central heating and system choice (yet again) (long)

[David WE Roberts]

Hi,

Explanations first, then questions at the bottom.

I have read the FAQ from Ed (thanks) but it still hasn't really answered all my questions.

I have a fairly large 1950s 3 bedroom semi - the lounge is roughly 21 feet by 11 foot 6, with another 9 feet of extension on the end.

The current boiler is an ageing Baxi back boiler in the middle of the lounge - fitted to a flue which originally has an open fire. This does central heating plus a hot water cylinder in a cupboard in the hall.

Although the system still functions, and I am told I could get a replacement for the hideous fire at the front of the boiler, I would really like to replace the system completely.

If possible I would like to reclaim the downstairs cupboard for storage, (or shelve as a proper airing cupboard with a rad at the bottom). I wouldn't mind losing the tanks in the loft and associated pipework either.

I currently have an electric shower, but am used to a power shower; I would like more flow rate than an electric shower if possible. Currently planning on only one bathroom, and showers are the norm; we very rarely fill the bath.

Minimum stay here one year plus; possibility of renting afterwards but may sell.

I have done a rough flow rate calculation using the cold tap at the bath - I calibrated an orange B&Q builders bucket at 10 litres up to the spout, then counted 'one and two' etc. as I didn't have two extra hands to work the stop watch. It takes about 10 seconds to fill a 10 litre bucket including the turn on time so flow should be at least 60 litres per minute.

I am working full time at the moment so DIY is not an option.

I am now torn between expense and functionality.

The options as I see it:

(1) Replace gas fire and old cylinder; fit shower pump; larger tank in loft. Move/replace most of the radiators. I will have to fit TRVs, the radiators are nasty looking and old, possibly slightly undersized. It is likely to cost more in time/effort to clean and repaint them to an acceptable standard than to just replace them.

(2) Large Combi - minimum components but limited throughput of hot water. Since there will be only one shower, and rare filling of bath, this could well do as long as it can also heat the radiators. (I am not fond of Combis after a bad experience in a holiday bungalow where I couldn't get it to supply hot water to fill the bath).

(3) Pressurised system - I lose the loft tanks but still need someplace for the hot water cylinder.

(4) Heat store - much the same as (2) if I understand correctly.

As an added complication; I have a downstairs toilet at the back of the main garage, and I keep thinking that this could be extended to make a downstairs shower room if I can only work out the logistics. The biggest problem is having to walk through the back of the garage to get to it. The second problem is that doing it will probably not add much value to the house. Still, I would like enough spare capacity to work a second shower if required.

Yet another complication - where to put the boiler. There is plenty of room in the loft, and this would suit a Combi, but if I have a pressurised system or a heat store then either the storage also goes in the loft (where it will need pretty good insulation) or I have a long run from the boiler to hot water tank (though this may not be a major problem).

Final issue for the moment - I have one small run of pipe under a floor (under the doorway to the front room). The concrete covering is crumbling. I would like to get rid of any underfloor piping if possible. Are there any problems in running a feed down from upstairs (the radiator will be under the front bedroom radiator).

QUESTIONS

Which of (2) (3) (4) seems the most cost effective solution?

If I go for (3) or (4) can I have everything including the cylinder/heat store in the loft?

I have had an outline quote of £4,700 to replace everything with another non-pressurised system; does this seem reasonable? I guess this is (1a) as I see I haven't included this in my option list :-)

FURTHER RAMBLINGS

The information I have read in the FAQ has been very useful; however it doesn't include stuff like the crossover point in cost between the largest combi and the smallest heat store solutions. The area is further greyed/water muddied by mixed solutions such as combis with small additional heat stores.

Real world experience of people who have done a similar job recently would be most welcome.

Cheers

Dave R

[Jeff]

"David WE Roberts" wrote

Just had a Alpha CD50 fitted which comes into your grey area above. It is fitted in the loft on the gable end wall and is superb. I get power shower performance from a mira excel thermostatic mixer shower and never ending hot water. We only have occasional baths so the normal combi issue does not apply

Regards Jeff

[Owain]

Suggests a combi, but for 3 bed it is quite likely in the morning to have the shower running and also the kitchen tap whilst preparing breakfast.

It can be an advantage as a landlord to have a storage system as this allows use of an electric immersion as a back-up. Or you could use an instant electric shower in the shower room.

