Combi or heat only?

Sent you a pm.

 

Two bathrooms then defiantly heat only, if you want decent DHW pressure consider upgrading to an unvented system, or as you say keep the existing.

 

Whether defiantly or not (my absolutest fav Freudian ever), Hunter does have an option here, and it's fair to give him the pros and cons.

It really comes down to what each individual's priorities are, although the OP has already mentioned one of the main ones - that space ain't a problem.

Vented System:
+ Properly designed, there's no shortage of water flow to taps even when run at the same time.
+ Turning on a cold doesn't affect a hot.
+ Hot cylinder provides airing-cupboard warmth.
+ Water still available if mains supply interrupted.
+ System boilers will generally be more reliable.
+ Stored hot cylinder allows for addition of solar heating...
+ Immersion heater can provide back-up hot water if boiler is poochied.
- Hot water is not instant - a pre-heated stored supply is required. Coupled with delay in recharging.
- Stored hot water supply wastes energy thro' heat loss.
- Hot cylinder takes up cupboard space
- Storage tanks in loft are a potential leak hazard, and will require maintenance.

Combi System:
+ Instant, endless hot water supply.
+ Can provide an excellent flow for superb showers.
+ Reduced energy use - heats only the water required...
+ Frees up cupboard space and removes need for tanks in t'loft.
- Can only provide one hot tap at a time.
- Running a cold tap will affect hot top flow.
- More moving parts - generally more to go wrong.

Anything to add to the above?





(Can someone explain to me how a stored-water 'unvented' system provides a better flow of water than a combi? After all, they are both mains-driven?)

 

Chust to add - I have a 3-bed, 3-bathroom hoosie and cannot recall a time when I've regretted going combi'.

Yep, when girlie had to fill a bath last night, I knew I couldn't have a shower for 10 minutes. And there have been one or two times when the temp in the shower fluctuated a bit - shower went cool for a few seconds when someone ran a hot tap - but other than that it's all good for me.

Mind you, a priority for me was to remove tanks from the loft and ideally a hot cylinder from a cupboard, so that's what drove the original decision. But, regrets? Non. Showers are awesome. The one-tap-at-a-time issue just not a problem in practice; I do think peeps make a greater issue of that than is needed. Work it out - just how often are two taps run at the same time?


But, for Hunter, I would suggest he sticks with what he's used to - there is no obvious advantage for him to change to combi.

 

I go for combi, there's not a lot of differance betwix flow rate for a new combi replaceing an old vented, on your system I guessing that if you open 2 hot taps, one will slow down,
Mr Devs has mostly covered the advantages except fo a major one that WILL be important to you, ECONOMY, a combi only heats the water you use, whereas a heat only will heat the cylinder twice a day and if you don't need it, you wasted money, its like boiling a kettled then throwing down the grid,

 

you'll only waste money heating a cylinder twice a day if it's not properly insulated and if you've actually set your programmer to heat it twice a day - it won't magically heat it all on it own, nor will it empty your wallet every time you don't use the entire contents of the cylinder - that's just a silly reason for having a combi

4 beds, 16 room, 2 bathrooms - that's not a small house - if you do change to a combi life might get a bit shouty at certain times of the day if more than one of those rooms is occupied, if you are happy with your systems performance now then just simply swap for another system boiler

but there's other options you might want to consider, perhaps a little out of the scope of understanding of your average tap washer changing plumber, such as solar thermal and PV feeding into a thermal store, these will clearly cost more initially, but can, given the right conditions, reduce the cost of your energy bill for home heating to zero

 

...ouch...

 

what's good for the goose

 

Plucking?

 

hunter came on here for some advice from people in the heating industry with knowledge and experiance, but looneys are offering him a way of getting FREE heating, lets just ponder how that works for a minute,

free energy means the power suppliers are no longer needed, can that ever happen? only on paper, there's a true saying thast all folks with common sence know,


ya don't get owt for nowt,

 

I'm guessing you've not done much solar thermal work them Tom, or maybe you don't understand it - so you've dismissed it, that's fair enough

but just for clarity, this is what I actually said

 

One other option you could is to have a look at the Vaillant ecoTec plus 937 power store combination boiler. Its a combination of a combi with a small storage of ready use DHW, it is specifically designed for a larger house have a look on the Vaillant web site

 

we have a WB Greenstar Combi with a internal store - I've wondered why there are so few gas fired versions with a store available

 

Tap washers!

 

(Can someone explain to me how a stored-water 'unvented' system provides a better flow of water than a combi? After all, they are both mains-driven?)

In order for the combi to deliver hot water the water mains generally needs to be considerably throttled down (whereas the unvented cylinder does not).

Anything to add to the above?

Yes,
No hot water back up when the combi goes down (a big thing when working on maintenance contracts that demand a same day repair to "No hot water")
Tappy,

 

Thanks Crow's.

With a stored/unvented system, doesn't turning on one tap affect others too? To some extent? Or it must rely on a much better mains flow than is often available?


(Added 'hot-water back-up' to my list )

 

If my customers want really good flow with an unvented I'll always install an accumulator with it,you can have as many taps open as you like then.

 

Not so much that you'd notice.
A poor mains flow in the property,then you would have to fit something else (other than an unvented cylinder).
Tappy,

 

Thanks Plumbs and Crows.

What's an accumulator? (Well, I know what an 'accumulator' is - a store - but how is it different here from, say, a CWS tank?)