Accumulator & Expansions Tanks

[Clodi]

Is there any reason why I need to by marine Expansion/Accumulator tanks for my central-heating & hot water systems ?

Screwfix, Toolstation etc offerings are a lot cheaper.

[Tony Brooks]

No need as long as you ensure they are for potable water.

[Boater Sam]

Red ones need checking as they are normally for heating system expansion, not fresh water.

Blue and white are usually for potable water.

[ditchcrawler]

How much do you hope to save https://www.midlandchandlers.co.uk/store/product/ws-023.aspx

                                                       https://www.screwfix.com/p/reflex-potable-expansion-vessel-18ltr/7598r

[Troyboy]

Charlie Fox at March fitted out my narrowboat 32 years ago and used an upturned wine bottle as an expansion vessel . I've never replaced it and it still works fine . It is a while since I looked but I think it was a German white wine bottle definitely not champagne .

[Boater Sam]

I did a couple of economy heating jobs on boats using discarder fire extinguishers with tank connectors fitted in the bottom. On their wall clips too. Conversation pieces.

[alan_fincher]

4 hours ago, Boater Sam said:

Red ones need checking as they are normally for heating system expansion, not fresh water.

Blue and white are usually for potable water.

 

I keep hearing this, but it is not my own experience.

SureJust accumulators for potable water are definitely red, for example.

[Clodi]

4 hours ago, ditchcrawler said:

How much do you hope to save https://www.midlandchandlers.co.uk/store/product/ws-023.aspx

                                                       https://www.screwfix.com/p/reflex-potable-expansion-vessel-18ltr/7598r

What is the size of the midland chandler one in litres?. Not so much for the accumulator side of things but I thought the expansion tank needs to be a certain size depending on the setup.

[Ex Brummie]

Given the dimensions of the Midland Chandlers unit, it is probably about 5 lts. As an accumulator, you don't want too much, just enough to stop the pump cycling too often when the taps are turned on for a moment. However, if you are looking for an expansion vessel to protect a calorifier, you may need a larger capacity, but 15 lts should suffice.

The need for an expansion vessel on your heating dependson whether or not you have a sealed or open system. What heating do you have?

[alan_fincher]

9 hours ago, Ex Brummie said:

The need for an expansion vessel on your heating dependson whether or not you have a sealed or open system. What heating do you have?

I don't undertand this.

 

The EV will be connected to the freshwater part of the tank, not to the heating circuit.

 

I would say an EV becomes most important if......

 

1) There is a no return valve on the cold feed to the calorifier,

or

2) You have no accumulator at the pump

 

If there is no NRV, and you have a cold water accumulator, then to some degree the latter can act in the role of an EV, but it is not ideal.

Surejust/Surecal, (who's pre-plumbed accumulators have an inbuilt NRV say you must fit an expansion vessel.   That has nothing to do with whether your heating circuit is open or sealed.

15 hours ago, ditchcrawler said:

How much do you hope to save https://www.midlandchandlers.co.uk/store/product/ws-023.aspx

                                                       https://www.screwfix.com/p/reflex-potable-expansion-vessel-18ltr/7598r

The Screfix one is 18 litres.  Far bigger than you need with a typical boat calorifier, and you are going to need a lot of space to accommodate it.

Chris_W once did some very detailed calculations.  IIRC they concluded that for any typical boat calorifier about half that volumed is more than enough.

[system 4-50]

The surecal website should have a list recommending Expansion Tank sizes for various cauliflower sizes somewhere (it used to).  You don't need a potable one for hot water 'cos you never use hot water for consumption at least my family folklore is than you never should.

I understand that 8L expansion tank is ok for a 55L cauliflower but I can't quote a reference.

[philjw]

Surecal say this:

What size should I fit?

The expansion tank should measure 10% of the calorifier capacity. I.e. the 2 litre expansion tank would work with the 10-22litre calorifier, the 5 litre expansion tank with the 30- 55 litre calorifiers and the 8 litre with the 55-75 litre calorifiers.

[Jen-in-Wellies]

40 minutes ago, system 4-50 said:

The surecal website should have a list recommending Expansion Tank sizes for various cauliflower sizes somewhere (it used to).  You don't need a potable one for hot water 'cos you never use hot water for consumption at least my family folklore is than you never should.

I understand that 8L expansion tank is ok for a 55L cauliflower but I can't quote a reference.

My family had the same folklore. I think it comes from the water to the hot water tank coming from the water tank in the attic, with the traditional collection of dead pigeons rotting in the bottom. Cold water tap in the kitchen came directly from the mains. Not applicable on a boat, but the habit is too well engrained now.

 

Jen

[Alan de Enfield]

54 minutes ago, system 4-50 said:

The surecal website should have a list recommending Expansion Tank sizes for various cauliflower sizes somewhere (it used to).  You don't need a potable one for hot water 'cos you never use hot water for consumption at least my family folklore is than you never should.

I understand that 8L expansion tank is ok for a 55L cauliflower but I can't quote a reference.

 

10 minutes ago, Jen-in-Wellies said:

My family had the same folklore. I think it comes from the water to the hot water tank coming from the water tank in the attic, with the traditional collection of dead pigeons rotting in the bottom. Cold water tap in the kitchen came directly from the mains. Not applicable on a boat, but the habit is too well engrained now.

