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Diesel water heater


sambo

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Can anyone point me in the right direction of a guide to diesel water heaters? I've searched the threads here and on the web but still have some questions - 

Would something like this work and if so is this a complete system? 

https://www.ebay.co.uk/itm/252144112661

I take it this is installed inside the van and then the exhaust is attached outside with a hole drilled through the floor to attach the exhaust? Do you need to find a motorhome mechanic to install it?

I only ask because I was about to set up an eccotemp in my new electric van but when I read the manual today for the van to find out what a random switch was for I found I have a 13l diesel tank above the rear wheel behind the ply boxing used to fuel an auxiliary heater for cold climates so the traction battery isn't unduly affected....made me think this would be a doable idea.

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1 minute ago, sambo said:

Can anyone point me in the right direction of a guide to diesel water heaters? I've searched the threads here and on the web but still have some questions - 

Would something like this work and if so is this a complete system? 

https://www.ebay.co.uk/itm/252144112661

I take it this is installed inside the van and then the exhaust is attached outside with a hole drilled through the floor to attach the exhaust? Do you need to find a motorhome mechanic to install it?

I only ask because I was about to set up an eccotemp in my new electric van but when I read the manual today for the van to find out what a random switch was for I found I have a 13l diesel tank above the rear wheel behind the ply boxing used to fuel an auxiliary heater for cold climates so the traction battery isn't unduly affected....made me think this would be a doable idea.

Grippatank do diesel heaters they are very good take a look in there site , pure freedom and Varitech also do them .

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5 minutes ago, Pjj said:

Grippatank do diesel heaters they are very good take a look in there site , pure freedom and Varitech also do them .

Gulp not at those prices!!!

@spruce I know from years past you are the man with the knowledge!  I barking up the wrong tree thinking I can get this done at a reasonable cost?

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5 minutes ago, sambo said:

Gulp not at those prices!!!

@spruce I know from years past you are the man with the knowledge!  I barking up the wrong tree thinking I can get this done at a reasonable cost?

Any diesel heater fitted will cost 3:5-4:5 k , you can build it all yourself if you know what you are doing but parts alone will be in excess of £1,500 by the time you get everything.

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1 minute ago, Pjj said:

Any diesel heater fitted will cost 3:5-4:5 k , you can build it all yourself if you know what you are doing but parts alone will be in excess of £1,500 by the time you get everything.

Argh thought the idea was too good to be true. I take it that system on the link no good then?

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1 minute ago, sambo said:

Argh thought the idea was too good to be true. I take it that system on the link no good then?

It would take the chill off the water but to be honest if you go dine this route you need 60 degrees minimum to make a difference to the clean , if you just want more supple hoses in winter the 5 kw will give you that . If you want cheap warm water have you thought about the immersion heater route ?? 

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14 minutes ago, Pjj said:

The one in your link is only 5 kw that will only give you Luke warm water at best , you want the thermo 90 series 9 kw 

Just want it to stop the water freezing on the glass during cold spells.

Does the heater heat water as you use it on demand or does it recirculate on a loop from and to the water tank? 

 

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15 minutes ago, Pjj said:

It would take the chill off the water but to be honest if you go dine this route you need 60 degrees minimum to make a difference to the clean , if you just want more supple hoses in winter the 5 kw will give you that . If you want cheap warm water have you thought about the immersion heater route ?? 

My last van had an immersion heater but got fed up with the condensation dripping on my head in the mornings!

16 minutes ago, Pjj said:

It would take the chill off the water but to be honest if you go dine this route you need 60 degrees minimum to make a difference to the clean , if you just want more supple hoses in winter the 5 kw will give you that . If you want cheap warm water have you thought about the immersion heater route ?? 

Doesnt 60 degrees risk breaking glass on cold days?

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3 minutes ago, sambo said:

Just want it to stop the water freezing on the glass during cold spells.

Does the heater heat water as you use it on demand or does it recirculate on a loop from and to the water tank? 

 

It heats   it up as you use it but to keep the boiler running you need a return to tank feed or the boiler will shut down after every job or when you stop using water , gradually during the day the water in the tank will warm up , you want the boiler running all the time or it will carbon up the burner with  start stop start , it will also take a lot of juice out of the battery on start up as  well 

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5 minutes ago, sambo said:

My last van had an immersion heater but got fed up with the condensation dripping on my head in the mornings!

Doesnt 60 degrees risk breaking glass on cold days?

We use 60 + degrees and don’t have any issues just keep the brush moving don’t let the water stay on one point , depending what heat exchangers you use you can alter the temperature from just a few degrees to maximum 

You will also loose some heat into the ground from the hose the more hose off the reel the more heat it will loose .

