Heat­ing a boat prop­erly can be no­to­ri­ously tricky, but get the plumb­ing right and it’s a lot sim­pler

Canal Boat - - Contents - WORDS BY PETER COL­LARD

Heat­ing a boat prop­erly can be tricky, but get the plumb­ing right and it’s a lot sim­pler

It’s all in the plumb­ing, get that right and any heat­ing prob­lems will be much eas­ier to solve

How of­ten do you hear the cry “my boat takes hours to warm up”, “my sa­loon’s hot but my bed­room’s cold”, “my boat’s too cold”, or “my boat’s too hot, my feet are al­ways cold!”. All of those com­plaints are usu­ally down to your plumb­ing not be­ing quite right.

So to clear up some of the con­fu­sion around the pipes, here’s a guide to mak­ing sure your boat and heat­ing sys­tem is plumbed cor­rectly so that your boat will warm up faster with a more even heat spread.

Nar­row­boats nor­mally use the same com­po­nents for plumb­ing as you would find in a typ­i­cal mod­ern house­hold sys­tem, but a boat shouldn’t be treated the same; you don’t have a large, vari­able speed 240v wa­ter pump, clean burn­ing gas for fuel or large vol­umes of coolant.

Tak­ing this into con­sid­er­a­tion, it’s prob­a­bly eas­i­est to break it all down by look­ing at a typ­i­cal nar­row­boat lay­out as pic­tured right and ex­am­ine each part in de­tail to find any glitches in your sys­tem.

1. Diesel-fired heater con­nected to a ba­sic coolant cir­cuit with the hot flow pipes shown in red and the cooler re­turn pipes shown in blue.

2. Op­tional ser­vice valves. If fit­ted they will en­able a much faster, eas­ier re­moval and re­place­ment of a heater with­out in­tro­duc­ing air into the sys­tem. This can cut ser­vice labour costs con­sid­er­ably as the sys­tem will not re­quire drain­ing; it can be quickly bled from the heater’s bleed screw with­out the need to re-bleed the whole sys­tem. 3. Twin pipe header tank with the re­turn flow pass­ing through it. Why two pipes?

(1) To act as a per­ma­nent auto bleed in the sys­tem, any air re­turn­ing to the heater must come out in the header tank.

(2) To mix any an­tifreeze added to the sys­tem. Neat an­tifreeze will not mix in a sin­gle pipe header tank.

(3) The header tank will add a more coolant vol­ume to the sys­tem. This makes the heater work for a lit­tle longer to heat this ex­tra vol­ume, but once the heater reaches tem­per­a­ture and shuts down, the coolant pump will con­tinue to run; this ex­tra vol­ume keeps the heater off for a lit­tle longer too. This can help soften out any rapid short-cy­cling (see be­low).

If you have an open header tank you are in­tro­duc­ing oxy­gen into your coolant and this will de­grade the an­tifreeze much faster. If you have a self-fill­ing header tank, check your an­tifreeze con­sis­tency on a reg­u­lar ba­sis.

4. Do­mes­tic hot wa­ter tank, (calori­fier). Usu­ally, one of the first com­po­nents in the sys­tem. It’s com­monly be­lieved that the more flow you put through a calori­fier from the heat­ing cir­cuit, the faster it will heat up.

Sadly, this is rarely the case. Most com­mon, nar­row­boat calori­fiers (55 to 75ltr), will gen­er­ally have a very ba­sic cop­per coil inside, ca­pa­ble of trans­mit­ting ap­prox­i­mately 1 to 1.5kW of heat en­ergy into the do­mes­tic hot wa­ter. So pass­ing 75% of your avail­able flow rate through the calori­fier is fairly point­less. If too much flow is go­ing through the calori­fier cir­cuit it can ad­versely af­fect the heater.

Once the calori­fier is up to tem­per­a­ture the coolant from the heater can re­turn hot enough to shut the heater down; only then to have the coolant com­ing back from the ra­di­a­tors start it up again.

(Short-cy­cling). Most boats I look at have no bal­ance valve, or if they have, it’s wide open. As all the heat and pump pres­sure is at the back of the sys­tem, ap­prox­i­mately 75% of the heated coolant will be go­ing through the calori­fier and back to the heater, leav­ing just 25% to heat the rest of the boat.

