Radiator Balancing - is there an idiots guide?

[marko (Marko Cosic)]

@Zarch

So it turns out my installer used very nice IMI lockshield valves, which are “Kv per part turn” as you say @marko

Praise be the installer! Credit where well earned etc.

@Zarch

Using the IMI Hytools app on my phone, I put in the size of each rads (height, length, type) and the target flow and return which gave the DT.

From there the app gives you the number of turns to hit the correct flow required for each rad.

I assume this is the technique you are referring to?

Exactly this.

There will be slight differences in practice due to the pressure drops in the pipework. (the app will assume a certain differential pressure at all radiators, but in practice the pressure drops in the pipework will mean that each radiator valves see slightly different differential pressure)

If the pipework is VERY large then these will be negligible and you just balance on the lockshields.

If the pipework is VERY small (e.g. microbore) then these pressure drops may be large or even dominant and balancing is more of a faff.

The “easy” way of correcting for these pressure drops is from “cold start” with a thermal camera. With the radiators at an even temperature; crank the heat on and watch how quickly the radiators “fill” with the hotter water. They should all take the same time to fill if they’re the same style. You can also run around putting fingers on return pipes and guesstimating the moment they become say 5C warmer. Then tweak the baseline Kv from the app up/down to suit.

[HydroSam]

Inspired by @Zarch experience and diagram I thought I’d revisit my balancing, which was a right faff to start with, and still the playroom is slow to heat up. Hoping to get a bit more efficiency from my over-sized heat pump system.

Below I have sketched out my layout, and annotated some bits, not as nicely I’m afraid. Please don’t laugh, if I knew when the building work was going on, what I know now, I would do it completely differently, but it’s not all my fault. Part was a previous extension when it was a bungalow, that I left as was and the heat pump installer (who is mostly at fault) didn’t even look at most of the internal pipework, and they are now AWOL (and kicked off MCS).

If you have any tips for where I might start please let me know. Most of the pipework is inaccessible, but there are sections of plastic I can swap if it’s worth it, just most of the plastic is hidden under floors. Can the IMI software make suggestions for a good starting point for the existing lockshields even if it won’t be perfect?

[Timbones (Tim)]

I’m also trying to balance my radiators, and have started by measuring the temperatures at both ends of each. Some of them have a smaller dT, yet they’re all warm and the rooms are also warm, so not sure what to do next. Any pointers would be appreciated.

[Zarch (Mick Wall)]

22mm copper has a limit of 6kW at DT5.

Heat Pump Piping: Do You Really Need to Upgrade Your Pipes?

So that isn’t a great start on that first leg.
You only lose 1kW on the way, so you’ve then got 5kW heading down 22mm plastic.
22m plastic internally is about 18mm? So that’s only capable of around 4 to 4.5kW?

You might just get away with as you’re losing output along the way. And only 4.5kW at -2C.

How did you end up with an 11kW heat pump for a 4.5kW heat loss!! Save that for the other thread!!

The problem I see and one you might wanna get an expert to look at is, can the pump in the Daikin overcome the resistance to reach the furthest away radiator (the index circuit). This is the individual pipe route with the highest pressure loss. This what you size your pump against.

You could try and balance all you want, but if the pump just can’t physically shove the water down all the narrow pipes, then you’ve got no chance.

Think about how hard it is to blow water down a straw compared to blowing water down a 1 inch pipe.
That’s essential asking the pump to do with narrow pipework, blow it down a straw.

This can be overcome perhaps by fitting an extra pump.
Or perhaps replacing the pump. Does the daikin use an internal or external pump?

But this would all need calculating.

It’s amazing that you know all the layout. That will really help.

You could still try balancing to get that playroom rad warm.
You’d close rads down before that playroom rad, ie, all the other rads.

For example, if I fully open all my rads the ones near the heat pump get warm and the ones furthest away stay cold. I start closing down the rads and the furthest away ones start heating up.

You need to provide enough resistance so that the pump can get to these furthest rads (if the pump can that is)

The IMI app will tell you flow rates required for rad sizes, but it can’t tell you what to do with different lockshields.

Heat Geek do a great vid about the differences in lockshield performance

We always thought Lockshield Valves were the SAME!!? WHO KNEW!?

The chart they create in the vid is here

What You Don't Know About Lockshield Valves!? - HeatGeek

Does that help at all?

[Zarch (Mick Wall)]

@Timbones

I’m also trying to balance my radiators, and have started by measuring the temperatures at both ends of each. Some of them have a smaller dT, yet they’re all warm and the rooms are also warm, so not sure what to do next.

In an ideal world you’d have the output of the rads match the heat loss of the room. This is what I’ve tried to achieve with my rad upgrades. So that if I put the correct calculated flow rate through the rads, all the rooms in the house should be balanced.

