Cutting Barrel Steel Pipework For new cylinder

[JackK]

Do you mean the cylinder primary return is at 50°C? That's what I would have assumed, but then you refer to the shower, which is obviously on the secondary. You wouldn't want the 2ndary to be anywhere near 80°C, if that's what you mean.
Does it behave different from the old cylinder?

Have you tried throttling the rad pipe, at any valve as it's a 1-pipe system? To force the water through the coil. As somebody said, an air vent (manual) in the horizontal pipe would have been a good idea, but pushing all the water through the coil should push the air round the system and out via the vent (can't remember where that is).

Thanks - I mean the water when you open the hot tap is only lukewarm and certainly not red hot - I normally mix hot and cold water to get a good temp whereas now I only use the hot water tap.

There is no way to throttle the radiators as there is one big flow pipe which then tees off for the hot water cylinder and then continues for the rads. Previously all the boiler flow water would go to the cylinder - Now it seems that the radiators are taking it as if the flow pipe is not getting round the cylinder

Is it an idea to adjust the pump speed? Here is the pump at the boiler - Is this set to max or min

 

[roguetrader]

Think you're missing the point made previously. Air will collect in that loop up and over the MV. Cut in a manual vent.

 

[jeff the gasman]

I am a DIY man trying to do it myself because of funds and because I enjoy it - If there was air in the system would that not get pushed all the way up the one pipe flow and therefore the air vent needed in the loft rather than the hot water cylinder? Please educate me so I do not make a mistake

Right mate. That vertical rise from the motorised valve and then down to the cylinder flow will be clogged with air apart from what is displaced by the system head pressure.
Fitting a manually operated vent will eliminate this but I would recommend an automatic air vent personally?
This will get rid of the trapped air and ensure it stays free of air.
Let us know how you get on!

 

[JackK]

I still dont get it - This is a low pressure vented boiler / hot water system setup

Wouldnt any air flow round and escape from the fande tank?

Why put the air vent at the point in the picture rather than elsewhere (if its needed)

 

[JackK]

Right mate. That vertical rise from the motorised valve and then down to the cylinder flow will be clogged with air apart from what is displaced by the system head pressure.
Fitting a manually operated vent will eliminate this but I would recommend an automatic air vent personally?
This will get rid of the trapped air and ensure it stays free of air.
Let us know how you get on!

Thank you - If you can help with one small thing

I cannot find a 22mm compression bottle vent on screwfix / toolstation which can be inserted in the middle of the pipe - Any links for something suitable please? Cheers

 

[fixitflav]

I mean the water when you open the hot tap is only lukewarm and certainly not red hot - I normally mix hot and cold water to get a good temp whereas now I only use the hot water tap.

Was it different with the old cylinder?

There is no way to throttle the radiators as there is one big flow pipe

OK, I was thinking (wrongly of course) that it went through all the rads in series. Sounds like a good time to put a motorised valve in the pipe and use it as S-plan.

Is it an idea to adjust the pump speed?

Increasing speed would give a better chance of getting flow through the coil.

Here is the pump at the boiler - Is this set to max or min

Can't tell, the adjuster is out of shot. But it should be marked for speeds 1, 2 and 3.

 

[JackK]

1) On the old cylinder the cylidner would swallow all the flow before the rads got heated up

2) I would like to add a splan - The problem is all the pipework is barrell steel and hard to cut out to put another two port valve on - Plus I would need to bypass the circut when the heating is satisfied if I did this which is not trivial

3) actually was thinking of reducing speed so it had time to get round the coil rather then flow up quickly into the hot water and then the rads

4) The pump pic is clear - I can post another another

 

[denso13]

The pump pic is clear

Yes, but the speed adjuster isn't. It's on the right hand side.

 

[JackK]

Isnt it the dial at the front of the pump with an arrow on it that controle the pump speed?

 

[jeff the gasman]

I’d stick to your day job mate,x
22x 15 centre tee on top of the cylinder flow with 15mm automatic air vent!
Vent it S l o w l y if you go manual. It’ll work a treat

 

[jeff the gasman]

Isnt it the dial at the front of the pump with an arrow on it that controle the pump speed?

No, that’s a venting port!

 

[roguetrader]

Isnt it the dial at the front of the pump with an arrow on it that controle the pump speed?

That's a vent plug.

 

[jeff the gasman]

I still dont get it - This is a low pressure vented boiler / hot water system setup

Wouldnt any air flow round and escape from the fande tank?

Why put the air vent at the point in the picture rather than elsewhere (if its needed)

Air is lighter than water so rises to the top!
Look at your photo and determine the top of your flow pipe.
Let the air out and it’ll work!

 

[JackK]

I’d stick to your day job mate,x
22x 15 centre tee on top of the cylinder flow with 15mm automatic air vent!
Vent it S l o w l y if you go manual. It’ll work a treat

Thanks - I can see what you mean - A 22mm tee soldered with a vent on top

I will put that in as soon as I can

 

[fixitflav]

I would like to add a splan - The problem is all the pipework is barrell steel and hard to cut out to put another two port valve on - Plus I would need to bypass the circut when the heating is satisfied if I did this which is not trivial

On S-plan each valve actuator has a microswitch which closes when the valve is fully open, and fires the boiler. This ensures at least one valve is open when the boiler fires, so unlikely to need a bypass. You can check there's a microswitch on your existing HW valve.