New boiler to a single pipe system?

[outmyway]

Are their any implications to replacing my existing Kingfisher RS80 boiler with a condensing one, using my existing single pipe CH system?

The house has 3 floors - Each floor seems to have a seperate single pipe loop.
ie. If I turn off a rad on a any floor then all the rads on that floor go cold. Except the lower floor that seems to be on a 'twin pipe' layout.

The boiler currently has two zone valves, and I have thermostats on the upper two floors.

 

[Keston]

fit a low loss header?

 

[gas4you]

No problems.

I finished one about 2 weeks ago, new boiler, fully pumped controls, all on the VERY ancient one pipe system

 

[Agile]

There is a small problem and that is the flow temperature from a condensing boiler is going to be lower than the old boiler if its to be used efficiently.

On a one pipe that means the last rad in a single pipe loop will be even cooler than before.

Only you can judge how much of a problem that may be.

Tony

 

[gas4you]

Didn't get that on mine, all rads heated up the same and all very hot.

Flow set to 70c.

I must add though that most of the single piping appeared to be 3/4".

 

[outmyway]

Thanks for the replies.

My chap says I must have TRV's - but surley not on a single pipe?!

I'm thinking of replacing some rads to get a better amount of heat out in a few of the cooler rooms.

 

[mickyg]

Depends how its installed. In theory it should be achievable in reality its hit and miss. Each case is different and only a bit of investigation into piperouting and system design will make it clearer

 

[Keston]

As stated by Tony and my previous post, the only problem I see is your delta T being off the scale and the boiler not liking it, I know the kestons like a 12-20 degree DT so if your getting anything above that once you have set up your boiler then I would recommend a low loss header

 

[outmyway]

Whats a DT (delta T) ?
Difference between flo and return temps?

... so what is a low loss header?

 

[ianniann]

Yes, delta T is the difference between the temperature of the water leaving the boiler and the temperature of the water coming back to it. Older boilers didn't much care. Condensing boilers work best when the return temperature is low enough to condense the combustion gases and extract heat. This must be below 60C and preferably quite a bit below. If the return temperature is too high then you lose about 10% of your heat straight out the vent. I bet half the users of condensing boilers do this for much of the time anyway, but you don't have to join them You can run with appropriate return temperatures but the last radiator in line might be quite cool. Personally I find 60C is plenty warm enough for radiators anyway and if your single pipe system works now then I don't think you'll have major problems.

A low loss header is a system which creates a primary water flow circuit with one or more secondary circuits running through the radiators. You can have multiple heating zones run this way, or just one in your case. The primary circuit runs through the header and the secondary circuit then runs from and back to the header. I'm not entirely sure which of your potential issues this would solve but it could give you more control without adding a complete new set of pipes. Perhaps Keston could give more detail of the controls you'd want since I haven't used one of these.

P.S. On a simple boiler replacement you don't have to have TRVs fitted. That's a little known fact that was discussed here (or somewhere) recently. You have to have them, or some other means of independently controlling at least two heating zones, with a new central heating system. TRVs can be used on a single pipe system but it isn't recommended and can lead to problems.

 

[mickyg]

ianniann- i think what your failing to see is the main issue, which is that if the delta T goes over 20 or beyond, many modern boilers will see this as a fault condition in the flow and go to a fault condition. That is why Keston suggested the header, as you could spec it to achieve to perfect flow rate and delta T for that particular boiler and this would then allow you to connect your existing system which may have 30C delta T which would otherwise cause the boiler to fail.
Its not just about getting the return temp low, but it should be in relation to the flow temp. Ideally 15-20C .

 

[Keston]

ianniann- i think what your failing to see is the main issue, which is that if the delta T goes over 20 or beyond, many modern boilers will see this as a fault condition in the flow and go to a fault condition. That is why Keston suggested the header, as you could spec it to achieve to perfect flow rate and delta T for that particular boiler and this would then allow you to connect your existing system which may have 30C delta T which would otherwise cause the boiler to fail.
Its not just about getting the return temp low, but it should be in relation to the flow temp. Ideally 15-20C .

spot on!!

 

[heatingeng]

i have fitted many boilers into 1 pipe systems and i have never had any problems at all.
it is advised to update to 2 pipe but as long as you give the best advice to the customer then there is normally no problems ..

 

[Keston]

i have fitted many boilers into 1 pipe systems and i have never had any problems at all.
it is advised to update to 2 pipe but as long as you give the best advice to the customer then there is normally no problems ..

Bet you havn't fitted a Keston to one then lol

 

[heatingeng]

i have fitted many boilers into 1 pipe systems and i have never had any problems at all.
it is advised to update to 2 pipe but as long as you give the best advice to the customer then there is normally no problems ..

Bet you havn't fitted a Keston to one then lol

i wouldnt fit a keston boiler at all ..but i have fitted WB, Baxi, glowworm..
i fitted one a few weeks back and it had about 15 rads all piped in 15mm pipe ..i told the customer it needed repiping but they wouldnt listen ...worked fine with new boiler