Radiators Problem

[Spinny]

Not been able to get all 4 downstairs Rads running at full temperature.

 

I have 4 new rads that were installed downstairs as part of our new heating system using plastic press fit pipework (copper upright stems). Two modern panel type radiators - one medium - one small, and then two old fashioned style column radiators - one 4 column medium size, one 3 column medium size. Builders plumber came 3 times to rebalance them and couldn't get tham all fully up to temp, eventually resorting to going behind my back to turn the boiler temp up to 65C and then claiming he had fixed it (not).

 

Have had suggestions it is likely a pipework/flow problem and column rads take more flow to drive them.

 

Replacing all the pipework not an attractive option as much of it is now under glued down boarding. I do have two lengths of empty conduit going back under the floor to the boiler location that were put in in case of future desire to extend the underfloor heating. So if an additional pipe loop was created via this conduit to take a column rad off the current loop, and put it on a second loop of its own - is this going to provide a solution to the problem ?

 

 

 

 

 

[John Carroll]

Some column rads must have the flow at one particular end because they may have a flow diverter, they may have a arrow somewhere, if not you could try one of these, of suitable length, it  force the water up through one column, it will then flow down equally through the remaining 2 or 3 columns. Are they (column) hot along the bottom and cool along the top??.

 

 

 

Edited 23 hours ago by John Carroll

[marshian]

1 hour ago, John Carroll said:

Some column rads must have the flow at one particular end because they may have a flow diverter, they may have a arrow somewhere, if not you could try one of these, of suitable length, it  force the water up through one column, it will then flow down equally through the remaining 2 or 3 columns. Are they (column) hot along the bottom and cool along the top??.

 

 

 

 

Just a word of warning on the diverters above - if you are running TRV's on the majority of the rads when TRV's shut down it is possible to invert the diverters above - no need to ask me how I know this!!!

[SimonD]

1 hour ago, marshian said:

Just a word of warning on the diverters above - if you are running TRV's on the majority of the rads when TRV's shut down it is possible to invert the diverters above - no need to ask me how I know this!!!

 

PITRVs are your friend here. I don't know why more people don't use them, but both Screwfix and Toolstation now stock and sell the Danfoss ones - great for gas systems but less so for really low temp heat pump systems with very large radiators

 

5 hours ago, Spinny said:

Have had suggestions it is likely a pipework/flow problem and column rads take more flow to drive them.

.
Flow rate is more linked to the difference in temperature between flow and return. As highlighted above, the problem is that many column rads don't have baffles so you get flow straight through the radiator if the valves are both at the bottom of the rad. This then provides a bypass through the system. I still get customers who ignore me when I tell them to make sure they're baffled when they order them. Better then to connect them up top-bottom-opposite-ends, but sometimes not pretty. The thing to do is get some cheap clip on pipe thermostats to measure the actual flow/return temps, but first you could test by shutting down your trvs upstairs to see if the temps of these new rads is better. That'll tell us a bit more.

[John Carroll]

Measuring flow/return temps is generally OK also for calculating rad outputs as long as the plumbing is done correctly, I assisted someone  with a HIU system who not only was being overcharged by ~ 30% but was also not getting the required rad output, the heating engineer who came to investigate it insisted that the BTOE system was fine and would work just like TBOE and of course he used the flow+return measurements to "prove" it, to disprove it I piped one of my own rads, below, using both methods, they then plumbed up the system correctly.

 

Edited 19 hours ago by John Carroll

[SimonD]

4 minutes ago, John Carroll said:

BTOE system

 

Isn't that a bit like plumbing in a heat exchanger the wrong way round?

[John Carroll]

I must confess that I thought at first that it might work, if one thinks that a BOE works so well even though one might think that in a pumped system that the hot water might just go straight out the opposite bottom end.

[marshian]

9 hours ago, SimonD said:

PITRVs are your friend here. I don't know why more people don't use them, but both Screwfix and Toolstation now stock and sell the Danfoss ones - great for gas systems but less so for really low temp heat pump systems with very large radiators

 

Exactly why I now have Danfoss ones on all the rads 

 

9 hours ago, SimonD said:

Flow rate is more linked to the difference in temperature between flow and return. As highlighted above, the problem is that many column rads don't have baffles so you get flow straight through the radiator if the valves are both at the bottom of the rad. This then provides a bypass through the system. I still get customers who ignore me when I tell them to make sure they're baffled when they order them. Better then to connect them up top-bottom-opposite-ends, but sometimes not pretty. The thing to do is get some cheap clip on pipe thermostats to measure the actual flow/return temps, but first you could test by shutting down your trvs upstairs to see if the temps of these new rads is better. That'll tell us a bit more.

 

Verticals especially really large ones even with Flow Diverters aren't great heat emitters at lower flow temps - they do get closer to the claimed outputs as the temps get higher but in the 26 to 35 deg flow temp range they need a lot more flow than a conventional panel rad 

 

I have connected one of my tall rads TBOE and it's performance is much improved (but as you say it doesn't look that pretty)

 

I got the feeling @Spinny wasn't talking about tall column rads but more the old fashioned cast iron style column rads (probably better to call them period correct)

 

 

Edited 10 hours ago by marshian

[John Carroll]

What is a PITRV?.

[marshian]

@Spinny

 

The other thing that can be worthwhile is to get a thermal camera and take pictures of the rads

 

This is a K33 1400 x 700 Fed BBOE with low flow temps 

 

 

This is a tall vertical (fitted with one of the diverters mentioned earlier in the thread)

 

 

 

 

 

[marshian]

3 minutes ago, John Carroll said:

What is a PITRV?.

 

Pressure Independant TRV - adjustable for flow rate which doesn't change even if circuit pressure increases

 

Danfoss RAS B2 are what I am using

[SimonD]

2 hours ago, John Carroll said:

What is a PITRV?.

 

2 hours ago, marshian said:

Pressure Independant TRV - adjustable for flow rate which doesn't change even if circuit pressure increases

 

Slightly more than that, not only do they prevent too much flow at full load like a flow regulator, they are differential pressure controllers so they also ensure required flow rates are maintained under partial load conditions, which is essential for efficient modulating systems - obviously within their design Delta P range.

[SimonD]

2 hours ago, marshian said:

Exactly why I now have Danfoss ones on all the rads 

 

2 hours ago, marshian said:

have connected one of my tall rads TBOE and it's performance is much improved (but as you say it doesn't look that pretty)

 

You have been round the block haven't you! 😊

[marshian]

25 minutes ago, SimonD said:

You have been round the block haven't you! 😊

 

You could say that!!!

[marshian]

4 hours ago, SimonD said:

Slightly more than that, not only do they prevent too much flow at full load like a flow regulator, they are differential pressure controllers so they also ensure required flow rates are maintained under partial load conditions, which is essential for efficient modulating systems - obviously within their design Delta P range.

My boiler doesn’t have control of the pump and I run a fixed flow rate (constant curve) so the only time TRV heads intervene is in rooms with a lot of solar gain - most of the heating season I don’t get any solar gain so the system is getting a constant flow all the time.

 

Appreciate the point being made to clarify my simplistic response