New CH System advice.

Hi all,
Yes, it may be the first failed diverter valve of the year, and it has inspired me to thing about replacing my whole system. Firstly a bit of background about the current system.
House is a 2 bed end terrace, currently only has 5 radiators, one in the lounge (open plan to dining room), one in the kitchen extension (which gets really cold in the winter - insulation problem there i think), one in the master bed, one in the hall and one in the bathroom. Second bedroom doesnt have a rad. They are all old rads, no TRVs or anything. The system as a whole is absolute crud. Some of the rads are in series with each other, some (in the kitchen extension) are teed off. Hot water is heated indirectly in a standard cylinder in the second bedroom airing cupboard. Theres a pump and a diverter under the floor(!!!) in the dining room, by the Baxi back boiler. As SWMBO wanted laminate, thats the replacement of that scuppered. I dont even think its all plumbed in right, you have to have the hot water on for half an hour before you have the heating on in order to get any hot water at all. I think that the hot water is pumped through the rads before it heats the cylinder water, so its cold by the time it gets there!!
Our only requirements of the new system are....
6 new radiators and pipework that must be hidden underfloor (floorboards and joists), sized to handle our heat requirements.
Keeping the ability to store hot water in the cylinder - two reasons here which i think are valid - 1. our venturi shower wont work without a hot water cylinder. 2. The wife likes the occasional bath.
I am umming and aahing about whether to do this diy, as it needs to be in before it starts getting really cold, and working full time, i dont have much of it spare to do something like this. And of course, i havent done a central heating install before. Im confident that my plumbing and electrical skills are up to it though.
Also, i need to keep the cost around the 1500 mark.
So on to my questions and musings.....
Can i easily keep the current indirect heating system used for our hot water, while replacing the central heating section. Can a combi/condensing boiler do indirect water heating efficiently.
Pipework under laminate floor - any suggestions. I think removal of aforementioned minging flooring is the best option.
TRVs/Thermostats etc... We just want the whole house to be warm, not really bothered about upstairs being cooler than downstairs etc. Whats the best way to do this. Im guessing at trvs on all rads (except bathroom one), but would you recommend a room thermostat in the lounge to tie in with these. If someone could explain the need for room thermostats when you have trvs i would appreciate it (seen a few installs with trvs and thermostats but dont really understand why you need thermostats when the temp is controlled by the trvs)
Types of boiler/boiler recommendations that fit in with our budget would also be appreciated.
Im sure there are a load of things ive missed out, but any pointers would be appreciated (and yes, i have read the faq etc)
Mark
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In an earlier contribution to this discussion,

