Plumbing in a back boiler

[Fuel__2001]

Im sure this has been done to death - used the search and couldn't really find an answer so could do with some

 

The current setup is an eberspacher which heats the calorifier and rads, which has a flow/return of 22m Hep2o.

 

I would like to plumb in a backboiler onto the stove to heat the radiators. We already have the back boiler which is 3Kw.

 

Also the stove is already in place and has been working for the last 2 winters. We'd now like to plumb it into the current system so we can have either the eberspacher, or stove working. Preferably heating radiators 2 to 5 as the calorifier can be heated by the immersion and also radiator 1 is in the same room as the stove.

 

As the rads are already fitted, and the pipe work in place, a gravity fed system isn't an option - well i suppose it is an option but possibly a load more grief.

 

 

The questions i have

 

what equipment(pump/valves/pipework etc) will i need, what makes/type?

 

Best way to isolate a system when the other is operational?

 

Safety considerations/BSS?

 

Where on the current system would be the best place to plumb in a water pump?

 

Where on the system would the best place be to hook into the flow/return?

 

Thanks

Edited December 27, 2010 by Fuel__2001

[Eddimonton]

Great diagram!

[blackrose]

The questions i have

 

what equipment(pump/valves/pipework etc) will i need, what makes/type? Anything that is compatible with your existing pipework - (22mm Hep20 for example) the first couple of metres from/to the backboiler should be in copper.

 

Best way to isolate a system when the other is operational? Probably a couple of L-port valves (available from Aquafax). Isolating is probably quite important as I'm not sure if you want to pump hot water though your eberspacher while it's not operating. I might be wrong - I'm not sure what damage that could cause? The thing is that at some point you're bound to forget and I imagine the other problem is that if the stove is going you might have to wait until it dies down if you want to start the eberspacher to get hot water for example. I know a few people have incorporated 2 heating systems into one radiator circuit, but personally it seems a bit complicated and I'd rather have 2 independent systems if at all possible.

 

Safety considerations/BSS? None that I can think of, apart perhaps from avoiding a pressurised system. I know a couple whose pump failed in the middle of the night and they awoke to find a burst pipe spraying jets of super-heated steam through the boat!

 

Where on the current system would be the best place to plumb in a water pump? I don't think it matters but perhaps not too close to the backboiler.

 

Where on the system would the best place be to hook into the flow/return? If it's a pumped system it shouldn't make too much difference.

 

Edited December 27, 2010 by blackrose

[Pretty Funked Up]

The eber should already have isolation valves on flow and return so you can easily disconnect and service it. Shutting either ones of those will stop the water flowing through the eber. Leaving it to flow through will not damage it, you just dont want to waste heat by sending it out into the engine bay and back again.

 

Dont expect you rads to get as hot as with the eber unless you run the fire flat out, which makes the area near the fire way too hot for comfort.

 

I used a bolin CH pump for circulation, expensive but very low consumption, something thats important as it will be running most of the hours in the day (around 20hrs I'd plan your power allowance for).

 

As mentioned use copper for atleast a metre from fire boiler befoer swapping back to hep. You may also want to T into the send and vent it to open air (higher than the highest water point) to help release any pressures that might build up.

 

Use a pipe stat on the flow from fire boiler to control the CH pump.

[Doorman]

Im sure this has been done to death - used the search and couldn't really find an answer so could do with some

 

The current setup is an eberspacher which heats the calorifier and rads, which has a flow/return of 22m Hep2o.

 

I would like to plumb in a backboiler onto the stove to heat the radiators. We already have the back boiler which is 3Kw.

 

Also the stove is already in place and has been working for the last 2 winters. We'd now like to plumb it into the current system so we can have either the eberspacher, or stove working. Preferably heating radiators 2 to 5 as the calorifier can be heated by the immersion and also radiator 1 is in the same room as the stove.

 

As the rads are already fitted, and the pipe work in place, a gravity fed system isn't an option - well i suppose it is an option but possibly a load more grief.

 

 

The questions i have

 

what equipment(pump/valves/pipework etc) will i need, what makes/type?

 

Best way to isolate a system when the other is operational?

