Adding radiators

[HenryG]

I have just added a radiator to an existing system to heat an extension.

I teed off the 15mm supply and return pipes to an existing radiator (furthest from the boiler) - new pipework approximately 4m from the tee. I now find I can get sensible heat out of either the new rad or the old one, but very poor performance if both are turned on together.

Everything else works as before. I assume the system needs balancing, but I would like some assurance that the problem is not more fundamental, like too small pipework.

Any comment or suggestions please?

 

[D_Hailsham]

It could be just a matter of rebalancing the system, or it may be that the pipe up to the new tee is now too small for the combined heat load of the two rads.

What kW are the two rads? (Use Stelrad Elite Catalogue if you don't know.)

 

[HenryG]

Thanks for a prompt comment from D_Hailsham.

Total load on the 15mm connection is about 3kW. I have an uncomfortable feeling you are correct about the pipe size. I had misgivings about it before I started, but to go back to the last 22mm pipe and extend from there was a major undertaking involving under-floor pipes. If that is the answer it will have to wait until redecoration of the room concerned. Just to help matters the old pipework is a plastic type no longer produced, so none of the modern fittings fit.

 

[D_Hailsham]

Total load on the 15mm connection is about 3kW.

15mm pipe can carry up to 6kW. So your existing pipe should be OK.

It looks as if the problem is caused by incorrect balance. See How to balance a CH system

 

[HenryG]

Many thanks D_Hailsham.

I have experimented today following advice on procedure, but with no thermometer to hand I have had to use the hand on the pipe test and guess!

Before I started playing with it all the radiators had both valves fully open (as left by the previous owners of the house). That was fine and they all got hot - no problem, so they were not touched. I have now found two thermostatic valves that stuck in the closed position when I altered them and one that will not move at all. It is a pity I did not find them before I refilled the system, now they will be replaced another day.

So far I have closed the lockshield valves on all radiators apart from the two in question, then opened them all by half a turn. After an hour or so for things to stabilize I checked the in/outlets (the hand test) and some got turned down a little further. This has improved matters - the new radiator gets reasonably hot without too much detriment to its brother.

The outlet pipe on the new one is much colder than the inlet, which would seem to indicate a low flow rate through that radiator. I will continue to adjust the other lockshield valves, as that certainly seems to be the way to go.

Thanks again.

 

[Agile]

You seem to learn quickly!

If standard boiler about 11 C diff and if condensing about 15-20 C diff.

Fairly easy to feel.

Not so easy to wait 15 min after every adjustment for the system to stabilise!

Tony Glazier

 

[HenryG]

Thanks for the compliment Tony. Amazing how a cold house and a cold wife accelerates the learning process! I have a long technical background, so understanding how it works and why is not too difficult - I have more trouble with the detail and knowing the best way to fix it.

My boiler is an oil-fired Worcester Danesmoor. I do not know the temperature drop across the boiler itself, but so long as things are producing the required result of warm radiators I am inclined to take the view that if it works, leave well enough alone. Is that a reasonable approach?

On a different issue, I mentioned before that my existing pipework is non-standard, so others may be interested in how I connect to it.

The pipe is labelled as Hunter Genova and the outside diameter is slightly larger than the modern equivalent so modern fittings will not fit. I contacted Hunter and was advised to grind down the pipe end with glasspaper or similar to reduce the wall thickness until a standard fitting will slip over. I have now done this successfully for 4 15mm joints and 4 22mm ones. It is a pain in the wotsit to do, especially in a confined space, but it seems to work. I have used the demountable plastic connectors that incorporate an O ring, preferably the grey ones with a screw down cap. I am wary of O ring connections and had misgivings over the seal that might be achieved if the grinding down process left any flats or grooves, but so far it has proved 100% OK. If in doubt I see no reason not to incorporate some sealing compound when assembling, but so far I have not needed it.