It sounds as if you currently have a diverter valve (as opposed to a mid position valve) and that it is set to heating priority - which is unusual. A diverter valve gives you either HW or CH but never both at the same time. A mid-position valve looks very similar - and can provide just HW or just CH, but can also do both together when in its mid position. At very least you should replace the diverter valve with a mid-position valve. From what you say, the pump and valve are inaccessible, under the laminate flooring. You need to do something about this *urgently* - either by moving them or by creating some sort of access hatch. These are the two components which most frequently need to be accessed whenever you need to do any trouble-shooting!
Do you need to replace the existing boiler, or does it have enough capacity to supply additional radiators? You would certainly get better efficiency from a new boiler, but this will involve a lot of plumbing because it seems that all the pipework currently leads to the existing boiler site.
You can use the CH side of a combi to provide both CH and stored hot water if desired, using zone valves (similar to your current setup) but there is only any point in doing this if you are also going to use the HW side of the combi to provide instant hot water to some of the taps - such as in the kitchen. Otherwise, use a conventional boiler.
With regard to room stats, you need a boiler interlock in order to satisfy the latest energy efficiency regs. This means that when the house gets up to temperature, the boiler must automatically be turned OFF. If you use TRVs on all rads but *don't* have a room stat, the boiler will remain on - keeping itself hot by cycling on and off via its internal thermostat even when no external heat is required. You therefore need to have one room with a room stat but no TRV on that radiator.
--
Cheers,
Set Square
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Mark,
To DIY go combi. they are a doddle to fit and are quicker too. It will modulate down to the heating needs of the small house. No complex zone vales or control wiring, etc. You will need a decent flowrate as you will want the occasional bath. A condenser? try the Worcester-Bosch Greenstar 40kW combi at 16 litres/min. You will not be disappointed.
You will be using most of the existing rads, so no great thing there. Put de-sludge in the system for as long as you can (max one month), before you rip out the old boiler. Flush well. Look at installing a kickspace heater in the kitchen. Put TVRs upstairs only.
http://www.discountedheating.co.uk/shop/acatalog/Greenstar_40HE_PLUS.html
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At 1300 for that boiler alone, i think my budget of 1500 can not be met by your suggestion.
Radiators will need replacing as they must be about as old as i am, no bleed valves on them or anything. Load of rubbish they are
And as much as i would love a TVR , it would probably break down on the way up the stairs :)
But thanks for the info anyway
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want
40kW
Put
you
http://www.discountedheating.co.uk/shop/acatalog/Greenstar_40HE_PLUS.html
bleed
way
The Alpha CB50, a non-condensing boiler is around 1100 and will deliver around 19 litres/min to fills a bath pronto. Great for showers and baths. 300 should be enough for rads in a two bedroomed house.
Or look at the two combi suggestion in one of my current posts. Two W-B Juniors for around 100-1100, to give bath flows. As a DIYer you should be looking at combi's, as they offer so much for a DIYer.
Here is a run down on combi's:
Firstly, a combi is a "combination" of the heating and water system in one case, eliminating external tanks and cylinders, and generally supply hot water at high main pressure. To confuse a little, some can run at very low pressures and even off tanks. Generally most are fed from the mains. It is generally a matter of mounting the boiler and connect up the pipes. The expert designers have done the hard work for you and put all in one case.
Types of combi:
1) The Infinitely Continuous Combi -
Heats cold mains water instantly as it runs through the combi. It never runs out of hot water. This is the most common type of combi, generally having lower flowrates than Nos 2 & 3 below. The largest flow rate instant combi is a two bathroom model, 22 litres/min ECO-Hometec. Being a condenser it is very economical too. http://www.eco-hometec.co.uk
2) Unvented Cylinder Combi -
An unvented cylinder is a similar to a conventional cylinder but run off the high-pressure cold mains. A combi with an integral unvented cylinder has approx 60 litre cylinder heated to approx 80C, with a quick recovery coil that takes all the boilers output. A fast acting cylinder thermostat ensures the boiler pumps heat into the cylinder ASAP with a recovery rate from cold around 5-8 mins (Ariston claim 8 mins). The 80C water is blended down to about 45-50C. e.g's, Ariston Genus 27 Plus, Glow Worm, Powermax, Alpha CB50.
3) Infinately Continuous/Unvented cylinder combi -
An example being the Alpha CB50, a combination of both having a two stage flowrate, of high flowrate when using the stored water with an automatic flow regulator switching in to reduce flow to an invinately continuous flowrate of approx 11 litres/min. http://www.alpha-boilers.com/products/CB50.html
4) Heat Bank Combi -
Incoming water is instantly heated running through a plate heat exchanger (as is most instantaneous combi's) that takes its heat from a "domestic hot water only" store of water at approx 80C (instantaneous combi's take the heat from a heat-exchanger heater via the burner). A fast acting thermostat ensures the boiler pumps all of its heat into the store ASAP with a recovery rate about 5-8 mins from cold. The 80C water is blended down to about 45-50C. They are generally two stage flow rates, in that when the thermal store is exhausted it reverts to what the burner can produce, which is approx 11-12 litre/minute. e.g. Vokera & Worcester floor standing models (standard washing machine sizes).
N.B. The heat bank is a variation of a thermal store, but is "not" a thermal store in the conventional sense in that a coil carrying cold mains water runs though a store of hot water kept at about 80C. Heat-banks are far more efficient and give higher flowrates than conventional coiled thermal stores. The stainless steel plate heat-exchangers do not scale up so easily.
5) Combined Primary Storage Unit
(Not classed as a combi, but a derivative of a combi, but still a one box solution, so still in the same family)
These are a combination of a large thermal store, or heat bank, and boiler in one casing. The units are large (larger than standard washing machine size) and floor mounted. The heating is taken off the thermal store, which in many cases the DHW taken off the store using a plate heat-exchanger (heat-bank). Unlike the Heat-bank in 3) above the thermal store supplies heating "and" DHW, giving the "combined" to the title. They are available from 1 to 2.5 bathroom models. Gledhill do an excellent condensing version, the Gulfsream 2000. http://www.gledhill.net
Nos. 2), 3), 4) & 5) have high flowrates. No. 1 "generally" has low flowrates but there are always exceptions and some can be high - e.g. the ECO-Hometec infinitely continuous combi, actually has a very high flowrate. Nos 2), 3), 4) & 5) use stored water, but in different ways. Unlike No. 1 "some" versions will eventually run cold, but that takes quite a time, hence some are referred to as "two bathroom" models, having the ability to fill two baths with very fast recovery rates. As hot water is being drawn off the high rating burner is also reheating. Very rare do these combi's run out of hot water in average use. When taking one shower the burner may be re-heating faster than what can be drawn-off. No. 3) above uses stored water but will not run out of hot water (high and low flowrates). Most versions of No. 4) above are two stage flowrate models (high and low flowrates) and will also not run out of hot water.
There are combi models that give hot water and heating simultaneously as Combined Primary Storage Units do. Most don't as they are hot water priority.
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In an earlier contribution to this discussion,

