How TRVs actually work?

[Harry Bloomfield]

I'm wanting to get a bigger difference between flow and return ro increase boiler efficiency.

Reduce the pump speed, and or control the flow via the lock shield valve, on the other end of the radiator, to the TRV.

 

[berty3000]

Reduce the pump speed, and or control the flow via the lock shield valve, on the other end of the radiator, to the TRV.

Is pump speed same as pump head setting? That is already on lowest setting.

So closing the lockshield a little on all the radiators will keep more heat in them? Does this idea work with TRVs fitted?

Also, should my boiler have a bypass fitted if TRVs are being used?

 

[Harry Bloomfield]

Is pump speed same as pump head setting? That is already on lowest setting.

Yes.

So closing the lockshield a little on all the radiators will keep more heat in them? Does this idea work with TRVs fitted?

Yes, the slower it flows into a radiator, the cooler it will be on exit.

Also, should my boiler have a bypass fitted if TRVs are being used?

Yes, though it can be in the form of a radiator which has no TRV fitted, and the lock shield open.

 

[berty3000]

Yes.



Yes, the slower it flows into a radiator, the cooler it will be on exit.



Yes, though it can be in the form of a radiator which has no TRV fitted, and the lock shield open.

In my case the water flows in at the TRV end, is the lockshield still relevant?

The radiator in my lounge where the central thermostat lives has no TRV - will that do? I don't know how open the lockshield is, but the knob where a TRV would go is open. There is also a towel rail with a knob on each side - would that work as a bypass if both knows are fully open?

What is the purpose of this bypass?

 

[Gasguru]

I'm wanting to get a bigger difference between flow and return ro increase boiler efficiency.

This is a pointless discussion given the excessive room temperatures.
Even a slight decrease in room temps will far outweigh any system twiddling to get the boiler condensing a little more.

 

[berty3000]

This is a pointless discussion given the excessive room temperatures.
Even a slight decrease in room temps will far outweigh any system twiddling to get the boiler condensing a little more.

This might just be the answer I needed! Not worth bothering. Flow temp is only 55C anyway.

What do you mean by excessive room temperatures? The highest temperature my rooms ever get up to is 21C. A couple of them make it to about 19C in the two hour blocks I use the heating.

 

[Gasguru]

21 is excessive....we've all gone soft over the last 30 years...average indoor temperatures were around 15 degrees up until the 90s.
It doesn't take long to acclimatise to lower healthier temperatures.

 

[Mister Banks]

21 is excessive....we've all gone soft over the last 30 years...average indoor temperatures were around 15 degrees up until the 90s.
It doesn't take long to acclimatise to lower healthier temperatures.

Low temps are unhealthy to. No one should have to endure 15c indoor temps, IMO 18-20c should be the aim for most people.

 

[Harry Bloomfield]

In my case the water flows in at the TRV end, is the lockshield still relevant?

Yes, of course - all you are doing, irrespective of on the flow or return, is restricting the flow.

 

[berty3000]

Ok, further question...

9 radiators, 7 have TRVs. The one in the room with the thermostat doesn't have one and nor does the towel rail.

Supposing the 7 with TRVs shut off the flow because they've reached temperature, does the boiler then start sending the full load to the towel rail and other one instead l, burning gas to heat two radiators, or will it adjust realising that that it has a surplus of hot water?

It is a Worcester 25i.

 

[berty3000]

Yes, of course - all you are doing, irrespective of on the flow or return, is restricting the flow.

So if the TRV is turned down and restricts flow, will there be more of a drop in temp across the radiator? Or does the lockshield have to be restricted as well. Does it have to be both together, or is it one or the other?

Basically, I've turned all the TRVs down to 3 (20C), so assuming they're accurate, which I doubt, but let's assume they are, and the flow rate is a fairly modest 53C, and I've got low pump speed and range rated boiler down to 10KW... can I better this in terms of getting more efficiency without being colder? I haven't fiddled round with the lockshields opposite the TRVs so could tighten them a little if it will help.

 

[Harry Bloomfield]

So if the TRV is turned down and restricts flow, will there be more of a drop in temp across the radiator? Or does the lockshield have to be restricted as well. Does it have to be both together, or is it one or the other?

Both work together, but with different purposes, at different periods. Your lock shield limits the maximum all the time, while ever the TRV allows flow. As the room nears the set temperature on the TRV, it will gradually shut the flow down,

 

[ericmark]

I first started looking at TRV's as a way to stop upstairs rooms over heating, down stairs being open plan, and they vastly improved the situation.

Next was my late mothers house, the use of a portable thermostat had failed, and I found adjusting TRV and lock shield valve near impossible, as one did not know which to adjust.

However changing the mechanical heads with Energenie electronic heads improved the situation, as could set head at say 20 degs C then adjust the lock shield until the unit reported 20 degs C as current. In all 4 heads fitted, and on mothers death house sold and changed back to mechanical and now lock shield set, they also worked well.

This house the 4 electronic heads from mothers house fitted, and also 5 eQ-3 heads fitted, the oil fired central heating unlike the gas fired with modulating boiler does not seem to work well with non linked TRV heads, there is no over heating, but the system seems to struggle getting the rooms to temperature set.

However the main problem is the location of the main thermostat, the hall cools too slow, and living room has open fire, it is hoped using two thermostats in parrellel will improve matters.

However TRV's clearly do work, but the machincal head set at say 2.5 will start closing at 17 degs and be fully closed at 21 degs, but a electronic head at 20 will start closing at 19 and fully closed at 21, so keeps the room better within the desired range.

I have one odd Kasa (TP-Link) head which also seems to work well, but looking spec wise the Drayton Wiser head seems about the best with algarithums able to work out when to switch on to get a room warm by set time, and links to the wall thermostat to also ensure the boiler runs.

The problem with 14 heated areas, is 14 x £54 is expensive, for Wiser, the eQ-3 bluetooth at £15 each in 2019 fitted my pocket better, the Energenie only sold in pairs, do connect to wifi, with a hub, but failed to work with Nest Gen 3, so when one smashed by carpet fitters went to Kasa which was cheaper and sold single but yet another hub which doubles as door bell.

 

[boringoldcodger]

Supposing the 7 with TRVs shut off the flow because they've reached temperature, does the boiler then start sending the full load to the towel rail and other one instead l, burning gas to heat two radiators, or will it adjust realising that that it has a surplus of hot water?

If you've got the Flow Temp set to 55C then the boiler will burn sufficient gas to heat the returned water (at whatever temp it's at) to 55C, so when the water is only going through 2 rads the boiler will burn less gas as the returning water will be at a, relatively, high temp.

the flow rate is a fairly modest 53C

I assume you mean flow temp

 

[Mister Banks]

@berty3000

Is your heating s plan, y plan or something else? This will determine if you need a bypass external to the boiler.