Single Pipe Central Heating New radiators

[andyjh31]

I just visited my mother and step father who have just had two new radiators fitted and some others replaced for newer style convecting type. The plumber in his own admittance after the first day of installation had never worked on a single pipe system before ! ( Alarm Bells !! ) and obviously was not AT ALL clued up on how to connect to it. Firstly the run for the new rads downstairs required a feed to come from the upstairs radiators ( so they said ) which I know is'nt ideal. They had fed two 15mm pipe's down from the front and back rooms thinking it was just a standard 2 pipe system and quickly realising after trying to re-commission the system it would not work. They have now fitted a 22mm pipe from a 22mm pipe coming from the floor to upstairs and fed it along to the new rads, putting tees by each trv and lsv. They then connected the end of these new rads to one of the 15mm pipes going back upstairs. The system worked with him leaving saying " leave it all on so to get all the air out etc !" The heating soon started to shut down with radiators going cold. He was then suggested by another EXPERT plumber to end the new radiator run at the last new rad by capping off the 15mm link back into the loop. As you guessed that did not work. This just created a branch off the loop which went nowhere. If someone could confirm if I have the following right please ?

1. I guess they have fitted standard TRV's which are a no no for single pipe systems ?

2. Will the 15mm pipe be ok for the return off the new radiators ? ( if i reconnect their mod )

3. Are there large bore lsv's available ?

It makes me angry that even after recommendation that some tradesman think a little bit of knowledge means they know what they are doing in jobs that aren't textbook jobs! In my job, if I dont now how to do something, you dont do it or have a backup plan to keep the customer happy !

 

[doitall]

A drawing showing the pipework would be great for a start.

 

[Agile]

Any somewhat experienced people would know what they are and how to deal with them.

I doubt that they are taught on plumbing courses for domestic work.

There are fairly rare so an apprentice just installing new heating systems would also be unlikely to encounter one.

Because they are pretty rare I can understand that many could overlook knowing what the system is when quickly visiting to quote for a simple sounding job.

Anyone who is reasonably experienced knows what clues can be found and when to look more carefully.

Tony

 

[andyjh31]

Sorry Agile. I think I was venting frustration from my step father ! Not constructive at all i know !
Wont be back to look till next weekend and then will try and draw a schematic of the existing circuits. Can either of you chaps answer the other points in the mean time ? If yes in your experience can you recommend any particular product range or suppliers maybe ?

Many Thanks for your prompt replies

 

[doitall]

TRVs should be the special ones although the normal ones do work sometimes, if your lucky.

point 2, yes 15mm will work provided it isn't overloaded.

most lockshield valve are full bore as far as I know.

I think before you worry about the above, lets see what sort of mess the plumbers made and how it can be sorted.

 

[stem]

One pipe systems work at their best if the following simple guidelines are followed:

1. The single pipe ideally should be in the form of one continuous loop, without branching off into other sub loops. It is practically impossible to balance the flow equally through more than one loop, as most of the water will take the way of least resistance. The single loop can rise and fall to cover more than one floor level.

2. Where possible the pipe should be located directly below the radiators so that they sit atop of it rather than being off to the side. A short distance of a foot or two won't cause a problem if the pipes incline towards the radiator, but extended 'side' runs should be avoided.

If you need to extend the loop, it can be broken into and extended as shown below. (I did this drawing for another post which had previously been a gravity system without a circulator pump, hence the reference to 22mm. Where a pump is used 15mm is OK for most domestic properties) Notice by removing a section of pipe, the extension forms part of the main loop.

Untitled

• stem
• 22 Feb 2010
• 2

I have a 15mm one pipe system in a large 3 bed 1960's detached house with 9 radiators. (& standard TRV's) It works perfectly well and all of the radiators get hot. I intended to convert it to a two pipe when I purchased the property 15 years ago, but it works so well, I've never bothered.