Combi boiler plus shower pump

[Gazzad]

Hi I have a 32kv combi boiler in my cellar, I am switching to a mixer shower from a cold water feed electric. Do I need to fit a booster pump in my bathroom. Or can I fit one using a combi boiler.
Any help would be appreciated

 

[steadyon]

1. You can't pump the output from a combi, so no, you can't fit a pump.
2. Assuming the pressure and flow rates are adequate you should be able to run a mixer shower off the combi with no difficulty and shouldn't need a pump anyway.
3. You will obviously need to run a hot feed to the mixer, as previously you would only have had a cold supply to the electric shower.
4. The cold supply will be at mains pressure as will (to all intents and purposes) the new hot feed from the combi.

 

[Gazzad]

1. You can't pump the output from a combi, so no, you can't fit a pump.
2. Assuming the pressure and flow rates are adequate you should be able to run a mixer shower off the combi with no difficulty and shouldn't need a pump anyway.
3. You will obviously need to run a hot feed to the mixer, as previously you would only have had a cold supply to the electric shower.
4. The cold supply will be at mains pressure as will (to all intents and purposes) the new hot feed from the combi.

Thanks so much, I was trawling the internet and was getting conflicting views on whether you were able to fix one on the output of a combi boiler.
My boiler holds well at 2.5-3bar will that be enough for a mixer and rain head shower which was my initial worry

 

[steadyon]

1. Your boiler should not be reaching 3 bar. It should be around 1.2 - 1.3 bar cold, perhaps rising to 1.7 - 1.8 bar hot.
2. Whether your system will run a rain head satisfactorily depends on the incoming mains pressure, the flow attainable at the shower, and the requirements of the head. If it will support 1.5 bar and around 12 litres per minute it should be OK, but will depend on pipe sizes, number of bends etc.

 

[Ben-gee]

I would check the spec of the head as 12 l/minute at 1.5 bar is inadequate for some (and I thought we were meant to be saving water...)
If you can get a pressure/flow performance graph for the head you’ll know where you are.

 

[Gazzad]

I would check the spec of the head as 12 l/minute at 1.5 bar is inadequate for some (and I thought we were meant to be saving water...)
If you can get a pressure/flow performance graph for the head you’ll know where you are.

 

[Timmy D]

You mention 2.5-3 bar, are you referring to the boiler pressure gauge? If so, this is the sealed heating circuit pressure and has no bearing on the hot/cold water pressure.

Test what litres per minute you get. Ideally use an outside hose tap and measure the flow rate.

A 30kw ish combi will supply around 14lpm of hot, mixed with cold at a comfortable shower temp, you’ll get around 18lpm. Which is a good shower.

However, if you mains can only supply 10lpm, the shower won’t be what you’re probably hoping for.

If your mains is below 12lpm, you can put a mains booster pump before the boiler (near the stopcock, before any take offs) and boost your whole system to the legal max for directly boosted mains of 12lpm.