Do I move to a Combi Boiler?

[chouglez]

My first post and thank you all for accepting me.

I have a real dilemma at hand and need some advice folks.

I currently have a storage talk + pump arrangement so that the pressure is good (not great) in the showers. I am in the middle of loft conversion and was advised to go with a combi boiler mainly because the storage tank in the eves does not fit as planned and would be stealing some more space from an already tiny study room in the loft. The plumber has confirmed that via the garden tap the current pressure is 2 bars and 14-16 litres.

My biggest worry is if I go with a combi boiler which is an additional cost of £2500 would I still get adequate pressure in showers (one existing and one new in the loft) as I do not have an option to attach a pump to a combi boiler setup?

Any advice is much appreciated.

 

[moggridgeplumbing]

If you go for the combi option, as you have two showers, you will need quite a good hot water output (above 15 ltr/min). As your existing showers are pumped you may want to check the output you are used to.

Stick the shower hose into a bucket and measure the amount of water you get in one minute. That will tell you the output you are used to.

Next ask the installer what combination boiler he would suggest. You can check the output of the boiler on the internet to confirm the above, and you could always check again on this forum, what others think of the choice.

If it's space you are after then tanks and hot water cylinder will be taken away, solving your problem. I hope this makes a start towards your decision.

 

[Agile]

I expect that your plumber is a nupty who thinks that an open pipe flow rate is what you need to measure rather than the dynamic flow rate.

Yours might be say 9 li/min @ 1 bar but that is only just adequate for the most basic 24 kW starting power of combi.

No current normal combi can supply two showers properly anyway.

If you wanted to run two showers together then a stored water cylinder is your only option.

An upgraded mains water supply would cost 1k to 2k but then you could have an unvented cylinder or a large combi or storage combi.

Tony

 

[echoes]

Combi boilers are great for supplying a single shower with no other hot water use at the same time, but you will need a very powerful one to be able to supply more than one shower at once, or a shower + a hot tap at once.

Your water pressure seems on the low side: 2 bar & 14 l/min.

 

[ajrobb]

I have similar decisions to make soon.

Unvented HWC can use existing boiler and provide main pressure up to 3 bar. They need installing by a plumber with a G3 certificate. You keep the option of an immersion heater as back up. However, you must have adequate flow and pressure from the water mains as these cannot be boosted.

Try and rig up a mains hose and two shower heads in the loft to check the existing flow when you normally shower. It can be worse between 7 and 8 a.m. If you can't run two showers adequately from the mains, you might be able to upgrade the mains feed from the street. If you CAN run two showers from the mains then an unvented cylinder would be a good option.

If you can't run two showers from the mains then I think you might need to go to a negative-head shower pump. A coffin CWS tank might fit better under the eaves.

 

[silverback18]

Why would you see the cylinder as stealing some space, your hot water is one of the most important things in your home, the trouble with the UK is homeowners have the same attitude as yours, tell your builder to work around the cylinder, relocate it if you have to, but keep it, you will regret a combi with the flow rate you have

 

[chouglez]

Why would you see the cylinder as stealing some space, your hot water is one of the most important things in your home, the trouble with the UK is homeowners have the same attitude as yours, tell your builder to work around the cylinder, relocate it if you have to, but keep it, you will regret a combi with the flow rate you have

Thanks Silverback18. Not it's not the cylinder (which is already in the airer cupboard) but it's the water tank which was in the attick so far but now it will be relocated in the eves because of the loft conversion and will be sticking out from it in the study room...

 

[ajrobb]

Will a coffin tank still stick out? As a side benefit, a new CWS tank will comply to modern bye-laws and prevent insects or larger animals getting into potable water storage.