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#4969
Just wondering how I approach this job I have been given.
I have to install a new Grant condensing oil boiler.
System is open vented with an old oil boiler with 4 of 28mm pipes, 2 of which are the pumped rads circuit and the other flow and return for gravity hot water circuit which has vent and a feed pipe connected to them at hot cylinder.
I don't want to consider partially repiping the system as near impossible and just want to connect these pipes to fully pumped, using zone valves etc.
Any ideas as to what to do about the obvious risk of pumping over?
My thoughts are should I install 2 pumps - one for the rad circuit and a low powered pump for the hot water circuit and fit a pipe and gate valve to act as a permanent bypass onto the now pumped hot water circuit?
I could change the system to sealed, but it is over 50 years old, so risky.
#4972
I'd go for the two pumps and maybe combine the feed and open vent or extend vent if practical.

Either that or pressure test existing and maybe run it at 3/4 of a bar.
#4976
SimonG wrote:
July 1st, 2018, 11:44 pm
I'd go for the two pumps and maybe combine the feed and open vent or extend vent if practical.

Either that or pressure test existing and maybe run it at 3/4 of a bar.
Thank you Simon for renewing my faith in myself. :D
I actually thought I would get ridiculed for the 2 pumps idea. Although someone might still condemn me.
Still the issue of how to control the heat at cylinder and rad zone.
I don’t fancy combining the vent and feed as I see a lot of magnetite problems with that done, for some reason. Plus the system hasn’t given any real trouble in well over 50 years unchanged.
Putting system on a pressure test for some reason I hadn’t considered and that might be my approach - particularly now that I think of they have air gathering in one rad constantly. Rads need replaced. Sealed system might work.
Good to see you back Simon!
#4978
bypass and two pump second being variable (p-regulater valve?)
pressure the whole lot might bring up a ballache as you dont want to risk popping joints where you cant get at them.
i always go on leave as be but mod it gently or price for the what if's

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