I have had a Valliant ecotec 832 fitted about a year ago and have recently found that two radiators are not getting hot, or even warm, they are next t o each other in terms of piping. If I turn off the other radiators they get hot, but otherwise they dont. Is it worth turning up the pump speed or flu shing or what, any help appreciated. Thanks
Try adjusting the 'balance' of the rads. Each rad has a lockshield valve at each end. One is for on/off, the other is to balance the system.
You can do it with temp sensors- setting for the right drop across each rad.
Or, simply adjust them to get the rooms / rads right.
Worth bleeding the system first.
I should have mentioned, some rads may only need the valve open a tiny amount and still get hot. I'd open the coldest one, close the others, then gradually open them, perhaps closing the cold one(s) a bit, until you are happy.
y found that two radiators are not getting hot, or even warm, they are next to each other in terms of piping. If I turn off the other radiators they g et hot, but otherwise they dont. Is it worth turning up the pump speed or f lushing or what, any help appreciated.
your rads aren't balanced.
NT
Well worth getting an infra red thermometer and measuring the temperature drop across the rad. No point in having more flow through it than needed.
y found that two radiators are not getting hot, or even warm, they are next to each other in terms of piping. If I turn off the other radiators they g et hot, but otherwise they dont. Is it worth turning up the pump speed or f lushing or what, any help appreciated.
Thanks, what is the temp drop across a radiator to balance it correctly
According to this:
Having done a load, you can get quite far forward just by shutting all the lockshields off, then opening either 1/4 or 1/4 turn (depends on the make).
Also, jack all TRVs full open for the duration.
Then look for rads that aren't getting warm and crank those full open (in case there's any air - the extra flow can dislodge it and bleed it).
Then shut it back to maybe 3/4 and go from there.
If you want to really balance it, a dual input thermometer with a pair of pipe clamp thermocouples makes the job go a *lot* quicker - tweak each rad for about 10-12C difference and not the inlet temperature. If that's a LOT less than the boiler flow, you might have a restriction in your pipework.
tly found that two radiators are not getting hot, or even warm, they are ne xt to each other in terms of piping. If I turn off the other radiators they get hot, but otherwise they dont. Is it worth turning up the pump speed or flushing or what, any help appreciated.
they should be balanced of course. That's the point. What the figure is dep ends on the system.
NT
Start here ...
Thanks, will try tonight
Yes, but last time I looked it missed the last step. The final goal is not identical rad temp drops, it's same room temps. The one often does not follow from the other.
NT
Wouldn't a TRV take care of that aspect?
I do wish you would moderate your sig line a bit. It offends me as most people are clueless about people who need benefits. Brian
I've no issue with those who need benefits. It is those who don't that are the problem. They take money from everyone.
Maybe. Eventually. Some rooms would heat up really quickly, and some much more slowly. If you're lucky the TRV will turn down the rad in the warm rooms, and then the cold ones will heat up too. Better (usually) if they all do it together.
Andy
That thought occurs to me too. In fact, I rather think the value of lock shield valves for balancing is overrated when all (except one[1]) of your radiators are equipped with TRVs. You want to keep the LSVs as wide open as possible by determining which, if any, rads aren't receiving sufficient flow with all LSVs and TRVs wide open before attempting to balance the hottest (flow hogs) by adjusting their LSVs.
A well planned out pipework run[2] should result in a reasonably balanced system to start with before any fine tuning adjustments with LSVs on the 'hottest' rads[3] are applied. Once you've got the system balanced with the TRVs wide open and a minimum of throttling on the LSVs, the TRVs should take care of room temperatures automatically without unduly starving the flow and return rates on the more remote rads.
[1] The one exception, usually located in the coolest least occupied room in the house, being typically a small rad or heated towel rail in a shower or bath room to act as a permanent bypass to protect the pump from excess back pressure in the event that all the other rads shut off their TRVs when the room temperatures reach their target temperature settings. [2] The Boiler 28mm flow/return pipes should feed a main floor distribution manifold flow/return set which in turn feed each floor manifold flow/return set in 22mm pipe (ideally central to each floor's radiators) with each feeding their rads, typically in 10mm pipe in most modern day domestic central heating systems.That's certainly the case in our own 6 bed 1898 Victorian Semi-detached home built on three floors with basement. In a modern 3 bed semi, it might be more practical to pipe the boiler flow/return to a single set of manifolds feeding all of the rads directly without resorting to a floor manifold feeding two seperate radiator manifolds (one on each floor).
[3] Assuming no obstructions in the coolest rad(s) or their pipework, the low flow rate could simply be on account of them being on significantly longer pipe runs compared to the rest of the rads serviced by that floor's distribution manifold.In a properly considered layout, such extra long pipe runs would use the a larger bore pipe for the main run between manifolds and rad to compensate for the higher resistance to flow and return over longer runs of 'standard bore' pipe as used by the more proximal rads.
In practice, unless there's a very obvious disparity in flow resistance, such measures (larger bore pipework to the more remote rad(s)) are rarely implemented since the difference in flow rates can usually be balanced out using the LSVs without unduly compromising overall system performance. Typical issues being high noise levels when LSVs are seriously throttling the 'hot rads' at a maximum pump speed setting required to provide the required flow to the 'coldest, most remote rads in the system.
If the coldest rads are in bedrooms, you can afford to leave the system balanced in favour of better heat flow to the main living areas since the bedroom rads will eventually see improved flow once the TRVs on the hotter rads respond to the warmer room temperatures and throttle back the flow on these 'energy hogs', to divert more flow to the bedroom rads later on in the evening before the CH system is shutdown by the timer/ controller just prior to 'bedtime'.
With a sealed system, it's less of a problem. With an open vented one, there was the danger of pumping over.
not identical rad temp drops, it's same room temps. The one often does not follow from the other.
No, a TRV does not solve it. TRVs are often thought of as thermostatic in t he usual sense, ie maintaining a steady room temp. They are not however. Th eir sensors are more thermally attached to the primary water flow than room temp, so they tend to partially regulate the primary flow. They don't regu late room temp to a significant extent - more than 0% yes, but that's all.
When designing a CH system, heat calcs are approximate. They're often based on guesses about construction details which are not consistently correct. (I had one professional offer an estimate 3x actual power consumption). The y also vary room to room depending on north/south facing & other details th at may be ignored.
When picking a rad, the nearest size is generally picked, not the exact siz e/output calculated. So with those 2 factors, if you get all rads at the sa me temp you often will not have consistent room temps. It's a good start, b ut the aim is consistent room temps, or sometimes some variation by choice. Balancing all rad temps does not give you a properly balanced heating syst em. Doing that in houses where layouts have changed after fitting CH can se e room temps be wildly out.
Systems should be set up with all TRVs fully open. The TRVs can then be use d to manually reduce room temps as desired.
NT
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