Fully pumped conversion query

[EliteHeat]

I have a customer who has a profile with an airlock on the gravity circuit. The airlock appears to be within the cylinder HE and since my first attempt at sucking the airlock out failed, the customer would prefer to convert to fully pumped rather than pay for an inherent defect to be temporarily fixed, which is fair enough.

The layout is as follows:-

The boiler is in the kitchen with horribly twisted and mangled 28mm gravity primaries behind a bit of studwork which will have to be removed.

The pump is in an adjoining cupboard and is on the return side of the CH. The CH flow is easiliy accessible.

The cold feed and open vent are both in 15mm and are connected to the gravity return and flow respectively. The tappings for the HE are completely inaccessible. The HWC is located in the first floor bathroom.

It would be extemely difficult and disruptive to to extend the cold feed and open vent down to the adjoining cupboard (the proposed location for the new 3PV).

So, my query is as follows:-

It will be easy enough to alter the pump so is is on the flow side, It should also be easy enough to install the motorised valve, new programer, room stat and wiring centre. It would also be easy enough to convert the cold feed and open vent to provide a neutral combined cold feed and open vent on the flow side - which would also allow me to fit a manual vent on the HW return side. The reason why I can't do this though is that when just the heating circuit is on, there will be no open vent accessible since it is located on the HW flow. If I convert it so that the flow and return are on the return side, the open vent will always be there since the return is common but I am concerned about sucking air in.

Could I have your comments and thoughts please?

Regards

 

[kevplumb]

I have a customer

so learn yer flaming job or leave it alone

 

[Paul Barker]

You are way over my head, but how about a seperate pump on the hot water, but don't use zone valves, just use two relays one for each pump. Use s plan controls send live call for heat to relevant pump and that pump via a relay (so that other pump doesn't also come on) operates boiler. The addition of zone valves could cause problems in such an old system with heat dissipation.

 

[kevplumb]

don't forget the NRV

 

[ChrisR]

I can follow some of what you're saying in your last paragraph!

The reason why I can't do this though is that when just the heating circuit is on, there will be no open vent accessible since it is located on the HW flow.

I think you mean that the pump will be in the way, between the boiler and the vent, as the vent is off the hw primaries?

If I convert it so that the flow and return are on the return side

eh??

It's obviously an old system where the boiler & cylinder will be going in the forseeable future so I'd do what's easiest for the interim. The pump could stay in the return - mine's been there for 20 odd years on a fully pumped system. You can put a zone valves in the returns if you want to, but not a 3 port.
It sounds like the 15mm feed/vents may be blocked. You can't leave it with 15mm vent I'd say, but A 22mm combined one won't suck air by itself wherever it is.

Sticking a pump on the HW return might be a solution. Relays are a bit of a pain - a box with one in costs far too much for what it is! Instead you could power the hw pump from a pipe stat on the cyl flow, cyl stat and timer all in series, so the hw pump comes on of the timer and cyl stat are calling AND the flow pipe is hot.


Sorry if I can't answer questions on this but I'm going on hol to the dark (in)continent so the brain's getting into "have I got enough toilet paper " mode.

 

[EliteHeat]

I think I over complicated the description of this, so I'll have another go. Sorry to try your patience!

I would like to convert this semi pumped system to fully pumped. There are complications in that a lot of the pipework is inaccessible - mostly 'cos there is laminate flooring everywhere.

There is a 15mm cold feed tee'd onto the gravity HW primary. The 15mm open vent is on the gravity flow. Neither are blocked. I can convert the 15mm to 22mm without too much difficulty although access is severely restricted.

Happily, the 28mm and 22mm primaries from the boiler are relatively accessible, so I can mess around with these as much as I like. Currently the pump is on the return side of the heating circuit, in a cupboard near to the boiler. Both the 22mm flow and return are accessible.

What I would like to do is as follows:-

1) Disconnect the 28mm gravity flow and extend to the cupboard in 22mm
2) Interrupt the existing 22mm flow on the heating side and move the pump to here
3) Remove the pump from the 22mm heating flow circuit and make continuous
4) Convert the 15mm cold feed on the existing gravity return to 22mm combined feed & vent
5) Install a manual vent on the current gravity flow - 'cos I can & it seems like a good idea
6) Install the rest of the 3PV kit after the pump as usual. Using the extended gravity flow (now reduced to 22mm as in (1)) to be the new pumped HW flow.

My concern is that I will pump over and that I always have an open path to the vent. Since this will be on the common return I can't see a problem. Obviously this would be the case if I had it on the HW flow - as it would not be open all the time.

So that's the plan. My question is does anyone have any comments as I have not done a conversion like this before & I would naturally like to avoid anything exploding!

Thanks

P.S. Always learning Kev

 

[Softus]

I'm going on hol to the dark (in)continent.

Is that Asia Chris? Or Africa perhaps? Or Clacton?

 

[Nige F]

Strange name Elite.........like Special forces are to the Army?.....Heat..as in installing and altering boilers and C/ Heating systems? Me, I`m just a fecking ejit...it`s in my profile Good to have a laff on a Monday

 

[dal5band]

To start with, just do 5 - put an air-vent in the H/W circuit - even an automatic one.
I've got an old automatic air vent - it's a little cup shaped thing with a float in it. The water rising shuts off the air vent, it's in the H/W circuit on the higher connection to the tank. Even though my system is fully pumped, you still need the air vent because of air getting trapped at the high point.