Powerful shower from a combi?

[darkside]

We are in the process of redoing our bathroom and I have to replace the weedy electric shower with something that has enough ooomph to wake me up in the morning and get me clean after my mountain biking!!!

I have searched this forum and can't seem to find an answer to my problem so hope someone can help.

We currently have a combi boiler for the heating system but the shower, as mentioned, is electric.

The combi does a great job of heating the house but it does not seem to produce much flow from the hot taps - especially the bath takes which ages to fill up. Therefore I was concerned about my plans to run the shower from the same boiler due to the hot water flow rate.

My question bascially is:

- is there potentially a problem with our combi and should it provide good flow to the hot tap (boiler downstairs at the back of the house and tap upstairs at the front of the house).

- will an electric shower come close, or exceed, a good combi shower

- apart from fitting a pump and tank, are there any other options to maximising shower pressure?

Hope someone can help!

 

[Bahco]

Check your flow rates by running hot water into a bucket.
Measure how long it takes to put 9 litres of water into it. It should take about 1 minute on normal boilers.
if this is fine you can fit a thermostatic shower to hot and cold supplies and have a good shower

 

[darkside]

Hi - thanks for the pointers!

I ran the taps and measured the flow rate into a jug (with a fiddle factor and a few splashes for emptying time) and the results are as follows:

Cold - 21 l/min

Hot - 5 l/min!

Shower - 4.5 l/min!

This is about half quoted and sounds about right for the 'feel' that it is not nearly powerful enough for a shower!

I tested all the taps in the house and the results were the same, making me feel that the constrictions are in the boiler.

Is there a cure or does it sound like we could do with replacing the combi? I think it is about 9-10 years old and a 'Ferolli' model.

Cheers!

 

[oilman]

It may be your secondary heat exchanger is scaled up, this can be descaled then look here .

 

[darkside]

Thanks for the tip - sounds far cheaper than a new boiler! Would most competent 'boiler servicers' be able to do this?

 

[ollski]

Of course there's nothing to stop you puttin a cold water storage tank and a hot water cylinder with an immersion element in the loft. Specify the cylinder big enough for your morning shower demand and heat it via a mains timer. Providing you get the head of water pressure you could then run a power shower at up to 18 litres a minute.

 

[oilman]

Would most competent 'boiler servicers' be able to do this?

This'll be difficult. Good ones will, (by definition), but lots will suck air through teeth and say your boiler's on it's last legs. Speak to someone who does powerflushing as well as boiler servicing.

 

[ChrisR]

Most of the middle aged Ferroli's didn't have a secondary heat exchanger - they used a separate waterway in the main heat exchanger. Powerflushing would help, though "doing" the rads may not be really necessary. An injection of sumat like Fernox H Duty System Restorer could be well worthwhile. Are you in a hard water area? That could llimescale the tap water side. Also cleanable by a bloke with a machine.

Breezer's Puma works in a similar way (though it has a diverter) & it scaled up its h/e - dunno if he told us how it was descaled......

 

[darkside]

We are not in a particularly hard water area - we have next to no limescale on a 5 year old kettle!

Further research shows that the Ferroli is an Optima 800 and this not only has a poor flow rate of 8.1 l/min but the stated efficiency is evidently only 70%.

For enviromental as much as economical reasons I am a big fan of A rated kit. Since we are about to gut the kitchen in 6-8 months, I don't want to have to touch the boiler thereafter! I may well look into an A rated boiler with a flow into the teens (there are some around 13ish) - this sounds like it could be a great (if more costly) solution.