Balancing

[brighton68]

I have a Viessmann Boiler installed (on the lower ground floor) that provides for 14 Radiators (all fitted with TRV's - that are always on max anyway) of various sizes throughout a 4 Storey House. 5 on the lower ground floor, 5 on the ground, 2 on 1st, 2 on 2nd. The bathroom radiator runs independently on the Hot Water Only Circuit.
Two radiators, in particular, never get very hot but only really lukewarm. They are 2 upright radiators and are both on the lower ground floor and only get lukewarm at the top and remain cool/cold at the bottom.
My assumption is the system needs re-balancing.....
My question is.....where to begin
Should I fully open all valves at the non TRV end and start reducing the flows at the top of the house first or start at the bottom? OR Do I need to establish how the circuit is connected so I start with the first or last radiator and so on and if so how best to do that?
It's really annoying that at the moment I have to light all the rings on my hob to warm the kitchen!!

 

[denso13]

//www.diynot.com/wiki/plumbing:faq:faq2

 

[brighton68]

I have followed these instructions implicitly. When I fire up the boiler all the radiators heat up except four of the five on the lower ground floor. If I close the LS valves on all the radiators on the 3 higher floors, those 4 then heat up (though very slowly) - Any ideas?

 

[ALEC1]

under sized pipe work...is it all in 15mm...

 

[brighton68]

I'm guessing so.....i've not got as far as lifting carpets/floorboards etc at this stage.

 

[ALEC1]

IMO 15mm is good for one large radiator or two small ones...

much better to do everything in 22mm just the tails to 15mm

 

[D_Hailsham]

I have a Viessmann Boiler installed (on the lower ground floor) that provides for 14 Radiators (all fitted with TRV's - that are always on max anyway) of various sizes throughout a 4 Storey House. 5 on the lower ground floor, 5 on the ground, 2 on 1st, 2 on 2nd.

Which Viessmann?
Why are the TRVs on Max?

 

[brighton68]

Alec1 - the replacement boiler was connected to an existing system, some of it looks like 22mm, but I think thats the Hot Water Circuit.

 

[brighton68]

D_Hailsham - It's a Vitodens 200-W.
TRV's are always on max because none of the rooms ever get too warm...its a Victorian Mid Terrace, so not eco insulated like todays houses - guess I shouldnt have bothered with TRV's

 

[D_Hailsham]

D_Hailsham - It's a Vitodens 200-W.
TRV's are always on max because none of the rooms ever get too warm...its a Victorian Mid Terrace, so not eco insulated like today's houses - guess I shouldn't have bothered with TRV's

Setting a TRV to Max will not make the room any warmer! Your heating system is under-sized for the heat loss. This could be the boiler, but more likely to be the rads.

Use Whole House Boiler Size Calculator to find the required CH output of the boiler (set Domestic HW Allowance to 0 if you have a combi)

Use Stelrad Elite Catalogue, first table, to estimate the outputs of your rads.

Which version of the 200-W do you have? There are seven.

 

[brighton68]

Condensing Boiler Type WB2B 8.8-35.0 kW

The required boiler output from your link is 13.37kW

 

[D_Hailsham]

Condensing Boiler Type WB2B 8.8-35.0 kW. The required boiler output from your link is 13.37kW

Is it the combi or system version, i.e do you have a hot water cylinder?
If you have a combi, the boiler is probably correctly sized; but if you have a system boiler it is oversized, the 19kW or 26KW would have been more suitable.

Now we have established that your boiler can produce the correct amount of heat (plus plenty extra!), you need to check the rad outputs using the link I gave earlier.

 

[ChrisR]

Could be balancing/rads/pipe size/sludge etc but first see what's controlling the boiler. You could be on a mission here...

I'm guessing it's weather compensated. It may not be but I haven't seen one of those boilers that wasn't. So...
Is there an internal sensor? If not, I'd get one fitted by someone who understands how it's supposed to work. The simplistic weather-driven controls are frequently set up to provide too little output - saves you money so must be efficient , so they'll be too slow in all weathers, automatically. Set too high and great, it "works", trumpets and joy, but there's no savings so it's all a waste of time and money.
Installers of them have to guess the settings, if they bother which most don't, then don't want to go back.
There's huge avoidance of the troubles, and ignorance, of weather compensation so you'll probably have to educate yourself - and still be left somewhat in the dark on the detail.
Most suitable people would be on the individual boiler's manufacturer approved installer list, but that's not any guarantee.

With 4 floors you'd expect to particularly need trvs upstairs, esp if you leave doors open.

+
Lower ground floor rads not heating is probably sludge, which would say something about the installer.

 

[Agile]

We now know the rads are undersized.

The partial cure may be to provide better insulation.

How much loft insulation?

Are the windows double glazed?

What flow temp is the boiler set at?

Can you keep your hand on the tops of the radiators?

Tony

 

[xr4x4]

How the hell does any of this advice solve why all his rads don't heat up?

Putting bigger rads in will only make the problem worse.

Whats the Pump speed?

Has it always had this problem.?