new house - can't work combi boiler

we've just moved into new house last week, and there's a long list of jobs to be done... but top of the list is get the hot water/central heating working.

I've read the instruction manual but maybe I've misunderstood as still can't set the combi boiler (it's a Vokera excell 80SP) to provide decent flow of hot water for baths or shower. The temp varies from cold - tepid to hot (just briefly), and flow rate is poor.

any suggestions much appreciated - thanks

- Katya

Reply to
Katya Robin
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Combi boilers heat the cold water as it passes through the device. For that reason the water-flow is restricted because if it passed through at normal 'speed' it would not be heated up enough. Personally I wouldn't touch a combi boiler with a barge-pole. Several relatives and friends of mine have them, and they do nothing but complain about the unreliability, frequent need to call out plumbers, and the excessively long time it takes to fill a bath. Certainly the water temperature should not fluctuate while the tap is running so you seem to have a problem somewhere - but what may be causing that is anyone's guess without examining the thing.

Kev

Reply to
Uno Hoo!

The 80SP is a now an old model, but repairable.

More old wives tales. They bought cheap crap combi's that break down. Don't complain if you buy a Lada and it breaks down a lot. Combis are available with high flowrates that fill baths pronto.

In short:

  1. Get the combi with the flowrate you need
  2. Get a good quality model.

If you don't fulfil Nos 1 & 2 above then don't complain.

Reply to
Doctor Drivel

Not at all. They are not imagining the problems that they have!

They bought cheap crap combi's that break down.

Worcestor Bosch? Baxi?

Well I've yet to find anyone who owns one! Every single person I know who has a combi says the same thing: "Takes bloody ages to fill a bath."

Worcestor Bosch? Baxi?

I'm not complaining - because I don't have one of the wretched things. But everyone I know who has one has exactly the same complaints. They can't all have cheap 'crap' with poor flow rates!

Kev

Reply to
Uno Hoo!

Did you read what I wrote. More combi's are sold in the UK, and the EU, than any other type of domestic boiler. They don't all fail every other week.

W-B did make the odd dog, and Baxi? Forget it.

Because you not seen one doe not mean they are not there. Look at the Alpha CD50

You have been told, can't you focus and understand? High flowrate models are available, and have been for a long time. Read it all again if you can't understand it.

W-B did make the odd dog, and Baxi? Forget it.

Then don't whinge then.

Reply to
Doctor Drivel

Did you read what I wrote. More combi's are sold in the UK, and the EU, than any other type of domestic boiler. They don't all fail every other week.

W-B did make the odd dog, and Baxi? Forget it.

Because you not seen one doe not mean they are not there. Look at the Alpha CD50

You have been told, can't you focus and understand? High flowrate models are available, and have been for a long time. Read it all again if you can't understand it.

W-B did make the odd dog, and Baxi? Forget it.

Then don't whinge then.

You are dumb. Read what I wrote. They got the wrong models with the wrong flowrates.

They obviously have. For every dope who bought a cheap and nasty combi with a poor flowrate, there are 1000s of satisfied owners of good quality combi's with decent flowrates.

Now read what I wrote and understand.

Reply to
Doctor Drivel

In message , Uno Hoo! writes

All the ones you have heard complaints about could have low flow rates.

Most Combis that I have seen have flow rates of 9 or 11 l/m with a 35C temp change. They tend to be 24K or 28K BTU which, in theory, is enough to heat a medium 3 bed semi. However, the flow rate is crap.

Spend more money, and a much greater flow rate can be obtained, but plumbers tend to suggest the cheapest to compete with competitive quotes, and the customer tends to know no different.

Reply to
Richard Faulkner

Actually, during my poorer years I owned two Ladas in succession over eight years and neither of them broke down ever!

Combis are

Yes - it sounds impressive - but at over £1000.00 plus fitting charges it's more than most householders would be prepared to pay!

So I'll modify my criticism of combi's to: The majority of moderately priced combis will take ages to fill a bath!

Kev

Reply to
Uno Hoo!

