Central heating set up issues

[Katie]

Hi 

 

I’m trying to set up my central heating system ready for my first winter aboard.

 

ive got a multi fuel stove with back boiler and a pump to feed 3 radiators. I’ve tried filling the system (which was dry) CIA the header tanks and bleeding the radiators to remove any air. Lit the stove and turned the pump on. The pump has a thermostat attached though which seems to determine when the pump kicks in. So I set the thermostat to a lower temp and lit a small fire. Pump came on and couple radiators started to heat up ever so slightly. Then the header tank seems to overflow and warning light flashes on the pump. The water is only warm that overflows the tank. 
 

Any suggestions what I’m doing wrong or what the problem could be? 
 

Someone told me that I really shouldn’t light the stove without the pump on as risk over pressurising the system…?

 

a plumber/heating engineer friend thinks the pump is knackered so looking to replace that and see if it helps. 
 

thoughts? 

[Tracy D'arth]

45+ years plumbing and heating experience.

I disapprove strongly of solid fuel heating systems on a boat that rely on a pump for circulation. 

Consider what is likely to happen when in the depth of winter with a big roaring fire going, the pump stops working.

[Katie]

Great thanks for the nightmares! 
 

So you are in agreement pump must always be used whenever fire is Lit? Will the water not just overflow to the header tank if pump stops? 
 

afraid I didn’t design the system just trying to figure it out! 

[Tony Brooks]

No idea what pump has a warning lamp on it.

 

I suspect the circulation may not be sufficient, so the water in the boiler boils and drives the water out of the system with steam. Until the boiling water gets into the header tank, the water will not be that hot.

 

Could the pump be air locking? It depends upon the pipework layout.

 

 

5 minutes ago, Katie said:

Great thanks for the nightmares! 
 

So you are in agreement pump must always be used whenever fire is Lit? Will the water not just overflow to the header tank if pump stops? 
 

afraid I didn’t design the system just trying to figure it out! 

 

The tank should not overflow, as long as its not over filled, until the water in the stove boils. I assume that you are leaving a couple of inches of free space in the header tank to allow for expansion as the water heats up.

Edited September 21, 2021 by Tony Brooks

[Tracy D'arth]

Thankfully there is a header tank and its not a sealed pressurised system.

[Tony Brooks]

1 minute ago, Tracy D'arth said:

Thankfully there is a header tank and its not a sealed pressurised system.

Does anyone actually fit them with stoves? If so, they are grossly negligent - even if they do fit a safety valve!.

Edited September 21, 2021 by Tony Brooks

[MtB]

6 minutes ago, Tracy D'arth said:

45+ years plumbing and heating experience.

 

Same here.

 

7 minutes ago, Tracy D'arth said:

I disapprove strongly of solid fuel heating systems on a boat that rely on a pump for circulation. 

 

Same here.

 

7 minutes ago, Tracy D'arth said:

Consider what is likely to happen when in the depth of winter with a big roaring fire going, the pump stops working.

 

Just to clarify, all the water in the back boiler turns into steam, many cubic metres of the stuff, pretty quickly and it all comes out via the open vent pipe and cold fill pipe into the boat. The mess it can make is unbelievable with rusty brown water sprayed everywhere and steam filling the boat. 

 

I've probably understated it...

[TheBiscuits]

10 minutes ago, Tracy D'arth said:

45+ years plumbing and heating experience.

I disapprove strongly of solid fuel heating systems on a boat that rely on a pump for circulation. 

Consider what is likely to happen when in the depth of winter with a big roaring fire going, the pump stops working.

 

It's a shame @Boater Sam stopped posting, because he would agree with you ...

 

2 minutes ago, Tracy D'arth said:

Thankfully there is a header tank and its not a sealed pressurised system.

 

There's no guarantee it's not an automotive expansion tank with a pressure cap on it!

[Katie]

3 minutes ago, Tony Brooks said:

No idea what pump has a warning lamp on it.

 

I suspect the circulation may not be sufficient, so the water in the boiler boils and drives the water out of the system with steam. Until the boiling water gets into the header tank, the water will not be that hot.

 

Could the pump be air locking? It depends upon the pipework layout.

 

 

 

The tank should not overflow, as long as its not over filled, until the water in the stove boils. I assume that you are leaving a couple of inches of free space in the header tank to allow for expansion as the water hats up.

