Advice re new boiler - combi or pressurized tank?

[Caagh]

Hello all, first time poster but really hoping for advice.

Housing/social situation : Detached house, two adult occupants, often at work during week. Current boiler which supplies hot water and radiators circa 10yrs old, gravity system with header tanks in roof and hot water tank on landing.

Project : New bathroom, which involves removing hot water tank on landing to fit a new separate shower into the bathroom. We've had architect draw up plans and a schedule of works, and am currently actively getting quotes together.

Architect has said we should have a combi boiler with a pressurized water tank in the roof - he says this would mean that water will gush out of bath and the new shower. He says combi boiler won't give us this, bath would fill slowly and to get a good shower in particular, we would need pump.

Friends and some of the people who have quoted say that combi boiler is more efficient, pressure isn't going to be very different as long as our mains water pressure is good (think it is fine). Then it gets technical about pressure/flow rate and cost of heating water just to sit in a pressurized tank. Also, one builder said pressurized systems need annual checks which would mean running costs are more expensive (no idea if this is true?)

Can people please tell me what I should do?

Many many thanks for any advice
Confused of Bath

 

[bellairaphon]

dont listen to a architect or a builder. u need to get roughly 3 seperate quotes from a registered gas installer.

what your architect is suggesting is an unvented cylinder but would require a system boiler if your wanting heating too.

a check of flow rate and water pressure will be done by an installer who could then inform you on what are your options to a combi or system boiler.

a system boiler a combi boiler need a yearly gas safety check every year. also an unvented cylinder does need to be checked yearly too

if you check out www.gassaferegister.co.uk you can find a rgi

Nath

 

[mickyg]

check the flow rate. no point deciding anyhting til you know that. By the sound of your spec I'd say a combi is more than adequate. I'd be looking at something around 30-35kw to give a sensible flow at taps, again, assuming you have adequate flow.

 

[oilman]

Friends and some of the people who have quoted say that combi boiler is more efficient, pressure isn't going to be very different as long as our mains water pressure is good (think it is fine). Then it gets technical about pressure/flow rate and cost of heating water just to sit in a pressurized tank. Also, one builder said pressurized systems need annual checks which would mean running costs are more expensive (no idea if this is true?)

As well as not listening to an architect, don't listen to your "friends" either, they are about as useful as an architect. Pressurised tanks should be inspected, but very few ever are. Have a combi boiler. That way when it breaks down, you have no hot water as well as no heating. Saves all that worry about finding the immersion heater switch. You just have to boil kettles and wrap yourself in blankets.

 

[Caagh]

I have now rung my water company (Wessex Water) and found out that they offer free water pressure and flowrate tests, so I have booked an inspector to call, and once I know this information I'm probably going to be able to make a more more informed decision. Thanks for your help with this.

 

[mickyg]

Have a combi boiler. That way when it breaks down, you have no hot water as well as no heating. Saves all that worry about finding the immersion heater switch. You just have to boil kettles and wrap yourself in blankets.

yep cos a couple of times in 12 years, thats gonna be a massive inconvenience!
still with the amount saved in not heating water needlessly and having the UV serviced, there'll be plenty of funds

 

[doitall]

The architect is suggesting a combi boiler serving the kitchen/utility and an unvented cylinder serving the bathrooms on a Y plan.

Perfectly good sense.

Who are the architects, I know must in the area.

Wessex water is normally a good, 3bar ish, flow rate depends on the pipe size.

 

[bengasman]

Architects are not plumbers/RGI's, and neither are builders. The worst advice usually comes from people who know a little more than you do, as they sound like they know what they are on about.

The real answer to your question is actually fairly simple; find a good RGI, and follow his advice.
In general, a large combi, 35 kW and up, is perfectly capable of supplying 2 baths/showers. Provided your watersupply is up to it, 22/25 mm or more all the way to the streetvalve and enough pressure, you can't beat a sizable unvented cylinder. A lot more expensive though, both to install and run.