Auto bypass valve | Advice on how to fit with a 160cm wide radiator

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chatmandu

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The furthest radiator from my boiler is a 160cm x 50cm Type 22 in my living room.

It has always been set as the bypass, but this isn't ideal. The living room can overheat, whilst the kitchen is cold. The obvious answer would be to set a lower temperature on the TRV in the living room, but this would disable the bypass and could lead to boiler pump damage.

If I were to fit an auto bypass valve, I think the obvious place would be in the living room, because that's the 'end' of the system. The only issue is the width of the radiator. I don't really fancy having a 160mm length of 15mm copper pipe hanging unsupported below the radiator. It would only be a matter of time until my 3 year old son started standing on it to look over the windowsill. The flow and return pipes are under the floorboards, but I'd rather not start pulling up the flooring and, unless it has flow, the bypass pipe might be prone to freezing?

Any suggestions on how best to fit an auto bypass when you have wide radiators?

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Edit

Ok, so it looks like auto bypass valves are 22mm and there's no practical way to fit one at the 'end' of my heating system.

Is there anything wrong with fitting one to link the combi boiler's flow and return pipes? Is there a minimum recommended distance from the boiler?
 
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If the radiator is fitted with a TRV ,what makes you think it has anything to do with being a by pass ?
What boiler do you have ?
 
terryplumb said:
If the radiator is fitted with a TRV ,what makes you think it has anything to do with being a by pass ?
What boiler do you have ?
Click to expand...

That radiator is used as a bypass (lock shield valve is fully open and TRV set to max temp).

I don't think the system installer was very good

My boiler is a Vaillant Ecotec Plus 835.
 
In the unlikely event that the rad was ever intended to act as a bypass ,it wouldn't have a TRV for starters.
 
terryplumb said:
In the unlikely event that the rad was ever intended to act as a bypass ,it wouldn't have a TRV for starters.
Click to expand...
I'm not in the trade, so I'll take your word for that

Does this mean that running the living room TRV and lockshield valves 'fully open' is pointless in terms of preventing pump damage?

I thought the purpose of an automatic bypass valve was to prevent damage when all the TRVs close. Surely having one that is 'open' prevents that scenario from occurring?
 
You can get reducers for 22 to 15.
First question is does your boiler need a bypass- some don't, some have them fitted internally.
Don't rely on your installer to have determined this correctly, if your installer 'wasn't very good ' chances are they've assumed a bypass is required and fobbed you off with a non-compliant bodge.
A quick look at the installation manual says there's an internal bypass BUT best waiting for one of the more knowledgeable to confirm that it's part of the heating circuit rather than dhw (I'm fairly certain but I ain't no gas engineer)
 
Harry Bloomfield said:
and the one radiator which has no TRV, should be the room where the thermostat is located.
Click to expand...

This is the current situation.

Boiler in upstairs bathroom cupboard.
Radiators in order:
Upstairs bathroom > Landing >Tee for downstairs > Back bedroom > landing (thermostat) > small front bedroom > large front bedroom

Downstairs from Tee > Kitchen > Dining room > Hallway > Living Room

There is no obvious radiator that can be set to 2x fully open lock shields. If I did that in the kitchen (coldest room), the other radiators may struggle to get enough flow. The living room is the furthest from the boiler, so I've always run that as fully open TRV and lockshield. This is the radiator that I'd like to control with the TRV, but setting a room temp of 21C could end up with all TRVs closed and potential boiler damage.

I balanced the system yesterday and some of the TRVs are quite noisy - especially when they approach the set temperature. There are quite a few threads that recommend fitting an auto bypass valve to fix that.

As I said in a previous post, I don't think the installer was very good and I'm working with what I have. Maybe he didn't fit one because he knew the boiler had one or maybe he just wanted to get out of the door ASAP?
 
The purpose of the bypass is to protect the boiler and pump should both the CH and DHW valves close. A radiator will not perform this task as it is beyond the CH valve.
 
The 835's have a settable internal bypass and whilst it's doesn't negate the standard need to have an ABV it does mean that the boiler overrun and min flow is catered for by the boiler.
 
Madrab said:
The 835's have a settable internal bypass and whilst it's doesn't negate the standard need to have an ABV it does mean that the boiler overrun and min flow is catered for by the boiler.
Click to expand...

So does that mean it is 'safe' to run the system using the TRVs to control the temperatures of all the rooms, even though that might result in all TRVs automatically closing?

Basically, can I rely on the boiler's automatic bypass valve or is it likely to break at some point and then result in a knackered boiler pump?

Would a £15 auto bypass valve, fitted between the flow and return pipes coming off the boiler, be a good idea? I've looked online and replacement pumps are £212+VAT, so fitting one seems to make financial sense.
 
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