 

[Itwashim]

Hi HenryG

I read with interest you have Hunter Genova pipework. We have just moved into a property which has it too. There are a couple of leaks on a (heating) T connector 22mm to 15mm which is sandwiched between 2 more HG pipes (heating and cold water). Having read up about it's cement bonded connections, manufacture discontinued and it's brittle structure I have something of a thorn in my side.

General advise seems to be to rip it out, but having consulted several plumbers it seems nobody has even seen the stuff before, let alone ripped it out or repaired it and it's removal appears very complex and very distructive. They can't price the rip out which means it's cost is completely open ended starting at £2k. It's taken me a couple of months to get this far and it's like wading through treacle. It's making me reconsider a repair. But I fear for the strength of the existing and new joints.

How old is your original HG pipework? Has any of it failed? Where repaired/altered what preperation and fittings have you used? And how long ago? Did you try anything that didn't work/worked well I could learn from? To be honest I simply need to learn all that there is to learn so any help you or anyone else with experience of it could give will be very much appreciated.

Fingers crossed, thanks.
Rebecca

 

[HenryG]

Hi HenryG

I read with interest you have Hunter Genova pipework. We have just moved into a property which has it too. There are a couple of leaks on a (heating) T connector 22mm to 15mm which is sandwiched between 2 more HG pipes (heating and cold water). Having read up about it's cement bonded connections, manufacture discontinued and it's brittle structure I have something of a thorn in my side.

General advise seems to be to rip it out, but having consulted several plumbers it seems nobody has even seen the stuff before, let alone ripped it out or repaired it and it's removal appears very complex and very distructive. They can't price the rip out which means it's cost is completely open ended starting at £2k. It's taken me a couple of months to get this far and it's like wading through treacle. It's making me reconsider a repair. But I fear for the strength of the existing and new joints.

How old is your original HG pipework? Has any of it failed? Where repaired/altered what preperation and fittings have you used? And how long ago? Did you try anything that didn't work/worked well I could learn from? To be honest I simply need to learn all that there is to learn so any help you or anyone else with experience of it could give will be very much appreciated.

Fingers crossed, thanks.
Rebecca

Hi Rebecca,

You have the same problem as me with HG pipework! Mine was installed somewhere around 1980 I think. The whole house is plumbed with it.

So far I have rebuilt the kitchen, needing connection to both mains pressure cold supply and the hot water tap at 15mm and both supply and return for the central heating at 22mm, then further work on the heating with connections to 15mm. The kitchen was done in 2005 and the latest heating work just last year.

I contacted Hunter and was told to file down the outside of the pipe until a modern fitting will slip over. I then used a plastic compression type fitting which incorporates an O ring for the seal. You put the cap nut on the prepared pipe, then the O ring and then push the remaining part of the fitting onto the pipe and tighten the nut. Modern pipes fit into the other end of the fitting as designed. I do not recall the manufacturer of the fittings, but they are pretty standard and came from our local Plumbase or similar. I did not try the quick fit push on type of connector as these go on but will not come off again. Using the screw down type connector leaves the option of dismantling it to add sealant or similar if necessary -an option I have not needed so far.

A few comments. If you have a leak on a junction I think you will have to cut it out and replace it - a new T with short stubs of pipe to straight connectors joining to the three branches of the HG pipework. As a temporary fix you might try some self-amalgamating tape if it is a heating pipe with limited pressure. Stretch the tape to about twice its length and wind round in several turns pulling tight. It will fuse to a solid lump of rubber and may solve your problem, at least for a while. I have not tried this myself but have seen it recommended.

When connecting to the HG pipe, be careful to file the pipe down evenly to preserve the round profile and maintain even wall thickness. You need to do this over about 40-50mm until the cap nut of the new connector will slide on far enough to make the connection and the end of the HG pipe will slip into the end of the new connector. According to Hunter this has been tested to a pressure signficantly higher than any domestic application.

As for pipes being brittle, yes they are if pushed too far but I have not had a problem so far. I have even used bits of removed pipe for various other purposes and found it to be quite strong and useable even after being left out in the weather for a few years.

Hope this is useful - good luck!

HenryG