Radiators on with hot water or not?

purpleparrotuk

ThisIsWeird said:

Ah, that makes sense.
Whenever the boiler fires up - for whatever reason - the towel rad will receive a flow as it's connected across the boiler's flow and return.
Probably not a bad thing - it'll give you warm towels winter and summer. But, you should have control over it, and that can be simple 'manual' via a hand valve.
So you still need an access to that boxing-in.

I already have a manual trv on the towel rad so I can turn it off if I want. 

FFHillbilly

purpleparrotuk said:

ThisIsWeird said:

Ah, that makes sense.
Whenever the boiler fires up - for whatever reason - the towel rad will receive a flow as it's connected across the boiler's flow and return.
Probably not a bad thing - it'll give you warm towels winter and summer. But, you should have control over it, and that can be simple 'manual' via a hand valve.
So you still need an access to that boxing-in.

I already have a manual trv on the towel rad so I can turn it off if I want. 

I'm fairly sure he's confused this thread with another towel rail related thread 

FreeBear

molerat said:

ThisIsWeird said:

Ah, that makes sense.
Whenever the boiler fires up - for whatever reason - the towel rad will receive a flow as it's connected across the boiler's flow and return.
Probably not a bad thing - it'll give you warm towels winter and summer. But, you should have control over it, and that can be simple 'manual' via a hand valve.
So you still need a access to that boxing-in.

Before my son had a new combi installed the downstairs hall rad was plumbed between the pump and the DHW and CH valves.  It was supposed to be a heat sink for boiler overheat - if boiler overheated pump kept running through that rad even if zone valves were closed - didn't work though !

Modern boilers will modulate down to match heat generated to the demand. If it senses an over-heat condition, it should shut down. Pumps are also a lot smarter than they used to be, and will throttle back if flow pressure increases too much (if set up correctly).

purpleparrotuk

One more question though. 

Is it ok for the boiler to be at 2.5 bar when heating a few radiators from cold on an unvented system? Also I have had the new radiator (installed Friday on existing pipework where one was removed 5 years ago) on a few times and it is supposed to be 20 but is overshooting to 22 according to my evohome app. Maybe it’s because I’ve only had the heating on 2 days and it’s been off all year so needs to learn the timings to come on again without overshooting.  I have never seen a lock shield valve on the same side as the trv. Does it need adjusting? The other side of the radiator has an hexagonal lock shield valve.

FFHillbilly

2.5 is a bit high it should be between 1-2. just open a bleed valve on a rad and you should loose a bit of pressure

ThisIsWeird

FFHillbilly said:

purpleparrotuk said:

ThisIsWeird said:

Ah, that makes sense.
Whenever the boiler fires up - for whatever reason - the towel rad will receive a flow as it's connected across the boiler's flow and return.
Probably not a bad thing - it'll give you warm towels winter and summer. But, you should have control over it, and that can be simple 'manual' via a hand valve.
So you still need an access to that boxing-in.

I already have a manual trv on the towel rad so I can turn it off if I want. 

I'm fairly sure he's confused this thread with another towel rail related thread 

Fairly? Totally! :-)

ThisIsWeird

purpleparrotuk said:

One more question though. 

Is it ok for the boiler to be at 2.5 bar when heating a few radiators from cold on an unvented system? Also I have had the new radiator (installed Friday on existing pipework where one was removed 5 years ago) on a few times and it is supposed to be 20 but is overshooting to 22 according to my evohome app. Maybe it’s because I’ve only had the heating on 2 days and it’s been off all year so needs to learn the timings to come on again without overshooting.  I have never seen a lock shield valve on the same side as the trv. Does it need adjusting? The other side of the radiator has an hexagonal lock shield valve.

As Hilly says, 2.5 bar is too high. The Q is - is it at 2.5 when cold, or just after it's heated up?

I have a Hive controller, with one rad using their Smart valve. That does take hours of 'proper' use before it is fully auto-set-up. The App tells me it hasn't had enough time, which is not surprising as I only want it on for a half hour in t'eve and ditto in t'morn - it's a bedroom. Presumably yours is similar.

