Tepid hot water - what to check...

gregcope said:
Any gotchas/clues as to why our domestic hot water is no longer hot. Barely tepid?

For various reasons Spindrift has had a long time out of the water; So work included replacing the perished clarifier feed hoses, changed the engine coolant as well as replacing the taps.

The taps work as in water comes out when hot is selected.

Engine has been run multiple times for around 30mins each, and there is no hot water. I have topped up the coolant a few times since replacement.

The engine feed hoses get vhot to the touch (both feed and supply) at the clarifier end, which suggests there is enough coolant and no airlock.

Their is a mangy old thermostatic valve on what i assume is the engine feed side.

I am pretty sure before (it was a while ago) even a short motor would produce piping hot water.

Any thoughts / things to check?

thanks!
Click to expand...
The only vaguely mechanical thing that can have stuck over the long period of disuse is the thermostatic valve. If every thing was fine previously then that almost certainly must be the problem
 
I exercised the thermostatic valve "valve" a little metal pin that would move 3mm ish in/out. It defaulted to the out position which I assume is "open" as turning the thermostatic valve "down" moved its plastic pin (that interfaces with the metal pin) down/out (ie would push the metal pin down).

Due to age/corrosion still no joy on removing the plumbing... Now home so this is one for another day.
 
1500 rpm probably isn't enough to get up to temperature, even in gear. I run mine at about 2300-2500 if I want to get it going.
 
If the temperature of the hoses both to and from the calorifier (i.e. the heating water) is properly hot , then the water from the engine is hot 'enough' and a significant amount of it is flowing through the calorifier,

If the above is the case and water coming out of the calorifier chamber (i.e. the supposedly heated water) is not hot, then it seems likely that either
(a) the calorifier chamber(heated side) may be largely filled with air, so that there is little contact of the water intended to be heated with the heating coil, or perhaps
(b) the calorifier is too large to be much heated by the engine unless it is much hotter and/or longer running , perhaps compounded by the 'heated' water being drawn off from the lower, rather than upper end of the calorifier chamber.

If the calorifier has an electric element, checking whether operating that delivers hot water will help narrow down the options.
 
Y
gregcope said:
Any gotchas/clues as to why our domestic hot water is no longer hot. Barely tepid?

For various reasons Spindrift has had a long time out of the water; So work included replacing the perished clarifier feed hoses, changed the engine coolant as well as replacing the taps.

The taps work as in water comes out when hot is selected.

Engine has been run multiple times for around 30mins each, and there is no hot water. I have topped up the coolant a few times since replacement.

The engine feed hoses get vhot to the touch (both feed and supply) at the clarifier end, which suggests there is enough coolant and no airlock.

Their is a mangy old thermostatic valve on what i assume is the engine feed side.

I am pretty sure before (it was a while ago) even a short motor would produce piping hot water.

Any thoughts / things to check?

thanks!
Click to expand...
You have junked some piping and probably thrown out a one way valve check so allowing cold water to dilute the hot output. Run through the water flows and ensure hot water output from the calorifier does not drift back. Fit valve in this pipe. Simple job. Whale valve will do the job. Use metal version not plastic.

PWG
 
Hi @peter gibbs

I replaced the engine coolant hoses from / to the clarifier not the domestic side. No view of any one way valve. There is a valve on domestic hot outlet which no longer appear to fully close/work.

thanks for the idea mind, I did not know those could be fitted.
 
gregcope said:
Hi @peter gibbs

I replaced the engine coolant hoses from / to the clarifier not the domestic side. No view of any one way valve. There is a valve on domestic hot outlet which no longer appear to fully close/work.

thanks for the idea mind, I did not know those could be fitted.
Click to expand...
Assuming all worked before you changed the hoses from engine to calorifer then probably that is where the problem is. Did you check out your "mangy old thermostatic valve " i refered to in my post munber 20?

Www.solocoastalsailing.co.uk
 
@Plum I tried to remove it but the plumbing fittings were all corroded, so I gave them a gentle dousing of plusgass and will come back to them.

i did remove the top and excercise the little valve by moving the little pin in/out.

i will post a picture soon... but the forum software does not like an iphone picture size...
 
