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Gas water heater connected to calorifier


auslander

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Just now, auslander said:

Hi, question for the plumbers: can you connect the hot water out of the calorifier into the cold input of a gas water heater? If not, why?

 

Thanks!

 

You can but it would be dangerous, very ill advised, and may well ruin the gas water heater as the already hot water flashes off into steam. To say nothing about super-heated steam coming from the hot taps.

 

The way to do it is to use an three port L valve so you ca direct calorifier hot water OR gas heated hot water to the taps.

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7 minutes ago, auslander said:

I had considered using a thermoswitch to disable the gas heater if the water temp was above 40. Still not recommended I suppose?

 

That switch will be a mechanical or elector-mechanical device so a potential failure point. An L valve is manually operated so the boater knows if it has  jammed so can't be set as desired. It is your boat so you can do as you like but I think "keep it simple" is the best way.

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Thanks for the original question and the answer - I was thinking about this myself.   Is there anything in the Boat Safety Certificate about this sort of setup that would preclude it?  I have seen a boat with just this arrangement, reliant upon turning the boiler off post-cruise - and it has a BSS certificate just issued. 

 

Presumably if it were inspected by a Gas Safe engineer it wouldn't pass for that reason - if they were able to tell/took the time to investigate the supply.

 

But, if the boat had a gas bubble tester, then no Gas Safe inspection would be necessary - just a BSSC inspection. 

 

Hence the situation as to why a boat with this arrangement is by the inspection/certification requirements okay - even if not by the common sense/safety standard.  

 

Thoughts on that? 

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Nothing in the BSS about this. But a Gas Safe registered inspector might take the view that such an installation is not covered by the heater manufacturer's installation instructions, so should be a fail.

 

The more practical issue might be that an instantaneous water heater has a fixed gas throughput so essentially raises the water termperature by a fixed amount. There is an overheat protection device which cuts the gas flow if the outlet temperature is too high. This could mean that with warm water input from the calorifier, and the heater going, then the overheat device cuts out, now the oulet water is below the overheat device setting, and the flame starts up again, so you end up with the water heater cutting in and out, and the hot water temperature switching between too hot and too cool, which isn't much fun if you are in the shower.

Edited by David Mack
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57 minutes ago, Tony Brooks said:

 

You can but it would be dangerous, very ill advised, and may well ruin the gas water heater as the already hot water flashes off into steam. To say nothing about super-heated steam coming from the hot taps.

 

The way to do it is to use an three port L valve so you ca direct calorifier hot water OR gas heated hot water to the taps.

Is just one valve required or is another required at the calorifier as well?

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1 hour ago, auslander said:

Is just one valve required or is another required at the calorifier as well?

Just one valve, turn one way for calorifier hot water and the other for gas hot water.  It has three ports. calorifier in, gas heated in, and out to the taps.

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3 hours ago, TandC said:

Am I right in that point about that if you have a bubble-tester it negates the requirement for a Gas Safe inspector to still be able to achieve a BSSC?   

Answering a slightly different question that you didn’t ask - my BSS Examiner advised that having a bubble tester with an instantaneous gas water heater was “not allowed”, and he would fail a boat so fitted if called upon to examine it. Something to do with the maximum rated throughput of the largest available bubble tester being insufficient for the throughput required by a gas water heater (possibly in conjunction with an oven and hob?). Or something along those lines, I’m a little hazy on the details as it was a couple of years ago, and the question only arose through a discussion on where to put the test point when I was revamping the galley.

 

(I think the answer to the question you did ask is that a bubble tester would permit a non-Gas Safe registered BSS Examiner to carry out a soundness test on a boat which fell under the GSIUR regulations, such as a residential or hire boat (and some others). That Examiner would not be permitted to carry out a manometer test on such a boat. There’s more detail in the new checking procedures document on the BSS website.)

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4 minutes ago, AndrewIC said:

Answering a slightly different question that you didn’t ask - my BSS Examiner advised that having a bubble tester with an instantaneous gas water heater was “not allowed”, and he would fail a boat so fitted if called upon to examine it. Something to do with the maximum rated throughput of the largest available bubble tester being insufficient for the throughput required by a gas water heater (possibly in conjunction with an oven and hob?). Or something along those lines, I’m a little hazy on the details as it was a couple of years ago, and the question only arose through a discussion on where to put the test point when I was revamping the galley.

 

(I think the answer to the question you did ask is that a bubble tester would permit a non-Gas Safe registered BSS Examiner to carry out a soundness test on a boat which fell under the GSIUR regulations, such as a residential or hire boat (and some others). That Examiner would not be permitted to carry out a manometer test on such a boat. There’s more detail in the new checking procedures document on the BSS website.)

Ah yes it was that second aspect I was referring to.  I wonder if that is what explains why the boat I refer to has a BSSC.   

 

What a bloody minefield with zero consistency between the approaches and advice that the professionals are able to give.

 

 

 

 

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On 29/03/2022 at 17:54, auslander said:

Is just one valve required or is another required at the calorifier as well?

 

With the L-port valve all you're doing is connecting both hot water sources to each side of the valve and the main hot water pipe (leading to taps, shower, etc) to the valve outlet in the middle. It's very simple and lots of boats have this setup, mine included.

 

Ignore the T-port vale diagrams.

 

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