plumbing help required please

[magnet]

I have bought a second hand morso boiler stove it has 4 tappings on the back 2@28mm for the hot tank and 2@22mm for the heating. I was wondering if I would need a ch pump on the heating side or would it be ok relying on it circulating on its own with say 28mm pipes. And would a heat sink rad be a good idea across the flow and return on the hot water circuit to stop back boiling into the header tank. Also if I wanted to could I safely blank off two of the tappings and use the other 2 for hot water and a single rad in the bathroom for instance. Answers to any or all of these questions gratefully received. Thankyou .......Magnet

 

[garethp]

First of all you need to try and find out how much heat the boiler produces and how much heat the stove puts into the room, you need to try and get a load via the tank and rads that roughly matches the heat output of the boiler, otherwise you'll either boil the water quickly or it'll never warm up. Some stoves have several different boiler options to give different ratios of heat to room / boiler.

Gravity flow can be very sensitive to pipe runs, you might find its easier and cheaper to use a combinations of a pump and 22mm for the main ch runs and 15mm to individual rads.

Have a look at the forum on www.navitron.org.uk as there will be loads of folk using a similar setup to what you propose

 

[rtbcomp]

I'd consider pumped for downstairs and gravity fed upstairs.

 

[mike os]

given the cost of a pump and the potential difficulties with gravity systems, why bother? at keast that way you know it will work

 

[rtbcomp]

You'll still need to dissipate heat if the pump fails.

 

[KemppiFrog]

We had an oil AGA with a backboiler for hot water. It worked on thermosiphon to the tank above. AGA recommended leaving the 1" pipes un-insulated to act as a heat sink to avoid boiling the circuit.

 

[captain-destructo]

hi there
at a guess
28mm gravity feed to the tank
22mm feed to the rads with a pump wired to a thermostat on the tank so once its up to temp the pump kicks in to stop it boiling

or

28mm gravity feed up to a dunsley neutralizer that then feeds the tank and the heating and you can also plumb a backup gas/oil or another woodburner into it

 

[julianthegypsy]

How are the tappings configured? Are you sure its not two sets with 28mm for the run up and 22mm for the returns, with a set on both sides for radiators each side of the boiler? Either way, gravity will work providing it's installed properly, and it's normal to have a small header. As long as you have one radiator permanently on that will provide the safety. That and having an unpressurised system with a header.:-)

 

[magnet]

How are the tappings configured? Are you sure its not two sets with 28mm for the run up and 22mm for the returns, with a set on both sides for radiators each side of the boiler? Either way, gravity will work providing it's installed properly, and it's normal to have a small header. As long as you have one radiator permanently on that will provide the safety. That and having an unpressurised system with a header.:-)

Hi Julian the tappings are configured diagonally opposite top left 28mm bottom right 28mm top right 22mm bottom left22mm looking at the back of the stove I am a bit out of my comfort zone with the 4 tappings the only other one I have plumbed in had only 2 .......... cheers Magnet

 

[pedrobedro]

Pump the heating circuit return into the boiler. that's all I know.

 

[wookie]

Pump the heating circuit return into the boiler. that's all I know.

Sorry but that's wrong !

If the pump is pushing water into the boiler you will can get problems with the thermo-syphon loop to the tank not working.

It's better to have the pump pulling water from the boiler around the heating loop and let the 28mm connections work as a thermo-syphon to the hot water cylinder.

 

[magnet]

thanks

Thanks to everyone who to took the time to respond its much appreciated.......Magnet

 

[rtbcomp]

I was told to put the pump in the return because the water's cooler.

I don't see what difference it makes to the thermo-syphon, you've still got pumped water going through the boiler at the same rate regardless of where the pump is.

 

[garethp]

Pump position varies, new boilers have it in the return to keep it cooler and solar pump stations are the same.

Two old boilers I've come across recently had it in the flow, both were pumped CH and gravity HW. However I don't know if the pump position has an effect on the gravity flow circuit or whether it was simply a spare place inside the boiler case.

The OP needs to plan it properly to get a safe system with decent output, Gravity systems are simple but slow to transfer heat.

 

[gaz1]

pump is always placed on the return pipe to the boiler

however if using a gravity fed system the feeder pipe from the tank must be before the pump this stops the pump pumping direct to the tank and gives much better circulation than a gravity fed system

ex plumber that knows the old systems rather well and going back to them

 

[rtbcomp]

Couldn't the tank feed connect to the gravity ports on the opposite side to the pump? (Assuming there are 4 connections to the boiler).

 

[garethp]

If you're interested I've got a manual for an ideal boiler from ages ago, there's half a page on setting up gravity pipe runs to the tank.