 

Safety considerations/BSS?

 

Where on the current system would be the best place to plumb in a water pump?

 

Where on the system would the best place be to hook into the flow/return?

 

Thanks

 

Hi,

 

You're right, this topic has already been covered previously, but if any of the members can offer more advice, I'm sure it will help.

 

Here's my advice, based upon our own c/h system that was originally meant to be powered only by a Mikuni MX40 diesel boiler, that's situated in the engine room on a trad stern narrow boat. As the boat build progressed, we asked the builder to add a back boiler to the Morso Squirrel stove, which is positioned at the fore end of the boat.

 

As this was an alteration to the original design, the builder had to make the final connections from the system to the back boiler, by extending the 22mm Hep2o recirculation pipes in copper and placing the back boiler in series to the system along with the Mikuni, only at opposite ends of the boat. So, as this was an amendment, it was similar to what you are proposing to do!

 

In addition, we specified a Jabsco variable speed 12v resirculation pump which is fitted close to the back boiler (on the return pipe), a bleed valve positioned at the highest (flow) side of the back boiler outlet, together with a pressure relief safety valve mounted close to the bleed valve. At a later date, we replaced the original 'open' type header tank, with an Eberspacher unit that has a filler cap incorporating a pressure relief valve.

 

The recirc pump is energised by a 'Jumo' thermostatically operated switch, which has its sensor positioned on the back boiler copper outlet pipe and is set to switch at 10 degrees celsius. Both the pump and the back boiler, have isolation valves for maintenance purposes.

 

Because the Mikuni MX40 has its ECU control unit mounted away from the body of the boiler

and is effectively isolated from the direct heat of the system, we can run the back boiler without being concerned about the effect it may have on the Mikuni, without the need for isolation valves. In your case, with the Eberspacher, I would certainly consider an isolation system in order to protect the integral ECU unit that normally relies upon the forced air fan to keep it cool. If your stove is mounted at the opposite end to the Eberspacher, you may find that the heat generated in the recirculation pipes is negligible, by the time it reaches the diesel boiler.

 

We run the two systems simultaneously each morning. As the Morso has been ticking over during the night, the Mikuni is set to operate at 6.30am, heating the boat in readiness for yours truly to get up at 7am and stoke the stove back into life. Once that happens, the Mikuni is turned off and the Morso then takes over.

 

We find that this system works very well and is worth the effort to either incorporate from new, or, as you intend, add at a later date.

 

I hope that this long winded account will assist in some way and good luck!

 

Mike

Edited December 27, 2010 by Doorman

[Fuel__2001]

I used a bolin CH pump for circulation, expensive but very low consumption, something thats important as it will be running most of the hours in the day (around 20hrs I'd plan your power allowance for).

 

As mentioned use copper for atleast a metre from fire boiler befoer swapping back to hep. You may also want to T into the send and vent it to open air (higher than the highest water point) to help release any pressures that might build up.

 

Use a pipe stat on the flow from fire boiler to control the CH pump.

 

 

Originally, the idea was that I would make the final connections from the system, to the back boiler, along with a variable speed 12v resirculation pump, a bleed valve positioned at the highest (flow) side of the back boiler outlet, together with a pressure relief safety valve, mounted close to the bleed valve.

 

Thanks for your replies.

 

Firstly the pump - ive seen Jabsco do a 12v heating pump, not cheap but are there any others to consider? (links would be good;))

 

Bleed valve and a pressure relief safety valve - if i move the eberspacher header tank connection so it can feed either system, like in this alternative setup im considering, would i still need to fit the bleed and PR valves into the alternative system?

 

Edited December 27, 2010 by Fuel__2001

[ditchcrawler]

Thanks for your replies.

 

Firstly the pump - ive seen Jabsco do a 12v heating pump, not cheap but are there any others to consider? (links would be good;))

 

 

I have one of these and its not the quietest of things, I wouldn't want it running overnight

[sharpness]

If you are only planning on using the eber when the stove is not running, why not just leave out the L port valves and put a full flow iso valve in the flow & return next to the eber.

With the ISO valves closed the stove will then heat the whole lot (except the eber) & put a TRV on rad 1 as it is in the same room as the stove. You wouldnt need a PRV with an open feed & expansion (header) tank.