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29 minutes ago, Pjj said:

We use 60 + degrees and don’t have any issues just keep the brush moving don’t let the water stay on one point , depending what heat exchangers you use you can alter the temperature from just a few degrees to maximum 

You will also loose some heat into the ground from the hose the more hose off the reel the more heat it will loose .

Ok sooo 5kw one doesn't heat it enough, fair enough. I'll stick with the eccotemp then. Cheers for your help

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If you want to look at the kits then is is what you get for £1300 https://pbautoelectrics.co.uk/shop/webasto-thermo-top-evo-5-rv-welfare-hot-running-water-kit-pbttevo-hotwash/ The window cleaning supply companies are doing the pipework and putting them in a box for their money!!!!!!!

There is a web site that calculates how much heat and what temp rise you get over time here:

https://bloglocation.com/art/water-heating-calculator-for-time-energy-power

Basically water starting temp at 8DegC at a flow rate of 3 litres a min needs 3mins to heat to 60DegC with 5Kw or 2mins with 9Kw. So the pure needs to be in the heat exchanger for 3 mins on 5Kw and 2mins for 9Kw. The above is only a simple guestimate as efficiency of heat exchanger is an issue but also what heat is the Diesel heater putting into the exchanger. You could quite easily add a return to tank that would pre warm up the pure so giving a higher starting temp. You could even add a timer to start the heater circulating tank water 1hr before you are due to start.

In my opinion, if you can get mains to the van, an immersion heater is the best bet with an insulated tank. It's cheap to install, simple, and cheap to run. 

 

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@sambo. These diesel heaters are complex, hence the reason why they are expensive. The best heaters are Webasto and made in Germany. They are renowned as good quality but are very expensive to buy and to repair. There are Chinese knock offs at a more reasonable price. Not sure how they perform against the Webasto. It could well be the Webasto is Chinese made anyway, who knows?

Your gas heater is a tankless design which is pretty straight forward as it heats the water you are going to use. In other words water is pumped through the heater and out to your brush head.

Once water starts to flow through it a spark ignites the gas and the flame heats the water via a heat exchanger.

Diesel doesn't ignite with a spark. It needs compression or heat to start it to burn. These heaters are very complex in that they have a glowplug that heats the incoming diesel up to start a burn. Firing a diesel heater up takes around 90 seconds to get it going and uses a fair bit of battery power. The heater has an internal water circuit that heats up and uses a header tank and water to water plate heat exchangers within that circuit. (Think of it as a central heating boiler heating the radiators in your house. That water is circulated around in a closed loop.) 

A plate water to water heat exchanger has 2 separate circuits which allow the hot water in the internal circuit to transfer heat across to the cold water flowing through the other circuit. This cold water circuit is the one that heads off to the brush head. On the heat exchanger is a thermostatic control valve similar to that used in a shower in your bathroom. Set the temperature low, lets say 50 degrees C, and this valve will regulate the temperature to 50 degrees leaving the heat exchanger even if the internal water circuit in the diesel heater is higher.

Here's the problem with that Thermo Top you linked to. It doesn't produce enough heat to do anything more than keep your hoses supple. In the dead of winter with hoses running across freezing lawn 50 degrees at the heat exchanger ends up as lukewarm at the brush head as you will have experienced with your gas heater.

A popular heater years ago was an 8 litre per minute tankless water heater rated at 16kw. This was slightly hooter than the ideal for window cleaning. That diesel heater you linked to on eBay is a 5kw heater and the most common heater used these days is a 9.1kw heater. A 9.1 KW heater just keeps up with 2 of us. (These heaters run at about 50% efficient, so a 5kw heater will only heat the water using 2.6kw. The rest of the heat is lost through the exhaust and radiation etc. The heat coming from your vent on your gas boiler is wasted heat. The reason why condensing boilers have become a legal requirement.)

As @Pjjsays, you need to keep the furnace running all the time. It isn't a true heat on demand system. This is the challenge.

These furnaces were designed as engine preheaters. They switch on and heat the engine up by heating the cooling water in the engine. Having its own pump that hot water also passes through the internal heater in the cabin to warm that and defrost the windscreen. The industry has taken this a furnace and used it for window cleaning which isn't exactly what it was designed for.

A 13 litre diesel tank is rather small as a secondary fuel tank. On full burn that 5kw heater will draw just less than a litre an hour.

Edited by spruce
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9 hours ago, sambo said:

My last van had an immersion heater but got fed up with the condensation dripping on my head in the mornings!

@Danfire mentioned this stuff https://www.dodomat.com/search?q=Dodo+mat in another post looks good stuff for insulating and should prevent condensation and reduce heat loss, the immersion option looks to be the cheapest, cleanest and easiest option to go for, 

Hopefully he will see this and say which product he used to insulate his van.

