New Central Heating system advice

[mecster09]

We've recently moved into a new property that has a very old boiler with a vented cylinder (assuming that's the right term) and looking at upgrading , photos can be seen here https://1drv.ms/f/s!AlVIX-jY2s6UxzX23mWmFy-Ksfsh

House is 5 bedroom detached with 2 main bathrooms (1 with pump driven Aqualisa shower) and a downstairs toilet. Boiler in kitchen, airing cupboard with hot water on 1st floor.

We've had the pressure and flow rate checked and it's 2.5 bar and 9l/m at the kitchen tap which is directly from the mains cold which enters the property below the sink. We've had the mains upgraded from 15mm to 32mm and no increase in flow rater annoyingly.

My question is which system would be the best for us? We've had so many varied quotes from megaflo, combi boilers, unvented and vented solutions I'm really not sure what make sense! We like having the powerful shower in the ensuite as the shower in the main bathroom dribbles out, also hot water to the kitchen sink takes 2 mins to heat up.

Any help would be appreciated

 

[MeldrewsMate]

You seem to have plenty of room at your new house, so a combi boiler will not work for you unless the only hot water delay complaint you have is at the kitchen tap. In that case a combi replacement for the Ideal Classic, located close to the kitchen sink, would solve your kitchen hot water delay problem, that is feed only the kitchen tap from the combi. You could then use the combi's heating output to heat both the house and the hot water cylinder through a standard (but sealed system) Y or S plan system....bear in mind that if your house total floor area exceeds 150m2 you must zone it into smaller zones of less than 150m2 (so typically upstairs and downstairs).
If you like powerful (I see it as WASTEful) showers then you may wish to consider a larger hot water cylinder, then install a pump to the main bathroom shower to get the flowrates you desire.

If other taps have long waits for the hot water to arrive, then consider the installation of a secondary circulating pump.

Hope that helps to bring joy to a corner of Stevenage,
MM

 

[wwwebber]

An unvented system on its own will not be sufficient as your water pressure and flow are rubbish. I see you have plenty of space ?, so to solve this I would install a large accumulator which will provide the cold water pressure that you need to run an unvented system and thus excellent pressure hot & cold water to every room in the house including all showers. This will push your hot water through much quicker too. You just need a good system boiler to underpin all of this. You might as well pressurise your heating too while you're at it as that has many benefits.

 

[muggles]

We've had the pressure and flow rate checked and it's 2.5 bar and 9l/m at the kitchen tap which is directly from the mains cold which enters the property below the sink. We've had the mains upgraded from 15mm to 32mm and no increase in flow rater annoyingly.

I very much suspect that your flow rate is not being measured correctly. If you've seen absolutely no improvement in performance after that mains upgrade, I suggest that there is a flow restricter in your tap supply limiting flow to 9L/min. Dip you have any other mains-fed cold outlets? An outside tap maybe? What flow rate can you achieve at 2.0 bar maintained pressure? Or 1.5?

 

[bernardgreen]

I would install a large accumulator which will provide the cold water pressure that you need to run..........

but only until the accumulator has emptied and then you are back to the poor flow that the accumulator was meant to improve. An accumulator cannot increase the pressure above the incoming static pressure. A cold water storage cistern in the loft is very much the same as a very large accumulator but with low pressure.

 

[muggles]

but only until the accumulator has emptied and then you are back to the poor flow that the accumulator was meant to improve. An accumulator cannot increase the pressure above the incoming static pressure. A cold water storage cistern in the loft is very much the same as a very large accumulator but with low pressure.

... but only until the cold water storage cistern has emptied, then you get no water at all

 

[wwwebber]

but only until the accumulator has emptied and then you are back to the poor flow that the accumulator was meant to improve. An accumulator cannot increase the pressure above the incoming static pressure. A cold water storage cistern in the loft is very much the same as a very large accumulator but with low pressure.

Yes, you need a decently sized one if you want to have simultaneous showers etc but for the most part they will refill quickly in between usage. And it will increase flow rates and pressure can also be boosted with a pump if necessary.

 

[bernardgreen]

but only until the cold water storage cistern has emptied, then you get no water at all

The cistern starts to refill as soon as the level drops slightly. The level in the cistern ( may after a very long draw ) drop as far as the take off point but mains water will still be flowing into the cistern and then straight out again. ( unless the incoming supply has ben shut off )

 

[wwwebber]

@bernardgreen thank you for the explanation - I think we know how they work . However, I gladly waved goodbye to my vented system last year - one of the best upgrades I have had done.

 

[bernardgreen]

I think we know how they work

but only until the cold water storage cistern has emptied,

suggests not everyone knows

 

[muggles]

The cistern starts to refill as soon as the level drops slightly. The level in the cistern ( may after a very long draw ) drop as far as the take off point but mains water will still be flowing into the cistern and then straight out again. ( unless the incoming supply has ben shut off )

Replace the word "cistern" with "accumulator" and you will have more or less described how an accumulator works. A correctly sized accumulator has no more chance of running out than a correctly sized cistern does

 

[Gasguru]

Can you test the flowrate at the end of the new 32mm pipe, you want to know the rate at say 1 bar...as muggles mentioned maybe there's and issue with the tap.

 

[muggles]

@bernardgreen thank you for the explanation - I think we know how they work . However, I gladly waved goodbye to my vented system last year - one of the best upgrades I have had done.

Bernie loves a bit of 1970s technology

 

[bernardgreen]

loves a bit of 1970s technology

it worked. I accept that some changes to that 1970's technology have improved the provision of water and heating to domestic properties.

But it is clear that some of the "improvements" come with disadvantages which have to be managed. The necessity to have reliable pressure relief devices on sealed and pressurised systems being one of those disadvantages.

 

[mecster09]

Thanks for all the replies! Interestingly I've had another quote for an unvented cylinder this time moved to the loft, needless to say I'm more confused than ever!