If the sys­tem is bal­anced prop­erly, you will usu­ally end up with 10 to 25% of your hot coolant go­ing through the calori­fier and 90 to 75% heat­ing your boat. Your hot wa­ter won’t take any longer to heat than it ever has but your boat will heat up a lot quicker (pre­sum­ing your ra­di­a­tors are big enough, of course).

If this is hard to be­lieve, bear in mind you will only nor­mally have a 1 to 1.5kW 240v im­mer­sion el­e­ment and that heats the wa­ter quick enough, doesn’t it?

Tip. Don’t be tempted to put the flow di­rectly through the calori­fier; it will ruin the flow rate for the rest of the sys­tem and take longer to heat the boat up from cold. It may force the heater to run in low power mode be­fore it should. Don’t take the calori­fier into ac­count when work­ing out your heater size, once it’s up to tem­per­a­ture, it’s out of the equa­tion.

5. Iso­la­tion valve. Do I need one? Yes. Un­for­tu­nately, many boats out there don’t have one fit­ted, or if they do it’s nor­mally wide open, but with­out one you can’t bal­ance your calori­fier (see No. 4). Worth ev­ery penny of the £2 or £3 cost.

6. Lock­shield valve. Used to bal­ance the flow through each ra­di­a­tor. Once set, they should be tam­per-proof. A lit­tle tweak on one ra­di­a­tor can ruin the flow through all the oth­ers. Bear in mind you have two flow anom­alies go­ing on in a typ­i­cal nar­row­boat pipe lay­out. At the heater end of the sys­tem you have the pump pres­sure and at the far end of the sys­tem you will have flow pres­sure, so don’t be afraid of re­strict­ing the flow through the last ra­di­a­tor in the sys­tem, too. Re­mem­ber, you can’t bal­ance the sys­tem if some­one has joined the flow and re­turn pipe un­der the ra­di­a­tor (Fig­ure 2).

7. Ra­di­a­tor. Sounds sim­ple doesn’t it? But there is much to talk about here, in fact, as far as nar­row­boat heat­ing goes this is a vast and com­plex sub­ject so we’ll ab­bre­vi­ate it as far as pos­si­ble.

Whether you have ra­di­a­tors, con­vec­tors, fin­rads (skirt­ing ra­di­a­tors), un­der­floor heat­ing, blown air ma­trix units or any such com­bi­na­tion, the main cri­te­ria for the heater is that at least 2.5kW of heat en­ergy is re­moved from the heater as the boat is be­ing warmed and as an owner you will want fast, even heat. Of­ten we see nei­ther of these sce­nar­ios.

The com­plaints of “my boat takes hours to warm-up”, “my sa­loon’s hot but my bed­room’s cold”, “my boat’s too cold” or “my boat’s too hot”, “my feet are al­ways cold”, are all is­sues caused by ra­di­a­tor size, type and lay­out.

Tip. Have enough ra­di­a­tors to do the job. Don’t be afraid of putting larger or more ef­fi­cient ra­di­a­tors in your boat. For ex­am­ple, on a 58ft boat if you put 5kW of ra­di­a­tors on a 4kW heater, you are still putting 4kW into a boat that only needs 3kW.

Ra­di­a­tors will give a more com­fort­able heat than con­vec­tors in a con­fined space. Ra­di­a­tors and con­vec­tors should be fit­ted as low as prac­ti­cally pos­si­ble to the floor.

Fin­rads should be used with cau­tion.

Sin­gle pipe fin­rads can’t be zone con­trolled so if it gets hot in your sa­loon, for ex­am­ple, you will have to switch the heater off. Twin pipe fin­rads should only have the flow pipe go­ing through them to get full ef­fi­ciency. Fin­rads can be com­plex to plumb in and con­trol to achieve an even spread of heat through­out the boat.

Blown air ma­trix units should be con­sid­ered if the boat lay­out does not al­low for enough ra­di­a­tors, the gal­ley for ex­am­ple. If the boat is only used on an oc­ca­sional ba­sis, blown air ma­trix units will warm the air quickly and give per­ceived heat while wait­ing for the ra­di­a­tors to bring the fab­ric heat of the boat up to tem­per­a­ture.

Un­der­floor heat­ing works well in wide­beams but it can be hard to find enough floor space in a nar­row­boat. In both cases, sleep­ing cab­ins will nor­mally re­quire some form of sup­ple­men­tary heat­ing such as a ra­di­a­tor or ma­trix unit.

