Installing smart TRVs on ALL radiators with use of a bypass valve

[d36csr]

Hi there,

I recently bought a bunch of Drayton Wiser Smart TRV heads. I wanted to install them on all of my radiators so that I have full control of which radiators are on. However, it specifies in the instructions that one of the radiators should be left with 2 x open lockshield valves. Now that I have the TRVs, I can see why. When only one TRV head is calling for heat, and it then reaches its goal temperature, it signals to the boiler to power down, and unfortunately shuts the valve body immediately, while the boiler and central heating pump are still running to dissipate the residual heat from the boiler.

I have a Worcester Greenstar 30SI MKIV, which according to the manual has a bypass valve integrated with it. However, I was concerned that my setup could nevertheless cause issues with the boiler/pump over time. Consequently, I bought a separate bypass valve, and installed it around 1m from the boiler, bridging the flow and return pipes. Frustratingly however, now that it's in, it seems to allow water to flow through it even when it's set to its maximum 0.5bar setting, and all 5 of the radiators are fully on! Mixing flow and return waters will reduce the ability of the boiler to condense water from the flue gasses, thus reducing efficiency, so I'm a bit peeved about that. Maybe this is what bypass valves normally do, or maybe I have a defective one? It was an unbranded one from a local supplier.

My question is, is there any way of making this work? I'm a plumber, but not a heating engineer, hence moderate ignorance in this field.

I imagine that a bunch of you will just tell me to take one of the TRV heads off, but I'm not keen on wasting gas by needlessly heating a room I'm not using at that moment.

Thanks loads for your time and thought.

Warm regards,
Benedict
Pedal Powered Plumbing, Bristol

 

[ShaunCorbs]

Bypass shouldn’t work when trvs open so either duff bypass or incorrectly set it’s fully wounded in ?

 

[d36csr]

Bypass shouldn’t work when trvs open so either duff bypass or incorrectly set it’s fully wounded in ?

Yes, fully tightened to 0.5 bar. Perhaps I should replace it with a decent branded one?

 

[ShaunCorbs]

Any pictures where you’ve located it ?

 

[Chuck]

I see nothing in the installation instructions that suggest an external ABV is needed or desirable. If it were needed, as on previous Worcester models, it would be mentioned. Neither of the example radiator circuits Figs 5 & 6 in §3) show one.

Adding a redundant external ABV seems pointless to me and it's already causing problems; wasting your time and money!

 

[ShaunCorbs]

I see nothing in the installation instructions that suggest an external ABV is needed or desirable. If it were needed, as on previous Worcester models, it would be mentioned. Neither of the example radiator circuits Figs 5 & 6 in §3) show one.

Adding a redundant external ABV seems pointless to me and it's already causing problems; wasting your time and money!

He’s installed trvs on every rad so if they all close instantly the pump overrun has no where to pump ?

 

[d36csr]

Any pictures where you’ve located it ?

Here you go. It's on the end of those flexis. I cobbled it together to see if it'd work. I promise you I'm a better plumber in other people's houses! 😅

 

[Chuck]

He’s installed trvs on every rad so if they all close instantly the pump overrun has no where to pump ?

Missed that, thanks. But in that case he's not complied with the MIs, page 13, which explicitly say

"Thermostatic radiator valves (TRV’s) must be used on all radiators within the sleeping accommodation but not the radiator where the room thermostat is sited. This must be fitted with lock-shield valves and left open."

An external ABV should help but he may need to form a loop that is longer than a 2m round trip (to avoid transient overheating of the HX).

 

[d36csr]

Missed that, thanks. But in that case he's not complied with the MIs, page 13, which explicitly say

"Thermostatic radiator valves (TRV’s) must be used on all radiators within the sleeping accommodation but not the radiator where the room thermostat is sited. This must be fitted with lock-shield valves and left open."

An external ABV should help but he may need to form a loop that is longer than a 2m round trip (to avoid transient overheating of the HX).

To clarify, I'm not using a room thermostat. I get that that's probably beside the point though.

 

[John.g]

If you can split the removed ABV you may find something under the valve seat.

If the ABV is passing and assuming its orientated correctly then maybe replace it with a Honeywell DU144 or the like, only other reason for this is if the pump head even when circulating through the 5 rads is > 5M, very unlikely.

 

[d36csr]

If you can split the removed ABV you may find something under the valve seat.

If the ABV is passing and assuming its orientated correctly then maybe replace it with a Honeywell DU144 or the like, only other reason for this is if the pump head even when circulating through the 5 rads is > 5M, very unlikely.

I have a DU144 on order. Thanks for the advice John. 👍🏻

 

[Ric2013]

Hi d36csr. You aren't a bicycle plumber are you? If so, I have a feeling we've met...

I'm not going to share your identity here if you don't wish to, but feel free to send me a private message.

Note to other forum users: if he's who I think he is, he's a good guy, but I respect his right to privacy.