mark chandler
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| posted on 31/1/11 at 09:43 PM |
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Boiler placement and sizing question
Hello
Small maisonette and want to install a combi boiler:
- Want enough flow for a fast hot constant shower
- Only need to fire three radiators
- Want to put the boiler in the loft as no space inside the house really so this will be the highest point of the system
So do I buy a boiler big enough for a 4 bed house or get a small one and try and be clever with the hot water element?
by keeping the existing eco7 hotwater tank and fill with hot water on demand (it does not have a HW loop) and leave the eco7 to maintain the heat (so
I am really just topping up)
or
Do I replace the tank with one with a HW loop?
Is it okay to have the boiler as the high point, just have a loop above with a vent valve?
Cheers Mark
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cliftyhanger
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| posted on 31/1/11 at 09:56 PM |
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The bigger boilers cost a little more, but remember it is the install that costs. So may be worth the extra. We have a 120, 000btu vaillant, very good
shower off a mira mixer. Saying that I have experienced the std 80,000 btu ones, and although the flow is a little less (not much at all, may be down
to th echeaper mixer) the flow was still very good.
Try to keep it simple, complicated normally costs way more and never works as well as hoped (painful experience)
In all honesty a std combi boiler should be just dandy. worth getting a good one (I like my vaillant, worcester not bad either)
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cliftyhanger
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| posted on 31/1/11 at 09:59 PM |
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To add, not sure how you would intend using a HW tank with a boiller, unless you get a tank with a loop and it is plumbed in as a radiator?
No reason for the boiler not to be at the high point, mine and I presume others have a bleed valve internally. A loop may be a good idea, possible to
fit an auti bleed valve if required.
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BenB
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| posted on 31/1/11 at 09:59 PM |
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Check what your water pressure is like. I fitted a big boiler so I'd get good DHW flow only to find didly squat pressure due to being on a hill
and having rubbish water mains 
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adam1985
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| posted on 31/1/11 at 10:17 PM |
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You could have system boiler this looses the header tank and has a pressure vessel inside the boiler.
Or if you go for a combi i would go for a small kw boiler ie 24 kw with the bigger boiler you get more
flow but this is only needed for bathes really its the pressure you need for a shower
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mark chandler
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| posted on 31/1/11 at 10:30 PM |
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My last house had a 120,000 btu combi, and got good flow of hot water.
Relative had a 24kw combi, start pulling a decent amount of water and it ran cold..... rubbish
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MikeR
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| posted on 31/1/11 at 10:45 PM |
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If its going in the attic, the attic has to be boarded and have a light - otherwise the installers aren't allowed to fit and service it.
Also, if its in the attic, make sure you're not going to have an issue with condensation, it will give off heat and potentially cause problems.
Finally, my dad had an issue with this condensing boiler over christmas, it was so cold it froze the overflow 22mm pipe and the boiler failed. He had
to clean out the pipe. Turns out when its REALLY cold its a common problem - you could end up with some interesting repair bills / scary moments up a
ladder if yours freezes at that height.
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slingshot2000
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| posted on 1/2/11 at 01:38 AM |
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quote:
Originally posted by MikeR
. Finally, my dad had an issue with this condensing boiler over christmas, it was so cold it froze the overflow 22mm pipe and the boiler failed. He
had to clean out the pipe. Turns out when its REALLY cold its a common problem - you could end up with some interesting repair bills / scary moments
up a ladder if yours freezes at that height.
Yep ! Lots of high level condensor pipes frozen and plumbers/scumbags/heating engineers are charging £200 to thaw them out ! Where-as f they had been
fitted and lagged as old-school plumbers would have done, there would nor have been a problem !
I know of one local 'heating-engineer' bragging that he has been making in excess of £2000 a week on call out to repair combi's
that he installed with this know problem !
He is using a hot-air paint striper to thaw the external pipes!
Regards
Jon
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markt0121
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| posted on 1/2/11 at 02:32 AM |
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If you are fitting a boiler in the loft then check the operating instructions to see if it needs to be reset after electrical power is interupted.
This seemed to be a common problem on a few of the combi boilers I was looking at last year. My concern was if there was a brief electrical power out
while I was away from home for a few days the boiler would stop working, then there would be risk of pipes freezing before I returned home to reset
the boiler. If it was in the attic you would need to go up in the attic to press the reset button on the boiler. I ended up getting a Ferroli as it
doesn't need to be reset after a power interuption. I think the Worcester I was looking at needed to press a reset button after power is
reconnected.
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