It’s a Dab Evolution pump of that helps? Has some sort of digital display that doesn’t make much sense to me except a definite flashing warning light 

 

I think it might be air lock in the pump yes as from what I can make out in the manual I found online that’s what the flashing light suggests. Don’t understand how though? Just faulty pump? 
 

yes I leave plenty of room in the tank but it is very small. I fill the tank and bleed the radiators and top tabk up as required until no air in radiators and small amount of water left in the tank well below the overflow/outlet pipe 

fire has gone out and can hear the water all trickling back into the system now. 

[Tracy D'arth]

And there is no good reason for not installing a proper gravity driven system with no pump.

[TheBiscuits]

1 minute ago, MtB said:

Just to clarify, all the water in the back boiler turns into steam, many cubic metres of the stuff, pretty quickly and it all comes out via the open vent pipe and cold fill pipe into the boat. The mess it can make is unbelievable with rusty brown water sprayed everywhere and steam filling the boat. 

 

The system on my boat went one better - the emergency pressure relief valve dumped out into the bath!

 

It's been replumbed since as a thermosyphon in 28mm tube, not as a forcibly pumped 15mm system.

[Katie]

3 minutes ago, TheBiscuits said:

 

It's a shame @Boater Sam stopped posting, because he would agree with you ...

 

 

There's no guarantee it's not an automotive expansion tank with a pressure cap on it!

Nope just a little non-sealed tank. Inlet pipe at the bottom, outlet at the top

[MtB]

1 minute ago, Katie said:

It’s a Dab Evolution pump of that helps? Has some sort of digital display that doesn’t make much sense to me except a definite flashing warning light 

 

 

That's a 230Vac domestic household pump. Cheapest money can buy, and will need either an inverter to run it or a shoreline. If you are running it off an inverter it will cane your batteries in the medium term. 

 

Pumped heating systems attached to uncontrolled heat sources are Bad News, and usually installed by fools who don't understand the issues that can arise. Yours may be the exception and very well designed.

 

 

[Tony Brooks]

5 minutes ago, Katie said:

It’s a Dab Evolution pump of that helps? Has some sort of digital display that doesn’t make much sense to me except a definite flashing warning light 

 

I think it might be air lock in the pump yes as from what I can make out in the manual I found online that’s what the flashing light suggests. Don’t understand how though? Just faulty pump? 
 

yes I leave plenty of room in the tank but it is very small. I fill the tank and bleed the radiators and top tabk up as required until no air in radiators and small amount of water left in the tank well below the overflow/outlet pipe 

fire has gone out and can hear the water all trickling back into the system now. 

 

I can't find an Evolution on the Dab website, but they all look like mains (230V AC) rather than 12V DC. This MIGHT be OK as long as you have a shoreline connected or if you are running it form an inverter AND your battery and charging system is suitable.

 

I wonder if the lamp means a low voltage.

 

Crossed with Mike. On a boat potentially very dangerous.

Edited September 21, 2021 by Tony Brooks

[Katie]

2 minutes ago, Tony Brooks said:

 

I can't find an Evolution on the Dab website, but they all look like mains (230V AC) rather than 12V DC. This MIGHT be OK as long as you have a shoreline connected or if you are running it form an inverter AND your battery and charging system is suitable.

 

I wonder if the lamp mens a low voltage.

Yes it’s powered through an inverter. Former owners were marina based so had shoreline power. I am also heading to marina for the winter so won’t be too much of an issue this year for me so long as it actually works!
 

so would I need whole boat re-plumed to switch to simple gravity fed system so I can ditch this problematic pump? 
 

7 minutes ago, MtB said:

 

That's a 230Vac domestic household pump. Cheapest money can buy, and will need either an inverter to run it or a shoreline. If you are running it off an inverter it will cane your batteries in the medium term. 

 

Pumped heating systems attached to uncontrolled heat sources are Bad News, and usually installed by fools who don't understand the issues that can arise. Yours may be the exception and very well designed.

 

 

Ok so what are my best options? Have the whole system re-designed? 
 

im not sure it’s that well designed if I can’t get it working. 

[TheBiscuits]

1 minute ago, Katie said:

would I need whole boat re-plumed to switch to simple gravity fed system so I can ditch this problematic pump? 

 

No, just the heating circuit from the back boiler in the stove.

 

If you're lucky, it won't be a huge job but it depends on how it's been installed. 

 

Can you provide a diagram of your system showing stove and radiator positions please?  A simple sketch will do.