You forgot to add "with lukewarm water suitable only for ducks"

Reply to
Matt

But only if the incoming mains flow rate is sufficient.

MBQ

Reply to
manatbandq

So one in a thousand combi's sold is cheap and nasty?

Lies, damn lies and Dribble's made up statistics.

Reply to
Matt

As you may have noticed you have just asked the "holy war" question - so you may find rather more (not too useful) responses than you need to this question!

With regard to your boiler, there are a few possibilities. One may be that it has a fault and needs fixing, however it is also possible that you just need to understand its quirks to get anything useful out of it!

The model listed is quite ancient, and in common with many combis of the era they are more quirky than current models.

The first thing to note is that with any instantaneous water heater the thing that will determine the performance more than anything else is the power available from the boiler - since it needs to heat water on the fly. More power = more hot water.

Your boiler is probably just under 24kW input - this is about the smallest you can get today. To make matters worse, it is also only just over 70% efficient. So of those 24kW, 7 of them will go straight out of the flue and not do anything to heat your bath. That leaves you 17kW to play with.

Doing some quick sums suggests that this time of year you can have a maximum of just over 9L of water per min at bath temperature. That is not much. In the winter when the ground water is 10 degrees cooler, that will fall to under 7L per min. So don't expect a bath in less than 15 mins if you like it full.

So the first thing to realise is that if you turn the hot tap on hard, the water will come through the boiler too fast, and it won't have chance to heat it enough. So you need to turn down the tap to have less flow, but of hotter water.

The other trick that some old combis played was that they needed the tap to initially be turned on quite hard to start them running. So the procedure is turn the tap on hard, but then turn it down until the required temperature is reached. Some people prefer to tweak the cold input isolation valve on the boiler down so that the maximum flow through it will not exceed its capacity - that way you can turn on the tap harder and not need to be so delicate with adjustments. (it won't give you any more hot water thought!)

With showers you have another potential problem. The boiler will have a water temperature thermostat, that will set the maximum temperature of water it can produce. If you demand too little hot water than the temperature will rise to the point where it gets too hot and the thermostat will cause the boiler to turn of its burner. Your shower now goes cold, it turns the burner on again, it gets too hot, and so on!

To fix this try turning the shower on harder if you can. If that does not work, see if leaving the hot tap in the basin running a little while having your shower is enough to keep the demand for hot water up to the point that will keep the boiler firing.

Modern combis are better in these respects since they tend to be more powerful (and efficient) and are also able to better control their burners to actually match the demand for water. If you replace it with another, then you really need to look at the top end of the power inputs (i.e. 35kW and better) to get decent bath filling performance.

Reply to
John Rumm

I've never stated that they do. But the experience of every owner of combi boilers that I know is that they break down far more often than conventional boilers. My central heating boiler is now thirty years old, It has been serviced about twice and has had one replacement thermo-couple. That's it. My son's Worcestor Bosch combi has caused him endless problems and my Mother-in-law's Baxi combi has required plumber attendance three times in four years. Both say they would never even consider a combi-boiler again.

What you forget is that probably 99% of householders don't have the knowledge to make an informed choice - many buy new/second hand houses in which the combis are already installed. Those who decide to switch from conventional to combis rely on the advice of so called 'expert' plumbers.

What you seem to be arguing is that you agree with me that the majority of combis are useless - and you only get a good one if you are prepared to pay the earth. Bit like telling the driver of a troublesome Focus/Punto/Astra etc that they have only themselves to blame for not buying a Merc!

It would appear that the only combi with a flow-rate even approaching that of a conventional system is the Alpha CD50 - and that is comparatively extremely expensive. I take it you agree with me then that the majority of combis are pathetically useless?

I'm not whingeing - I'm merely pointing out an absolute fact - that everyone I know who has a combi boiler tells me that they are crap.

Yes - they should have bought a Mercedes!!

I would suggest that your statistics are arse about face. For every 1 satisfied combi owner there are thousands who think they are rubbish!