If you wanted you could put ISO valves between the calorifier & rad 1 so that you could run the eber for hot water when the stove is not burning. (You would of course need a 2nd feed from the header on the eber side of those ISO valves, just tee into the existing).

 

Steve

[Pretty Funked Up]

Thanks for your replies.

 

Firstly the pump - ive seen Jabsco do a 12v heating pump, not cheap but are there any others to consider? (links would be good;))

 

Bleed valve and a pressure relief safety valve - if i move the eberspacher header tank connection so it can feed either system, like in this alternative setup im considering, would i still need to fit the bleed and PR valves into the alternative system?

 

 

You diagram should work ok, but remember you need a way to bleed the fire boiler much the same as all the rads for obvious reasons

 

I wouldnt use L port . T port gives ultimate flexibility

On 20 hrs/day the bolin uses 3Ah and the equivilent jabsco is 24Ah

Edited December 27, 2010 by Pretty Funked Up

[Fuel__2001]

If you are only planning on using the eber when the stove is not running, why not just leave out the L port valves and put a full flow iso valve in the flow & return next to the eber.

With the ISO valves closed the stove will then heat the whole lot (except the eber) & put a TRV on rad 1 as it is in the same room as the stove. You wouldnt need a PRV with an open feed & expansion (header) tank.

If you wanted you could put ISO valves between the calorifier & rad 1 so that you could run the eber for hot water when the stove is not burning. (You would of course need a 2nd feed from the header on the eber side of those ISO valves, just tee into the existing).

 

Steve

Cheers Steve

 

Some great ideas to consider which might actually be a better way to go. The only drawback I can see is the output for rads 2 to 5 which combined is about 3Kw. The backboiler is rated to 3Kw so adding in the calorifier, the back boiler might not be enough, but still a great idea.

 

 

You diagram should work ok, but remember you need a way to bleed the fire boiler much the same as all the rads for obvious reasons

 

I wouldnt use L port . T port gives ultimate flexibility

On 20 hrs/day the bolin uses 3Ah and the equivilent jabsco is 24Ah

Thanks for the info on the bolin pump

 

Just curious why you would consider using the T valve over the L valve?

 

I need to get the back boiler out as im not certain if there is a bleed valve incorporated into it (like a radiator) - is this valve something that usually is, or has to be fitted into the pipe work behind the stove?

[Pretty Funked Up]

Just curious why you would consider using the T valve over the L valve?

 

is this valve something that usually is, or has to be fitted into the pipe work behind the stove?

 

T port allows you to choose: (in your setup)

rad 1 and cal only

or

rads 2-5 only

or

everything

or

nothing

 

The boiler bleeder is something you'll have to add in the pipe work. I simply put a drain cock on the top of a vertical pipe, T'ed off the send from the fire, this allows you to pop on a standard garden hose and vent whatever comes out to the outside rather than inside the cabin.

[blackrose]

Just curious why you would consider using the T valve over the L valve?

 

He's right. I meant T-port valve earlier for switching between backboiler and webasto. It's an L moving within a T so that while the supply side gets switched the outlet side is always open. That's the best way of switching between two different supplies which go to one outlet.

Edited December 28, 2010 by blackrose

[Doorman]

I have one of these and its not the quietest of things, I wouldn't want it running overnight

 

This has been suggested before, but we find ours to be totally quiet in operation. I think as PFU has pointed out, the Bolin pump is superior to the Jabsco, specially when you see the power consumption comparison!

 

Mike

[Doorman]

Eberspacher Info

 

The backboiler is rated to 3Kw so adding in the calorifier, the back boiler might not be enough, but still a great idea.

 

You're right, the backboiler is not sufficiently rated to heat both the rads and the calorifier, whereas the Eberspacher should cope with both.

 

One way of overcoming this, is to fit a thermostat valve on the flow from the diesel boiler to the calorifier. This has two advantages. Firstly, it allows the radiators to heat up quickly prior to the thermostat opening, allowing the calorifier to absorb much of the heat produced. Secondly, depending on the temperature setting on the valve, when heating the system from the back boiler, the thermostat should not open, preventing the 3kw of back boiler heat from being dissipated through the calorifier and concentrating it on the rads.

