ok got one question
old system was primatic, the boiler installer did not even know anything about it. and neither did many others.
anyway had a in and out feed down stairs
had a return feed from up stairs to downstairs..
Created new in feed from up stairs bathroom radiator.. kept the return feed going to downstairs return feed. what should have been done with the in feed downstairs????? (connected to the return feed?????)
Don't quite know what you mean?
How can the installer not know this is a primatic? , how did he/she drain the system without noticing the feed & expansion cistern gone walk abouts

............................from what you are saying i'm guessing that you are asking where to connect return from primatic cylinder into system pipework? ................has any inhibitor been used?
ok the original ideal mexico boiler blew up. This was in the summer. The Engineer/Gas fitter came around looked at the system and said that he would recommend a vaillant 428, to give enough energy around this house. So he came a week later with a big smile and tghe boiler.
Dismantled the old boiler, and I also took a week off to give him a hand.
He thought there were two tanks in the loft one for water and one for radiator. While investigating he realized there was only one tank and it took part of two days for him to figure out hos the system was being filled. Luckily I read Primatic on the cylinder, so googled it and it works on some bubble system, hence sometimes we used to get brown water in hot water taps as the bubble broke. But I never mentioned anything as the gas fitter thought i did not know anything. anyway i let him carry on.
Four pipes were running from the original boiler with pump on the return.
The engineer said that the pump now needs to on on the flow. He connected up everything according to the book as far as i know.
The only thing is that the in flow for the radiators downstairs is connected to the return flow, which i don't think is correct or is it? When i asked he said that the return will feed the radiators downstairs but i fail to understand how.
Anyway I decided to do the electrics my self and not knowing much about gas, they work in perfect harmony with the boiler after a few hiccups.
The only problem now is that the upstairs radiators are nice and hot, and even the thrmostats work, although there is no thermostat in the bathroom.
But downstairs heaters are not hot at all and i think its cos the in flow downstairs as been connected to the return flow from upstairs.
I think there should be a in flow connection from upstairs to downstairs in flow instead of downstairs in flow being connected to the return pipe. This is my personal feeling, i don't know if this is correct. but again i have not mentioend it to the engineer till i am sure.