And now a photo - unless I am missing something the forum software does not like posting from an iphone, so had to massage it on a laptop first;

tank.jpg
 
Those Drayton valve s do tend to stick shut . I used to have them on the central heating system.

But if it is stuck shut the coolant return hose to the engine wont get hot
 
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gregcope said:
And now a photo - unless I am missing something the forum software does not like posting from an iphone, so had to massage it on a laptop first;
Click to expand...

As LadyInBed has said, that's a thermostatic valve for a domestic radiator, and it's absolutely no good for your purpose. You need to replace it with a proper thermostatic mixing valve, such as this one - Thermostatic Mixing Valve for Hotpot Calorifiers (15mm)
 
pvb said:
It's not, and it won't.
Click to expand...

It looks like a Drayton Tapstat Cylinder control valve and it did work according to the OP



Its not the most sensible way to contol the temeprature of the domestic hot water though. It would be better to heat the calorifier fully and then control the temperature of the water going to the taps with a thermostatic mixer valve. You get more hot water that way.



1620057576849.png
 
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VicS said:
It looks like a Drayton Tapatat Cylinder control valve and it did work according to the OP
Click to expand...

Do you know how these things work? They're designed to control the water temperature in domestic applications. There's no way it's appropriate or necessary in a boat calorifier installation.

Edit: I see you've edited your post since I replied....
 
The Drayton tapstat are really only meant to be used on domestic central heating systems , you will probably find the through put hole in valve severely reduced in diameter ,therefore restricting water flow. Even when new the restriction in a 15mm valve is down to 10mm due to valve seat machining.
As already stated , these valves are notorious for sticking in the closed position. Though if this was your case you would not get hot flow and return pipes.
My first guess is the valve seat is heavy fouled and the valve stuck in a partially closed/open position allowing enough warm water through to heat the pipes, but not enough flow to transfer heat fully to clarifier.
You could try removing the thermostatic valve head ( simply unscrew the chrome ring t base of white plastic housing) may need grips. No need to drain anything to do this. Under this housing you will find a small protruding pin in the center . If pin is almost flush its stuck closed . If pin is 10 mm ish proud and will push in and spring out its working correctly. Usually you can tap repeatedly on a stuck pin and they will eventually free themselves.

Sorry my post is abit longwinded
 
A far better solution is remove this valve and install a blender/ mixer valve on the domestic hot outlet. More hot water will be available, only clean potable water flow through the valve, obviously less restrictions on primary circuit (pipes from an too engine).
Downside is the preasure relief blow off will probably open more frequently

As PVB linked too above
 
VicS said:
It is surely a thermostatic control valve for a domestic hot water cylinder.........and should work just fine on the boat calorifier. It used to work OK according to the OP

Similar I must admit to the radiator TRVs

.See here Drayton MK4 TAPSTAT 15mm 2 Way Cylinder Control 07 45 015 0745015 5016254101160 | eBay
Click to expand...

yes that looks like the one!

wingcommander said:
The Drayton tapstat are really only meant to be used on domestic central heating systems , you will probably find the through put hole in valve severely reduced in diameter ,therefore restricting water flow. Even when new the restriction in a 15mm valve is down to 10mm due to valve seat machining.
As already stated , these valves are notorious for sticking in the closed position. Though if this was your case you would not get hot flow and return pipes.
My first guess is the valve seat is heavy fouled and the valve stuck in a partially closed/open position allowing enough warm water through to heat the pipes, but not enough flow to transfer heat fully to clarifier.
You could try removing the thermostatic valve head ( simply unscrew the chrome ring t base of white plastic housing) may need grips. No need to drain anything to do this. Under this housing you will find a small protruding pin in the center . If pin is almost flush its stuck closed . If pin is 10 mm ish proud and will push in and spring out its working correctly. Usually you can tap repeatedly on a stuck pin and they will eventually free themselves.

Sorry my post is abit longwinded
Click to expand...

The little copper pin moves around 4mm up/down.
 
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