Freezing 3yr old son's bedroom HELP!

[smglasgow]

doitmyself: inlet is too hot to touch and IR themometer says mid to high 60's normally at inlet pipe and 20-degrees less at outlet. This is for a flow temp (at boiler of ~70) so only losing 5 degrees in the long run to the final radiator (upstairs and down). I have 2 rads with same issue recall.

Coming back to pump speed for a moment, is it common practice to set the pump at fastest speed on a combi system? Father in law has vented system and say pump doesnt do any work other tehn circulate and so setting at 1 shoudl be fine. He compromised at setting my system speed at 2 yesterday, but the system was originally going at 3. To my mind the pump speed determines a) flowrate for a given system pressure drop (resistance) and b) temperature difference between flow and return for a given set of radiator lockshield settings. If the system wont balance because all the rads only drop say 5 degrees then the flow is too high and the pump needs knocking down a speed. Conversely if all the rads drop 20 degrees even after opening the lockshields fully then the system needs more pump speed. On that, I understand I should be aiming for a temp drop of 12 degrees between inlet and outlets to each rad.

 

[stevetheplumber]

change the trvs

 

[SimonG]

Hurray. Common sense wins the day. The 3 year old is freezing and your discussing temp drops across a radiator. FFS.

 

[smglasgow]

starting to think this might by the issue right enough, even if pin is apparently freely moving up and down, as I have two other radiators on the system that will not "close" when I screw the TRVs down to OFF position (one past frost setting). Even taking the TRV heads off a pushing down the pins on those TRVs does not stop flow through the radiator. Once is on a towel rail so not concerned by that and the other is on a radiator close to the room thermostat and I leave that at FULLY open anyway (setting 5 on the TRV) - but does make me wonder about the quality of the supposedly excellent danfoss TRVs!

I take it to change the TRV bodies I need a full system drain down or pipe freezing kit! Think I will go with the former, re-dose fernox and replace all TRVs that are not fully closing (2) as well as the TRVs on the suspect radiators...........would you recommend changing the lockshields on the two problem radiators at the same time, to take them as a possible source of issue out the equation?

Still curious about the pump speed setting - any advice?

 

[SimonG]

Wiggle pins, not too hard, and tap trv with something heavy. Will confirm. As for pump speed, whatever it says in the manual. More than just the heating circuit to consider on a combi.

 

[PhoenixServices]

My two penny worth, some of these designer rads have baffles and should be piped up a certain way round. I.e flow to inlet. Had this before they don't perform as well. If rebalancing and changing trvs fail, flip the rad round and see how it performs.

 

[doitmyself]

I know the limitations of an IR THERMOMETER and have also recorded inlet and outlet temps at each radiator in the system (have excel sheet with data representing hours work). I use black tape on the copper pipe to get more reliable reading. Top of rad (white surface) is reasonable indication with IR thermometer.

You seem to be doing everything 'by the book'. Could you post the most recent results?

I see no change in the system temps at speed 2.

Interesting. Increasing the speed should produce a reduction in the differential, and vice-versa.

checked the thermostat pins, problem rads have pins which stick out the same amount at the pins on TRVs on rads that work fine, and are free to move up/down, so again doubt that is the issue. The lockshields are also fully open.

On some TRVs the pins are not connected to the plunger which blocks the flow, so free movement of the pin is not significant. Try giving the side of the TRV body some sharp taps with a hammer.

You say the LS valves are fully open, is this because you have balanced the system using the built-in balancer of the Danfoss TRVs?

 

[Geyser]

My two penny worth, some of these designer rads have baffles and should be piped up a certain way round. I.e flow to inlet. Had this before they don't perform as well. If rebalancing and changing trvs fail, flip the rad round and see how it performs.

Had this as well. Do we know what these designer rads are?

 

[PriestyUK]

Phoenix Services may have a point, I have also found on one job in a small-ish office block that 2 end rads didnt get very hot (one of which was the MD's office) We changed TRV's and radiators, we pulled it through on the drain cocks to make sure no air or $hit in the pipework and still the same problem. All the other rads got hot, it was only by chance that we thought lets just change the pump that it cured the problem. Pumped seemed to be running fine but some how it just wasn't man enough anymore to reach them last 2 rads whether the impeller blades had worn down I don't know but changed that pumped and MD was finally happy.

 

[Leo21]

You seem to be doing everything 'by the book'. Could you post the most recent results?



Interesting. Increasing the speed should produce a reduction in the differential, and vice-versa.


On some TRVs the pins are not connected to the plunger which blocks the flow, so free movement of the pin is not significant. Try giving the side of the TRV body some sharp taps with a hammer.

You say the LS valves are fully open, is this because you have balanced the system using the built-in balancer of the Danfoss TRVs?

You dont tap trv,s from the side. Specially not sharply, you tap them on the pin! Get your facts right before giving advise. Perhaps contact the mods with your qualifications, so we know your actually qualified to advise these poor unsuspecting people.