Correct Boiler Plumbing?

[ElectricEe]

Some background about my system…

Boiler: Glow Worm Ultimate 50BF
System: Twin Pumped, one pump near boiler that circulates the CH and another pump near the cylinder that circulates the feed to the cylinder’s coil.
Controller: Honeywell ST699 controller

I’ve been in my new house for about a year and have had slow reheat times for my hot water cylinder since the beginning – from cold to about 45 degC takes about 2h40m, which I think you’ll agree is crazy.

In my mind there could be two possible causes

1) Poor flow in the pipes to and from the cylinder’s coil
2) Calcification on the outside of the cylinder’s coil

Well that’s the background. Whilst investigating the problem I noticed that the plumbing of the boiler was a bit strange and this is what I’m after some advice on.

In Diagram 3.3, page 9 of the installation and service manual …

http://www.glow-worm.co.uk/products/pdf/discontinued/boilers/Ultimate50BF_UIS.pdf

… you can see the way that my boiler should be plumbed, although it’s not a gravity system but pumped to the cylinder. The way that it has been installed completely baffles me; the left pipes, GF and PR, are connected to the central heating and the right pipes, PF and GR, are connected to the cylinder coil (by 15mm pipe).

Here are a few pictures to help explain…

http://photos.homeinbath.co.uk/main.php?g2_itemId=7691
http://photos.homeinbath.co.uk/main.php?g2_itemId=7683
http://photos.homeinbath.co.uk/main.php?g2_itemId=7687
I got a bit techie on this one...
http://photos.homeinbath.co.uk/main.php?g2_itemId=7702
Edit:
System Diagram: http://photos.homeinbath.co.uk/main.php?g2_itemId=7709

My question is this: Is this a reasonable way to plumb the system or was the installer, as I think they were, completely mad because the flow is not going across the boiler’s heat exchanger and is therefore not running efficiently?

On another note: my boiler is cycling with a frequency of about 3 minutes on and 3-6 minutes off when heating just the hot water cylinder. This is clearly a problem but is it caused by the plumbing?

Any help will be really appreciated

Mark

 

[kevplumb]

this is a wind up right

whats the hose on the drain cock for

 

[kevindgas]

PF - pumped feed
PR - pumped return
GF - gravity feed
GR - gravity return

yes they are meant to be opposite to each other, PF/PR are the heating pipes but are also used for the water circuit in a fully pumped S or Y plan

GF/GR can be not used, gravity or pumped (like your describing) are you sure the water is going the right way in each circuit? is there a zone valve in the water crcuit? as there should be, controlled by the cylinder stat it should activate the pump and the boiler

 

[ElectricEe]

this is a wind up right

Erm, no it's not a wind up. I take it from your response that you agree that it's been installed totally incorrectly!

 

[kevplumb]

you could put it that way

 

[bengasman]

On another note: my boiler is cycling with a frequency of about 3 minutes on and 3-6 minutes off when heating just the hot water cylinder.

That would give a " boiler on"status of between 20 and 40 minutes per hour; that is enough to warm up the cylinder.
Your data must be wrong.

 

[kevindgas]

On another note: my boiler is cycling with a frequency of about 3 minutes on and 3-6 minutes off when heating just the hot water cylinder.

That would give a " boiler on"status of between 20 and 40 minutes per hour; that is enough to warm up the cylinder.
Your data must be wrong.

not if its plumbed up in reverse on one circuit as heat will go in the wrong direction especially if no non return valves are fitted.

 

[ElectricEe]

GF/GR can be not used, gravity or pumped (like your describing) are you sure the water is going the right way in each circuit?

I'm positive that the central heating is pumped into the left hand pipes, GF and PR and that the hot water cylinder feed is pumped into the right hand pipes, PF and GR.

is there a zone valve in the water crcuit? as there should be, controlled by the cylinder stat it should activate the pump and the boiler

There are no zone valves in the system. The cylinder pump is controlled by a cylinder stat. I've yet to prove it but I think the boiler still fires when the cylinder is hot and only cuts out when the temperature inside the boiler is too high. But as I said I've yet to prove this.

 

[kevindgas]

I'm positive that the central heating is pumped into the left hand pipes, GF and PR and that the hot water cylinder feed is pumped into the right hand pipes, PF and GR.

There are no zone valves in the system. The cylinder pump is controlled by a cylinder stat. I've yet to prove it but I think the boiler still fires when the cylinder is hot and only cuts out when the temperature inside the boiler is too high. But as I said I've yet to prove this.

so theres your answer!! plumbed up incorrectly

 

[bengasman]

On another note: my boiler is cycling with a frequency of about 3 minutes on and 3-6 minutes off when heating just the hot water cylinder.

That would give a " boiler on"status of between 20 and 40 minutes per hour; that is enough to warm up the cylinder.
Your data must be wrong.

not if its plumbed up in reverse on one circuit as heat will go in the wrong direction especially if no non return valves are fitted.

Guess I have to change my way of thinking from: "what is the fault?" to: "how many ways have they found to completely eff this up?"

 

[Agile]

I take it that you have TWO pumps?

Oddly, these boilers are surprisingly tolerant of wrong connections! I went to one to help the Pleasing Plumber and it had been connected with reversed flow since it was fitted about 18 years before!

Its not ideal but they still work.

Even if you change it over you will probably find it makes little difference!

You need to measure the flow and return temperatures on the cylinder coil connections. Even a hand assessment would help.

You are in the same town as DIA who posts on here!

Tony

 

[ElectricEe]

You need to measure the flow and return temperatures on the cylinder coil connections. Even a hand assessment would help.

This link has all the temperature information...
http://photos.homeinbath.co.uk/main.php?g2_itemId=7702&g2_imageViewsIndex=1
But to put it in words, the flow and return temperatures differ by about 10 degC with the flow ranging from 45 degC to 60 degC depending on cylinder temperature. I did think that cylinder coil flow should be around 80 degC though. I don't know exactly how hot it gets at the boiler end but by touch it's about the same as the cylinder end.

 

[Agile]

You have not advised how many pumps you have. Is it two?

The very good temperature information shows the heat source turning off BEFORE it reaches the set temperature and then going into an anticycling delay, probably as a result of thermostat differential.

I would conclude from a rather limited understanding of your system that the boiler connections are causing the boiler stat to turn off prematurely.

An old boiler like that was designed to give an operational flow rate of about 82° but that relies on a cylinder stat to limit the temperature there to about 55°C.

Tony

 

[kevindgas]

You have not advised how many pumps you have. Is it two?

Tony

tony either read the post properly or go back to sleep "twin pumped" is in the first post!!

 

[knuckles]

I'll bet that when the DHW pump is running, it's taking cold water from the return of the central heating. Does the situation improve when the heating is on and all rads hot? You need check valves.