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Central Heating - TRVs Advice


Captain Colonial

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Once spring is fully under wayand warm and the home central heating is no longer needed, I'm going to drain the central heating system down and replace some old-fashioned radiator valves with TRVs.  At the moment it's impossible to balance the radiators and heating around the house due to the old ones being stuck wide open - rooms in the house that don't need to be heated that warm are dragging down the reposnse time for rooms where the warmth is needed.  Using a thermal temperature gun, I now know which end of the each of the radiators in question is the inflow (gets hot first) and which end is the return, as I understand the TRVs must go on the inflow side - is this correct?  Any advice or experience anyone can pass on?

 

TIA :)

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Hi Scott,

 

Most TRV's don't care if they are on the in or the out. I've tried this balancing game. It's slow, painful and noisy. If you have females in the house, my experience has been they will still not understand the the overall room stat which calls for heat doesn't know the temperature in other rooms and hence if the room with the room stat in has reached temp, the central heating will be off and no amount of TRV adjustment will bring on the rad in another room.

 

Once you start throttling back the lock shield valves, you'll find they are noisy!

 

Good luck!

 

Ian

 

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Thanks Ian. :)  I've got some Hive TRVs which once installed will allow me to control the worst offending rooms a lot better and set the times of day and evening and the temps I want to achieve or limit to during those times.  On regular TRVs I'd be up and down like a fiddler's elbow making adjustments!

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1 hour ago, Ian Kinder (Bagpuss) - Joint Peak District AO said:

Once you start throttling back the lock shield valves, you'll find they are noisy!

 

Good luck!

 

Ian

 


The women or the valves?

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Surely the radiators should be balanced using the lockshield valves? Although TRV's are good too.

 

To balance, open everything fully, turn on heating, then close the lockshields slightly on the rads which get hotter first, repeat until even ish. 

 

Our plumber fitted 'Danfoss RTW' units when we asked for a good quality trv, they appear as good as any other.

They are a mix, but about 70% are on the outlet side, I guess cooler end gets better room-temp response? 

 

 

Daniel

 

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The old valves on my system can now only be adjusted by using a spanner due to being so stiff to operate. :(  The new ones will have Hive TRV heads which I can temperature control individually in each room via an app down to 0.5 of a degree at whatever time I like.

 

Its also good for when I have guests over (three spare bedrooms) as they can set it for whatever temp they like during their stay... and if they outstay their welcome, I can override it via the app and boil or freeze them out. 😄

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dhutch is quite right, the balancing should be done using the lock valves, preferably with the TRVs fully open, or even with the heads removed.  Bear in mind that a simple TRV will only measure the temperature of the room at the position of the TRV, and may be overly affected by the air temperature around the pipework, especially if there are curtains etc in the vicinity.  The gold plated solution is a room stat in each room, connected by wire or wireless to the respective radiators' actuator valves.  This means you can put the room stat in a sensible position, and alter each room's temperature without getting on your hands and knees.  I'm sure they can be HIVEd too, so you can change the temperature while you're in the pub.  However, 'Smart' valves are double the cost of normal TRVs, and you also need several room stats.

I'm in the process of moving my house stat at the moment... coupled with MHRV installation which is almost no fun at all.

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2 hours ago, IainCameron said:

However, 'Smart' valves are double the cost of normal TRVs, and you also need several room stats


Very true.  However, I caught a sale lucky.  Normally Hive TRV heads are an eye-watering £54 each but British Gas had a sale and I got 5 for £20 each.  They are all thermostats and each communicate individually via WiFi to the central hub so extra room stats aren’t required.

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That's a bl**** good price! We went with Wiser (I believe all the z-wave based kit will talk if you ask it to) but with over 20 radiators, two for most large rooms, so far we have held off! Plus you can't seem to be trv bodies without the heads, so might as well use the new heads for a bit. 

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Whilst you are fitting the new TRV’s. (Good price by the way),  fit new lock shields and bleed valves as well.  They do tend to block up with lime scale and other crud and why you had problems balancing the old valves.   You should balance up the rads even with TRVs fitted. They can be fitted on the flow or return if they have a adjustable tab inside the valve,  check the instructions.   

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Thanks for the advice gents, I’ll fit new lock shield valves at the same time.  Much appreciated :) 

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Definitely fit new lockshields at the same time, the danfoss ones can come as packs, which are nicer quality than the own brand ones we ended up with which I am sure will fail earlier! Bleed valves are less of an issue, as they dont have seal on the stem and are only closed off fully in normal operation.

 

Daniel

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I recommend not using an IR gun to test your radiator temps, if your pipes are chromed, as it will give incorrect readings of the temperature due to the reflection from the chrome (emissivity), not a problem if you are only looking at the difference from each end, ie balance, but the temps will not be correct.

If your TRV valve has a facility to adjust it under the head, like the Honeywell ones, then it doesn't matter which side it goes on, as you can adjust each side for get the balance.

Don't be surprised if it takes you ages, and the results change on a daily basis......get them somewhere near then leave them alone.

good luck

regards

scott

 

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Rads and pipes both painted, not looking for exact temps, just wanted to see which end got hot first but good points, thank you. :)

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16 hours ago, dhutch said:

Definitely fit new lockshields at the same time, the danfoss ones can come as packs, which are nicer quality than the own brand ones we ended up with which I am sure will fail earlier! Bleed valves are less of an issue, as they dont have seal on the stem and are only closed off fully in normal operation.

 

Daniel

I have Danfoss TRVs and they certainly seem better made than the cheaper unbranded ones. However it is prudent to open them wide in summer in my experience or they tend to stick closed over the warm weather. It is easier to ease off an open valve than a closed one. We're in a hard water area so YMMV

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