Can't get 1 radiator to heat when all radiators turned on

Bargain_Hound

Hi there,

Hoping someone might have experienced something similar and could offer advice.

We recently bought a new (~15 year old) house. Prior to us moving in, the previous owner fitted a new Ideal s24IE gas boiler.

I've noticed since the cold weather kicked in, one radiator in the kitchen (Closest to boiler) never heats up. Originally I thought the issue was sludge build-up so I removed the rad and flushed it out but flow through it seems fine from what I was able to push through.

I re-bled all radiators and with noticed through the process that with all other radiators in the house switched on, the one in the kitchen just fails to heat (barely luke warm) but If I switch off all other radiators at the inlets or outlets, the kitchen rad heats up to full temperature, but as I slowly start to switch on the others back on it eventually looses all its heat again within minutes.

System is full up to pressure (2bar)
All radiators bled, no air that I can get out
Hot water cylinder is heating up perfectly

It's a pretty simple system, no zoning with a thermostat downstairs and hot water cylinder thermo thats up pretty high so I don't think its a zoning or electrical issue.

Any ideas? Driving me mad!

EDIT: should also mention
4 Radiators downstairs, 2 towel rads & 3 radiators upstairs.

listermint

Is there a TRV on that rad, it might be stuck closed or close to closed. the pins in them are notorious for sticking. and a rap of a spanner pops them up and out

lucernarian

Bargain_Hound wrote: »

Hi there,

Hoping someone might have experienced something similar and could offer advice.

We recently bought a new (~15 year old) house. Prior to us moving in, the previous owner fitted a new Ideal s24IE gas boiler.

I've noticed since the cold weather kicked in, one radiator in the kitchen (Closest to boiler) never heats up. Originally I thought the issue was sludge build-up so I removed the rad and flushed it out but flow through it seems fine from what I was able to push through.

I re-bled all radiators and with noticed through the process that with all other radiators in the house switched on, the one in the kitchen just fails to heat (barely luke warm) but If I switch off all other radiators at the inlets or outlets, the kitchen rad heats up to full temperature, but as I slowly start to switch on the others back on it eventually looses all its heat again within minutes.

System is full up to pressure (2bar)
All radiators bled, no air that I can get out
Hot water cylinder is heating up perfectly

It's a pretty simple system, no zoning with a thermostat downstairs and hot water cylinder thermo thats up pretty high so I don't think its a zoning or electrical issue.

Any ideas? Driving me mad!

Seems like the radiator nearest the kitchen is unbalanced? There is a valve setting for most radiators which is semi permanent, in other words it's typically adjusted during installation and then it's good to go. They are for adjusting the flow into radiators so that they will all heat up at the same time?

Some experts here might be able to explain better, or give other ideas

GreeBo

Is the one in the kitchen first or last in the run?
Seems like its last.

Check that you dont have the LSV too open on the other rads, they control the flow of hot water out of (and hence in to) each rad.
If all the hot water is going into the earlier rads then there wont be any left for the last rad so it will never get hot.
It also means that you are returning hot water too quickly to the boiler, it should be staying in each rad and only leave when its ~12*C colder than when it entered. (Temperature differential between flow and return)
If your LSH is too open then it will be leaving at much the same temperature as it enters, which is inefficient.

GreeBo

/edit
You once balanced, you should not be adjusting the LSV (outlets)

Bargain_Hound

Thanks everyone!

I really don't think there is an issue with the radiator itself as it heats up to full temp with others switched off.

I really couldn't tell if its the first or last rad. Its physically closest to the boiler but definitely the coldest in the house and the only one I can determine definitely only heats up when some are shut off upstairs. I think the rad upstairs furthest away from the boiler is getting hot water first, it heats up within seconds of boiler switching on.

Seems like its a balancing issue - I didn't realize such a thing existed. I may have to get someone to come and do it professionally if I can't get it balanced myself.

GreeBo

https://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php

Above is a balancing guide, there are many!

Basically you close everything and start from the first rad, you get it balanced (to get the correct temp differential between the valves) and then you move into the next one until you get to the end.
If, after this, all rads arent warm then your boiler isnt powerful enough.

Bargain_Hound

GreeBo wrote: »

https://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php

Above is a balancing guide, there are many!

Basically you close everything and start from the first rad, you get it balanced (to get the correct temp differential between the valves) and then you move into the next one until you get to the end.
If, after this, all rads arent warm then your boiler isnt powerful enough.

Thanks for the above. I will have a go at that tomorrow.

Regarding TRV’s, upstairs rads have them all fitted(what look like TRV). Downstairs is just normal valves. Upstairs rads are all up to temperature.

One question; is it possible upstairs and downstairs rads have their inflow/outflow the opppsite?
Very sure upstairs rads the inflow is on the left and downstairs the inflow is on right?

Bargain_Hound

So with my first amateur attempt at balancing by following the above guide, I have the radiator in the kitchen up to what I would estimate to be 60-70% temperature, while the remainder of the house staying up to temperature. Maybe a bit more fine tuning might get it there.
From stone cold to getting fairly warm, it's a step in the right direction.

GreeBo

Bargain_Hound wrote: »

Thanks for the above. I will have a go at that tomorrow.

Regarding TRV’s, upstairs rads have them all fitted(what look like TRV). Downstairs is just normal valves. Upstairs rads are all up to temperature.

One question; is it possible upstairs and downstairs rads have their inflow/outflow the opppsite?
Very sure upstairs rads the inflow is on the left and downstairs the inflow is on right?

Yeah there are no set rules, but the flow side will either have a TRV or a valve you can turn by hand, the return will have a LSV that you need to get a pliers/spanner on to open/close.
Also the flow side will always be the warmer of the two.

Bargain_Hound

GreeBo wrote: »

Yeah there are no set rules, but the flow side will either have a TRV or a valve you can turn by hand, the return will have a LSV that you need to get a pliers/spanner on to open/close.
Also the flow side will always be the warmer of the two.

Thanks again!

I still haven't got this perfect but I think I have identified that upstairs, the TRVs are fitted to the outlet of the rads. The lockshields are definitely on the far hotter pipes, what I am assuming to be the inlets. perhaps what's going on here is the TRVs are effectively not allowing the system to balance correctly if they are fitted on the outlets and not inlets. What a mess.

GreeBo

Bargain_Hound wrote: »

Thanks again!

I still haven't got this perfect but I think I have identified that upstairs, the TRVs are fitted to the outlet of the rads. The lockshields are definitely on the far hotter pipes, what I am assuming to be the inlets. perhaps what's going on here is the TRVs are effectively not allowing the system to balance correctly if they are fitted on the outlets and not inlets. What a mess.

The TRVs should have an arrow on them indicating which direction the water should flow through them, some are bidirectional and can be installed on either side in either orientation, older ones will be single direction, so these need to be installed either vertically (if on the flow side) or horizontally (if on the return side)

When balancing a system with TRVs its important to remove the TRV head, otherwise its all changing as you are adjusting it.

You can still balance them even if the TRV is on the return (as long as its in the correct orientation) all the LSH and TRV do is control the rate of flow through the rad and since water cant come in unless the same amount of water is going out, it kinda doesnt matter.

However I would say that its easier to balance them when the TRVs are on the flow side!