Balancing rads - strictly necessary if using TRVs??

[Nickthedentist]

Hello everyone,

My CH system consists of a Baxi Bermuda back boiler, an indirect hot water cylinder with gravity circulation, and 7 rads fed from a conventional 2-pipe system.

Although the boiler is newish, the rads have got to be 30+ years old and are showing their age All their valves were leaking badly and/or had seized spindles.

Anyway, spent a fun Saturday replacing all the valves. I used decent ones (Pegler), upgrading to TRVs everywhere - except the hall (where the room stat is), where I fitted a lockshield valve at both ends. Much to my amazement, nothing leaks and all the rads get nice and hot

I can recall someone saying that balancing isn't really necessary if TRVs are used. Is there any truth in this, or were they having a laugh?

If balancing is necessary, are those infra-red thermometers (under £50) any use, or would I be better buying a pair of clip-on dial ones instead?

Cheers,
Nick.

 

[chrishutt]

If all the radiators are getting hot enough and doing the job, then you don't need to bother with balancing. It's perfectly possible for a system to be fairly well balanced by chance.

 

[Softus]

IMO TRVs don't remove the need to balance.

The effect of a system being poorly balanced is that the flow will favour certain rads over others.

Whilst the use of TRVs will limit the duration of this effect, it doesn't eliminate it, so the favoured rads will still heat up first, then shut off when the room up to temperature, and then the other rads will get their share of the heat.

If you want all rooms to heat up at broadly the same rate, then you need to balance the system.

I don't bother with themometers though, just estimate the likely run of pipework and progressively turn down the lockshields to limit the flow to the nearest rads. You'll soon know if you've got it right. You'll have to remove the TRV heads while doing it of course.

 

[croydoncorgi]

Used to be the case that balancing was only to ensure that all the rads heated up, at the same time.

No more! If individual radiators have to much volume going through them, this may upset a condensing boiler, irrespective of whether all the rads are working properly or not.

A key objective when setting up a system with a condensing boiler is to minimise Return temperature, so that the boiler spends as much time as possible in condensing mode. So flow through all the rads should be minimised, consistent with the total flowrate through the system will always stay above the minimum specified for the boiler. The 'better quality' condensing boilers modulate the burner AND the pump to match actual demand (usually based on the difference between Flow and Return temperatures) - but this of course implies that they are combis or system boilers. Systems with a separate pump present further complications with temperature control.

 

[Softus]

A key objective when setting up a system with a condensing boiler is to minimise Return temperature
.
.
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So flow through all the rads should be minimised...

 

[Paul Barker]

I open trv full, balance the rads and explain to customer how to operate trv's but let them find comfort for each room as it suites them. My aim is that the house should be evenly heated dependent on room function regardles of trv's. They are a poor control device.

 

[noonespecial]

My aim is that the house should be evenly heated dependent on room function regardles of trv's.

Yes I agree with that - the TRV's provide the facility for closer room control by preventing excessive temperature from heat gain from people, solar, electrical equipment, etc

They are a poor control device.

They are not precise but I find they work to a reasonable standard and are well worthwhile having. I think they are a good investment.

Also for the user they are easier to turn on and off than IV's....until they get stuck

 

[Paul Barker]

Many times the radiators are not large enough, so fitting trv's to an old system is a waste of the planets resources, but we have to do it.

 

[chrishutt]

More to the point, how many consumers understand how TRVs work? Most of my customers (who I like to think are a cut above the average ) treat them as on/off controls, either on max or 0. One result is that when unnecessarily turned fully off for a long time they jam shut.

Even those who have some idea that the numbers between max and 0 might signify something think it relates to the temperature of the radiator. when I try to explain that it relates to the air temperature around the TRV you can see their eyes glaze over.

 

[noonespecial]

More to the point, how many consumers understand how TRVs work?

Yes it is strange that-what seems quite obvious to the 'pros' is beyond understanding of some intelligent laypeople.

The number of times people have said to me that their radiators are not heating up correctly. I always feal almost embarrassed to say well that is because your room is up to temperature and the TRV has shut off the hot water flow

 

[Agile]

You would be surprised how many people call me to complain their their boiler works for an hour and then goes off!!!

I calmly explain thats totally correct and its because the thermostat has been satisfied because the house has become hot enough.

Tony