Switch to a combi boiler

[Randers123!]

My main water feed goes upto airing cupboard into a tank boost that’s mounted next to the combi ( where a unvented cyclinder could go ) that pumps/feeds everything , is plumbed off that including all taps and combi boiler , cold water supply is fantastic , just the hot water is not as it’s restricted through the combi

 

[Elsa TLC]

My main water feed goes upto airing cupboard into a tank boost that’s mounted next to the combi ( where a unvented cyclinder could go ) that pumps/feeds everything , is plumbed off that including all taps and combi boiler , cold water supply is fantastic , just the hot water is not as it’s restricted through the combi

IF your cold water is as good as you say
then use
your combi for heating only then the cylinder would give you all the hot water you need.

 

[Randers123!]

The cold water pump pushes out 3bar and upto 80l/min , so I spose that would push the hot water out the cylinder and a very good rate , the only problem I could see here is in the summer when the heating is not on how would the hot water be heated ? Via an immersion ? Also it’s the space to fit another cylinder , thanks for your input though I had thought about that.

 

[Elsa TLC]

The cold water pump pushes out 3bar and upto 80l/min , so I spose that would push the hot water out the cylinder and a very good rate , the only problem I could see here is in the summer when the heating is not on how would the hot water be heated ? Via an immersion ? Also it’s the space to fit another cylinder , thanks for your input though I had thought about that.

I think your looking at how it'll work in the wrong way.


You would need a good plumber/ heating engineer to carry this out.

Depending on the layout of your home and the space you have, then it may be you best option without wasting good money you have already spent.

 

[Randers123!]

I understand the system , but the water is only heated when the central heating is on or it uses a diverter valve , which I spose I could fit for use in the summer months.
Been trying to get a decent plumber or heating engineer for months they all just wanna rip the arse out of you with no real solutions. Hence why I’ve tackled the issue myself I’m handy on the tools just not gas safe.
Thanks for your input

 

[Elsa TLC]

I understand the system , but the water is only heated when the central heating is on or it uses a diverter valve , which I spose I could fit for use in the summer months.
Been trying to get a decent plumber or heating engineer for months they all just wanna rip the arse out of you with no real solutions. Hence why I’ve tackled the issue myself I’m handy on the tools just not gas safe.
Thanks for your input

You don't understand rightly..

The boiler flow and return would become your primary's. You would have two 2 port valves. One serving the heating and one serving the hot water.

In summer, the boiler would only heat the hot water side. There is no need to activate the heating, if done correctly.

 

[SimonH2]

You'd setup the boiler's heating connections to an S-plan. That has two (or more) 2-port zone valves to direct the water as required. As a minimum, one zone for heating, one for hot water.
When there is no call for heating, that zone stays off - and the boiler will just run when needed for hot water.

As already pointed out, you really need someone who knows what they're doing - which it sounds like you haven't had so far.

With storage, you decouple demand (hot water out) from supply (boiler output). The boiler keeps the store full, if demand exceeds boiler capacity then the store makes up the difference - for a while.

As said, an unvented cylinder will do the job. Personally I prefer a thermal store which gives mains pressure hot water - and also allows me to run the heating off the store and decouple that from the boiler, while not having a large pressure vessel full of hot water.

 

[Randers123!]

Yes ok I understand by using valves , originally I was thinking of using the cold inlet as the hot water output from the boiler .
My other problem is fitting another bloody tank somewhere wish I’d stayed with the old gravity system worked a treat . Only reason I changed was to free up space in the loft

 

[Randers123!]

In an ideal world with only 11l/m incoming and 1.8bar pressure , which system would you install bearing in mind I like a nice powerful shower , plus once the loft is done it will have to be pumped up there from the airing cupboard on floor 1.
I’m considering ripping it all out and putting in an unvented system which means I can loose the 450l accumulator tank and put a hot water tank there.

 

[Randers123!]

Thanks guys so much for your input

 

[Madrab]

I’m considering ripping it all out and putting in an unvented system which means I can loose the 450l accumulator tank and put a hot water tank there.

You cant really put an unvented in, not with the mains at 1.8bar @ 11L/min, I presume that's dynamic? How much does that drop when say 2 or more outlets are open?

The problem with an unvented supplied by an accumulator is that it would probably run out after about 10mins. Typically a 450L accumulator can supply around 220L actual before it's back to the mains supply. If it's using a 3bar pump then it's probably pushing around 30L/min max - the shower output would then dictate how long the store would last (hot and cold combined)

Has the mains been looked at? Might be an idea to get your water transporter out - tell them you're having mains pressure and flow issues - and get them to survey the mains and see what it can deliver, that'll give you a proper starting point which TBH is what the installers of the boiler should have done to start with.

 

[Randers123!]

Sorry I wasn’t clear it’s a tank booster so is 450l of water pumped ( salamander tank boost) 3 bar upto 80l/min .
Yeah I’ve had the water board out checked it in the road was 11 they said that’s plenty good enough they have to supply a min of 7 .
I think the easy answer is to just get a better combi with higher flow rates.

I can’t fit both the tank and a hot water cylinder in the airing cupboard , I would have to loose one

 

[Madrab]

which means I can loose the 450l accumulator tank

Apologies I took from this that you had an accumulator - which is the Accuboost

The Tank boost is obviously different and is basically a cold water storage that's pumped, which would be the same as having a 100gallon Cold Water Cistern in the loft and then using a whole house pump. Then an unvented cylinder could go where the tank boost was and hey presto, turbo'd hot and cold water.

Shame about the mains though they are right - they are only obliged to supply 9L/Min @ 1 bar as per OFWAT standards.

A storage combi (half combi/half unvented) may be an option though need to check to see how they would or if they could cope with a pumped supply.

 

[Johntheo5]

The problem seems to be a power problem, apparently plenty of pressure available from the pumped CWSC.
If say 42C is a accceptable DHW temperature then the (a) 35kW combi will supply this at a flow rate (from a present 12C mains) of 16.72LPM, in winter, with a mains of say 5C, will give a flowrate of 13.56LPM, So, 16.72LPM/13.56LPM.
A 40kW will give, respectively, 19.11LPM/15.5LPM
A 45kW, 21.5LPM/17.43LPM
A 50kW, 23.89LPM/19.37LPM

A storage combi can also be considered but will only give a high flowrate for a limited time.

The problem with installing a 50kW boiler, apart from pipe sizing etc is that the heating demand will/can be way out of step with the HW demand resulting in frequent boiler cycling at low heating demands.

 

[DP]

Was the gas pipe gas meter to boiler replaced or size of pipe checked that gas delivery is as it should be? If the gas pipe to boiler is undersized, often when the gas hob ( if you have one) is running, observe size of hob flame, then run a hot tap. Hob flame will diminish in size. It is not unusual for installers to sling a 35 or a 40kW combi on existing gas line that was previously correctly sized for a 15kW boiler