But we know this isn’t always the case in a lot of installs. There will be imbalances in heat loss and rad output.

But I still think you start by aiming to get the correct flow through each rad and then you adjust up or down whether you want more or less heat from the rad.

As Heat Geek told me this week, you’re ultimately balancing room temperature.
No own really cares about flow/return or MWT of the rad. The just want warm and balanced rooms.

Obviously from a heat pump point of view, as I’ve found to my cost, you need to ensure there is enough flow going through the rads to ensure you have enough working system volume in the system.

I’d throttled down my rads so bad chasing DT5 across the tails I’d restricted by working volume to barely nothing.

My COP has shot up this last week since opening the rads up. I’ve now given the heat pump more system volume to work with. So excuse the pun, but there is a balance to be had here.

1. Enough system volume to allow the heat pump to thrive
2. Rads closed down enough to ensure resistance so that all the rads in the circuit get some heat
3. The rooms across the whole house are balanced with enough heat being emitted

Obviously, there could be challenges with undersized pipework like @HydroSam has above.

And as Marko days, the underlying pipework adds complexity to the party.

@marko

There will be slight differences in practice due to the pressure drops in the pipework. (the app will assume a certain differential pressure at all radiators, but in practice the pressure drops in the pipework will mean that each radiator valves see slightly different differential pressure)

If the pipework is VERY large then these will be negligible and you just balance on the lockshields.

If the pipework is VERY small (e.g. microbore) then these pressure drops may be large or even dominant and balancing is more of a faff.

Does that help?

[HydroSam]

Really interesting Mick @Zarch
It reinforces what I thought, and what I tried to convince OVO of at the time, but they weren’t having any of it, I have a thread on my pump where we could dig in to the heat loss subject if you are interested.

I think the pump is big enough in the monobloc outside, it can draw 100w. The far rad in the playroom does get warm, just not as warm as others.

I can’t adjust the flow rate of the pump, but I can alter the target deltaT. I wonder if I target dT 7 whether that would help. Reading the heat geek link on pipe sizing this suggests I can get more heat output, but I wonder what the compromise/effect will be? Maybe something to try out over the weekend.

[marko (Marko Cosic)]

Raising the dT from “5” to “7” means that for the same radiator output your flow temperature is 1 degC higher (slightly reduced COP) but your flowrates are (N/7) instead of (N/5) - so 70% of what they would have been if targeting dT5.

[Stephen_Crown]

@Zarch

can the pump in the Daikin overcome the resistance to reach the furthest away radiator (the index circuit). This is the individual pipe route with the highest pressure loss. This what you size your pump against.

If it’s the same as mine (EDLA 11kW) then here is the spec sheet, which when on space heating at max output, I believe you can take the max flow rate (mine was 24l/m (110kPa) prior to unclogging both strainer/filters and has shot up to 34l/m (95kPa) on space heating afterwards) and get back to the overall static pressure on this graph (please someone correct me if I have misunderstood):

Here is the pump in mine which is the same across 9/11/14/16 units from the datasheet

Here is the data book for the EDLA Daikin Altherma 3M units:

e-b-d-la09-16d-3-v3-w1-eeden20-data-books-english.pdf (3.3 MB)

I should add that with ESPAltherma I’m able to read the water pump signal, so I know when full pump speed signal is generated.

[Stephen_Crown]

@HydroSam

I think the pump is big enough in the monobloc outside, it can draw 100w.

@HydroSam

What flow rate are you getting on space heating (not DHW) at max output?

[HydroSam]

@Stephen_Crown looks to be 22.6l/min in the OEM data, 26l/min when do the DHW cycle. Filters are clean.

I have the older Altherma 2 model. I haven’t checked the pump, I’ll try and do that later.

[Stephen_Crown]

@HydroSam 22.6l/m is 7.84kW @ ΔT5 - so likely to be an issue if thats max output flow rate.

Edit just seen you have an older unit EDLQ011CV3, sorry!: For the newer models, the expectation is 102kPa for ~30L/m (10.43kW at ΔT5) flow rate (it’s how I knew I had a blockage or something on mine):

Let us know if you’re running ΔT5 or otherwise (you mention further up moving to ΔT7).

[HydroSam]

I have been running with dT5. I mentioned above I could change to dT7 because of my pipework restrictions

[Stephen_Crown]

@HydroSam

@Stephen_Crown looks to be 22.6l/min in the OEM data, 26l/min when do the DHW cycle. Filters are clean.

I have the older Altherma 2 model. I haven’t checked the pump, I’ll try and do that later.