If you need replacement rads anyway this applies regardless of the type of boiler; ditto fitting TRVs and updating the controls.

I would expect that to be used more for washing kids/dog and not concurrently with main bathroom. You could put an electric shower in there which would also act as a back-up.

Almost anywhere where you can exit the flue or, using a small-pipe flue system, almost anywhere. You will need a condensate drain.

Long pipes between HW cylinder and boiler is not a problem; long pipes between a combi and HW taps is.

Quite a usual way of doing it.

Owain

[Ed Sirett]

I'm glad the FAQ has been useful for you.

Even the most modest combi will provide more than twice the flow rate of your electric shower.

Since you have a back boiler (which I assume was adequate albeit inefficient) we can be pretty certain the heating load will be satisfied with 18kW or less.

Without a good look at your house no one can say just where the new boiler should go. The loft is perhaps the least favourite choice as there are a number of restrictions if doing the job proerpy which make everywhere else less hassle.

A properly installed 28kW plain combi sounds like it might be OK for your needs.

There is not much in cost-wise to choose between a thermal store and an unvented cylinder (of an appropriate size), since your not diying this aspect you can go either way.

Stored hot water is likely to add around £1000-£1500 versus the plain combi option.

A new vented cylinder would probably add around £500. The cylinder being cheaper to purchase, but the location would best be below the loft. however once you have adding in a decent shower pump the cost differentials start to close up between all the forms of stored HW.

The radiator replacements would add around £50-£150 per rad depending on the quality of the radiator.

HTH

[David Hansen]

On Sat, 18 Feb 2006 14:27:51 +0000 someone who may be David WE Roberts wrote this:-

Depending on where this is situated in relation to the rest of the house it may well not be sensible to take hot water from the house. If this is the case a better solution is local instant heating, either electric or gas.

The main source of hot water is best situated near the tap that is used the most, usually the kitchen one. If the other rooms that have hot water are clustered tightly around this, horizontally or vertically, then that minimises losses.

[Doctor Drivel]

The loft is the best place. All you need do is board it out from hatch to boier, a permanent light and if the boiler is near t the hatch a rail around the hatch (wood on the rafters will do) and fit the combi high up so it cannot be used to items on.

I would go for the highest flowrate combi he can get. He have two showers on the go. Alpha CD50, Baxi 133 HE Plus (can use TRVs opn 'all' rads with this boiler, W-Bosch 40kW, highflow Glow Worms. All wall mounted.

Avoid an unvenetd cylinder as it requires an annual service charge. No service and a flood and the insurance company will not pay up. They can also explode.

was half the size odf a normal domestic cylinder. They can take down the side of a house.

Yep.

..and the rest

A combination cylinder can be fitted in the loft.

Yep. And the noisey, space consuming and prone to leaking pump.

[Doctor Drivel]

If gaining space is the aim then put the combi or water store. when convenient and install a DHW secondary circulation loop. Lag 'all' DHW draw-off pipes.

[David WE Roberts]

Thanks for all the responses so far.

Looking through them, I can see I left out an important part of the explanation.

There is a problem about siting the boiler.

All the drainage is at the back of the house. So is the kitchen, bathroom, toilet. This is where the water main comes up through the floor.

I can't put the boiler at the front of the house as there is not much wall which is not lounge window or front door. In the hall it would block the lounge door or the stairs. In the lounge it would be an eyesore. I would also have to run the pipes up the wall and through the upstairs floor to get to the kitchen and bathroom at the back.

I can't put the boiler on the LHS (looking from the front) as it is a semi and it might make my neighbour's lounge cloudy.

I cant put the boiler on the ground floor RHS as I have an integral garage which runs the full length of the house, and links to the old garage at the rear of the house.

I can't (I think) put the boiler in the garage as it runs right up to the boundary and the vent would therefore be into the neighbour's property. Perhaps I could vent vertically through the flat roof? Another possibility is the downstairs toilet, which is at the back of the garage where it reaches beyond the back of the kitchen and has some outside wall space. Not a massive amount of floor space, though. Cold and damp in the winter.

The only obvious place on the ground floor is in the kitchen, where I have about 1 metre of outside wall to the right of the window. However I don't have that much room in the kitchen and I was planning to hang storage cupboards there.