The lockshield is normally on the opposite end of the rad to the 'control' valve. Lockshields are set-and-forget, but that's not to say it has been set properly. In essence, lockshields are meant to provide the correct supply for each rad, so that each one is 'balanced' in relation to the others. Larger rads and those further away from the boiler will tend to be tweaked more open, smaller/closer rads will barely be open at all. Once 'balanced', the 'control' valves do the actual on and offing, and the temperature setting.

You can always contact Evo and ask them.

But - is that system pressure when cold? And, does it change at all when hot?

purpleparrotuk

ThisIsWeird said:

purpleparrotuk said:

One more question though. 

Is it ok for the boiler to be at 2.5 bar when heating a few radiators from cold on an unvented system? Also I have had the new radiator (installed Friday on existing pipework where one was removed 5 years ago) on a few times and it is supposed to be 20 but is overshooting to 22 according to my evohome app. Maybe it’s because I’ve only had the heating on 2 days and it’s been off all year so needs to learn the timings to come on again without overshooting.  I have never seen a lock shield valve on the same side as the trv. Does it need adjusting? The other side of the radiator has an hexagonal lock shield valve.

As Hilly says, 2.5 bar is too high. The Q is - is it at 2.5 when cold, or just after it's heated up?

I have a Hive controller, with one rad using their Smart valve. That does take hours of 'proper' use before it is fully auto-set-up. The App tells me it hasn't had enough time, which is not surprising as I only want it on for a half hour in t'eve and ditto in t'morn - it's a bedroom. Presumably yours is similar.

The lockshield is normally on the opposite end of the rad to the 'control' valve. Lockshields are set-and-forget, but that's not to say it has been set properly. In essence, lockshields are meant to provide the correct supply for each rad, so that each one is 'balanced' in relation to the others. Larger rads and those further away from the boiler will tend to be tweaked more open, smaller/closer rads will barely be open at all. Once 'balanced', the 'control' valves do the actual on and offing, and the temperature setting.

You can always contact Evo and ask them.

But - is that system pressure when cold? And, does it change at all when hot?

Hi. It’s only near 2.5 when it’s hot. It’s only just over 1 from cold. Maybe it’s been like that for 5 years but I haven’t really noticed to be honest. The only think wrong with my system and it still happens now is some of the radiators hiss a bit like kettles boiling now and again. 

ThisIsWeird

Ok, a 1 to 2.5bar increase when getting hot suggests an Expansion Vessel that needs attention. It isn't 'critical' until it gets close to 3bar, as that's the point when a safety valve blows open and discharges excess system water outside. 
Altho' not ideal, as long as there's no other issues, 2.5bar can keep on trucking, but it just isn't 'ideal'. Do you have your boiler serviced? If so, bring it to the fellow's attention - to check and recharge the EV should be straight forward.
Anyhoo, this hiss. Could be some trapped air, so have you tried bleeding the rads when cold? Or, it could just be normal moving-water noise. Your boiler output temp isn't silly-high, is it?

purpleparrotuk

ThisIsWeird said:

Ok, a 1 to 2.5bar increase when getting hot suggests an Expansion Vessel that needs attention. It isn't 'critical' until it gets close to 3bar, as that's the point when a safety valve blows open and discharges excess system water outside. 
Altho' not ideal, as long as there's no other issues, 2.5bar can keep on trucking, but it just isn't 'ideal'. Do you have your boiler serviced? If so, bring it to the fellow's attention - to check and recharge the EV should be straight forward.
Anyhoo, this hiss. Could be some trapped air, so have you tried bleeding the rads when cold? Or, it could just be normal moving-water noise. Your boiler output temp isn't silly-high, is it?

We have only just had the boiler and tank serviced last month. I looked again and it was on 2 bar when hot tonight. I think it’s only a bit higher than 2 when quite a few rads needed heating up. I don’t think anything would is wrong with the vessel. Surely increasing from just over 1 cold to just over 2 when red hot is ok? The flow temperature is set to 68. I’ve bled the radiators and no air in them. This hissing has been there for a few years now.