Modify TRV so that combi boiler always has a heat dump?

[tonton]

I have a combi boiler and all my rads have TRVs installed. If the heating is on but all the TRVs are set to 0, the boiler makes some horrible noises and then shuts down. What is the best solution? I was wondering if I could modify a TRV so that it isn't able to completely shut off one radiator (a stack of washers around the valve's pin?), or should I replace one TRV with a lockshield valve?

 

[big-all]

no expert
buuutttt ----------------you cant use a trv as a heat dump as it can fail or be accidentally closed

 

[ianmcd]

just remove the sensor head on the valve you wish to use as a by-pass, usually bathroom one, if you have a room thermostat there should not be a TRV in the same space so use that one

 

[tonton]

just remove the sensor head on the valve you wish to use as a by-pass, usually bathroom one, if you have a room thermostat there should not be a TRV in the same space so use that one

I could remove a TRV head, but the other side of each radiator has a manual valve, so I'd have to replace that as well to remove the possibility of all the radiators getting closed. I wonder if one radiator had been assigned as the bypass when the system was originally installed but at a later date the TRVs were added and the idea of a bypass was never considered.

I don't currently have a room thermostat, but yes, if I install one I would remove the TRV from the radiator in that room.

 

[BlueLoo]

Your system is missing an ABV.

Many ways to do this.

1) Locking open a zone rad (No TRV) often a bathroom.
2) Fitting a ABV between boiler flow/return (Not suitable for PP pumps)
3) Fitting a preset manual bypass. (For PP pumps)
4) Using a actuated NO valve

 

[BlueLoo]

I could remove a TRV head, but the other side of each radiator has a manual valve, so I'd have to replace that as well to remove the possibility of all the radiators getting closed. I wonder if one radiator had been assigned as the bypass when the system was originally installed but at a later date the TRVs were added and the idea of a bypass was never considered.

I don't currently have a room thermostat, but yes, if I install one I would remove the TRV from the radiator in that room.

No stat?

Odd.

Fit one and use the rad in that room to be the bypass.

 

[ajstoneservices]

Why would you want the heating on with all the trv's closed

 

[Harry Bloomfield]

I could remove a TRV head, but the other side of each radiator has a manual valve, so I'd have to replace that as well to remove the possibility of all the radiators getting closed. I wonder if one radiator had been assigned as the bypass when the system was originally installed but at a later date the TRVs were added and the idea of a bypass was never considered.

You can remove the knob from the manual valve, and replace it with a cover. Either set the TRV to MAX, or remove it and cap the valve.

I don't currently have a room thermostat, but yes, if I install one I would remove the TRV from the radiator in that room.

The thermostat, really needs to be in the same room as the rad with no TRV. In my case, that radiator is the hall radiator.

 

[tonton]

Your system is missing an ABV.

Many ways to do this.

1) Locking open a zone rad (No TRV) often a bathroom.
2) Fitting a ABV between boiler flow/return (Not suitable for PP pumps)
3) Fitting a preset manual bypass. (For PP pumps)
4) Using a actuated NO valve

I will have to do some research to understand what 2, 3, and 4 are and what they would involve. Presumably 1 is usually the easiest for retrofitting?

I believe it was common to have no room thermostat for this type of install, at least I have seen it a lot. And perhaps it's not as bad as it sounds: The combi boiler has a dial which you turn to control the temperature of the heating. The heating will turn itself on and off despite there being no separate room thermostat.

 

[tonton]

Why would you want the heating on with all the trv's closed

You wouldn't, but I don't want to have a situation where it's possible to accidentally damage the system by doing so. Or a pin could get stuck down in one of the TRV valves, so it remains closed despite turning the TRV on.

 

[BlueLoo]

I will have to do some research to understand what 2, 3, and 4 are and what they would involve. Presumably 1 is usually the easiest for retrofitting?

I believe it was common to have no room thermostat for this type of install, at least I have seen it a lot. And perhaps it's not as bad as it sounds: The combi boiler has a dial which you turn to control the temperature of the heating. The heating will turn itself on and off despite there being no separate room thermostat.

Have a read of the boiler manual.
Some boilers require a bypass, some don't.
The manual will also give you best practice for the plumbing which you can check against yours. You might be surprised what you find.
Option 1 is the easiest but means you burn gas unnecessarily.

Options 2,3,4 are because the industry is still stuck in the 70's and have yet to grasp system engineering.

I did option 4 on mine because being an engineer, i liked the challenge and did it as a project. Works great for me.

 

[ianmcd]

I could remove a TRV head, but the other side of each radiator has a manual valve, so I'd have to replace that as well to remove the possibility of all the radiators getting closed. I wonder if one radiator had been assigned as the bypass

what are you on about ? just remove the head and leave th lockshield vale open at the other end and you have your by-pass

 

[tonton]

what are you on about ? just remove the head and leave th lockshield vale open at the other end and you have your by-pass

It's a manual valve, not a lockshield on the other end of each radiator. Do people use the terms manual and lockshield valve interchangeably? I thought a manual valve is one that can be turned by hand whereas a lockshield needs a spanner.

 

[Harry Bloomfield]

I believe it was common to have no room thermostat for this type of install, at least I have seen it a lot. And perhaps it's not as bad as it sounds: The combi boiler has a dial which you turn to control the temperature of the heating. The heating will turn itself on and off despite there being no separate room thermostat.

It was a cost saving/more profit for the installer, method of fitting a heating system - and very short sighted. The customer would then pay for that short coming, in his energy bills, and extra wear and tear.

The dial on the boiler, only controls the temperature the water in the heating system, is heated to.

 

[denso13]

I believe it was common to have no room thermostat for this type of install

Regs require that a boiler interlock is fitted, normally a room thermostat.