size boiler and type of system

[nysk2008]

Hi all,

Went to see a customer today and they are complaining about not enough HW, CH is slow to warm up and their boiler is going through heat exchangers like theres no tommorow.

They currently have a Vaillant Turbomax and 2 x 210 ltr unvented cylinders linked together. The property is 6 bedrooms, 2 shower rooms, 3 bathrooms, 12 rads (doubles). HW is used mainly between 6-10am and 6-10pm with up to 3 HW draw offs being used at any one time.

The system is full of sludge so a decent powerflush is first on the list but does anyone have anythoughts on what install would suit the size and requirements of this property best? Unfortunately at this stage I have no idea on flow rates or pressures.

In an ideal world I would like to install one decent size system boiler and one decent size megaflow. Another firm has recommended a 40kw system boiler to run house and cylinders and a seperate combi to run upstairs. i'M not convinced that is the best option though.

Appreciate your thoughts

Cheers

 

[Davinder]

i'M not convinced that is the best option though.

neither am I.

I agree with you (assuming that you have adequate flow rate andpressures), don't forget about the secondary return.

 

[Gray0689]

12 rads that don't sound right for a property of this size what else is it heating?????

 

[Davinder]

12 rads that don't sound right for a property of this size what else is it heating?????

Strange that, I was thinking the opposite. Nysk2008 has already listed 11 Rads in the OP, which leaves only 1 left to heat the kitchen, lounge, hallway, landing and cloakrooms, not to mention any other internal space that requires heating.

unless i'm reading it wrong, - in that case you have my apologizes.

 

[Gray0689]

I ment there has to be a lot more rads/ underfloor heating in a house of this size

 

[GrahamM]

You do not mention any living areas or hallways in your radiator figures. You sure there only 12 rads? Is it a detached property, 2 floors?

 

[nysk2008]

Hiya,

Yeh sorry, 2 floor detached property, I don't think I made my OP too clear in the first place. Agree though, needs more heating in the property I was thinking in region of 15 - 18 rads to be fair

1 rad in each of the bed rooms = 6
1 rad in hallway = 7
1 rad in upstairs hallway = 8
1 rad in utility room = 9
1 rad in reception room = 10
1 rad in dinning room = 11
1 towel rad = large bathroom = 12

 

[Gray0689]

So 2 shower rooms with no heat 2 bathrooms no heat and a towel rail is not big enough to heat a big bathroom
This house sounds like it needs a lot of work
Have you sized the rooms to see what heat is required to what heat output they have?

 

[nysk2008]

Hi Gray,

Cheers for your response, no room sizes and no calculations have been made, I had about 30 mins there to do a brief suvey so to be honest i'd like / need to work from a blank canvass. They claim not to use the other rooms you mentioned very often but complain there cold (believe there for entertaining purposes). Looking at the property I would say around 20 years old. How would you approach this and what would you think best with the limited info you have. Fully appreciate you have little to go on.

 

[Gray0689]

Well these rooms will be cold if no heat lol
You need to measure rooms and size what kw/btu is required per room
And tell your customer what is required and price accordingly
What was you there to do if you don't mind me asking??

 

[nysk2008]

Hi mate, to be honest I was there to have a look at their under-performing system and the reasons why and give advice whether to rectify or change. they have taken the change route as an option so i guess I will need to go back round and conduct a more comprehensive service. appreciate your interest though mate

 

[Gray0689]

No bother mate what size is the boiler

 

[nysk2008]

believe it or not I believe it to be a 28kw, (they had an extension and didnt upgrade). This is a big job for me, only used to the standard 2-3 bed combi installs, but at least something that I can really try and get my teeth into and have some fun with.

 

[smhstu]

hi mate

I do a few installations on larger domestic properties, most of the tome i fit two boilers cascading.
The first thing to consider is the gas consumption.If you say fit two 30kw system boilers then there is no scope for any other gas appliances in the house if they only have a u6 or g4 meter.
The last one i did was two 26kw system boilers and a 300ltr twin coil cylinder, they where both set up as four pipe systems witha reverse return, the upstairs and downstairs zoned seperatley.
A bronze pump timed for peak demand times on the secondary hot water return.
The twin coils are both connected to each boiler and recovery time on the cylinder is great. In the future the customer is going to have solar thermal fitted so hence the twin coils, but for the time being both are connected to the boilers.
Also when cascading boilers if one boiler develops a fault then the other will take the lead and keep the system running.
If you need any drawings just let me know.

Stu

 

[Gray0689]

It's a big job yes but nothing that can't be sorted with a bit of work and a kango lol
You will need to work out the heat requirement for the house and hot water 28kw is going to be to small if the house is as big as I think if you can't increase the boiler size if there is room you could go for a buffer tank

 

[nysk2008]

Hi all,

Well went back with my old boss and he carried out a few heat cals. He thinks we have 2 options, 1x 40kw system boiler and a 300l unvented zoned or 2 x combi (he suggested 24i junior) on each floor and maybe add 3-5 more rads. any other options or is this a good bet? My old boss is a sound engineer but like me he is more install and less design. Sorry Gray I know that helps about as much as a chocolate fireguard

 

[Gray0689]

Don't put combis in not on a house like that to many draw offs IMHO
You need to size it all properly I agree a 300ltr cylinder should be fine but need to look at
How many people live in this house what ages (most teenagers need lots of hot water then some need none lol) how far away are the draw off points from the cylinder
If there is room a buffer tank can be used with a smaller boiler
Is the house zoned
Controls
Water pressure and flow rates
These are some of the questions that will need answering to determine what you would put in
And digest question is what budget can you work too

 

[nysk2008]

Cheers Gray, appreciate all of your help and patience with me, I am pretty new to the world of gas and when on your own its hard going when/if you get out of your comforte zone. Thanks again mate and thanks to all posters on this one, i'll let you know what I end up with, apart from a massive headache, loads of paper around my dining room table and the bes mag taking my missus place in the bed!

 

[Gray0689]

No bother mate we are here to help if you need any help give me a shout I'll do my best to give you advice