One for Ferg... Combi Boiler Questions
Discussion
Due to the demise of our (god knows how old) 'ordinary' boiler, and the subsequent inspection by a plumber which discovered we also had a well below standard HW cylinder, his honest suggestion was to upgrade to a condensing combi, rather than try to fix or replace what we've got.
I've done some reading, but most of what google turns up is similar questions without very good answers - I was hoping you'd have a few minutes to help?
FWIW, there's just me and the OH, the house is a 3 bedroom, 1 bathroom.
What is a good incoming water pressure / flow rate? Is it simply a case of counting buckets of water under the kitchen tap, or will the plumber have some sort of gauge?
Shower. We want to ditch the current electric shower and replace with a thermostatic mixer. Are all units created equal? And is the figure of 15L/min (picked up from another thread on here) about right for a decent hot shower?
Boiler choice. Worcester Bosch and Vaillant are the two brands that seem to come up time and again when recommendations are asked for. Is either preferable in terms of servicing, parts availability, etc?
All the figures quoted are for either 30 or 35 deg above ambient. Is this the maximum the boiler is capable of, or just a peculiar standard way of measuring?
The Worcester Bosch website recommends a Greenstar 24i Junior - which by its name and description immediately leaves me thinking it wouldn't cope very well - it only manages a flow rate of 9.8L/min. To have a flow rate of 15L/min we'd need the 37CDi, or 42CDi to give a bit of headroom. (Is that desirable or necessary?)
The only option from Vaillant seems to be the Ecotec Plus 937, which although it has a storage facility (dubious about how useful this would actually be) is probably more expensive to buy and run than the equivalent WB, the 37CDi.
Timer/Stat. We don't currently have a room stat, we're working on TRV's in each room - and to this end I want to go wireless, rather than messing up any more plasterwork. Is the Honeywell CM927 still a good piece of kit in this respect?
Radiators. We have a single panel rad in each room. When the Monsters-in-law had a combi fitted, they had all their rads replaced with double panel ones, under the impression they were either more efficient or better at the job. Do we need to think about this as well, or will the single panel ones work ok?
Thanks in advance for any help
I've done some reading, but most of what google turns up is similar questions without very good answers - I was hoping you'd have a few minutes to help?
FWIW, there's just me and the OH, the house is a 3 bedroom, 1 bathroom.
What is a good incoming water pressure / flow rate? Is it simply a case of counting buckets of water under the kitchen tap, or will the plumber have some sort of gauge?
Shower. We want to ditch the current electric shower and replace with a thermostatic mixer. Are all units created equal? And is the figure of 15L/min (picked up from another thread on here) about right for a decent hot shower?
Boiler choice. Worcester Bosch and Vaillant are the two brands that seem to come up time and again when recommendations are asked for. Is either preferable in terms of servicing, parts availability, etc?
All the figures quoted are for either 30 or 35 deg above ambient. Is this the maximum the boiler is capable of, or just a peculiar standard way of measuring?
The Worcester Bosch website recommends a Greenstar 24i Junior - which by its name and description immediately leaves me thinking it wouldn't cope very well - it only manages a flow rate of 9.8L/min. To have a flow rate of 15L/min we'd need the 37CDi, or 42CDi to give a bit of headroom. (Is that desirable or necessary?)
The only option from Vaillant seems to be the Ecotec Plus 937, which although it has a storage facility (dubious about how useful this would actually be) is probably more expensive to buy and run than the equivalent WB, the 37CDi.
Timer/Stat. We don't currently have a room stat, we're working on TRV's in each room - and to this end I want to go wireless, rather than messing up any more plasterwork. Is the Honeywell CM927 still a good piece of kit in this respect?
Radiators. We have a single panel rad in each room. When the Monsters-in-law had a combi fitted, they had all their rads replaced with double panel ones, under the impression they were either more efficient or better at the job. Do we need to think about this as well, or will the single panel ones work ok?
Thanks in advance for any help
You will have a problem if say, you are in the shower and your other half turns the kitchen tap on or starts the washing machine. Your shower will slow, go cold/hot etc. Make sure you use a shower unit with a good thermostatic control.
A combi is not ideal for a house of your size, you will get by if there are just two of you and you obey the rules when someone is in the shower!
A combi is not ideal for a house of your size, you will get by if there are just two of you and you obey the rules when someone is in the shower!
spikeyhead said:
Shaolin said:
Ferg said:
YHM.
Any chance of posting it here? - we're in a very similar situation though currently just have a bath and not a shower.Simpo Two said:
Interesting point about water temp vs radiator size. I'm surprised that radiators are allowed to be too hot to touch, what with the little children and all that.
Yes - I understand the efficiency etc; our house has relatively small single panel rads with fins and they run HOT and we have to be careful if we have small kids in the house. The rads get the rooms warm but the issue we have is the temp varies a lot, I presume just because of the smaller water content. Boiler is just an ordinary one.Next door (identical house) have a combi but they had MASSIVE double panel with fins in the middle rads fitted. They're never more than warm to the touch but their house feels so much more comfortable than ours does. The only control they have is a wireless programmable room stat and that links directly to a receiver in the Worcester combi boiler.
Another thing to bear in mind when considering a combi is, they are priority hot water.
It proved a bit of a problem for me in the winter. Me and my partner rise at 6:45 and we are out of the house by 7:30, if we both shower in the morning, that is about 25 minutes of hot water being drawn off or 25 minutes of the heating not working.
Not so much a problem in a well insulated home, but I live in a poorly insulated dormer bungalow. So the house only ever manages to reach 17 degrees in the morning. Its even worse if someone runs a bath, the flow rate is so poor in my house that it takes over half an hour to fill the bath.
Also when a combi fails, you have NOTHING. At least when your conventional boiler breaks down you can flick the immersion heater on and still have hot water.
I'd personally rather have a conventional system with a Hot Water cylinder.
Have a think about whether or not a combi is right for you and don't let your plumber talk you out of it.
Most recommend them because they can make more money from them and they get money from all the scrap too.
Also I know a few "Heating Engineers" that don't know what a fully pumped set up is and wouldn't have a clue how to wire one!
It proved a bit of a problem for me in the winter. Me and my partner rise at 6:45 and we are out of the house by 7:30, if we both shower in the morning, that is about 25 minutes of hot water being drawn off or 25 minutes of the heating not working.
Not so much a problem in a well insulated home, but I live in a poorly insulated dormer bungalow. So the house only ever manages to reach 17 degrees in the morning. Its even worse if someone runs a bath, the flow rate is so poor in my house that it takes over half an hour to fill the bath.
Also when a combi fails, you have NOTHING. At least when your conventional boiler breaks down you can flick the immersion heater on and still have hot water.
I'd personally rather have a conventional system with a Hot Water cylinder.
Have a think about whether or not a combi is right for you and don't let your plumber talk you out of it.
Most recommend them because they can make more money from them and they get money from all the scrap too.
Also I know a few "Heating Engineers" that don't know what a fully pumped set up is and wouldn't have a clue how to wire one!
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