Here are the relevant pump/pressure/flow rates for your model - note it states capable of 46l/m (!) (which is 15.98kW @ ΔT5) at just under 30kPa

Newer Daikin Altherma 3M seem to have a significant upgrade on pump power I think comparing to the older “2” model:

Below, red is where you’re at from your reported numbers, green is max flow rate given low enough pressure drop, and blue is (the minimum) where you need to aim for at ΔT5 to get 11kW out of your unit.

At 62.3kPa, you should expect ~31L/m - I assume the “62.3kPa” figure has been given as the max pressure to get that flow rate for ~11kW - so you still need to get to 31L/m @ΔT5 to get ~11kW output (or increase ΔT)

Data book reference:

EB-DLQ011-016CV3_CW1-EKCB-CV3-EK2CB-CV3-EKMBUHC3V3-EKMBUHC9W1_EEDEN18_Data-books_English.pdf (7.9 MB)

[HydroSam]

So it looks like I’d never be able to achieve the max output this heat pump is capable of with significant alterations to the pipework? Eek! Good job I only needed 5kw when it was -6C last winter. The house was warm enough but I wouldn’t have got what I needed if the MCS calcs had been correct.

In danger of taking this thread off on a tangent…

[tomasmcguinness]

I’m about to embark on balancing my system. I’ve a gas boiler, but my dT is very tight as my flow is down at 40 at the moment. Boiler can’t go any lower than 43 (it’s a 35kW beast) and the return is 37, so it’s pretty tight.

Lock shields - I think they are Danfoss, for the most part, but haven’t a clue if they are any good. The rads weren’t sized - they were eyeballed by the plumber.

System is currently all open and I’ve instrumented each radiator, so I can track the flow, return and
mean temperature. (https://youtu.be/YUV8U6BC5oQ)

Here is a timeseries from Influx for today. As you can see, the warmer radiators are those at the top and they are closest to the boiler. I’m doing to start experimenting and actually tracking how the system behaves when I start to close down each lock shield.

The information in this thread has been very interesting and I’m hoping it will come in handy!

[Stephen_Crown]

Hi @tomasmcguinness welcome.

For a condensing gas boiler post ~2005, in case you were not aware, the target ΔT a modulating pump (assumed) inside the boiler will be hunting for is around ΔT20 (vs ΔT5 for standard heat pump config) as gas boiler condensing efficiency is all about driving the return temperature as low as practically possible (whereas for heat pumps, flow temperature is what drives efficiency)

Also, given the modulating nature of the pump, running the system at max output will likely run the pump at max output, and should be considered to avoid a feedback loop of shutting down flow, and then the pump reacting and vice versa.

Your system in the video looks pretty neat, and would save a lot of time! Good stuff. Would be good to try it out!

[Zarch (Mick Wall)]

@tomasmcguinness

Lock shields - I think they are Danfoss, for the most part, but haven’t a clue if they are any good.

See below, you may have kopped lucky Tom!

@marko

Buy nice valves. Lockshields that they you KV per part turn from fully shut, such as danfoss RLV

@tomasmcguinness

The rads weren’t sized - they were eyeballed by the plumber.

Tut tut, those pesky “plumbers” !!!

[Timbones (Tim)]

@Zarch

I’d throttled down my rads so bad chasing DT5 across the tails I’d restricted by working volume to barely nothing.

@Zarch

Does that help?

I think the lesson here is to not be chasing dT of 5 across the rads? Is the happy medium for them to be the same as each other?

The one radiator I have fiddled with is the one in the bathroom, which is small, old and closest to the heat pump. On 1/4 turn of the lock shield, the dT is higher than average, but the mean temperature is lower than the rest. This suggests that I’ve throttled it down too much? Maybe give it another 1/4?

[Timbones (Tim)]

Love your radiator monitor, Tom. That would be so much easier than running around the house with an infrared thermometer, and one can’t have too many charts.

[Zarch (Mick Wall)]

@Timbones

I think the lesson here is to not be chasing dT of 5 across the rads? Is the happy medium for them to be the same as each other?

Looking back at my notes / spreadsheet, there’s a direct correlation between the size (output) of the rads and the amount I’ve opened them.

3 examples from my rad list:

• Small rad (600 x 600 K2) - 0.3 of a turn
• Medium (1400 x 600 K2) - 0.5 of a turn
• Largest rad (1400 x 600 K3) - 0.8 of a turn

But these are turns on my IMI valves, calculated from their HyTools app.
Your number of turns may well be different.

I posted a video and article from heat geek earlier in the thread where they show the difference a quarter turn can make across a variety of lock shields. It’s wild.

If you used the IMI hytools app and put your rads into there, you’ll get to see the recommended flow rate for each one. If you note them all down you should see your own sliding scale?