Similar problems upstairs. No back wall space obvious ( although it could perhaps go in the toilet above the low level cistern). It would have to be a slim as the cistern, though.

No side wall space (all stairs, window, and smallest upstairs bedroom to the front).

My favoured place would be in the loft at the gable end. Loads of unused space, close to bathroom and toilet, directly above the kitchen, and I can use the gable end or the roof for a vent.

Closest suggestion so far is Jeff's Alpha CD50. Any known problem,s with this unit, or good alternatives (Jeff, close your eyes at this point since you have already bought one and don't really want to know)?

Cheers

Dave R

[Doctor Drivel]

Sounds good. More hassle but if you can get it through the roof, much neater.

Excellent choice. 5 year guarantee. and a highflow rate that fills a bath very quickly. Will do two simultanteous showers. Look at the other boilers I mentioned. They are all wall mounted units. In the loft they can be on a Unistrut frame off the rafers, so no need to actually be on the gable end. There are also high flowrate floor mounted units that give excellent flowrates. The Potterton Powermax breaks down so it can be lifted into the loft. Make sure it is well supported on the loft though. The Viessmann 333 is a floor mounted job and of RR class. You get what you pay for.

[David Hansen]

On Sun, 19 Feb 2006 11:38:07 -0000 someone who may be "Doctor Drivel" wrote this:-

Provided one is prepared to put up with the standing losses over a decade or two. When these are pointed out some decide that saving a bit more space isn't as great a priority as they thought it was.

[Owain]

Yes, with an appropriate boiler/flue combination

Wall hung boiler could go above the WC cistern or storage units. The boiler does *not* have to be on an outside wall, just the flue outlet. You can run flue for metres with some boilers. Residual heat loss from the boiler would help keep the toilet room less cold (frost thermostat location)

Bring the WC/cistern forward to increase the depth available?

Owain

[David WE Roberts]

In my particular case, putting the boiler in the loft should place it closer to the bathroom and as close to the kitchen as the current hot water cylinder.

I don't think I need a loop - the runs aren't that long.

Cheers

Dave R

[Jeff]

even with hindsight I dont think I could choose a better boiler. If you are near the midlands you are welcome to have a look. People talking flow rates and seeing for yourself are totally different, I would have loved to have seen before I bought.

Regards Jeff

[Doctor Drivel]

IFAIAC, 'all' DHW draw-off pipes should be lagged. An insulated secondary loop will not loose too much heat and with a pipe state the pumps will only come on when the loop has cooled. With a secondary circulation loop you waste far less water keeping water bills down. Water flow at each tap can be throttled back as hot water is instantly available at the tap. People will accept low flows as long as there is instant water at the taps.

[David WE Roberts]

Only if I want to sit with my feet sticking out onto the landing :-)

Dave R

[sponix]

I'd get a cheap Combi fitted. (B&Q were recently selling combis for £299 upwards.)

The logic behind this is that it'd probably be the cheapest option overall and will allow you to recoup cuboard space.

The fact it's a new boiler will almost cerrtainly help the sale of the house rather than detract from it because it's cheap.

You'll only be living with the thing for a few years so quality and longevity isn't a hugely important factor.

sponix

[Doctor Drivel]

The logic behind that is that he will have stiil trouble from a cheap and nasty product as he is renting out. Whether he is there or not it is still his problem. Best get a quality product that will give some sort of longevity and reliability.

[Capitol]

Invalid for flow rate. Measure at kitchen cold tap, at 9 am,12.00 and

6pm to get a clearer picture.

Regards Capitol

[Ed Sirett]

To date Alpha have not been known for their offerings being even half way up the spectrum. However it is possible that they wish to reposition themselves in the market.

The lift weight of 70kg is something of a challenge for a loft installation.

The price from one online store was 1490 including VAT. However other boilers I know the price of were somewhat up on that site. So quite possible £1350 (inc) would be the going trade rate.

This certainly puts it in the right segment of the market if Alpha are genuinely repositioning themselves.

[Doctor Drivel]

They were always in the middle.

With new designs and 5 year guarantees they obviously intent to. Many have integral cyclone filters on the return to catch solids. Crud in boiler exchanges is a major cause of boiler problems

Look at:

inc VAT and delivery