Adding pump to gravity HW circ

[JohnD]

I am thinking of adding a pump to the 28mm gravity flow from a Potterton Profile 100E to the indirect Cylinder. The route is about 3m vertical and 6m horizontal. I have fitted 3C&E cable from the cyl to the boiler room ready for a cyl stat.

will the pump (when not spinning) obstruct the gravity flow enough, or will I need a zone valve as well? I have already bought a 28mm zone valve before I thought about adding the pump, but I am all for keeping it simple. The zone valve also has a switch (I have an idea it is the white wire) to prevent the boiler running when Cyl Stat is satisfied, unless CH is on.

The boiler flow goes to 22mm Up rads, 22mm Down rads and 28mm HW flow so I don't want to put on a 3-port valve as it would have to be huge and also I would have to reconfigure all those pipes

This is in my old mum's house who is short of cash and I think the current gravity HW is wasteful of energy (I have lagged the pipes wiuth Climaflex) as well as slow to heat the cyl.

 

[cider]

sorry its a no no.
You can add a zone valve on cylinder after tee to cold fee and vent and switch via stat but cannot pump the gravity without converting the system to fully pumped. The cold feed and vent need to run to the suction side of the pump.
Adding a pump without altering the pipework correctly will cause havock in the loft tank and when the pump is not running shall cause a restriction.

 

[JohnD]

the cold feed and vent are both in the airing cupboard by the cylinder. I was planning to put the pump by the boiler, but I suppose I could put it by the cylinder if that is better. I might have to run an extra cable if the 3&E already run for the cyl stat is not enough, but it will be a lot of work as it means lifting floors again.

CH is already pumped under the control of the wall stat.

I am quite happy for the HW pump to cause a restriction when not running, as it will prevent unnecessary gravity circ when the cyl stat is satisfied.

 

[kevindgas]

putting the pump on the return rather than the flow just before it goes back into the boiler will work. but it will not stop the gravity effect to stop it needs a zone valve
wired with a 3 core + earth
take LNE as normal to the valve using the Live to also supply the grey wire which in turn supplies the orange via micro switch take the spare live from orange to pump live

you must maintain a direct link from boiler to loft tank (flow pipe will be adequate) without any restrictive device.

 

[JohnD]

OK, thanks, so I can do it but should use both the zone valve and a pump?
and from the airing cupboard I just need the 3&E I have already run from the cyl stat into a wiring centre, where I do the rest of the wiring?

I presume the pump need not be anything special as it is just to waft through 28mm and the cyl coil.

looking at the boiler connections, IIRC it has a 28mm flow and return, each of these has two tees on it, the first tee sends 28mm up to the cyl, and 28mm to the second tee; the second tee is 28mm in, and 2x22mm out each to the upstairs and the downstairs rads. The Profile 100 is pretty powerful and looks oversized to me, though there are about 40 metres of rad panels at 600mm high in the house, plus the cylinder, with two bathrooms. Not all rooms are heated at the same time as most bedrooms are currently unoccupied

 

[kevindgas]

simple wiring

timeclock H/W on - cylinder stat use LNE (may not need N &/or E just make safe in stat if you don't)
Cylinder stat (calling) - Zone Valve use 4th wire (Live)

4th wire joins to valve Live (brown) and perm live (grey) link together

orange wire back to wiring centre and using a seperate terminal connect to the pump live

pump Neutral and Earth take direct from wiring centre to pump

 

[JohnD]

Thanks!

will have a go when the heating season is over

 

[kevindgas]

Thanks!

will have a go when the heating season is over

so you'll never do it then!! LMAO

 

[JohnD]

Kevin was wrong

My BiL is over from Australia and kindly did the wiring and helped me with the pipes. We used a printout of this thread to supplement the MIs.

Thanks everyone

Here's a pic:

BEFORE

View media item 11526
AFTER

View media item 11525
some oddments cropped up regarding flow, which I will raise separately.

edited to add the "before" pic

 

[kevindgas]

good boy !!
funny enough my customer tomorrow is...........
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my mum LOL

 

[heytesto]

Just tried to take in the gist of what you have done. During hot water operation, are you experiencing any 'pumping-over' problems into the header tank?
Also, during HW operation, are you experiencing reverse ciculation through the radiators?

 

[JohnD]

have described it in my new post //www.diynot.com/forums/viewtopic.php?p=1229268#1229268