[Tony Brooks]

Just now, Katie said:

Yes it’s powered through an inverter. Former owners were marina based so had shoreline power. I am also heading to marina for the winter so won’t be too much of an issue this year for me so long as it actually works!
 

so would I need whole boat re-plumed to switch to simple gravity fed system so I can ditch this problematic pump? 
 

 

The problem will be what happens if the shoreline fails with the stove burning. Certain inverters can be set to step in and take over, but then you run into battery capacity and recharging it. If the batteries go flat enough for the inverter to shut down, then you will get boiling water spurting out.

 

A 12V pump MIGHT use less electricity than a mains pump plus inverter  but it  depends upon make & model. It may also depend upon the pipe size used.

 

In an ideal world you would get it re-plumbed to work on gravity circulation, but that uses large pipes and if the stove is at the front of the boat it may not work with the top pipe under the gunwale.

[Katie]

Excuse very crude drawing of the layout/set up of the boat’s heating 

And a pic of back of stove for info. 

[TheBiscuits]

Are the radiators and the stove on the same side of the cabin?

[Katie]

Just now, TheBiscuits said:

Are the radiators and the stove on the same side of the cabin?

Yes they are all on same side 

[Katie]

18 minutes ago, Tony Brooks said:

 

The problem will be what happens if the shoreline fails with the stove burning. Certain inverters can be set to step in and take over, but then you run into battery capacity and recharging it. If the batteries go flat enough for the inverter to shut down, then you will get boiling water spurting out.

 

A 12V pump MIGHT use less electricity than a mains pump plus inverter  but it  depends upon make & model. It may also depend upon the pipe size used.

 

In an ideal world you would get it re-plumbed to work on gravity circulation, but that uses large pipes and if the stove is at the front of the boat it may not work with the top pipe under the gunwale.

Ok so just replacing the current potentially faulty pump for replacement new one not best idea then really? Shame as that was the cheapest option! Haha 

[MtB]

That looks like a pipe thermostat to me. It ought to be attached to the flow pipe (top) in order to turn the pump ON when the stove gets hot.

 

The problem with marina power supplies can a bit more subtle than Tony set out. All is usually fine until the first sub-zero night, then all the electric heaters on thermostats set low in the non-liveaboards turn ON and collectively they overload and trip the marine power supply.  First you know about it is your stove boiling over as the pump has stopped. 

[Bee]

How long is the boat Katie?  With the fire / boiler at the back of the boat a simple system would work well without a pump - its because the boat will almost certainly slope up to the front. Snag is that there will be a good bit of disruption to rejig it.  However I am with Tracy D'Arth on this and at times I cut corners, bodge and generally keep fingers crossed and hope but I would change your set up to a simple, trouble free and safe system.

[Katie]

1 minute ago, Bee said:

How long is the boat Katie?  With the fire / boiler at the back of the boat a simple system would work well without a pump - its because the boat will almost certainly slope up to the front. Snag is that there will be a good bit of disruption to rejig it.  However I am with Tracy D'Arth on this and at times I cut corners, bodge and generally keep fingers crossed and hope but I would change your set up to a simple, trouble free and safe system.

It’s 68 foot long! Yes I don’t really want to bodge anything safety related and would prefer to not have to rely on an electric pump for my heating! Just concerned how big a job this will be and if I’ll be able to realistically afford it! 

4 minutes ago, MtB said:

That looks like a pipe thermostat to me. It ought to be attached to the flow pipe (top) in order to turn the pump ON when the stove gets hot.

 

The problem with marina power supplies can a bit more subtle than Tony set out. All is usually fine until the first sub-zero night, then all the electric heaters on thermostats set low in the non-liveaboards turn ON and collectively they overload and trip the marine power supply.  First you know about it is your stove boiling over as the pump has stopped. 

Yes I believe that’s what the thermostat does. No idea what temp is best to set it to though and like I said I set it to a lower temp. When testing the system with a small fire as I didn’t want to have to get the system too hot and pressurised. 
 

Fair point about power at the marina. I’m going to brand new one so hopefully little problems with power cuts. 

[MtB]

5 minutes ago, Katie said:

Fair point about power at the marina. I’m going to brand new one so hopefully little problems with power cuts. 

 

Hmmm. Southern Oxford then? 

 

The likelihood of a new marina not suffering this effect is wholly dependent on the electrical systems architect anticipating this effect when doing his or her diversity calculations.