 

Eberspacher can supply this type of valve together with directional control valves. Please see link at the top of the page (my lap-top is having a menstrual cycle and won't put the link in the right place!)Technical Manuals/Hydronic 4&5 Downloads.

 

Finally, I have photo's of the bleed valve and PRV set-up on our boiler on the computer back at our boat. When we return there from our temporary manic home visit, I'll post the pictures on here and hopefully it will clarify the situation.

 

Mike

Edited December 28, 2010 by Doorman

[Doorman]

You wouldnt need a PRV with an open feed & expansion (header) tank.

Steve

This is true and was what the builder had originally fitted to our boat. The main problem with the solid walled open header tank that we had, is that if you do get a pressure surge associated with expansion, the heating water then flows over the

top of the tank, creating a possible scalding risk, not to mention (as was in our case) short circuiting electrical components installed directly below the tank

 

The Eberspacher tank seals the system of unwanted air and being translucent, allows you to check the minimum fluid level without having to lift the top off the tank. Also, if there is expansion in the system, there's a pipe outlet near the filler cap that enables you to fit a small bore drain hose to safely vent the overflow into the bilges.

 

Mike

[sharpness]

This is true and was what the builder had originally fitted to our boat. The main problem with the solid walled open header tank that we had, is that if you do get a pressure surge associated with expansion, the heating water then flows over the

top of the tank, creating a possible scalding risk, not to mention (as was in our case) short circuiting electrical components installed directly below the tank

 

The Eberspacher tank seals the system of unwanted air and being translucent, allows you to check the minimum fluid level without having to lift the top off the tank. Also, if there is expansion in the system, there's a pipe outlet near the filler cap that enables you to fit a small bore drain hose to safely vent the overflow into the bilges.

 

Mike

I understand exactly what you mean except the "pressure surge". Surely the level in the header tank simply rises and falls with temperature level, where does the "surge" come from? If the header is the correct size (a couple of pints?) once it has overflowed the first time it should never do so again unless the system gets even hotter.(or you add more water)

This bit is much the same as the thread a couple of months ago about keep topping up the engine coolant because it kept overflowing.

 

Steve

[Fuel__2001]

Eberspacher Info

 

You're right, the backboiler is not sufficiently rated to heat both the rads and the calorifier, whereas the Eberspacher should cope with both.

 

One way of overcoming this, is to fit a thermostat valve on the flow from the diesel boiler to the calorifier. This has two advantages. Firstly, it allows the radiators to heat up quickly prior to the thermostat opening, allowing the calorifier to absorb much of the heat produced. Secondly, depending on the temperature setting on the valve, when heating the system from the back boiler, the thermostat should not open, preventing the 3kw of back boiler heat from being dissipated through the calorifier and concentrating it on the rads.

 

Eberspacher can supply this type of valve together with directional control valves. Please see link at the top of the page (my lap-top is having a menstrual cycle and won't put the link in the right place!)Technical Manuals/Hydronic 4&5 Downloads.

 

Finally, I have photo's of the bleed valve and PRV set-up on our boiler on the computer back at our boat. When we return there from our temporary manic home visit, I'll post the pictures on here and hopefully it will clarify the situation.

 

Mike

 

Those photo's would be a great help

 

The eberspacher is a hydronic 10 and whilst it works does a good job - although the exhaust has decided to fall apart which is why its time to get this other system operational. The eberspacher typically always breaks down in the winter!

One of the issues with the current setup is the the length of run of pipework. Even the eberspacher has trouble heating the single bedroom as this is the last rad on the 'pipe run' and about 60' away from the burner. The pipe work runs up the left and partially down the right. Rads 4&5 are opposite rad 2, although on different sides of the boat.

 

Currently all the rads have TRV, hopefully the picture has more info

 

 

The idea of putting a thermostatic valve on the calorifier is excellent, as this might actually help to increase the output to rad 5 using the eber. I did try putting another pump on the pipe work but this didnt help either in getting heat to rad 5.

