conventional boiler swapto a combi?????

12 Feb 2004
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United Kingdom
About to get a new central heating boiler and would appreciate any opinions on the following:

At present i have a back boiler & cylinder, one heating engineer recommended a combi but i am not sure, i get 11 litres a minute out of my cold mains tap, I dont have a bath only a shower but at present it is a power shower, i know i would have to replace it 'but' would i get a descent shower off a combi or should i get a conventional boiler and cylinder.

:confused: :confused:
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[code:1]11 litres a minute out of my cold mains tap[/code:1]
Depends if the limitation is the tap.
Try Garden tap + kitchen and add them together?
We need to know what the capacity of your main supply is. To discover this you need to open at least 2 taps, maybe more (but only those running directly off mains), measure the flow rate of each one and then add them together.
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so i should put a bucket under my kitchen tap and also my garden tap then fill both at the same time for 1 minute then add quantity together??
Yes, or just leave both taps running and time each tap to fill a bucket (of known capacity) one after the other. The flow won't fluctuate significantly in that time.
turned garden tap and kitchen tap on full whilst doing so filled a 9 litre bucket up from garden tap and this took 37 seconds, then filled same bucket up from kitchen tap and this took 1 minute 51 secs. Is this what you meant.

garden now flooded!!!! :eek:
Splendid. Punter gets wet for a change :evil:

Well I make it 19.46 litres/minute, which is typical. OK for a combi, until somebody turns a tap on somewhere else in the property. Go for a 28kW one. You'll get a shower of about 11 litres/minute. Now take yer bucket into the shower and see how it compares!

If it's a 10kW electric shower it would only be about 4 litres/min.
as i said at present i have a power shower (pumped) which when my son uses it probably wastes enough water to fill a bath

Will i be able to run the combi to a conventional shower mixer??? and will it perform ok
Now take yer bucket into the shower and see how it compares!
Yes just get a thermostatic mixer shower suitable for a combi.

But why have a combi? Must you get rid of your airing cupboard? If not, hang a system boiler where the combi was destined to go upgrade the cylinder to present british standards if it isn't already so, and you don't have to change the shower. Put some sort of flow restrictor in the existing shower if you wish for when your son has a shower, or put pump on a timer so it cuts out after 5 minutes. Better still get a slot meter like the tv rental boys used to use and make him pay for his showers. Or kick him out and tell him to find a place of his own.

Does he pay rent?

Oh and of course you'll need a new fully pumped control system for your heating and hot water I recommend s plan but plenty of boys here like y plan. TRV's programmable room stat (preferably intelligent one or modulating) Lag pipes outside heated space blah blah blah
never mind blah blah all advice greatly received

will there be a great difference in price for the type of system you recommend compared to a combi???

whats a y plan compared to a s plan

will you come and fit it??? :LOL:
You can get a high quality system boiler for about £750, an S plan control pack costs less than £100, lagging will now need doing, definately won't have been done, For 22mm correct thickness (it should be diameter of pipe but 19mm would be OK would cost 1.20 a meter off the top of my head) TRV's vary £5 to £10.

Quite a few fittings and pipework because you almost certainly have gravity hot water and a pump under the floor near the chimney or else in some boxing beside it, but it would want to be moved/renewed probably.

You'll need a good flush with sentinel x400 or similar, preferably a powerflush and then when system flushed and refilled the umpteenth time finally add x100 inhibitor.

If your Hot water Cylinder isn't BS1566 you need a new one circa 150£

I charge £200 a day for big jobs like that in my local area, I'd have to charge more if I travelled. Am booked for 4 weeks but that'll soon worsen because people are turning on their boilers now (or failing to) it's going to go manic.

S plan is a dual sytem where heating and hot water have their own circuit and their own control valve of a simple type. Y plan boiler only works for heating if it gets a feed from cylinder stat so a little cross polination there. There is a shared valve which is a very clever thing but depending where it was when you turned off the system it can still have a voltage across it which may shoirten it's life. Other people don't agree with me that it is less reliable than the zone valves used in s plan. There are certainly loads of call out's due to them never being wired up right or failing.

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