System Venting

[wildobc]

Have recently installed a new multi fuel stove with back boiler to heat radiators only - totally a ground floor system. Have used an expansion tank with cold feed and also a 22mm vent pipe to the top of the expansion tank. Have used a pipe stat to kick in the pump and have currently set this at 60deg. The problem is that when the pump kicks in, water immediately vents to the expansion tank (it's clearly not boiling) However, when I close the cold feed valve, the venting stops. Other than that, the system has worked perfectly for 3 days, solving the problem of a very cold kitchen. I have kept a close eye on the venting but if the cold feed is open, the system vents every time the pump kicks in. The bottom of the expansion tank is 1.7m from the 28mm flow with the vent pipe 2m from the flow. Pump flow rate is set at I

 

[WHPES]

F&E connections on circuit probably incorrect. Check.

 

[wildobc]

F&E connections on circuit probably incorrect. Check.

Many thanks for taking the time to reply. How would they be incorrect please as I have the 15mm cold feed going directly to the 28mm return pipe and the 22mm vent pipe going off from the 28mm flow pipe. I did follow a diagram.

 

[Best]

You haven't said where the pump is & how high the vent goes above the expansion tank, etc. Needed more details.
Have you fitted 2 of 28mm pipes to a hot cylinder that work by gravity, & 2 other pipes that do the rads using a pump?
You should have a feed pipe of no less than 22mm & you shouldn't have fitted an isolating valve on it as it is a safety pipe same as vent. Besides, what would you ever need a valve on the feed pipe for??? Just needs an isolating valve on the mains supply pipe to the expansion tanks ball valve!

 

[AWheating]

great post from best.

what part of the uk are you from? in england building regulations require you to control the temp of the hot water, what control of the hot water temp do you have? if fitted is the zone valve normally open?

 

[wildobc]

Thanks for taking the time to reply and for your considered comments. My responses are: The pump is on the 28mm flow side and the outlet is only 1m away from the expansion pipe 22mm vent ( perhaps I should move this to the other side of the pump) Unfortunately too, due to lack of space the the vent can only go some 15cm above the xpansion tank. I do not have a hot cylinder but was merely running radiators off the boiler. I put a valve on the cold feed purely to isolate a tank full of water if I needed to drain the system down, but I agree it's not really necessary. I could move the expansion tank and vent some 4m further away but only about 50cm higher. Should I consider moving the pump to the 28mm return side?

 

[wildobc]

Thanks for the reminder regarding bldg regs. The last full soild fuel system I installed was 30 yrs ago so regs must have changed. I will look

 

[Best]

How's the system going to lose heat to rads if there is a power failure or pump stops? Sounds dangerous.
If the vent pipe can go no higher dead vertical, but the roof is an angled roof, then the vent can be bent the angle of the roof, run up several feet & bent in a U & back down into expansion tank. All clipped & lagged obviously.

 

[wildobc]

Thanks for the advice - will look at that.