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2 hours ago, spruce said:

Diesel doesn't ignite with a spark. It needs compression or heat to start it to burn. These heaters are very complex in that they have a glowplug that heats the incoming diesel up to start a burn. Firing a diesel heater up takes around 90 seconds to get it going and uses a fair bit of battery power. The heater has an internal water circuit that heats up and uses a header tank and water to water plate heat exchangers within that circuit. (Think of it as a central heating boiler heating the radiators in your house. That water is circulated around in a closed loop.) 

I've stumbled on a great way to always have my water at a high temperature. I plug in both reels to recirculation hoses and just swap over at each job. It means when one has cooled down I plug it in to recirculate hot water and use the other one. Lucky I have a 2 man system with only one man operation. 😉

I forgot my rectus fitting hose for my backpack so I just used the 30m tail off my reel. Handy having the tails joined to the thermal hose with rectus fittings.

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10 hours ago, spruce said:

@sambo. These diesel heaters are complex, hence the reason why they are expensive. The best heaters are Webasto and made in Germany. They are renowned as good quality but are very expensive to buy and to repair. There are Chinese knock offs at a more reasonable price. Not sure how they perform against the Webasto. It could well be the Webasto is Chinese made anyway, who knows?

Your gas heater is a tankless design which is pretty straight forward as it heats the water you are going to use. In other words water is pumped through the heater and out to your brush head.

Once water starts to flow through it a spark ignites the gas and the flame heats the water via a heat exchanger.

Diesel doesn't ignite with a spark. It needs compression or heat to start it to burn. These heaters are very complex in that they have a glowplug that heats the incoming diesel up to start a burn. Firing a diesel heater up takes around 90 seconds to get it going and uses a fair bit of battery power. The heater has an internal water circuit that heats up and uses a header tank and water to water plate heat exchangers within that circuit. (Think of it as a central heating boiler heating the radiators in your house. That water is circulated around in a closed loop.) 

A plate water to water heat exchanger has 2 separate circuits which allow the hot water in the internal circuit to transfer heat across to the cold water flowing through the other circuit. This cold water circuit is the one that heads off to the brush head. On the heat exchanger is a thermostatic control valve similar to that used in a shower in your bathroom. Set the temperature low, lets say 50 degrees C, and this valve will regulate the temperature to 50 degrees leaving the heat exchanger even if the internal water circuit in the diesel heater is higher.

Here's the problem with that Thermo Top you linked to. It doesn't produce enough heat to do anything more than keep your hoses supple. In the dead of winter with hoses running across freezing lawn 50 degrees at the heat exchanger ends up as lukewarm at the brush head as you will have experienced with your gas heater.

A popular heater years ago was an 8 litre per minute tankless water heater rated at 16kw. This was slightly hooter than the ideal for window cleaning. That diesel heater you linked to on eBay is a 5kw heater and the most common heater used these days is a 9.1kw heater. A 9.1 KW heater just keeps up with 2 of us. (These heaters run at about 50% efficient, so a 5kw heater will only heat the water using 2.6kw. The rest of the heat is lost through the exhaust and radiation etc. The heat coming from your vent on your gas boiler is wasted heat. The reason why condensing boilers have become a legal requirement.)

As @Pjjsays, you need to keep the furnace running all the time. It isn't a true heat on demand system. This is the challenge.

These furnaces were designed as engine preheaters. They switch on and heat the engine up by heating the cooling water in the engine. Having its own pump that hot water also passes through the internal heater in the cabin to warm that and defrost the windscreen. The industry has taken this a furnace and used it for window cleaning which isn't exactly what it was designed for.

A 13 litre diesel tank is rather small as a secondary fuel tank. On full burn that 5kw heater will draw just less than a litre an hour.

I knew you would give a logical explanation of it all spruce 😂😂

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20 hours ago, scottish cleaning service said:

I've stumbled on a great way to always have my water at a high temperature. I plug in both reels to recirculation hoses and just swap over at each job. It means when one has cooled down I plug it in to recirculate hot water and use the other one. Lucky I have a 2 man system with only one man operation. 😉

I forgot my rectus fitting hose for my backpack so I just used the 30m tail off my reel. Handy having the tails joined to the thermal hose with rectus fittings.

What you are doing is actually good for the boiler as it keeps it from cycling on and off.

Over the years you end up with all sorts of adaptions. We had one job we needed just a little more than 100 meters of hose for. We had a fitting with a male Rectus connected to a Hozelock tap connector so we could daisy chain 2 reels together. Haven't used it in years now but we still carry it on the van just in case.

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