Fixing a pumped Back Boiler system - questions!

[rjh123]

I'm looking at fixing a pumped back boiler system on a mates boat. It's running off 22mm copper pipe, with two bottom entry/exit radiators tee'd off using 15mm plasti-pipe with a small header tank running off a 15mm plasti-pipe Tee. This does not appear to be gravity fed and nor does it appear to be connected to a calorifer (?) to provide hot water - this is done by engine circ or a mains immersion it would seem.

 

Anyway, Pump has gone and rads don't work. System seems to have been let run dry - no water in header at all. I cannot identify the pump from it's markings - it's a 12v bottom entry, side exit cylinder style.

 

What I would like to know is; (see photos!)

 

• The brass pushfit connectors you can see on the braided hoses - are they removable? if so, how? I haven't come across this type before and there is usually a knack to them
• Should I refit using "rubber" hosing and clips suitable for temp, rather this braided hosing - ease of connection, replacement etc. and was thinking of one with a tee'd bleed valve on it too
• What is the component bridging the feed to the pump? Looks like a resistor? To slow the pump perhaps??
• Do I need any form of Pressure Relief Valve in this system, or will the open header deal with this?
• Do I refill with Water/Antifreeze or a commercial Inhibitor mix
• Yes, it's gash wired... This will be fixed..

Plus any recommendations for a source of a reasonably priced 12v replacement pump (!) gratefully received.

 

Thanks in advance,

 

Rich.

 

 

[BEngo]

I'm looking at fixing a pumped back boiler system on a mates boat. It's running off 22mm copper pipe, with two bottom entry/exit radiators tee'd off using 15mm plasti-pipe with a small header tank running off a 15mm plasti-pipe Tee. This does not appear to be gravity fed and nor does it appear to be connected to a calorifer (?) to provide hot water - this is done by engine circ or a mains immersion it would seem.

 

Anyway, Pump has gone and rads don't work. System seems to have been let run dry - no water in header at all. I cannot identify the pump from it's markings - it's a 12v bottom entry, side exit cylinder style.

 

What I would like to know is; (see photos!)

• The brass pushfit connectors you can see on the braided hoses - are they removable? if so, how? I haven't come across this type before and there is usually a knack to them
• Can't help, sorry.
• Should I refit using "rubber" hosing and clips suitable for temp, rather this braided hosing - ease of connection, replacement etc. and was thinking of one with a tee'd bleed valve on it too
• No. These look like tap tails so will be quite happy at CH temps
• What is the component bridging the feed to the pump? Looks like a resistor? To slow the pump perhaps??
• Looks like a capacitor- probably to cut down on RF noise
• Do I need any form of Pressure Relief Valve in this system, or will the open header deal with this?
• The open header deals with it.
• Do I refill with Water/Antifreeze or a commercial Inhibitor mix
• 50% water (demin/deionised ideally- certainly soft) and 50% antifreeze. Add CH inhibitor at the end of the 'life' of the antifreeze- this can be 2-5 years. See tin.
• Yes, it's gash wired... This will be fixed..

Plus any recommendations for a source of a reasonably priced 12v replacement pump (!) gratefully received.

 

There are several 12V pumps on solar heating sites which are cheap enough ( compared with Johnson and equivalents) that they might be worth a try if the pump is reasonably easy to access/change. Look for one that is continuously rated and has a decent predicted life- 10K hours. Bolin have ceased producing I believe, but if you can get one they are worth the money.

 

Thanks in advance,

 

Rich.

 

There are some answers in your list. For some reason the editor doesn't want to do pretty colours today I'm afraid.

 

N

Edited August 8, 2013 by BEngo

[Pete & Helen]

• What is the component bridging the feed to the pump? Looks like a resistor? To slow the pump perhaps??

Looks like a capacitor- probably to cut down on RF noise

This looks more like a high power ceramic wirewound resistor and has been used to drop the voltage to either slow the pump down a bit, or more probably to keep the voltage supply to the pump within limits. Its not easy to see in the picture where the component end and the blue wire go but I would assume the are connected together putting the resistor in series. A capacitor would be across the supply.

 

[nicknorman]

Yes, its a resistor, looks like 18 ohms, for slowing the pump down probably for noise reasons.

 

Ive used these pumps on a couple of heating projects on our boat. I'd go for one of the faster options, the 8 or 11 litres/minute. There are pretty cheap and cheerful but seem to do the job. Since they are cheap and plastic, it would probably be wise to fit isolating valves either side to allow quick replacement, though so far mine have perfomed impeccably and are quiet. They are also easy to connect to with tap fittings.

Edited August 8, 2013 by nicknorman

[rjh123]

Thanks chaps. Great stuff. Looks like the connectors are TecTite and will need a removal tool to get them off

[smileypete]

If it's completely dry it may just have been emptied for frost protection, but running the fire when the back boiler is empty may damage the back boiler.

 

The system must have an 'open' header tank with effective vent pipe and NO valves between back boiler and vent, never allow it to pressurise in any way.

 

The braided hoses should be OK as long as not pressurised and allow enough flow. You might be able to get the Tectite connectors off using a pipe clip like a Talon clip pressed against the ring at the end with water pump pliers or adjustable spanner.

 

Normal CH inhibitor won't give any frost protection, if filling with antifreeze mix the solution first or it may stratify and reduce circulation.

 

cheers, Pete.

~smpt~