 

Ive had a look at the two 12v pump options bolin/jabsco - does anyone no if these limited by a length of pipe run? Ive not had a measure up yet but i would assume somewhere in the region of 40'-50' of pipe run for the 12v pump just to heat rads 2-5.

[Pretty Funked Up]

I have a 60ft boat around 50ft cabin. bolin moves the water the entire length through 3 rads and cal plus eber with ease. in fact it moves it a little too fast, wish i'd placed it further from fire boiler.

 

I've been looking into thermo valves on cal feed as youve probably guessed the whole system works in reverse once the fire is on a low burn. It removes the heat from the cal to the radiators and fire. thermo valves are going in next summer

[Little Gold Nugget]

I understand exactly what you mean except the "pressure surge". Surely the level in the header tank simply rises and falls with temperature level, where does the "surge" come from? If the header is the correct size (a couple of pints?) once it has overflowed the first time it should never do so again unless the system gets even hotter.(or you add more water)

This bit is much the same as the thread a couple of months ago about keep topping up the engine coolant because it kept overflowing.

 

Steve

 

Hi Steve,

 

if you recall my comment, I stated 'if' you get a pressure surge, not when. This relates to if you allow the stove to overheat, the coolant will expand (creating a pressure surge) potentially beyond the level of an open header tank, causing it to overflow. Since fitting the sealed Eberspacher tank, I've not had this experience, even when I've neglected to close the bottom door of the Morso, causing the stove to overheat!

 

Mike

 

Edited to say that my missus has neglected to sign out, hence the reason why this post appears to be from another member

Edited December 29, 2010 by Little Gold Nugget

[Little Gold Nugget]

Those photo's would be a great help

 

The eberspacher is a hydronic 10 and whilst it works does a good job - although the exhaust has decided to fall apart which is why its time to get this other system operational. The eberspacher typically always breaks down in the winter!

One of the issues with the current setup is the the length of run of pipework. Even the eberspacher has trouble heating the single bedroom as this is the last rad on the 'pipe run' and about 60' away from the burner. The pipe work runs up the left and partially down the right. Rads 4&5 are opposite rad 2, although on different sides of the boat.

 

Currently all the rads have TRV, hopefully the picture has more info

 

Ive had a look at the two 12v pump options bolin/jabsco - does anyone no if these limited by a length of pipe run? Ive not had a measure up yet but i would assume somewhere in the region of 40'-50' of pipe run for the 12v pump just to heat rads 2-5.

 

I'm quite surprised that you have a Hydronic 10 installed on a boat of that size. If you recall, I mentioned that we have a Mikuni MX40 heater on our boat, which is also 60' in length. Although its output is less than half of the Hydronic 10, it supplies enough energy to three double radiators and the calorifier, to heat the boat and the domestic hot water sufficiently.

 

It may well be that your heater is over-specified and it heats up too quickly, causing it to idle too often during its operational cycle. This could be why you're having annual problems with reliability. We once had neighbours who owned a 57' x 10' widebeam that had a Hydronic 10 installed. They too had similar problems, until they replaced it with a 5kw alternative. These heaters have to be worked hard, in order that they don't 'coke-up' inside the combustion chamber and around the flame detection device or glow plug.

 

With regard to the capacity of the pumps, I wouldn't think either of those would have trouble with your system. Remember that they're not actually having to pump a head of pressure, but simply recirculating an otherwise static volume of coolant around a level with a very small gradient. If you were to consider a gravity fed central heating system, where there's no pump installed, the water circulates efficiently simply by its difference in weight in relation to heat absorbed.

 

You also mention that the heater struggles to warm rad 5 in the single bedroom, have you tried balancing the system using the lock-shield valves on the rads. By metering the coolant through rads 1 to 4 and leaving rad 5 almost fully open, you may find that it heats up more efficiently. It's certainly worth a try!

 

Mike

Edited December 29, 2010 by Little Gold Nugget

[Fuel__2001]

I'm quite surprised that you have a Hydronic 10 installed on a boat of that size. If you recall, I mentioned that we have a Mikuni MX40 heater on our boat, which is also 60' in length. Although its output is less than half of the Hydronic 10, it supplies enough energy to three double radiators and the calorifier, to heat the boat and the domestic hot water sufficiently.

