Getting hot water from shower to actually be hot

[funkyoldcortina]

[funkyoldcortina]

Maybe NZ isn't as advanced as AUS then because I've seen them there too.

[funkyoldcortina]

Vaillant 24kw combi & Deva Thermostatic mixer works fine for us.

If the OP is in a hard water area, how hot does the water come out of the hot tap if you turn the water temp control on the boiler up to full. It should be way too hot to put your hand in (assuming no thermostatic mixers), above

65degrees C.

If it is not and you're in a hard water area, check the secondary heat exchanger in the boiler isn't scaled up. That can make a world of difference.

A working, scale-free combi is fine for a good hot shower, even in cold weather when the incoming mains is colder.

[John Rumm]

There are a couple of scenarios with combis that can cause problems. One is too little flow to keep the boiler firing all the time. This often results in temperature swings. Can sometimes be fixed by running a basin tap while the shower is on to increase demand.

The other common one is where a high flow shower actually draws water too fast, and the combi can't keep up.

Since yours sounds like neither of these, I would suspect a fault with the temperature limit on the shower.

[John Rumm]

The solution is to not let a cheapskate specify the boiler power. A decent one (i.e. 35kW and over) will usually do a decent shower (i.e. 15 lpm) and possibly a pair of adequate ones.

[John Rumm]

Yup I would concur with that. Its frequently bath running they have problems with - but the combination of mains pressure hot and cold usually makes for a reasonable shower.

[John Rumm]

There may be times where a combi is in a kitchen say, and you have a long dead leg with a cylinder in another bit of the house. So use the CH side of the boiler to do the cylinder for most of the HW needs, and the combi side for the kitchen hot tap so you have potable hot water with no wait. Alternatively, sometimes you want a system boiler but the combi is cheaper!

[John Rumm]

messagenews: [e-mail]...

In my previous place I put a 35kW combi in the kitchen (when I converted the loft and had to reclaim the space occupied by the tanks). To be fair that really was about as instant as you will get without a secondary circulation loop on the hot water system. It was 1.5m of pipe run to the tap, and the boiler kept a few litres of hot water ready to go in an internal tank - so hot water hot the tap within a few secs.

[John Rumm]

You can throw way more than that at it if you have decent mains flow. Some of the heatbank solutions that heat water on the fly use 100kW+ HEs.

A decent boiler (combi or otherwise) should be able to do anything from tepid to 80+ at decent efficiency these days - albeit falling off at a bit at the higher temps.

[John]

> F-O-C

That's what I fitted - helped the combi to cope in the winter.

[Lee]

Vaillant 28kW combi works fine here, what are people calling a "decent" flow rate anyway?

Lee

[Gib Bogle]

Maybe it's just an issue of nomenclature. We have "hot water on demand" systems here, usually gas. This is basically the same as what used to be called a califont (perhaps that's a brand name). Water flowing through triggers gas flames. We replaced the cylinder in our previous house with one of these. It worked well enough.

[Dave Plowman (News)]

I'd expect 28kW to give a reasonable shower - given many put up with electric ones. Might be a bit slow for filling a bath, though.

[John Rumm]

Assuming it does just hot water (i.e. not heating as well) its what would usually be called a "multipoint" water heater here. There were popular a while back, but combination (aka "combi") boilers that can run the heating and do hot water on demand have largely replaced them in popularity.

[Man at B&Q]

If I'd plumbed it in, there'd be isolating valves on both hot and cold. Simples!

MBQ

[Man at B&Q]

If the combi can't cope in winter then it's not fit for purpose, but that's combis for you.

MBQ

[The Natural Philosopher]

that is my feeling more or less.

If they are an sized, they work well enough, but all too often when the house is full of people all wanting hot water..

Never forget the howl of anguish from a teenager upstairs, having a shower, when I the visitor, tried to wash my hands in the downstairs loo..

here, when doing the new build, I looked at all the options. Water softener and mains pressure tank and modest system boiler has given me the best water system I have ever used bar none.

Pressure is generally very good here, mind. Everyone who uses the showers comments on how much piping hot water they deliver.

and I have had no scale problems anywhere.

Drivel always says you can do just as well with a combi and a heatbank. Maybe so, but it would have cost more.

[Gib Bogle]

Ah! They may exist down south, but I've never heard of such a thing up here in the winterless north. No boilers here (in houses) as far as I know.

[jgharston]

Ah, you should've used the hand wash basin... ;)

Anyway, after a week of fiddling about crawling under the kitchen sink and wandering back and forth to and from the bathroom, I've got something acceptable. Shower runs at 45 degrees at slightly lower flow than I prefer, but still usable. Another advantage is that the cold water doesn't go bouncing out of the kitchen sink any more. Takes 9 seconds to fill a 1.5l kettle.

Will have to mark the main stop c*ck tap somehow so if it gets moved I can reset it fairly easily.

JGH

[John Rumm]

Rather than restrict the flow through the boiler with the main stopcock, its more usual to use the service valve where the mains cold waster enters the bottom of the boiler. That way you only throttle the hot water and not the cold.