Single Pipe System Radiators

[Livvid]

Hi all,

I have been asked to rerplace some radiators in a old house which has a single pipe radiator system in place.

The Client has purchased his nice shiny radiators and Honeywell TRVs and new lock shields.
Questions
The old radiators are top fed and low return, can the new radiators be bottom fed at each end???!!!!
Is it okay to put the TRV's on as I know these systems are not that efficient as in as the water passes each radiator, it will cool down, will it cause problems in the run by introducing at least 5 TRV's?
What do you charge to replace each radiator, just ball park please, bearing in mind Just rads and TRvs supplied, some pipework will have to be altered for some of the rads so draining down will have to occur.

Thank you in advance.

 

[MickBrown]

From my experience it is best to pipe flow to top of rad and return to bottom. If you connect both to bottom the radiators often do not heat right to top. You cannot fit normal TRVs, not sure which you have to use, probably a remote thermostat. In a normal 2 pipe system each rad has it's own supply, so when the TRV shuts down the rad the pipe cools and eventually the TRV opens again. In a one pipe system the pipe stays hot as it is the primary flow to all radiators, so the TRV closes and shuts down the rad. The flow continues around the circuit through the bypass and so the flow pipe stays hot and the TRV does not open again.
With draining down, refilling and some pipework changes I would suggest it would take most of a day to change 5 rads, so a reasonable figure would be a day rate whatever yours is.

 

[tamz]

You really need to use Trvs suitable for one pipe systems. ie low resistance valves like Danfoss RA-G or Belmont VBG.
You will most likely have problems using std valves.

 

[ecowarm]

I have come across single pipe systems where the pipe goes through the rads and not bypassing so if you turn off one rad it stops all rads after that point

 

[Blackcatgas]

Despite me telling a customer that you couldnt polish a turd ,at his insistance I fitted 7 new rads to a 8 rad one pipe system, I used standard TRVs, the system worked worse than before,no matter how hard I tried to balance it or what speed the pump was on I could only get 4 rads hot at a time.We then went with my original suggestion and I ended up 2 piping it in speed fit to keep time and costs down, it worked really well then, i dont do work for people like that anymore.

 

[Livvid]

So really I should advise the customer to buy TRV's Especially for the job, I know the customer doesnt want the floorboards up and a two pipe system in place.
So can I bottom feed??? Is it best to advise the customer that they may not heat up correctly am I walking into a world of pain if I fit TRvs to this system????

 

[fuzzy]

buy manual valves and feed it TBOE if possible, maybe even use swept tees, ive had to do that in the past

 

[Blackcatgas]

My customer didnt want his floor boards up etc, he was a miser.Bottom feeding (lol) the system wont make it that much worse although continental piping, flow top, return bottom does work better than bottom feeding, fire up the system leave it on for an hour, see how poor it is, then when you put in the new rads the customer cant say "it worked fine before you touched it",

 

[fuzzy]

continental system? why do you call it that? single pipe has always been TBOE, commercial systems are peiped up like that when 2 pipes

 

[Billy Bob Bob]

advise your customer properly put the one pipe system in the bin as its **** and convert him to 2 pipe,very good advice off BCG you could catch a cold here

 

[Blackcatgas]

continental system? why do you call it that? single pipe has always been TBOE, commercial systems are peiped up like that when 2 pipes

Its how they do it on the continent, ive heard it called that a few times, the heating systems a are more luxurious abroad, next time your at the ambassodors recption in Vienna or Berlin or somewhere like that and theres some germanic looking woman with 80s hair giving you some ferrero roche, stop and look at how the radiators are piped.

 

[tamz]

The reason std trv's don't work well on one pipe systems is there is too much resistance through the valve. Have a look inside one and see.
One pipe systems heat by gravity (feeding off the pumped circuit).
The pump speed does little to influence this as the pressure at both sides of the radiator are near equal.
The use of swept tees does influence it as the pump can then give a bit of a push to start it.
Piping them TBOE helps with the gravity circulation.
TBOE will also make fitting the rads easier if they are slightly different sizes as you have plenty space for an offset (just keep them all the same if you can)

So the resistance through the valves needs to be low. Hence the use of wheelheads or low resistance trvs.

Btw the valves which are suitable are not the best looking things you will use. They are designed mainly for commercial use.

 

[Blackcatgas]

That makes sense with the pump speed cheers for that.

 

[tamz]

That makes sense with the pump speed cheers for that.

The swept tee's make a difference because it changes the pressure.
It gets a slight push on the "flow" side and a slight pull on the "return" side because of the sweep.

 

[fuzzy]

Its how they do it on the continent, ive heard it called that a few times, the heating systems a are more luxurious abroad, next time your at the ambassodors recption in Vienna or Berlin or somewhere like that and theres some germanic looking woman with 80s hair giving you some ferrero roche, stop and look at how the radiators are piped.

lol, ill keep it in mind

 

[fuzzy]

id put swept tees on the flow only, not sure it helps as much on the return