I have and what you are suggesting is that out of all the combi boilers on the market - only one or two are any use!

Kev

Reply to
Uno Hoo!

Where did you get this statistic? Did you make it up?

Reply to
Doctor Drivel

Lucky man.

I can't account for cheapskates, and these whinge from the rooftops when they find their mismatched cheapo purchase doesn't deliver. An unvented cylinder, complete with valves, can cost around £1,500, then the boiler on top. The Alpha CB50, for what it offers, overall is cheap, and its saves a ton of space taken up by tanks and cylinders. Look at the big picture of the "system" rather than the box price.

That's getting better.

Reply to
Doctor Drivel

Very true. The sad thing is that most people, like this poster, think that all combi's are all the same. Even on his second post, after being put right, he was still insistent that all combis can only fill a bath in 15 minutes and break down every week, the indoctrination was so complete.

Reply to
Doctor Drivel

You more than implied that.

They do not. They are system boilers with a water section added. That's all. In a tank/cylinder/boiler setup, if the 3-way mid position valve or cylidner stat plays up no one blames the boiler. In a combi the 3-way valve is moved within the case, so if it goes the boiler is at fault. Virtually all the system is inside a combi. You have to compare faults in whole system v whole system

My God, a potential time bomb. If you went to a modern condensing boiler your bills will drops about 40%, save on CO2 emmissions and added safety too, so you don't blow up the street.

So, two lousy boilers.

I don't forget that at all.

They can always upgrade to a proper one.

Plumbers are good for drains and gutters.

I am not agreeing with you. They are not useless at all, they are misapplied, which is very different. There are far too many cheap and nasty models about for my liking. But you pays your money.....

The earth? Good combis are around that are well priced. It is a very competitive market. 60 to 70% of boilers sold in the UK each year are combis. 1 million boilers a year are sold.

Yep. Some models are known to be more reliable than others. Toyotas don't cost the earth and are highly reliable. So someone who buys a FIAT can't whinge when theirs keep packing up.

It is not extremely expensive at all. I have explained why it isn't.

Not at all. and you are talking out of your botty. I fitted a Microgenus combi (12 litres/min) in a flat. It is fed off a roof tank giving 1 bar constantly. It is mainly for showers. It heats the flat up in no time at all, like zippo, being around 100,000 btu/hr. It fills a bath up in about 8 mins, and faster in this weather as the incoming water is over 20C. Bath filling is not an issue as bath are rarely used. For this application it is the perfect choice. Horses for courses.

I relative contacted me and asked about a boiler for their extension, which will give them two bathrooms. I recommended an Alpha. Horses for course. If in a semi with one bathroom where they take baths every day then still an Alpha, or any floor standing unit (see other post).

Which have taken to be representative of all combis all over the world, which is talking out of botty talk.

No, just larger flowrate better quality models. You can buy a Viessmann, or MAN, if you like. RR quality but you pays your money.....

You should stop making things up.

What does "any use" mean? Quality? Fit for purpose?

There are many high flowrate models about - fit for purpose. There are many high quality boilers about, high and low flowrates - quality products.

So, analogies with cars again. If you need a van that is the size of a large Transit, then don't get upset if your tiny FIAT keeps breaking down and can't fit all the goods inside. A larger Merc would be reliable and fit all the goods inside. Got it?

Reply to
Doctor Drivel

Of course there is one additional problem with combis - no airing cupboard to dry your damp towels in!

Kev

Reply to
Uno Hoo!

Provided the mains supply is good enough to give about 16+ ltrs/min at the Kitchen Sink and 10+ ltrs/min through the hot taps then the most likely problem is scaling up of the secondary heat exchanger in the boiler.

Reply to
Ed Sirett

Three solutions:

  1. A ferrous free towel rail or rad in there on the DHW supply
  2. A ferrous free towel rail or rad in there on a DHW secondary circulation loop, which also gives instant hot water at all taps.
  3. A small rad in there on the CH circuit.
Reply to
Doctor Drivel

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