New Central heating but problems, Please help

[Last Plumber]

I have skim read this thread with there being 70+ posts so forgive me if I repeat anything that has been said.

Your Boiler will give 13 litres per min @ a 40 deg rise +/- 15%.

If you are testing the mains cold water flow rate at a tap, that does not mean the flow rate at the entry point on the Boiler will be the same. The standing pressure would be similar of course, (depending on how high the appliance is) but not the flow rate.

You will lose flow rate due to frictional resistances in the pipe work from the mains entry point in your property to the appliance. This may only be minimal.

I would ask the installer to test the flow rate beneath the Boiler and see what it is there. Then you can address whether the issue is a lack of flow or a problem with the Boiler itself.

There is a flow regulator inside these (erp version) and there is a strainer in the inlet.

If you want to run two taps you will be sharing the hot water from the boiler between them. There is nothing you can do about that with this Boiler.

Did you seek advice and discuss your requirements with Heating Engineers prior to deciding on a combi?
Unfortunately it does sound as though you have the wrong system for you. Even if the Boiler was delivering 13 lpm at 40 deg rise, it would still be unsuitable for you by the sound of it.

 

[Stigster]

I have always said if you have the required supply and room for an unvented cylinder, always install a cylinder. Combis are best for small properties with only one bathroom unless you can afford to go big kW and even then a cylinder will perform better in most circumstances. unfortunately OP doesn't currently have sufficient incoming mains flow and pressure to make an unvented cylinder work properly.

A 300 litre cylinder and an accumulator same size might do the job if there is enough pressure to charge the accumulator acceptably.

 

[Harvest Fields]

I have always said if you have the required supply and room for an unvented cylinder, always install a cylinder. Combis are best for small properties with only one bathroom unless you can afford to go big kW and even then a cylinder will perform better in most circumstances. unfortunately OP doesn't currently have sufficient incoming mains flow and pressure to make an unvented cylinder work properly.

A 300 litre cylinder and an accumulator same size might do the job if there is enough pressure to charge the accumulator acceptably.

But I am sure that Dale Sanders is on about pitting the accumulator onto there existing combi.

 

[Dale Sanders]

Yes so what I have been advised by the engineer who installed the system is if I want to increase flow I would need to add an accumulator, he is suggesting that i get a 240l mainsboost vessel with 22mm upstream system. I am being quoted £760.

 

[Last Plumber]

Yes so what I have been advised by the engineer who installed the system is if I want to increase flow I would need to add an accumulator, he is suggesting that i get a 240l mainsboost vessel with 22mm upstream system. I am being quoted £760.

Your Boiler will only give you 13 lpm at a 40 degree rise plus or minus 15%.

It does not matter what you connect it to, it will only give that.

If you think it is worth the money for the extra 3 lpm, that’s your choice of course.

 

[Dale Sanders]

If I get 13lpm then I'll be happy. At the moment I'm getting 9-10lpm.

 

[Last Plumber]

A 36 KW Combi, 240 litre vessel and £5670, to give you 13 lpm seems absurd.

Is this a DIY gone wrong ?

Sorry Dale but if it isn’t, you need to be asking for this to be put right without any further expense to yourself !

Surely the installer took measurements of pressure and flow amongst other things before doing the job ?

 

[Stigster]

But I am sure that Dale Sanders is on about pitting the accumulator onto there existing combi.

I know. The problem is that nothing OP does to his system will make that combi do what he wants. A good sized cylinder with a good supply (better than they have at the moment unfortunately) is surely the best way to achieve performance on two hot outlets simultaneously.

To fit an accumulator with its cost for the gain of 3 or 4 ltr./m of hot water performance is not worth it in my mind but it's not my money.

The only practical way I can see involves a cylinder.

 

[Dale Sanders]

Would that mean removing the the combi? I have already emailed the installer stating I am not happy. Just waiting a reply

 

[ShaunCorbs]

Would that mean removing the the combi? I have already emailed the installer stating I am not happy. Just waiting a reply

No you can fit a unvented cylinder on your combi but incoming flow and pressure is key