bad. Less in summer when the mains temperature is higher.

With combi's many people find it is best to fill the bath 1/3 full and then get in while still filling, as the Japanese do. But many people can't figure out this simple procedure. Some use a hair washing shower attachment while sitting in the bath, and this also fills as you go along.

Go for the high flowrates and you will not be that disappointed. There are combi's with higher flowrates than the best in the list, but they cost more.

Glow Worm. It is basically a Vaillant, and made in Holland. The Dutch invented condensing boilers, and 90% plus of boilers are condensers.

Control pack? Do you mean programmer? Timeclock? What make have you installed?

This is the Internet, so the loonies can have a say alongside all the bright ones. Sadly, the unaware may not know the difference.

[Doctor Drivel]

Not another know-it-all Internet amateur.

100 litres is the modern standard, as the baths are shaped for the human body.

See my other post.

[Doctor Drivel]

[Richard Conway]

What did she do :)

[Paul]

sadly the top where the flue joins is patched and on it last legs :(

Paul

[Paul]

snip

It is a Danfoss Control Pack from

66341-38 I guess I can utalise the programme, room stat and wiring box.

Paul

[Doctor Drivel]

Paul

I would say nothing salvagable from that setup. It can be used but not worth it for what it offers and the hassle. Go for: Honeywell T6667B1085 CM67 Prog Room Stat With Optimum Start £54.05 Including VAT

CM67 requires only a two core cable. Childs play to fit. This is the stat and programmer all in one with about 6 different temperature times during the day - you set temperatures. It optimum starts. That is, you tell it the start time in the morning and it figures out the time to take to warm up the boiler. If a warm morning it will hold off the boiler until the start time. Well worth it, and saves money on gas.

[Paul]

snip

Looks good ashfordheating.com do it for £47

Paul

[Christian McArdle]

I think someone has stolen his account.

Christian.

[s--p--o--n--i--x]

FWIW, the Biasi has a stainless steel heat exchanger with copper waterways.

sponix

[Doctor Drivel]

Go for it. But the optimiser model that I gave the number for.

[Doctor Drivel]

My tea account?

[s--p--o--n--i--x]

[Doctor Drivel]

..and secondary one too, so not worth a light.

[Christian McArdle]

Secondary exchanger designs are rehashed non-condensing boilers. As a non-condensing boiler doesn't produce streams of corrosive acid, they were often designed with a heat exchanger directly above a upward firing burner. However, by bolting an additional exchanger on, the boiler starts to condense (you'd hope so!). This acidic condensate then goes downwards (gravity) and lands on the burner, which corrodes. Meanwhile, the existing heat exchanger also gets covered in acid, which is was never designed to cope with.

Christian.