Here we go again - the answer's a Combi - now, what's the question!!!
The OP specifically said that he wanted to keep stored hot water for his venturi shower - not to mention baths! So, if he goes the combi route, he'll need to use the CH side for most of his requirements, and use zone valves to split CH from stored hot water.
--
Cheers,
Set Square
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IMM post was taken with a pinch of salt the moment he recommended a 1300 boiler for an installation with a budget of 1500.
My requirements also state that advice be given by someone who can both read my post, and perform simple arithmetic based on the facts therein.
Thanks for your input Set Square.
With regards to my current installation, im not sure if it is the diverter that has gone, from what i have read it is more likely to be the pump. I will get a big stick under the floor later and see if i can hit the pump a couple of times to get it going. Probably just sludged up.
If a pump is not accessible, will standard flushing methods clean it out??
Mark
wrote:

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wrote:

he'll
to
It is the bottom line that counts. A combi and buying a new thermostatic shower mixer will give great performance and be cost effective to him, as he is fitting it himself.
Please at least try to use some common sense.
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In an earlier contribution to this discussion,

It would appear that the OP prefers my flavour of common sense to yours!
--
Cheers,
Set Square
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I don't think he is that thick.
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In an earlier contribution to this discussion,

I don't think he's thick at all! But read what he said in resonse to your post!
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Set Square
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He is after advise and best solution. he is getting it from me. Art times he may think he know the solution, by not knowing all the facts.
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In an earlier contribution to this discussion,

So that's alright then.
I must remember to keep repeating "IMM's the only one in step", so as not to forget!
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Cheers,
Set Square
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to
Good. You are learning.
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Unfortunately for him , IMM's reputation precedes him. Even with the best intention of listening to what he says, it is nigh on impossible to take on his suggestions and believe that they are actually viable soultions to my problem.
Mind you, i did like his descriptions of combi boiler types, that has proved quite useful, thanks.
I believe that even useful suggestions from him, however rare people think they are, would be hit for six out of the newsgroup.
At the end of the day, advice is advice, and i am grateful for all of it, whoever it comes from.
It is up to me to take whatever advice I want, there is no gun pointed at my head. So i choose not to take IMM's advice, and go with Christian McArdle's, as it is more appropriate in my situation.
And anyone who's most common retort is "snip drivel" cant be taken seriously, no matter how valid his suggestions are. Unfortunately, he has dug his own grave here, so to speak
Looks like i can delay the work anyway, managed to get under the laminate floor through a vent and whack the pump with a bit of marley pushfit pipe. It kicked into action straight away.
Many thanks all
Mark
Mark
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not
on
Well seeing as you liitle about the subject, why otherwise ask, you had beter read hard at anything I say about this topic, as I know more than all of them put together. And that is for real. If you want to do things the expensive and hard way, go ahead, be a d***head.

proved
Useful for what?

???
my
McArdle's,
It is not. You are a fool. You have taken the advice of amateurs who attempt to show off their limited knowledge by advocating over complex solutions to simple problems.

You obviously can't see drivel when it is in your face.
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Yes. No problem whatsoever. Go condensing whatever you decide.
If you choose a combi boiler in a kitchen location, then you can use the mains DHW outlet from this for the kitchen sink, whilst still heating the cylinder. This could be useful if the kitchen is far from the cylinder location. However, there's no real need for a combi if the indirect system gets enough hot water to the right places in the right amount of time.

It is quite simple. The building regulations require you to have something called a "boiler interlock". What they mean is that the boiler must totally switch off when no rooms require heat. If you had TRVs on every radiator, the boiler will happily continue to pump hot water through the bypass, merrily wasting gas.
The room thermostat solves this problem by having a master room with a TRVless radiator. When this room warms up (and it is set to warm up ever so slightly more slowly than other rooms), it turns off the boiler. When it has cooled a little, the boiler fires up again and other rooms can top off with heat too.
Another solution is to have TRVs on every radiator, but use a flow switch to detect that the TRVs are actually passing water. When the flow switch indicates that all TRVs are closed, it turns off the boiler. The pump is left running, or is pulsed every 10 minutes are so to see if the TRVs ever open again.

I'd go for a inexpensive, but not too cheap, modern condensing system boiler such as an Icos or Glowworm, plumbed in S-Plan.
Christian.
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boiler
P.S. Approximate cost (inc. VAT) would be
Boiler = 700 Pump = internal Bypass = internal 2 x 2 port valves = 70 Programmer = 35 Programmable Thermostat = 30 Filling loop = 10 Radiators 6x60 = 360 TRVs 10 x 10 = 100
This leaves approximately 200 quid over for pipe, fittings, cable and other sundries, but assumes your existing tank and radiators are adequete. Note that the serial radiators will require fixing if you want the TRVs to be added to them, although you might get some results by adding one to the "cold" end of the chain.
Christian.
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other
Best he goes for a combi. far more cost effective and will meet his needs in DHW and fitting ability.
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in
How does it meet his need for a storage based hot water system? Or do you mean the combi just drives the kitchen sink? (Which although a perfectly reasonable solution, would actually require more fitting, sundries and costs that might tip it over the 1500 budget).
Christian.
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