central heating pump problem

[richard gordon]

I am trying to discover whether I need to upgrade my central heating pump.
I had an existing heating system updated and re piped by a heating engineer but all did not go according to plan and he left the job having not fully completed the task, he suggested that one of the problems he couldn't fix which was the radiators not heating fully, was because of an undersized pump but seemed unable to recommend the correct size other that telling me it needed to be "larger", so trying to understand what size I require.
Currently have a Grundfos UPS 15-50 130 which heats everything up to radiator 'G' fairly quickly and to a good temperature but radiator 'H' and 'I' don't really ever get beyond luke warm.
He originally balanced the system and I have since made a few adjustments but probably not correctly and still doesn't really improve.
All the radiators are existing cast iron column type that have been flushed and all the pipework is new 22mm speedfit
The area in use is an 1st floor zone and there are plans to re pipe the ground floor at some stage and add it in as a second zone but only using the one zone for now.
Any thoughts would be appreciated.
Thanks

 

[oldbuffer]

I'd be surprised if a 15-50 couldn't supply 9 radiators, even if they are cast iron column type. I assume the boiler and pump are on the ground floor.

Try turning off radiators A to F and see if G to I then heat up fully. If they do, then it could be a balancing issue, or a weak pump.

Other than that I'd be looking at the pipework from G to I, particularly if G was originally on the hot water circuit, as bathroom radiators sometimes are.

 

[Steelmasons]

Has a replacement boiler been fitted?
If so which boiler and what does it replace?

 

[richard gordon]

Thanks Old Buffer, that does work so clearly it seems to be a balancing issue, will do a bit of incremental valve opening on the others until I get the right distribution as I'm not sure how else to do it.

Also thanks to Steelmasons for getting back on this. The boiler was new a couple of years ago, it was just re sited indoors from an outdoor boiler room. It's a Worcester Greenstar 40CDi so should be big enough for the job.
Might have some problems with the pump once the ground floor zone is re piped as that will add about another 80mts of 22mm pipe plus fifteen more radiators. I'm guessing that zone will have its own dedicated pump, just need to find a replacement heating engineer...

 

[Agile]

As said, the 15-50 should be well able to supply nine rads from a condensing boiler.

A 15-60 is a little more powerful and would be a better choice for a zone with 15 rads.

You mention 22 mm tube. From the boiler to the zone valves often 28 mm is better for most larger systems.

 

[Steelmasons]

As said, the 15-50 should be well able to supply nine rads from a condensing boiler..

That would be dependant upon index circuit resistance , taking into account the resistance through 40 CDI heat ex the 15/50 is quite possibly undersized by a large margin.

 

[ianmcd]

Stop confusing him , he will end up missing his bus !!!!

 

[DP]

Ian, you working night shift?
Or unable to sleep

 

[ianmcd]

Ian, you working night shift?
Or unable to sleep

DP I am on a caravan site doing CP12s and staying here, major renovations going on at the Pool and they are working around the clock, cant sleep for the noise, going home tomorrow will be glad to get a full nights sleep

 

[Dan Robinson]

No wonder you're unable to put up with Tony's claptrap then

 

[ianmcd]

yes Dan I have been a bit grumpy, first to admit it , he just ****es me off with his stupid quotes

 

[oldbuffer]

I'd be careful putting an additional pump on for another zone. The boiler supplies the power for the pump, even though its external. You'd need to be sure the boiler is capable of supplying enough power for two pumps. You might have to look at having a low loss header installed, with a pump per zone off the header.

In terms of balancing what you already have, order should be I, H, G, F, A, B, C, E, D. Probably won't be easy with a minimum output of around 10Kw so be prepared for several hours of fun!

 

[ianmcd]

Check the pipe orientation of the column rads, standard rads will accept the flow and return pipes either way round but column rads sometimes have a baffle fitted and the flow must go to a specific side

 

[DP]

Check the pipe orientation of the column rads, standard rads will accept the flow and return pipes either way round but column rads sometimes have a baffle fitted and the flow must go to a specific side

Exactly what I told a client couple of days ago

 

[richard gordon]

ianmcd,
I had a bit of a row with the engineer regarding the placement of the valves as he said it didn't matter.
My feeling is that the gate valve should be fitted on the flow side nearest the direction it is coming from, i.e nearest the pump, is that right or is there some other way of configuring?

Also oldbuffer, the system hasn't been set up for the second zone yet so have no idea how that will be done but presumably there would be just on pump for the whole system, is that right, only the way it's plumbed at the moment means that the existing zone would always be running but I guess ith will need a complete pe pipe at the boiler, is that right?
Still working on the balancing because as soon as I opened some of the other valves a little it seemed to stop H and I performing again, probably need a lighter touch.

Steelmasons mentions the pump being undersized and that it depends on the Index circuit resistance, sounds complex, how do I begin to work out something like that, especially if I'm going to add another zone, is it possible to use booster pumps on other zones?

Thanks to all for the help so far