New Combi

[jp1*]

Hi,

I'm planning on replacing my 20 yr old heat only boiler and relocating it to the loft.

I currently have 2 bathrooms but we rarely operate both showers at once. We have a water flow rate of over 22 litres a minute.

I'm planning on changing the boiler to a Combi and either going to a Worcester 34CDI or 38CDI classic. I was considering a system boiler but I would also need to upgrade my water cylinder and pump which are end of life.

I will probably go for the 38CDI due to the better hot water flow rate it can offer (I know Combi's only support one hot water outlet at a time as a rule). I'm also going to get the Worcester Magnetic filter and Wave controller as all of this will give me a 10 yr warranty.

I've shortlisted the Vailant and Viesmann Combis but decided to go WB based on their warranty and customer service.

Is there anything else I need to consider / check or does this sound ok?
Any other advice is appreciated.

Thanks in advance

 

[ScottishGasMan]

A 38 KW will be much more than you need to run a shower, but will also give decent flow rate for a bath/taps, you'll be looking at 15 litres min with a 35*c rise in temp from the mains water, so at 11 or 12 litres per minute you will get toasty hot water.

Personally I'd go with the vaillant 838, but its your choice at the end of the day.

One thing to be aware of is if your current system is open vented then you will be putting it under more pressure so any leaks/potential leaks may show up after the new boiler is fitted

Make sure you are happy with it being in the loft as you will need to access it to repressure the boiler and to reset any faults etc.

 

[jp1*]

Do you think we have much chance of getting 2 showers running at the same time with a good flow rate with the 38cdi? Or do you think the 34 is more than sufficient.

Yes been made aware of the leak potential - thanks.
The loft is the only place we can fit it in order to make more room in kitchen. Is there much involved in terms of re-pressuring the system?

 

[ScottishGasMan]

Depends on the showers and pressure thats in your pipes while running, showers mix the hot and cold so rarely need the boiler to run at max rate to keep them warm, so assuming the flow/pressure in the house and pipework is ok you might be able to do both showers at once.

If there both thermostatic showers then when the flow rate drops to the hot side they should alter the mix appropriatley to keep the temp steady.

go for the 38 and give it a try, worst case you have great hot water to one, might be able to get useable hot water to two.

 

[vulcancontinental]

You can duplicate the pressure gauge and filling loop downstairs somewhere so a trip to the boiler is not necessary. Resetting lockout on a boiler or checking fault codes on the display are a PITA though unless you use a boiler and control that offer remote control.

My bette noir is putting the source of hot water as far away from the tap used most. You'd be better asking your next door neighbour if you could put it in their kitchen.

I worked it out in 2009 that not counting waste of cold water run while waiting for the hot to reach the kitchen tap, once the hot tap was closed 30' of lovely hot water then sits in the pipe between boiler and tap growing cold. Back then before 18%, 12% and 8% gas price rises it was worth around £35 a year just to heat that dead leg water and let it cool.

 

[jp1*]

The pressure is also good and we have thermostatic shower controls. The 38cdi only works out at 150 quid more so I will go for it although I know it uses more gas.

Two more questions:
would you recommend getting trv's in the living room (where wave control/stat lives)?
Power flush - I've heard that some fitters don't do this properly eg rush it. How can i try to avoid this / watch for?



Thanks a lot!

 

[jp1*]

That's a good point re the kitchen taps. We don't actually use that much hot water from the kitchen tap - the dishwasher is used for dishes etc. I will ask about the additional pressure gauge.

 

[ScottishGasMan]

Two more questions:
would you recommend getting trv's in the living room (where wave control/stat lives)?
Power flush - I've heard that some fitters don't do this properly eg rush it. How can i try to avoid this / watch for?

Your not supposed to use TRV's in the room that the Room Stat will be in, if you turn them down the room stat wont know when to turn off and over heat the house.

RE:Flushing, Its a tricky buisness, there are many variables (how didrty system is, what type of dirt it is, bore of pipework/size and type of rads/length of pipe runs/drain points available/number or rads)

To do it throuroughly on an average sized (8 rad system that is moderetly dirty but without blockages) a day would be reasnable, while a lot of the flushing can be done while other jobs are being done alongside, most companys only allow 4 hours for a flush (takes best part of an hour to get set up and then tyding up after again.

Best way is to get it flushed, then after a week or so of running the system take a water sample and send it off for testing.

 

[Agile]

Whilst its always better to do a power flush, the reality is that a good chemical flush is totally adequate for most systems when the water looks clean.

Many installers just fit a mag filter and don't do any cleaning at all which is rather naughty. Particularly as they don't even come back after a week or two to check/clean the filter.

Tony

 

[JohnHarrison]

Many rate the Intergas combi boiler. It only has 4 moving parts. The 30/36 will be more than good enough. It has the maximum flow rate of the Intergas combis.

 

[simond]

It is Water Systems, he's back. Now 100% certain, this is Dr Drivel, Water Systems, George somebodyorother etc etc.

Has he re-registered here to apologise to all the forum users who bought a Remeha Avanta on the back of his esteemed advice? I thought not.

If anyone isn't familiar with this troll, he gets his ideas from Google, then varnishes them with an overconfident written manner and tries to belittle and bully others who may be posting in good faith and using their in trade knowledge.

It's quite amusing for heating professionals, but unfortunately, if you have come here for DIY advice, you can be swayed by people who shout loudest. It's worth remembering that sometimes those with the most useful advice don't shout it out.

Most of the people on here who do heating for a living have tired of arguing with him, but remember, you can use Google too.

 

[vulcancontinental]

That's a good point re the kitchen taps. We don't actually use that much hot water from the kitchen tap - the dishwasher is used for dishes etc. I will ask about the additional pressure gauge.

So you will not be bringing water from the loft down to wash up, you'll be using electricity to heat it in the machine at double the cost of gas. Often I have noticed, people rinsing dirty plates in hot water before they put them into the dishwasher

It's your bill and I've always thought combi's in a loft a poor location but recently we have lived in a house with son and daughter in law with a dishwasher. I must say, although it was an expensive one apparently my wife and I laugh at the it's shortcomings and stuff often has to be washed again. Fill a bowl with hot water, wash up, look at the item, if not clean wash again, simple. Yes I ama fuddy duddy, amongst other things.

 

[Dan Robinson]

people rinsing dirty plates in hot water before they put them into the dishwasher

My missus more or less washes everything before it goes in the dishwasher.

She won't be told though. Tis why I only heat the cylinder after she's finished washing up

 

[Dan Robinson]

It is Water Systems, he's back. Now 100% certain, this is Dr Drivel, Water Systems, George somebodyorother etc etc.

If anyone isn't familiar with this troll, he gets his ideas from Google, then varnishes them with an overconfident written manner and tries to belittle and bully others who may be posting in good faith and using their in trade knowledge.

It's quite amusing for heating professionals, but unfortunately, if you have come here for DIY advice, you can be swayed by people who shout loudest. It's worth remembering that sometimes those with the most useful advice don't shout it out.

Most of the people on here who do heating for a living have tired of arguing with him, but remember, you can use Google too.

Perhaps you missed this doosey of a thread:

//www.diynot.com/diy/threads/choice-of-unvented-cylinder-and-boiler-combo.430374/

 

[vulcancontinental]

Ah!