eljan gas fired water heater

[meb]

Hi, we have warm air CH and the above water heater.
Having just had the hot water tank replaced with a vented indirect cylinder in place of pritic tank we are unable to get hot water via the gas. we can use the immersion heater into the tank OK.
The gas water heater has small header tank in loft (we are in bungalow) which is gravity fed to hot water system in heater unit.
when gas is lit it fires, the inlet flow pipe to hot water cylinder gets very hot and then the gas cuts out. there does not appear to be any hot water returning to the unit via the coil.
we have tried draining some water through drain cock on bottom of unit (there did seem to be some air in)but still no water seems to be circulating.
Any ideas please?

 

[Gasguru]

Is the cylinder specified for use on a gravity primary pipework system?

 

[wiggikins]

Is there an air release valve on the hot flow to the cylinder, probably requires air venting from pipework!

 

[namsag]

As gasguru says some cylinders now are fast recovery and designed to be fitted on a pump system.
But if yours is ok then you are going to have to take out the water heater thermostat and let it boil up for a bit to shift the air lock.
It will sound like someone is hitting it with a hammer and can sound quite scary allow it to boil for 10 to 20 secs max it may take a few attempts.