New boiler on old single pipe system

[echase]

I help maintain a village hall which needs a new boiler. It was built 30-40 years ago with a single pipe system with one loop feeding all rads. There are about 6 large rads in several rooms all on one floor. The main iron pipe is about 3” diameter and mainly mounted exposed at skirting board height.

If the floor mounted old boiler is replaced by a new wall hung condensing boiler of around 40kW is it legal/practicable to retain the single pipe system?

What kind of further life would be expected from these pipes as no problems/leaks are evident apart from one rad being cold, but may be just because it is full of air and can’t be bled due to seized bleed screw.

In the toilets the 3” pipes run through them to provide some heat but it is inadequate so we may add 2 small rads for this. Also there are 2 small rooms needing rads but need to divert the loop a bit for that. Would the need to do these extra rads change the above decision on whether to retain the single pipe system..

Rather fearful of the work involved in ripping out the pipe and replacing with say two 22m ones. Fortunately aesthetics is not a big issue but we do need to consider that a fairly elderly clientele use the hall and so may need to consider protecting the hotter pipes and rads against contact by them. Do skirting board levels pipes have to be protected like this as difficult to see how a person can easily touch one with bare skin unless stand against wall with no socks/trousers on.

 

[JayPage]

If your thinking of keeping the old system due to a budget that's fair enough, if not it would be better in the long run to rip it out and start again. A newer system would be far more efficient and for your additional rads to be installed with your old system would mean cutting the 3" and diverting it to the we location of the rads (running 2 seperate feeds from the 3" can be problematic as you can have issues with flow rates). Single pipe system trv's are also more expensive than standard ones. As for the radiaor temperatures, lst rads (low surface temp) can be installed, solving this problem.

 

[dcawkwell]

Rip it out. If the radiators are that old it needs a complete new system.
The new radiators will work better and be much smaller for the same heat output.

 

[RickMoore]

Rip it out. If the radiators are that old it needs a complete new system.
The new radiators will work better and be much smaller for the same heat output.

What, no Glowworm Ultracom ?

 

[Agile]

I dont see any need to change anything!

But do fit weather comp as that will enable the boiler to run more efficiently.

The boiler will be slightly less efficient when the full flow temp is needed in the coldest weather but thats only for 2-3 weeks in the year, the rest of the time the weather comp will reduce the flow temperature and the boiler will be more efficient.

A seperate parallel loop can be fitted for the rooms with no current heating.

Tony

 

[dcawkwell]

Rip it out. If the radiators are that old it needs a complete new system.
The new radiators will work better and be much smaller for the same heat output.

What, no Glowworm Ultracom ?

Well now you come to mention it not a bad idea.

 

[Dan Robinson]

I dont see any need to change anything!

But do fit weather comp as that will enable the boiler to run more efficiently.

The boiler will be slightly less efficient when the full flow temp is needed in the coldest weather but thats only for 2-3 weeks in the year, the rest of the time the weather comp will reduce the flow temperature and the boiler will be more efficient.

A seperate parallel loop can be fitted for the rooms with no current heating.

Tony

Would weather comp work well on a one-pipe system. Would of thought the lower flow temps would reduce the circulation up and though the rads?

 

[Agile]

The rad flow rate is primarily dependent on pump pressure. That is largely independent of the temp.

The viscosity of water does appear to reduce slightly as temperature rises but I don't think that will be significant.

Tony

 

[RickMoore]

On a two pipe I would agree Tony, but a one pipe relies alot on convection to create flow through the rads, the pump pressure keeping water flowing through the pipe does it not ?

Besides on every one pipe ive worked on, reducing flow temp by much would mean radiators later in the loop wouldn't get warm enough to heat the room.

while im not 100% the more I think about it the more I'm sure WC on a one pipe wouldn't work. Please do correct me though if im wrong.

 

[ALEC1]

special injector tees are probably installed as it was installed at a time when the public wanted higher standards...

weather comp with single pipe systems does work...its pretty common in europe..

As ever the application of weather comp is dependent on usage of the hall...if it is for a couple of hours a week then simple on-off will be fine..if how ever the hall is used more frequently then weather compensation is worthwhile..

 

[simond]

Keep the one pipe system, if it worked OK before it will work fine with a new boiler. If it is a simple 40kw system then a Worcester 40CDi conventional is arguably the most reliable out there.

Only problem with 1 pipe is that modern powerflushing doesnt work, so get a dirt filter fitted.

The Worcester system filter is a brilliant contraption, filtering out both ferrous and non ferrous particles. Sadly, it is awkward to install neatly, and fabulously un-customer friendly to open and clean. It is made for Worcester by Adey Magnaclean but the design is Bosch's own.

But get a Wocester accredited installer to fit the boiler, and wrestle with emptying the filter every service - and you will get an 8 year warranty gratis. The Worcester 40Cdi doesnt support weather comp.

 

[Agile]

Besides on every one pipe ive worked on, reducing flow temp by much would mean radiators later in the loop wouldn't get warm enough to heat the room.

while im not 100% the more I think about it the more I'm sure WC on a one pipe wouldn't work. Please do correct me though if im wrong.

This is NOT the domestic system with all the rads in series!

Its an industrial type system where a large 3" single pipe is kept hot by the boiler and convection into each rad lets it heat up.

On that kind of system ( designed without condensing boilers in mind ) the boiler just circulates water at 82 C/ 76 C and the rads take whats needed.

It will work fine with a condensing boiler.

The only slight problem is the boiler will be less efficient when its so cold the flow temp has to be at 80C.

At lower flow rates the boiler will be its normal efficiency. The difference is small anyway usually a maximum of 12% better.

BUT with weather compensation the flow temp will be automatically adjusted to the lowest commensurate with giving enough heat into the property. Hence the need for W/C to be fitted!

Tony

 

[Dan Robinson]

Keep the one pipe system, if it worked OK before it will work fine with a new boiler. If it is a simple 40kw system then a Worcester 40CDi conventional is arguably the most reliable out there.

.

VERY arguably

Would think the Intergas much better suited to this system.

 

[Agile]

I cannot see any arguments against using a new boiler on this one pipe. Several against a Worcester though.

These systems are what are normally used in schools, libraries, hospitals etc.

I don't see a Worcester boiler as being a very good choice as in my ( limited ) experience they tend to have very few user/engineer settings. Very annoyingly many don't even have a hot water temperature knob!

The Intergas do have many settable parameters and because they don't rely heavily on flow and return temperatures like the Vaillants would seem to be an excellent choice for a replacement boiler.

Tony

 

[RickMoore]

This is NOT the domestic system with all the rads in series!

Its an industrial type system where a large 3" single pipe is kept hot by the boiler and convection into each rad lets it heat up.

On that kind of system ( designed without condensing boilers in mind ) the boiler just circulates water at 82 C/ 76 C and the rads take whats needed.

It will work fine with a condensing boiler.

The only slight problem is the boiler will be less efficient when its so cold the flow temp has to be at 80C.

At lower flow rates the boiler will be its normal efficiency. The difference is small anyway usually a maximum of 12% better.

BUT with weather compensation the flow temp will be automatically adjusted to the lowest commensurate with giving enough heat into the property. Hence the need for W/C to be fitted!

Tony

I realise that Tony, and there's many one pipe domestics piped in the same way on a smaller scale. But surely lower flow temps from W/C would create problems from the later rads not heating up properly . Flow temp at the last rad will always be way below the flow temp at the first.

Yes a condensing boiler will work fine, and I completely agree with your recommendation of either a intergas or vaillant. The Worcester s have far too many plastic bits for my liking, and a vaillant is certainly alot easier to service than Worcester