It’s worth re­mem­ber­ing that if a ra­di­a­tor man­u­fac­turer states his ra­di­a­tor puts out 1kW of heat en­ergy then it should have been tested to an in­dus­try stan­dard with a set flow tem­per­a­ture at a set room tem­per­a­ture and a de­fined flow and re­turn tem­per­a­ture across the ra­di­a­tor. You should sub­tract 10% off a ra­di­a­tor’s stated out­put to al­low for a typ­i­cal diesel heater’s work­ing tem­per­a­tures and flow rates. So if you think you have 3kW worth of ra­di­a­tors on your boat, you may only be get­ting 2.7kW from them.

Tip. If you fit con­vec­tor ra­di­a­tors these should be within 150mm (6in) of the floor to stop the cold feet, hot head syn­drome. If you have high plinths, stick to ra­di­a­tors rather than con­vec­tors if you want warmer feet.

8. Ther­mo­static ra­di­a­tor valve (TRV). Why fit TRVs? Again a fairly long sub­ject, but very ba­si­cally, fit­ting TRVs will achieve a more even heat through­out your boat than you would get with man­ual valves or a room ther­mo­stat. Fit­ting TRVs may make the heater short-cy­cle for short pe­ri­ods of time now and then. Some man­u­fac­tur­ers rec­om­mend you don’t fit TRVs for this rea­son, but this is rel­a­tively old think­ing and goes back to the days of high sul­phur gas oil (red diesel). Now ev­ery­one is us­ing ul­tra low sul­phur gas oil, short bouts of short-cy­cling should not harm the heater and the tiny amount of ex­tra cur­rent used from the bat­ter­ies is a small price to pay for a boat that feels com­fort­able from front to back.

Fit­ting a room ther­mo­stat for tem­per­a­ture con­trol in a nar­row­boat rarely works well and there is no ideal place to fit one that will mon­i­tor both ends of the boat at once. If you light the log burner for ef­fect, a TRV will shut the sa­loon ra­di­a­tor or if you start cook­ing, a TRV will shut the gal­ley ra­di­a­tor while still heat­ing the com­pan­ion­way or bed­rooms.

9. Towel rail. Fit lock­shield valves to a small ra­di­a­tor or towel rail and set them both to fully open. This, com­bined with the calori­fier loop, will give you a by-pass cir­cuit for when all the ra­di­a­tor valves are shut. 10. Pipework. Again, very ba­si­cally, pipework must be a min­i­mum of 22mm from the heater to the last com­po­nent in the sys­tem, go through the last ra­di­a­tor or com­po­nent, re­gard­less of any valves or TRVs (see page 69). A com­mon mis­take here is to run the pipework un­der the last ra­di­a­tor and then re­turn to the heater, this leaves you with a sys­tem that is vir­tu­ally im­pos­si­ble to bal­ance. Seventy per­cent of your hot wa­ter will be rush­ing around the flow and re­turn pipe as that will be the path of least re­sis­tance (see fig­ure above).

If pipework is re­quired down both sides of the boat use the two last ra­di­a­tors or com­po­nents as re­turns.

Tip: Flow rate is paramount to get­ting the best out of your heater and sys­tem. Don’t fit too many el­bow fit­tings in the pipework, al­ways use swept bends where pos­si­ble. Oddly, when bal­anc­ing your sys­tem don’t be afraid of re­strict­ing the flow through the last ra­di­a­tor. Be­cause of the pipe lay­out in a typ­i­cal nar­row­boat, it is nor­mally the mid­dle ra­di­a­tors that suf­fer from lack of flow, not the be­gin­ning and end ones.

If your last ra­di­a­tor has been plumbed prop­erly, you will be able to slow the flow down and force more wa­ter through the mid­dle ra­di­a­tors. Al­ways keep the plumb­ing side as sim­ple as pos­si­ble, have one main flow and re­turn in 22mm pipe and tee all the com­po­nents off in 15mm.

Ev­ery­thing in this ar­ti­cle is just scratch­ing the sur­face of nar­row­boat heat­ing but it should give you a few point­ers if your boat is not heat­ing as you would ex­pect.

Don’t have too much flow through the calori­fier

A typ­i­cal nar­row­boat lay­out – or how a typ­i­cal nar­row­boat should be laid out

Make sure the pipe runs are cor­rect

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