New boiler, rads keep getting cold

[Mrs Naylir]

Hi we had a baxi18 installed June. From day one the plumber could not get all rads hot and to stay on. They came back and changed pump, no difference changed all trvs. Now, the problem is this They all come on and are hot after about 45mins one goes cold and does not come back on . There are two that come on and work as they should. The bathroom comes on and cools down alot but is hot on left trv side cold on right. The others soon cool down and only heat up a bit. Now I realise trvs work on ambient temperatures but my lovely old system never went off with the westherm trvs these are tower it is a conventional system. The plumber is a lovely lad but I rang him and asked what it could be and he said he didn't know when they came back on the 3rd occasion they got them all going but went before they went off. We have now paid for the new system, new pump and trvs. Cant keep paying out. We are elderly and stressed. They seemed to struggle balancing it as as soon as one warmed up another went off and they rebalanced and then another went cold. Any ideas

 

[Scott_D]

Did you have TRVs before?
Could it be a one pipe system?

 

[Deleted member 120897]

Did you have TRVs before?
Could it be a one pipe system?

my lovely old system never went off with the westherm trvs these are tower

It still seems like a balancing issue, all depends on how quickly they’re balancing them. If they’ve had to replace the pump and trv’s at your cost then it suggests to me they don’t really know what they’re doing - nice lad or not.

 

[Scott_D]

It still seems like a balancing issue, all depends on how quickly they’re balancing them. If they’ve had to replace the pump and trv’s at your cost then it suggests to me they don’t really know what they’re doing - nice lad or not.

True
But often if a system is that difficult to balance its due to bad design.
Multiple rads in micribore
Old rad pipes linked together under boards
Single pipe or part single pipe etc etc

Things that should never have worked but somehow did and a sight alteration throws it all out.

 

[Mrs Naylir]

Did you have TRVs before?
Could it be a one pipe system?

Yes for 30 years no problems till new boiler installed. It is 2 pipe system

 

[SJB060685]

So no new rads installed and worked fine before?
Was the system flushed during the installation?

 

[John.g]

Hi we had a baxi18 installed June. From day one the plumber could not get all rads hot and to stay on. They came back and changed pump, no difference changed all trvs. Now, the problem is this They all come on and are hot after about 45mins one goes cold and does not come back on . There are two that come on and work as they should. The bathroom comes on and cools down alot but is hot on left trv side cold on right. The others soon cool down and only heat up a bit. Now I realise trvs work on ambient temperatures but my lovely old system never went off with the westherm trvs these are tower it is a conventional system. The plumber is a lovely lad but I rang him and asked what it could be and he said he didn't know when they came back on the 3rd occasion they got them all going but went before they went off. We have now paid for the new system, new pump and trvs. Cant keep paying out. We are elderly and stressed. They seemed to struggle balancing it as as soon as one warmed up another went off and they rebalanced and then another went cold. Any idea

What make are the TRVs?

Were they replaced with the same make?.

Is the boiler still firing when they don't come back on?

Even though TRVs have a very small temperature hysteresis (ambient temp difference between fully open and fully shut) of around 1.5C to 2C they are still or should be relatively slow acting due to the volume of fluid in their actuators, they should not just act in a on/off manner, at least mine don't, presently using EPH make but did have Myson nd a few other types and all worked similarly and maintain very reasonable room temperatures as long as the boiler is firing continuously or cycling on/off in the case of a oil fired boiler.
I have them installed horizontally on the rad returns to sense a more representative room temperature and also, even though they are all bi-directional, installing them horizontally ensures that the water flow is "proper" ie from under the valve seat.
Of course if installed vertically on the rad flow (as most are) then flow is proper as well whether they are uni or bi directional.

 

[John.g]

Also just check that the actuators are properly attached to the valve body, ensure actuator fully opened ie anticlockwise to index 5 or whatever then ensure knurled nut fully (hand/finger) tightened (clockwise).

Also read somewhere that some TRVs had chromium bodied actuators (normally plastic) which were transferring the heat by conduction from the water in the rad and obviously would then take hours to reopen after closing off, no good.

 

[Mrs Naylir]

What make are the TRVs?

Were they replaced with the same make?.

Is the boiler still firing when they don't come back on?

Even though TRVs have a very small temperature hysteresis (ambient temp difference between fully open and fully shut) of around 1.5C to 2C they are still or should be relatively slow acting due to the volume of fluid in their actuators, they should not just act in a on/off manner, at least mine don't, presently using EPH make but did have Myson nd a few other types and all worked similarly and maintain very reasonable room temperatures as long as the boiler is firing continuously or cycling on/off in the case of a oil fired boiler.
I have them installed horizontally on the rad returns to sense a more representative room temperature and also, even though they are all bi-directional, installing them horizontally ensures that the water flow is "proper" ie from under the valve seat.
Of course if installed vertically on the rad flow (as most are) then flow is proper as well whether they are uni or bi directional.

New trvs Tower. Old ones westherm. Boer doesn't go on and off plumber says that's OK.

 

[Deleted member 123817]

If the boiler is still firing then the heat must be going somewhere.
If you open the TRVs fully will the rads that weren't heating then heat up?