 

Jen

 

Our family 'folklore' was that the hot water picked up 'nasties' from being sat in copper. (hot water and copper 'reacting')

The fact that our cold water came into the house in lead pipes was conveniently ignored.

For some reason, as a child, I was always impressed and amazed at the size and finish on the wiped lead joints - like a huge, smooth Plum.

Edited November 3, 2018 by Alan de Enfield

[MtB]

11 hours ago, Ex Brummie said:

The need for an expansion vessel on your heating dependson whether or not you have a sealed or open system. What heating do you have?

 

I think you have hold of the wrong end of the stick here. Or the wrong stick, even!

 

We are talking domestic water, not heating systems. And yes if you have a sealed heating system, one will be needed on that too. 

 

So possibly three in total.

 

 

[blackrose]

I bought a red accumulator type tank from Screwfix once and fitted it as a hot water expansion tank to my freshwater system near the calorifier. About 2 years later it started to leak because I didn't realise it was meant for heating systems used with inhibitor/anti-corrosive agent. If it's for your hot freshwater system it must have stainless innards. I think some are epoxy coated but not sure if they're for potable water. 

[blackrose]

12 hours ago, Clodi said:

What is the size of the midland chandler one in litres?. Not so much for the accumulator side of things but I thought the expansion tank needs to be a certain size depending on the setup.

It's supposed to be a certain % of your calorifier volume. From memory it's 8%

Edited November 3, 2018 by blackrose

[MtB]

5 minutes ago, blackrose said:

I bought a red accumulator type tank from Screwfix once and fitted it as a hot water expansion tank to my freshwater system near the calorifier. About 2 years later it started to leak because I didn't realise it was meant for heating systems used with inhibitor/anti-corrosive agent. If it's for your hot freshwater system it must have stainless innards. I think some are epoxy coated but not sure if they're for potable water. 

 

 

There are definitely two different formats of expansion vessel. One has a flange held on by a ring of bolts around the water connection, the other type doesn't. Potable water vessels usually have the ring of bolts in house installations. Non-potable vessels don't, whatever the colour.

 

I suspect on one the water fills the neoprene bag inside and the air/nitrogen is in the space between the bag and the metal shell. On the other type I suspect the air/nitrogen is in the bag and the water around the outside of it. 

 

I've never cut them open for a look though. Its on my long list of Things To Do. 

[blackrose]

1 hour ago, philjw said:

Surecal say this:

What size should I fit?

The expansion tank should measure 10% of the calorifier capacity. I.e. the 2 litre expansion tank would work with the 10-22litre calorifier, the 5 litre expansion tank with the 30- 55 litre calorifiers and the 8 litre with the 55-75 litre calorifiers.

Ok 10% then! I think that's a minimum figure.

Edited November 3, 2018 by blackrose

[ditchcrawler]

2 hours ago, alan_fincher said:

I don't undertand this.

 

The EV will be connected to the freshwater part of the tank, not to the heating circuit.

 

I would say an EV becomes most important if......

 

1) There is a no return valve on the cold feed to the calorifier,

or

2) You have no accumulator at the pump

 

If there is no NRV, and you have a cold water accumulator, then to some degree the latter can act in the role of an EV, but it is not ideal.

Surejust/Surecal, (who's pre-plumbed accumulators have an inbuilt NRV say you must fit an expansion vessel.   That has nothing to do with whether your heating circuit is open or sealed.

The Screfix one is 18 litres.  Far bigger than you need with a typical boat calorifier, and you are going to need a lot of space to accommodate it.

Chris_W once did some very detailed calculations.  IIRC they concluded that for any typical boat calorifier about half that volumed is more than enough.

Heating or Hot water, Hot water will be at pump pressure +thermal expansion, heating will probably be at atmospheric. Which are we talking about?

 

[Ex Brummie]

19 hours ago, Clodi said:

Is there any reason why I need to by marine Expansion/Accumulator tanks for my central-heating & hot water systems ?

Screwfix, Toolstation etc offerings are a lot cheaper.

 

1 hour ago, Mike the Boilerman said:

 

I think you have hold of the wrong end of the stick here. Or the wrong stick, even!

 

We are talking domestic water, not heating systems. And yes if you have a sealed heating system, one will be needed on that too. 

 

So possibly three in total.

 

 

The original post asks about central heating and hot water systems. In my mind, that is 'two sticks' to get hold of which is how I replied.

[Clodi]

Just to clarify, I need an Accumulator for the pump, an expansion for the hot-water and another expansion tank for my diesel central heating.

The Surejust 8ltr tank is £65 whilst the Toolstation 8ltr is £29 they also do a potable tank for around £35.

The central-heating system will be sealed and I'll be guided by the professional design as to the size of the tank but I really need to keep a tight check on the budget hence my original question.

However I always bear in mind the old adage 'Buy cheap buy twice' .

[Ex Brummie]

As long as you make sure you get the right vessel for the right system ,and  as long as you can fit it conveniently, buy the cheapest. Buying a potable unit where the diaphragm can be changed is IMHO a waste of money, as the cost of a diaphragm, if you can find one, will be as much as a new vessel.

I've only ever used those when the vessel is in an application that is essential, and I've bought a replacement diaphragm at the same time as the vessel so there is a spare immediately available.

[Phil Ambrose]

I've always bought EVs and accumulator from eBay best prices and value for money.

Phil