Backboiler gravity feed not warm

dbeermat93

Hi

I have a solid file stove with backboiler, with the past week or so I have noticed that the gravity feed flow pipe to the attic does not get warm at all whatsoever. Circulating pump kicks in for the radiators so no problem there but this cannot be right.

The gravity feed should be warm, no strange noises from boiler , I hope is not an airlock, any ideas or suggestions. The pump cuts in at 55 degrees for the radiators.

Thanks

Dbeermat.

aujopimur

The exp. pipe should not get hot under normal operating circumstances.

dbeermat93

I presumed with gravity feed, the cylinder should be getting heat every time the stove is lit, so why was it hot last week if circulating pump was working fine.

Thanks

Dbermat93

aujopimur

Gravity circulation only goes as high as the top of the coil in the cylinder, any thing above that is considered expansion.
Does the heating have a seperate cold feed, if so, where is it connected into the system.

dbeermat93

Yes there is a cold feed from the cylinder coil which is below the flow from the gravity, sometimes the oil boiler is heating the rads and there is two stats on the backboiler, the first stat when it hits 30 degrees shuts off the oil boiler and the second stat cuts in the circulating pump.

Could the heat from the rads cause the heat in the expansion pipe.

dbeermat93

Cold water feed comes from header tank in attic which is solely for backboiler

aujopimur

The cold feed for the back boiler should be should be run unrestricted from the header tank to the pressure side of pump on the boiler.
What you're describing as the cold feed appears to be the return from the cylinder.
The stove should should have been piped in a four pipe configeration, one unpumped gravity circuit to the cylinder, and one pumped for the heating.
Going back to your original query, the reasons for the expansion getting hot are either that it has overheated and expanded into the header tank, or has pitched when one or both of the pumps were running

dbeermat93

Apologies, the cold feed is coming from the header tank and the return pipe from the cylinder coil taps into the return feed which it should.

As I said when the oil boiler is on prior to the backboiler coming must be causing the expansion,whether this is what should happen, I do not know. As the oil boiler was not run this week, it seems to be the only explanation.

Thanks for the input

aujopimur

The circuit for the cylinder should be gravity only and unpumped.

dbeermat93

yes it is gravity only, there is no restricions on this feed, valves,pumps etc.

must be when oil boiler is on as water is pumped to rads, there is non retrun valves on system to stop water in bother boilers from heating each other, so this where the heat is coming from, will check it this evning to verify and update.

aujopimur

How many pipes are coming off the stove?.
Do you have dual coil cylinder?.

dbeermat93

4 pipes from the stove, one set is for the rads using a circulating pump and the second set is gravity.

i have a 300 ltr triple coil cylinder for ,oil,solar and solid fuel connections.

aujopimur

From what you describe everything seems to be done correctly, the expansion may may be getting warm from heat just creeping up the pipe, as long as the expansion pipe is not pitching hot water into the exp. tank when the pumps are running everything should be ok.

dbeermat93

thats what i was thinking and it does not pitch, just heats the water nicely in the cylinder, so happy days