The TRV mystery

[chieflasagnaeater]

Hi, should or should I not fit TRV's on all my rads?
having a new Vaillant 831 Combi installed next week and I'm thinking to fit TRV's in most rooms other than where the thermostat is sited.

This boiler is modulating which I understand modulates the flame according demand from the CH system so is there really a problem with fitting (and using) too many TRV's.

I have trawled through the forums here and there seem to be mixed opinions..

Thanks. (quality website by the way!)

 

[ddk]

personal preferance really. you shouldnt use a TRV on the radiator which is in the same area as the roomstat, but in my opinion there is no need to fit a TRV to any bathroom/shower room radiator, because whenever youre in those rooms you want all the heat you can get!

 

[gas4you]

Part L regs state that trv's should be fitted on all rads except the one in the room where the room stat is located.

 

[D_Hailsham]

Hi, should or should I not fit TRV's on all my rads?
having a new Vaillant 831 Combi installed next week and I'm thinking to fit TRV's in most rooms other than where the thermostat is sited.

No harm in putting a TRV on every rad except for the one controlled by the rooms stat. Buy good quality ones, e.g Drayton TRV4.

This boiler is modulating which I understand modulates the flame according demand from the CH system so is there really a problem with fitting (and using) too many TRV's.

Boiler modulation and rad TRVs are doing completely different jobs. The TRV controls the temperature of the room by turning the radiator on and off as necessary. Boiler modulation controls the amount of heat being generated to meet the current requirements.

 

[BigBurner]

Part L regs state that trv's should be fitted on all rads except the one in the room where the room stat is located.

Part L does not say anything of the sort.

 

[chieflasagnaeater]

Interesting...thanks.

So I pose no risk to the boiler by having all TRV's active and the room thermostat set high so calling for the boiler to engage?

In such a case I guess the boiler will simply heat the single rad in the room with the thermostat. My worry from reading other threads is the boiler will then only be heating a comparatively small volume of water which could lead to damage. Probably no risk at all as I would expect boiler manufacturers to test under all conditions.

 

[gas4you]

Part L regs state that trv's should be fitted on all rads except the one in the room where the room stat is located.

Part L does not say anything of the sort.

Wrong again Drwaterburner.

Part L refers to the Domestic Heating Compliance guide, in which it states the minimum requirements of heating controls.

Seems like you're getting too old to even google properly these days Drivel

But then if you were qualified you wouldn't have to google answers over Part L and CHeSS

 

[D_Hailsham]

In such a case I guess the boiler will simply heat the single rad in the room with the thermostat. My worry from reading other threads is the boiler will then only be heating a comparatively small volume of water which could lead to damage.

There will be a smaller volume of water to heat as the rest of the water will be trapped inside the radiators "closed" by the TRVs. One radiator open means that less heat will be extracted from the water, so the return temperature will be higher. The boiler will therefore not need to heat the water so much, which will be achieved by reducing (modulating) the boiler output. When the lower limit of modulation is reached, the boiler will revert to an on/off mode

The more important factor is the changes in pressure in the system due to TRVs opening and closing. This needs to be controlled by an Automatic Bypass Valve.

 

[squowse]

This needs to be controlled by an Automatic Bypass Valve.

to clarify for the OP these are fitted as standard in most boilers including the vaillant ecotec

 

[Softus]

Part L regs state that trv's should be fitted on all rads except the one in the room where the room stat is located.

Part L does not say anything of the sort.

Wrong again Drwaterburner.

Um, on this occasion, strictly speaking, WaterDrivel is actually correct.

Part L refers to the Domestic Heating Compliance guide, in which it states the minimum requirements of heating controls.

Part L was originally the name for Part L of The Building Regulations, but people also use it [incorrectly] when referring to Approved Documents L1A and L1B, and also the DHCG.

 

[Softus]

This needs to be controlled by an Automatic Bypass Valve.

to clarify for the OP these are fitted as standard in most boilers including the vaillant ecotec

To further clarify, the Vaillant spill valve is not a good automatic bypass, because you can't set the threshold to suit the system.

 

[Agile]

To further clarify, the Vaillant spill valve is not a good automatic bypass, because you can't set the threshold to suit the system.

Whilst YOU cannot, a CORGI ( who is qualified to open the boiler cover ) can adjust the built in by-pass as detailed in section 5.8 of the MI for the Erotic series of boilers.

Most combi boilers can create a pressure of 0.2-0.4 Bar so a typical setting of an auto by-pass would be about 0.42 bar for example although few have an accurate calibration and so they should be adjusted on test.

Many boilers with a built in by-pass do require an external by-pass as well although Vaillant do not.

Tony

 

[Softus]

a CORGI ( who is qualified to open the boiler cover ) can adjust the built in by-pass as detailed in section 5.8 of the MI for the Erotic series of boilers.

I don't really care, because nobody (other than you), was limiting their comments to the ecoTEC model.

Most boilers with a built in by-pass do require an external by-pass as well although Vaillant do not.

I reiterate - the Vaillant spill valve is not a good automatic bypass.

FYI #1 - I can do what I like with my own boiler cover.

FYI #2 - Some spill valves can be changed without removing the boiler cover.

 

[Homesafe]

To further clarify, the Vaillant spill valve is not a good automatic bypass, because you can't set the threshold to suit the system.

Whilst YOU cannot, a CORGI ( who is qualified to open the boiler cover ) can adjust the built in by-pass as detailed in section 5.8 of the MI for the Erotic series of boilers.
-------EROTIC ???????????he he looks like you need some 18stone babe to press you to shape again Mr T.
Tony

 

[Agile]

I don't really care, because nobody (other than you), was limiting their comments to the ecoTEC model.

In that case I am one of the few who keeps myself focussed on the OP's proposed installation of a Vaillant boiler.

I give advice in context and try not to be diverted by those seeking to widen the discussion beyone what is appropriate to the OP's situation.

Tony