Bigger meter and bigger pipes required - can SGN force me to do this?!

squirrelpie

In asnwer to your thoughts Changing the hob (the oven itself is electric) to induction is not an option as it is a specific cooker for
the space.

You can fit an induction hob in pretty much any space, so I think you'll need to provide some more detail if you want any further thoughts. A photo or diagram might help.

QrizB

When you say "you can supply a U2 meter through a 22mm pipe quity happily" I assume you mean the sizes are U2, U6 and U16.

Apologies, that was a mis-type on my part. I meant to say U6; I don' think there's a U2 size meter.

Largergaspipe45

https://forums.moneysavingexpert.com/discussion/comment/82073097#Comment_82073097

Thank you, I appreciate the feeback. It is not about physically being able to. It is a space that, from an aesthetic persepctive, I have designed around a gas hob (900mm wide x 740 deep) to compliment the historic features (it does have an electric oven). We mainy use a small, separated induction hob. Any thoughts that don't include replacing the gas hob (which accounts for a particularly minor part of the peak flow usage) still very welcome! Thank you.

TroubledTarts

With self management you should be able to be ok as long as you don't have everything going full pelt at the same time.

The tell tale signs will be boiler errors and weak gas for cooking on the hob.

The concern is you might be testing this theory in winter and being left with heating issues.

doodling

Sorry for the delay in getting back to this thread.

I suspect that the starting point is probably to understand what the issues with your existing heating / hot water are.

You say that you "have had terrible problems with the heating not reaching the furthest rooms of the house" - it is really unclear what this actually means.  Was the existing boiler running at full power at the time (i.e. the boiler couldn't keep up with the demand for heat) or was it that the pump in the boiler couldn't get the hot water to the radiators in the rooms that needed it (and the boiler itself was throttling back)?  In the former case a bigger boiler is the answer, in the latter case plumbing improvements or additional pumps are the solution.

Once you've got to the bottom of why your heating isn't working optimally then you will know whether your existing boiler has capacity to heat the hot water as well or whether an additional boiler is actually required.

My strong suspicion is that the existing boiler is plenty big enough and that the problem is that for some reason you aren't getting enough flow to the extremes of the central heating system.  If that is the case then fixing that will allow you to use your existing boiler to also heat your hot water and your gas supply problem goes away.

The next question is why do you need a 35kW boiler just to heat hot water?  A 35kW boiler will heat hot water (5C to 60C) at a rate of 9 litres per minute (assuming that the coil in the hot water tank is rated for it - it may not be).  If we assume that you are going for a BIG hot water tank at 1000 litres (a tonne of water - hope your roof structure is up to it - that is a commercial size, large domestic would be 300 litres) then you will heat it from cold in less than two hours.

Do you really use 1000 litres of hot water a day - what is the flow rate on the showers which are currently running out of hot water?  A quick Google suggests that 20 litres per minute is a sensible maximum for a shower, three would be 60 litres per minute. Assuming that your skin isn't asbestos then that would be at a temperature of 40C, not the 60C I have assumed for the two hour tank heating calculation above so the hot water flow for all three showers would be around 40 litres / minute, the additional 20 litres being made up with cold.  A 1000 litre tank will support that for 25 minutes.  Perhaps you could get away with 500 litres of hot water storage if 3x 12 minute showers were acceptable?  If you're willing to store your hot water at a higher temperature then you might be able to reduce the tank size still further at the expense of increased standing losses and fitting temperature regulating valves on the output of the tank.

Note my comment above, that a 35kW boiler will only deliver hot water at 9 litres per minute - that means that realistically you need to meet your showering requirements from stored water.  Whilst not negligible, the amount of hot water heating you get whilst showering does very little to compensate for the amount of water being used.

What will the new boiler be doing the rest of the time?  Realistically, with a sensible sized tank the boiler could be the smallest one you can buy (e.g. a 12kW model which would heat your 1000 litres of hot water in 6 hours).  That doesn't solve your gas supply problem though.

If you really do need an additional boiler then interlocking arrangements will be the only answer and for that you probably need to talk to those who work in the more commercial field rather than domestic.  At a simple level it should be easy to have a priority system which disables the pool boiler when the new boiler for hot water needs to run and as we've already established that with water storage commensurate with your showering requirements you don't need a big boiler for hot water the hot water boiler could be the same size as the pool boiler so your maximum gas demand won't change.  A priority system could be assembled from off the shelf components available from Screwfix by someone who knows what they are doing - the difficult bit might be getting the necessary wiring between the hot water controls and the pool boiler controls although a wireless solution might be possible.

Note that some fancy controls might be needed to make it practical to use your existing boiler for heating the hot water.  For example, if you have a hot water priority system then a two hour heating interruption to reheat the hot water might not be a good idea and you'd want to limit hot water heating to say 10 minutes out of every hour or half hour, unless there is no heating demand, to avoid the house cooling down too much.  That is again quite possible but probably not within the skillset of a domestic plumber. If you don't have a hot water priority system then that problem goes away but your heating may not be as efficient as it could be.

All the numbers above need to be validated in light of your actual installation but hopefully it gives you an idea of the possibilities.  As I've said several times, I suspect that your existing heating boiler has the capacity for the hot water as well, but I can't see what your plumber can see so I might be wrong.

squirrelpie

It seems to me that what @doodling has said is sensible, and that as you say you're a lay person you need some expert advice about the details of your particular situation, which you won't get from SGN and it sounds as though you're not getting from your plumber. So you might think about hiring a domestic gas consultant to take a look and come up with options? I'm no gas expert either, so I can't make any recommendations as to how to find somebody.