Draining and refilling a Worcester 12/14 Heatslave boiler

[docwatson63]

I have installed 2 new radiators in a loft conversion and I need to connect them into the CH system.
Does anyone know how to drain and refill the Oil Fired Boiler in my post title?

Do I actually need to do this or is there another way?

Any help appreciated..........

 

[jackthom]

How high up is the loft and how low down is the boiler? Depends where you are taking the new feeds but chances are you won't be draining the boiler as such. More likely just relieving the system pressure while adding the radiators, then topping up the pressure and bleeding when finished.

A bit more info about the system and maybe even some pictures would be useful if you need more help.

 

[docwatson63]

Thanks for getting in touch. It's a bungalow and all the pipework is just under the floor I have laid. You can see the loop that I think I can connect to. I'm a bit of a novice and not entirely sure about how to prevent the house from flooding!

 

[jackthom]

OK it looks like you are connecting the new rads up into the highest point in the existing system (correct me if I'm wrong), just above the ground floor ceiling.

Are the two 15mm pipes in the photo the flow and return from the boiler which you will be cutting into? If so, before starting you should first check how many existing radiators are already being run off this feed or you may find the radiators in the loft, or others elsewhere in the house, not heating up very quickly.

 

[docwatson63]

You are right. This is the highest point in the house. The pipe I intend to cut into is the 10mm microbore. The loop comes out of one manifold and goes back into the other as in the attached pic. There are 3 other pipes coming out and returning into these manifolds. The loop is connected with compression fittings and I thought this would be the obvious one to use.

 

[jackthom]

The manifold looks like 22mm to 3x 10mm which is a good place to go in but you might be pushing your luck taking 2 additional radiators from the one 10mm feed even though it is very close to the manifold.

I know your way looks easier but you might consider cutting into the 22mm pipes and fitting reducing tees to give a new 15mm feed which will happily supply more than enough hot water for both the new radiators. It will also prevent the radiator already on that 10mm feed being starved of flow.

Either way, to do the job you can bleed a downstairs radiator until the system pressure (dial on the boiler behind front panel?) goes close to zero.
This is all assuming it is a sealed pressurised system and you don't have a Fill and Expansion tank for the boiler in the loft.

Then when you open up the pipes in the loft very little water should come out. Be prepared to catch any that does or the ceiling might suffer.

When finished if you can't find the boiler filling loop (comes from house cold water supply) to repressurise the heating system, post some pics of the boiler innards and surroundings.

 

[docwatson63]

Thanks for that. I've already bought the elbows and tees and the run from the manifold to each rad is approx 1.5-2m. I am a bit worried that I won't have enough pressure but I haven't got the confidence to cut into the 22mm. If you had to do it, would you cut into the loop or disconnect it at the compression joint. One side of the loop has got a crimp in it. Looks like it's been done on purpose.
I appreciate the good advice from a fellow Northumbrian by the looks of it.

 

[jackthom]

Just swap the straight compression fittings for a couple of 10mm tees assuming you can easily run out from there, then split it in two again with tees to give 10mm feeds for each of the new radiators.

It's not such a great problem because If it doesn't work too well you can always go back and change it again. No fancy floor coverings until you're sure it's ok. Don't just check the new radiators work OK but make sure the old one connected to that 10mm pipe hasn't suffered.


I wonder if the crimp was accidental or some attempt to balance the system.

 

[docwatson63]

Okay. I'm hanging them now so I will be back in touch.

Pic shows why I'm converting the loft.

 

[jackthom]

Yes that's a very nice outlook but I don't instantly recognise the location. I'm in Ponteland BTW.

 

[docwatson63]

Thropton.

I've had a look at the boiler and I can't see a cold water feed but not sure what I'm looking at. No manual as the boiler is about 12 yr old. Not sure how I would get the corrosion inhibitor in either. There is an open cold water tank in the loft above the boiler that seems to be connected.

 

[jackthom]

Can you post a few more pictures of the boiler and the tank in the loft? If that is a Feed & Expansion tank for the boiler it may need to be raised if it isn't already higher than the top of the new radiators.

I'm assuming you don't have a hot water storage cylinder and that your hot water all comes directly from the boiler, ie it is a combi boiler.

 

[oilhead]

Heatslaves are built for sealed system, although there is provision in the M.I's for open vented system.
if it is sealed system, you will have a filling loop somewhere, usually close to the boiler and taken off the coldfeed pipe to the DHW heat exchanger.
look for a braided hose with a tap on each end. You can drain down from a drain cock at the base of the heatstore slave tank, and if you wish to add inhibitor, this is easily done by unscrewing the auto air vent from the top of the boiler and pouring it in. When refilling, there are bleed nipples on the pipework out of the DHW heat exchanger and also at the top of the main heating body. Put the diverter valve into the manual position first, and don't forget to bleed the pump.

 

[docwatson63]

Okay gents,

I'm still busy with pipework but here are the pics of the cold water tank in the loft. This is connected by the white plastic pipe to a copper pipe going into the boiler. You can see the old copper pipe has been bypassed for some reason. The bottom of the tank is about 400-500mm above the top of the rads. Also the pics of the boiler. It's old but still works well. I have to admit, this is the bit I'm worried about.

 

[jackthom]

It does look like the cold feed to pressurise the system comes from the tank in the loft.

Before opening up the 10mm compression joints to connect up the new radiators, you will have to tie up the ball valve in the tank so it can't refill and then remove sufficient water from somewhere convenient downstairs to empty both the tank and the pipework down to ceiling level. It's largely trial and error deciding when you have removed just enough.


The tank will at least make it easy to repressurise the system, plus you can add inhibitor there when refilling.

It's also a good idea to carefully clean out any debris in the tank while it's empty so it doesn't go down into the pipework later.