Restrictor?

Navy · 14 Aug 2006

Following on from a previous post, I would be grateful if someone could answer a question.
I have a Potterton Profile 80e running 12 rads and the problem is that when the hot water cylinder switches on the temp in the rads drops off to almost cold. At the same time the boiler starts to \\\'Gulp\\\' every 3 mins or so and air bubble rushes up the pipe and settles in the top rad. From a previous post I was told that the hot water from the boiler is returning too quickly via the hot water cylinder and I should place a restrictor on to the pipe entering the cylinder.
My question is can anyone tell me exactly what sort of restrictor I should buy and if it\\\'s o.k to place the restrictor on the pipe exiting the cylinder as there is no room on the the pipe entering the cylinder.....diverter valve is 1 inch away from cylinder.

p.s the rads all heat up perfectly when the hot water is off. the problem only starts when the hot water cylinder calls for heat.

Many thanks for your help.

croydoncorgi · 14 Aug 2006

Need more details of system. 2 zone valves? or 1 3-port valve? If it's a 3-port, the system is probably DESIGNED to do 'hot water preference' which means what it says: turn off CH while heating hot water!

But the symptom of air being drawn into the system suggests you might have a blocked cold-feed, or maybe just badly-designed pipework.

Navy · 15 Aug 2006

Thanks for the reply!

There is a 3 port valve next to the top pipe entering the hot water cylinder.

Every time someone opens a hot tap in winter the house drops in temp while the hot water heats up. I really thought that slowing down the amount of hot water from the boiler to the cylinder was the answer. If the system is designed to work this way then there must be a mid way compromise to enable the house to remain warm?It just could not live with turning the C.H off and On every couple of hours.

As far as I can tell, the air bubbling from the boiler only happens when the hot water cylinder is calling for heat. I thought that maybe the hot water was returning too quickly and some sort of overheat was taking place.

Thanks again for your reply.

fitz1 · 15 Aug 2006

put a gate valve on the return circ straight off cyl. where does your feed and expansion pipe connect to system.

chrishutt · 15 Aug 2006

Sounds like you've a lack of system water - check the feed tank.

Navy · 16 Aug 2006

Checked the valve today and read the following

Motorised valve details:

Honeywell 9238

Other numbers:

V4073A 1039

T50 Brass Ts88

Pump details:

Wilo -110 running speed 2, 2000rpm

Hope this helps
Thanks again

chrishutt · 16 Aug 2006

chrishutt said:
Sounds like you've a lack of system water - check the feed tank.

V4073 is the mid position valve, so should supply both HW and CH together. But have you done what I suggested above?

Navy · 16 Aug 2006

Checked the feed tank today and all seemed o.k apart from some surface scum, this being due to the Fernox inhibitor in the system I am told. Took off two rads and flushed them out and replaced them. The feed tank water level dropped and filled the rads fine. I can only guess that the feed tank is working o.k.

The boiler is situated on the ground floor and two floors directly above is the hot water cylinder and pump.

The sytem still works fine when switched to c.h only. Problem only starts when DHW kicks in.

Am I missing something???

Sorry to be a pain but I really want to get to the bottom of this.

Thanks again for all your help

fitz1 · 16 Aug 2006

whats the configuration of the feed and expansion and pump direction and position.

chrishutt · 16 Aug 2006

So fit a gatevalve in the flow or return to the cylinder coil, but not so that the vent from the boiler is interrupted. Then close the gatevalve and open very slightly. This should slow the flow to the cylinder and improve it to the CH.

Navy · 17 Aug 2006

I bought a Conex 22mm gate valve BS5154/B 9 Bar / 120c ( hope its the right part )

The configuration of the sytem is as follows -:

The pump is located in a cupboard and is connected from the boiler flow pipe 12 inches above the pump is the 3 way mid position diverter valve. Right off the valve is the hot water cylinder feed pipe. Return from the hot water cylinder heads into a Tee junction. 6 inches upwards from the Tee junction is a screw top air bleed. Down from the Tee junction heads towards the boiler ( Ground floor ) .
Left from the diverter valve heads off into the central heating flow pipe. Return from the central heating connects below the Tee Junction heading back down to the boiler.

Water supply connects into a Tee below the pump.

I'll probably need to double check the above if any issues arise.

Hope that makes some sense

Thanks again for everyones help

I'll fit the gate valve over the weekend and let you know how it goes.

fitz1 · 17 Aug 2006

is your cylinder a direct cylinder.

chrishutt · 17 Aug 2006

You can fit the gatevalve on either pipe connecting to the cylinder coil (flow or return), whichever is easier to access. I'm surprised that the vertical air vent connection comes off the lower, return pipe and not the upper, flow pipe - or are they the other way around?

Navy · 17 Aug 2006

Just checked it again and the vent pipe is on the return pipe to the boiler.
The screw air bleed is attached to 6" 15mm copper pipe which is soldered onto the 22mm copper pipe using a reducer.

Thinking about it, it seems to me that the whole sytem would not work if anything more than 6" of air collects in the pipe.

Should I extend the 6" pipe or not worry?

The cylinder is vented. Seems like a ordinary copper cylinder which has 22mm pipe coming off the top into a tee. Hot water goes off downwards and upwards heads off into the loft. It seems to vent at the top of the water tank ( larger ).

Thanks again

diynot

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Restrictor?

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