Sealed system boiler primary flow and return size

[Andygasman2010]

That pre-plumber pump which you refer to as a boost pump is designed to run the whole system and not just the cylinder (sorry if you know this already, maybe i'm not getting you) I think the problem will be something to do with having two pumps. I've never seen a system with two pumps in series at different points in the system, without a low-loss header. Hmm i'm not sure what the consequences of that would be. Maybe i'm way off the mark, maybe Tony could clarify this???

From the distances you describe I would say the flow pipe from the boiler should be in 28mm and go straight into each of the zone valves, and not via another pump (return 28mm too)

It sounds to me like the system has been poorly spec'd in the first place. Any plumber worth his salt would never have fitted a pre-plumbed cylinder with a system boiler.

Some photos would be handy if you can get some?

 

[Agile]

Thats a good length but again its the temp differentials which need to be measured.

You spoke about only the three CH circuits and I assumed the HW was off and its own pump was not working. I dont see why it needs its own pump in your kind of arrangement.

Again I dont know what your UFH circuit is doing. Its normal to have its own circulating pump and a blending valve which just tops up a little hot water from the CH circuit.

Without some temperature measurements I dont see that I can offer much more help.

Tony

 

[eltricky]

Sorry guys, im not explaining this too well.

The 22mm primary flow from the boiler feeds the pre-plumbed pump on the tank. The output from this is in 22mm and split 4 ways to feed the four valves still in 22mm. The tank pump runs when any of the 2 port valves are opened

Valve 4 when opened feeds the UHF manifold which has its own blend pump that only runs when the UHF 2port (valve 4)is opened.

I will get some pics sorted this week.

 

[eltricky]

BTW. I should mention that the reason for the 4 x 2 ports is that the client wanted independant control over the 3 heating circuits and 1 hot water circuit

 

[Agile]

Without total clarification of the exact arrrangement I am now beginning to visualise a system boiler whose flow output is now fed into the INLET of a pump on the cylinder ( which was intended as the only pump on a system with a heat only boiler ).

If the two pumps are in series immediately together then that should work and should compensate for possibly marginally undersize pipe work.

It will provide an excessive pump pressure and will make balancing more difficult still.

Can you tell me in detail how you have balanced the components in each CH circuit and the HW circuit?

When are you going to give me some temperatures?

Tony

 

[eltricky]

Thats it. The two pumps are in series although they are 15 to 20M apart.

I balanced the system as follows:- with the boiler on about 65 degrees I set up the UHF manifold.

Then with th boiler output at about 80 degrees opened both 2 ports for the radiators so that all three heating circuits were active. The lockshields had already some rough setting to allow for pipe runs.

Although not very scientific I felt the rads to monitor the heat up temperatures and made fine adjustments as I went. Also checking the UFH temp' was from 40 to 45 C

What ever I did I couldnt get max temp at all the rads simultaneously.

At this point I did not bother with the tank based on if I cant get the rads hot then opening the tank valve will only make the heating worse.

I should say that pre start up the temp on the stats was 18 C. So in the winter when outside could be 20 to 25 C cooler I cant see how the system can stand up.

 

[eltricky]

Will be getting temps and pics later this week

Thanks everyone for your help and comments

 

[Agile]

Presumably the rads are piped in 15 mm and not microbore?

There is no reason why properly connected rads should not have the nboiler's flow temperature at the flow connection. Its only the return which varies as they are balanced.

Tony

 

[eltricky]

The rads are fed with 22mm from the 2 ports and T off in 15mm to the rad valves