 

It may well be that your heater is over-specified and it heats up too quickly, causing it to idle too often during its operational cycle. This could be why you're having annual problems with reliability. We once had neighbours who owned a 57' x 10' widebeam that had a Hydronic 10 installed. They too had similar problems, until they replaced it with a 5kw alternative. These heaters have to be worked hard, in order that they don't 'coke-up' inside the combustion chamber and around the flame detection device or glow plug.

 

With regard to the capacity of the pumps, I wouldn't think either of those would have trouble with your system. Remember that they're not actually having to pump a head of pressure, but simply recirculating an otherwise static volume of coolant around a level with a very small gradient. If you were to consider a gravity fed central heating system, where there's no pump installed, the water circulates efficiently simply by its difference in weight in relation to heat absorbed.

 

You also mention that the heater struggles to warm rad 5 in the single bedroom, have you tried balancing the system using the lock-shield valves on the rads. By metering the coolant through rads 1 to 4 and leaving rad 5 almost fully open, you may find that it heats up more efficiently. It's certainly worth a try!

 

Mike

The hydronic 10 was on our 57'x10' widebeam when bought it from NBC. The five rads on there own are touching the 5.5Kw as rad 1 is a beast of a rad, thats not including the calorifier. Ive tried for days/weeks to balance the rads using the lock shields and i can get rads 1-4 roasting but rad 5 even with the other rads closed just doesnt get much heat. Im sure this is due to the length of pipe run and the eber not having enough power from its pump. Eber have some literature regarding the maximum length of pipe run and we go over the maximum length of pipe run

 

As for the eber being reliable - im sure theres plenty of posts on here about this For the first 3 years the eber was the only source of heating and with a 'new born' got a right battering. I know about the gas oil debate and its completely unreliable using this fuel. We had a lovely run just using paraffin/kersone until the local garage closed down. Been using ultra low gas oil since, and hasnt been to much of an issue other than a blower motor dying and new glow plug. The burner got coked up last winter, i actually cut the fuel pipe off the burner and got a friend to weld/braise the pipe back onto chamber.

 

In future if the chamber needs decoking the best place to gain access is to cut off the long cylinder, that way you can get right to the back of the chamber where the fuel drips into the chamber near the glow plug.

Edited December 29, 2010 by Fuel__2001

[Doorman]

This diagram illustrates how simple our present central heating system is. Although there is no method of isolating either the Mikuni, or, the Morso when either one is in operation, this does not have an adverse effect to the efficiency. Also, as previously stated, the two heating sources can be run simultaneously, to our advantage.

 

Mike

 

 

This diagram illustrates the rear view of the back boiler indicating where the bleed & pressure relief valve are positioned.

 

Photo's to follow on a separate post in order to conserve space.

 

Mike

 

Edited December 31, 2010 by Doorman

[Doorman]

I've kept these photo's at full size for clarity. Hope it doesn't take till next year to upload!

 

Mike

 

 

[Robbo]

This diagram illustrates how simple our present central heating system is. Although there is no method of isolating either the Mikuni, or, the Morso when either one is in operation, this does not have an adverse effect to the efficiency. Also, as previously stated, the two heating sources can be run simultaneously, to our advantage.

 

Mike

 

 

You say it can run simultaneously, which direction of the water flow? As won't the pumps be fighting each other? Presuming both "boilers" flow in the direction of the hot water.

[Doorman]

You say it can run simultaneously, which direction of the water flow? As won't the pumps be fighting each other? Presuming both "boilers" flow in the direction of the hot water.

 

Theoretically, I'd be inclined to agree.

 

The only explanation that I can conclude is that at some point in the circuit, when both boilers are in operation (say at the 'T' on the flow circ at rad 3), there is an equalisation of flow from each pump and the water simply circulates from this point through the Morso and back through rad 3 and likewise, the water circulates through rads 1, 2 and the calorifier and the Mikuni.

 

As water will always seek the easiest path, any pressure build up at this point will be relieved through the respective returns on each rad, back to the intake side of their respective pump.

 

Mike