Threre rads off one branch

[dazzlerpalmer]

We have two rads
One feeds another one. I know you should not really, but would it be ok to feed another rad from the fed rad.
This would mean that there would be three rads from the one branch. They are both ground floor rads directly under the central heating water tank and pump.

Cutting a separate branch will be nigh impossible since the new rad is going to be in a single storey utility room.

 

[kevplumb]

size of the rads and pipework might give one of us a clue

 

[dazzlerpalmer]

celsia multi-head Myson single pump on a four bed house connect to a Potterton Supima 60F boiler.

Boiler can do 60,000 BTUs
proposed rads total 60,000 - 12 rads

The three rads in question
toilet - 3000
kitchen - 3000
utility - 5000 (new rad)

 

[kevplumb]

Boiler can do 60,000 BTUs
proposed rads total 60,000 - 12 rads

what about the hot water

as for the rads i would think borderline

 

[dazzlerpalmer]

sh*t - forgot about the hot water - what a prat.

I have not yet ordered the rads. Probably had a bit of overkill for them anyway.

How many BTUs should I leave back for the hot water?

I think the boiler is not really man - enough for the house especially since I want to add a rad in the utility room (flat roof extension).

 

[kevplumb]

this might be useful to you

 

[dazzlerpalmer]

interesting - elbows reduce pressure big time

I remember now, in the winter, only when we select heating on its own do the rads get really hot. If we select heating and hotwater the furthest rads away from the bolier dont get hot.

I tried increasing the pump speed but this caused it so spill over into the header tank. I have been told to make sure there is not too much water in the header tank and balance the rads.

++++++++++++++++++++++++++++++++++++++++++

As a general rule how much BTUs should be reserved for the domestic hot water in case hot water and full central heating is required?

MOD

please see 10a

 

[kevplumb]

immersion heater is 3 kw which is approx 10,000

depends on the cylinder and reheat time

5 kw /17,000 would be ball park

would think you are pushing it with a 60,000 boiler

 

[ChrisR]

Ye rules of thumbe say max Btu of a single15mm pipe 14000, and allow 3000 for hW. Latter is a joke really, it depends how hot the water is. And some modern cylinders have a 20kW (68000) coil.

If you time HW separately it won't be a real problem unless you have huge HW needs, though yes I'd go for bigger boiler given a choice.

You probably will need your pump on full. It should not "pump over". If it's just a spurt when the pump starts or stops then make the vent pipego higher before it comes down again. If it's continuous though your system is designed wrongly and you need to change it. Easiest way is to make the vent a combined feed and vent (ask if need more info)

 

[dazzlerpalmer]

the pumping over is continuous on speeds 2 & three.

I can lower the water level (in the header tank) slightly but not more than say 2 inches.

The expansion pipe is right tight into the eaves so I cannot get any more height on it. The gas bloke told me ages ago that it is a sludge build up but after taking all the rads off in preparation for replacing them, they are not that bad. I think you are right, it is a poorly designed system.

Easiest way is to make the vent a combined feed and vent (ask if need more info)

How do you do this?

BTW thanks to you all for the tips - really helpful

 

[kevplumb]

see page 11

 

[ChrisR]

How do you do this?

Cut off the feed pipe(15mm one) as near to the CH circuit as possible and put a finger bleed point on it.

Connect the vent pipe (22mm or else you can't do it) into the f/e tank with a 22 mm tank connector.