Combi hot water - is this normal?

itm2

We've just had a combi fitted to our 3-bed, 3-storey house. It's a Worcester Bosch Greenstar 30CDI. We were told that our water pressure was very good (more than 18litres/minute), but have found that if someone turns a tap on while the shower is running the shower pressure drops to a trickle. Is this just a fact of life with combi-based systems?
The pressure gauge on the boiler isn't indicating a problem (it's in the middle of the green zone).
???

debbie42

itm2 wrote: »

Is this just a fact of life with combi-based systems?

It is with ours. When I have a shower I make everyone well aware of that fact! It is definitely a drawback, I'm afraid. Our bath takes a lot longer to run, too that it did with out old system.

Bromley86

Same here. We had a 40CDi in a 2 bath (soon to be 1 shower, 1 bath) house. It might have helped slightly if we'd had the boiler fitted on the 1st floor rather than the ground, but not in any significant way.

As there's only the two of us we're probably going to leave things as they are. We did have a 22mm mains connection laid to the old airing cupboard just in case we wanted an unvented cylinder put in later, but they're expensive and require annual servicing. We might look again at heat banks at a later date as they aren't unvented but still (in theory) deliver mains pressure hot.

BTW. AFAIK heating will not be a problem. That pressure guage refers to the pressure in your central heating system and has nothing to do with your water.

Woby_Tide

we had a Worcester Greenstar 35CDi in our previous 3 bed/2 floor property. I'm not an expert but I think despite you having a good inflow, the factis it may be underpowered for a 3 storey house and this is why you are being impacted. Ours had an output of about 14l and both filling a bath and having a showere were unaffected by running any other taps, the 30CDi only looks to have 11l throughput so maybe that is more the issue

itm2

Thanks for the feedback. I've just spoken to the plumber, who tells me that the taps in our bathroom are an old style which draw a much higher water flow than modern ones. He says that when he re-does our bathroom in a couple of weeks these will be replaced with newer taps which with reduced flow, which should resolve the problem. This seems to make sense, as the flow from the taps does seem to be unusually strong at the moment.

While on the subject of the boiler (Worcester Bosch 30CDI), I've read the user manual but am still mystified by parts of the control panel:
- what does the digital display indicate? It shows a value of about 30-40 most of the time, but will suddenly go up to 50-60 for a minute or two and then back down again. Turning the dials doesn't seem to affect its value either.
- What does the "Central Heating Boost" button do?
- If I switch the master switch "off" will this also stop the supply of hot water?
- What is ECO mode?
- On the hot water temperature dial, what does the "e" setting mean (between 4 and 6)?

Does anyone have any ideas?

leetread

Combination boilers are only designed to supply one outlet at a time, the reason the flow is reduced compared to a traditional stored system is that the boiler is heating the water directly from the incoming main.
For greater hot water demand combination boilers aren't really the answer a stored mains pressure cylinder something like a Megaflo to quote a recognised brand name is a far better solution.

graham47

itm2 wrote: »

While on the subject of the boiler (Worcester Bosch 30CDI), I've read the user manual but am still mystified by parts of the control panel:
- what does the digital display indicate? It shows a value of about 30-40 most of the time, but will suddenly go up to 50-60 for a minute or two and then back down again. Turning the dials doesn't seem to affect its value either.
- What does the "Central Heating Boost" button do?
- If I switch the master switch "off" will this also stop the supply of hot water?
- What is ECO mode?
- On the hot water temperature dial, what does the "e" setting mean (between 4 and 6)?

Does anyone have any ideas?

The digital display is the temp of the water in the boiler,
(run some hot water & watch it go up). If you alter the temp dial (up or down) then you alter the temp the boiler will heat to.
Yes, I would imagine the master switch switches everything off (for servicing etc).
ECO mode ... in non-ECO mode boiler will keep temp of water (in it) up to temp by cycling on/off so, when you want to draw hot water there will only be a small delay before you get hot water at tap. In ECO mode there is no cycling so you need to wait while boiler heats water from whatever temp it had cooled to. Try running in ECO & see how you get on ... you will be saving energy (although maybe only a small amount).
The "e" setting is Worcester's view as to the "optimum" temp they think is suitable for average household (about low 60's I think) again ... try it & see how you get on. If too cold set dial to higher hot water temp, if too hot ... set lower.

"CH Boost" I haven't seen but my guess it's to override your timer & give you a quick 'boost' to your radiators if e.g. you come home to a cold house ...

TomsMom

leetread wrote: »

Combination boilers are only designed to supply one outlet at a time, the reason the flow is reduced compared to a traditional stored system is that the boiler is heating the water directly from the incoming main.
For greater hot water demand combination boilers aren't really the answer a stored mains pressure cylinder something like a Megaflo to quote a recognised brand name is a far better solution.

I'm so glad you've given that explanation! I have the same problem as the OP and I have to warn hubby not to turn on a tap when I'm taking a shower, or ask him to turn off a tap when the washing machine is filling up etc. I thought it was just us and our peculiar house!

stu3105

This has set me thinking,so I wonder if anyone can assist. I also have 2 bathrooms and a new combi boiler suitable for its purpose.

I'm having a new mixer shower fitted to my downstairs Loo.
Should I have an electric one fitted to the one upstairs when it gets renovated so both can be used at once,or can both mixers be run off the same combi?.

Cheers

itm2

I decided to go for an electric shower as well as the combi-driven shower - not because of the need to run two showers at once, but as a backup in case the boiler fails (I no longer have a cylinder/immersion heater).

roddydogs

itm2 wrote: »

Thanks for the feedback. I've just spoken to the plumber, who tells me that the taps in our bathroom are an old style which draw a much higher water flow than modern ones. He says that when he re-does our bathroom in a couple of weeks these will be replaced with newer taps which with reduced flow, which should resolve the problem. This seems to make sense, as the flow from the taps does seem to be unusually strong at the moment.

While on the subject of the boiler (Worcester Bosch 30CDI), I've read the user manual but am still mystified by parts of the control panel:
- what does the digital display indicate? It shows a value of about 30-40 most of the time, but will suddenly go up to 50-60 for a minute or two and then back down again. Turning the dials doesn't seem to affect its value either.
- What does the "Central Heating Boost" button do?
- If I switch the master switch "off" will this also stop the supply of hot water?
- What is ECO mode?
- On the hot water temperature dial, what does the "e" setting mean (between 4 and 6)?

Does anyone have any ideas?

How on earth will "reduced flow" taps make any difference to the water flow? you might just as well just open you existing taps only a small amount!:cool: