Newbie questions about fitting TRVs and flow direction

[dalty]

My gas burner central heating system is about 40 years old. Piping is gun barrel.
I am thinking of fitting TRVs to several of the rads.
Before I hire an expert to do the job I have a few questions please: (words like 'draining' and 'airlocks' suggest it is not a DIY job!!!)

Forums tell me TRVs must be fitted on the 'inflow'. How can I know water flow direction by just looking at the rad?
All rads have an on/off valve at each end - one end has a static cap and the other a plastic fitting to turn on/off.
These I suspect have been reversed on some rads for ease of access.

Is flow direction important in fitting a TRV? I ask because the location of the valve is important for ease of access in some rooms.

Is messing around with 40 year old gun barrel likely to bring on leakage or other problems?

Looks like I can pay about £6 for a cheap valve or £20 for a Danfoss. Is it worth paying extra for the expensive one? Do these things tend to fail?

Thanks in advance

Dalty.

 

[Simon F]

as its such an old system, is it a one pipe set up?
that would affect the choice of TRV's

 

[davebigpipes]

If its a one pipe wouldn't bother with trvs if its two pipe then to find out which is flow, from cold turn on the heating and feel which leg feeding each rad gets hot first.

 

[mikeb]

blimey if its 40 yers old, it must costing a lot of wonga to run it, yep if its one pipe dont bother with trvs. save some wonga, just get it cleaned out, that shouldnt cost to much,

 

[dalty]

Sorry, forgot, it's two pipe.
Dalty.

 

[GQuigley67]

danfos are bi-directional valves, so that shouldnt be an issue, easiest way to find out which one is the flow is feel the pipes and whatever one gets hot first should be the flow

 

[dalty]

OK, thanks for those comments.

BUT

1. Does it matter if the TRV is installed on the outlet side of the rad? Is that a no-no?

2. Would a pro plumber be confident about tackling gun barrel on a 40 year old system (the burner is new!!)?

3. Should I buy Danfoss or is the £6 job OK in a domestic setup (Danfoss talk a lot about commercial installations)

Dalty

 

[GQuigley67]

as i said danfos are bi-directional, so they can be fitted on the flow or the return, if your thinking of getting a professional in to do it then post in "I'm looking for a plumber/gas engineer" on this forum

 

[GrahamM]

danfos are bi-directional valves, so that shouldnt be an issue, easiest way to find out which one is the flow is feel the pipes and whatever one gets hot first should be the flow

In my opinion these multi-directional valves do not live upto their name and should always be put on the flow for best results.
And the danfoss multi-directional valves are pure junk. This is the crap BG are fitting on their installs. I have lost count of the amount of jobs I have attended recently for these giving trouble. Most have been no more than year or so old.

 

[GQuigley67]

what kind of troubles ?? and what valves would you recommend then

 

[GrahamM]

I have replaced 2 in past month or so that have been leaking at the plastic directional collar. Others, the usual leak at pin.
They do not stand upto the constant turning up/down. Try to encourage customer to leave on one setting. In property's the customer leaves them on a constant setting, they fair better.
In my opinion, although bit more expensive drayton TRV4 are great. If system is clean I only get the odd sticky pin on these.