replacement boiler needed

Feb 10, 2018 35 Replies

This is tricky because I cannot supply full details but this is the tale (of woe).



I really need some informed advice here.



My daughter and her family are waiting to move into a flat that was previously my mother's. It has the original floor standing Celsia boiler, inside a kitchen unit. It is conveniently adjacent to the gas meter.



The pipes run horizontally behind the kitchen units, through a wall to the airing cupboard that houses both the cold tank and a hot water cylinder beneath it. So the pipe runs are neat and efficient.



Behind the boiler is the pipe to the flu that runs through an outside wall and can be seen at the front of the building.



The height inside the kitchen unit is 889/890 mm.



A British Gas salesman tested the cold water pressure (it looked pretty fierce to me) and said, "you cannot have a Combi. Pressures too low".



His suggestion was to plonk a wall mounted unit on the opposite side of the sink which clearly meant serious damage to the kitchen units and an inefficient pipe run.



This is a two bedroom flat with a largish main room and the kitchen (316 cm x 300 cm).



My four bedroom house has a 110,000 BTU boiler, so I would guess the flat would around 50,000 to 60,000 BTUs (Correct me if I am wrong).



Is there a floor standing boiler that could replace the Celsia?



The right answer must be worth a beer or three?



Seems OK size-wise, maybe overkill for a flat?

Get another firm round and see if they agree with BG.

Especially about the water pressure, although flow rate is usually more important than static pressure. From your post I am guessing that BG may have tested static pressure but that you estimated flow rate.

You can buy a water pressure meter quite cheaply if you want to test for yourself and it is pretty straightforward to time how long it takes to fill a container of known volume (such as B&Q orange buckets; ours have a scale on the inside).

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£20 and should, I think, fit onto the connector for a washing machine or dishwasher. Adapters for other fittings are only a few pounds.

Cheers

Dave R

I don't know - but does it really need to be floor standing? You can mount a wall-hung boiler a few inches off the floor, so that it would still fit in the cupboard currently occupied by the Celsia.

Flow rate is as important as - if not more important than - static pressure. The OP needs to measure the flow rate at the cold tap which is nearest to where the mains enters the house. You can do that with a bucket and a stop-watch.

Zero your bathroom scales with an empty bucket on them. Then hold the bucket under the full flow of the tap for 27 seconds. Then weigh the bucket again, so as to weigh the water you collected. The weight in pounds is the same as the flow rate in litres per minute.

I can't comment on the technical rights and wrongs of what you need or don' t need but just make sure you don't get British Gas to do it or you'll pay a lot more than you need to!

A few years ago I got a quote from British Gas to replace my boiler and the y quoted £3,500 - I said "I don't want all new radiators as well, just the boiler" and he said "that is just for the boiler"!!

This was at a time when a new boiler cost £800 from the supplier and f itting was £500 - which was what I subsequently paid to an independent installer.

The right answer (seriously) is to ask someone other than a BG salesman.

Get two or three local independents in to take a look.

Our BG quote (sent because we inherited a BG contract with the house) was for an undersized boiler at twice the price we eventually paid.

Run, don't walk, away.

Ask around for a local tradesman and see if a name or two repeatedly get positive recomendations (or negative...)

Others have suggested doing your own flow and pressure tests, if the pressure really is high you can get PRV's (Pressure Reducing Valves). I think they limit both the static and dynamic pressures.

Presumably the boiler change is to free up a bit of space by getting rid of the HW cylinder and header tank? Otherwise doesn't "if it ain't broke, don't fix it" apply?

No reason why a wall mounted one can't be put in the place of a floor standing one. That's exactly what I did here.

It may not suit a plumber, though. More bending down to install. So expect excuses why it can't be done.

That does not really make much sense - unless he means flow rate too low. (the mains pressure even if not that good is going to be higher than anything you will get from a combined cylinder / cistern on the same level as the main living space.

You could probably stick a wall mounted boiler low down in the space where the current one is.

The pipe run is less of an issue either way though - everything is fully pumped, and usually a sealed system these days.

For just heating, its seems likely that a 10 to 15kW (~35,000 to 50,000 BTU/h) boiler will be more than adequate.

If you do go the combi route, the 24kW would be a minimum spec to get an acceptable rate of hot water delivery. (24kW combi will do once decent basic shower (i.e. nothing fancy with soaker heads and body jets), or will fill a bath slowly.

Gas floor standers are rare these days, and tend to only be the larger more powerful models. Not really suited to your application.

No need to install a combi

Pounds/litres? Doesn't sound right

Need to check the installation manual too - my WB requires 200mm clearance underneath, so added to the unit height, that would probably bee too high for the OP - but it's worth checking some other manufacturers...

My old floorstander was too tall to fit under a normal height worktop anyway. So already had a custom housing. Which only needed slight modification.

Simples! A litre of water weighs 2.2 Lbs exactly. 60/27=22.22222 which is a close enough approximation that the number of Lbs of water collected in 27 seconds directly equates to a litres per minute flow rate.

You could, of course, collect a minute's worth of water (assuming a big enough bucket) and weigh the amount collected in Kg to calculate a Litres per minute flow rate. Alternatively, you could use a half or quarter minute filling time if you don't have a big enough bucket to catch all of the water flow and multiply up by two or four to calculate the per minute flow rate.

Of course, if you have to use a shorter filling time for want of a large enough bucket to cope with a high flow rate, you might as well use a 15 second fill time and multiply the weight in Kg (or the volume in litres) by the required factor of four to get the Litres per minute flow rate figure.

Alternatively, you could simply time how long it takes to fill a collecting vessel of known capacity and translate your figures into a litres per minute figure using whatever units of measurement are convenient (fluid ounces, Lbs, gallons/cubic feet[1] or WHY).

Once you're into "Calculator Territory", you may as well knock yourself out and calculate gallons or cubic feet per minute or litres per second figures as well as the more common litre per minute figure. :-)

[1] A gallon of water weighs 10Lbs which is also a cubic foot of water.

You are kidding? a cubic foot of water weights about 70lb. About 7 gallons/ 28l.

A UK pint is 20 fluid ounces so a pint of water weights a pound and a quarter. A gallon is 8 pints, so a gallon weighs 10 pounds.

I wonder if US gallons have muddied the water. 1 cubic foot of water =

6.22 Imperial gallons or 7.48 US liquid gallons (and is 62.2 lbs either way)

If that's figure's low, it's worth trying other taps (if you have other taps fed from the mains). The flow rate from my kitchen tap is rubbish, so I thought I wouldn't be able to install a combi, but checking the bath tap it was fine - it's just that the tap itself in the kitchen won't allow much flow.

Mike

My bad[1]. :-( I was getting myself confused between the 62.5 Lbs of water to a cubic foot and the convenient fact that a gallon of water happens to weigh 10 Lbs exactly which makes a cubic foot of water equal to 6 1/4 imperial gallons. These are figures which *used* to be firmly entrenched in my memory. Alas, no more it seems. :-(

Anyhow, the point still stands. If you can't use the "27 seconds fill test" and are forced to use whatever filling vessel and units of measure that come readily to hand to calculate the flow rate with a calculator, you may as well knock yourself out and calculate gallons per minute or second or even cubic feet per minute or hour or whatever other units take your fancy whilst you're at it (obtaining a Litres per minute figure, that is!). If you don't trust my freshly jogged memory on conversion factors, you can always google the information for yourself, I didn't! :-)

[1] The only upside to this lapse is that it showed that at least three of you were "paying attention". :-)

And, no, it wasn't a deliberate mistake I'm ashamed to have to admit. :-(

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