Hot & cold bar shower

[embis]

We have a bar shower fitted in our narrowboat. Hot water produced by the oil fired heating system. The water is either boiling or freezing never adjustable beyond these extremes. I have replaced the bar once, assuming that a thermostat on the mixer had failed, but it still does the same. Seems unlikely that the second thermostat is also faulty so that leads me to suppose the problem is elsewhere.

Not sure how the hot water arrives at the outlet, is there likely to be a separate pump for this? Might that be the issue? Whenever I turn on hot water elsewhere in the boat the main water pump kicks in... I assume that's pumping cold back into the calorifier?

Any suggestions gratefully the received.. it would be nice to be able to have a shower!

[stegra]

You normally need roughly equal pressure to both sides on these. Most specify that the pressure must be a minimum of 1 bar but I've seen a few where 0.5 bar is stated. In domestic situations this problem arises when there's low pressure with the hot side being gravity-fed and mains pressure on the cold. Fitting an inline pump in the hot feed normally resolves it but sometimes a cold header tank and dual pump might be needed.

Not sure how this relates to your system but getting the pressures approximately equal is important. It might be that there's too much resistance in the hot side thus reducing the pressure. These bar mixers don't like dirt in the water so be sure not to let them suck up any debris from a near empty tank and fit the filters on the inlets.

[Tacet]

Check that the hot and cold pipes are round the right way.  If not, it gives the effect you mention.

 

 

[ditchcrawler]

5 hours ago, Tacet said:

Check that the hot and cold pipes are round the right way.  If not, it gives the effect you mention.

 

 

Very true

 

[Ex-Member]

Our boat had the tiniest mixer bar you could imagine, 117mm centres, but with a TMV set at around 40degrees.  I am replacing it with a standard thermostatic bar valve and I might move the TMV as the hot water to the basin gets really hot.

[mrsmelly]

I never have thermostatic valves they are an unecessary pain in the posterior. We have as always a plain instantly adjustable mixer tap. Hot and cold water are pumped into the back of it and a twiddle either way lets in more cold water straight from holding tank or more hot water from cauliflower. Infinately adjustable in an instant and nowt to go wrong.

[dor]

I originally installed separate pumps for the hot and cold side.  Trouble was as each pump cut in at different times the pressure would change and the thermostat in the bar mixer couldn't react quickly enough.  I linked the two sides and just use one pump and the thermostat works fine.   I would be surprised if the differences in pipework between hot and cold sides was enough to trouble the mixer.

I agree that if the mixer is installed the wrong way round you get either hot or cold.

[Neil2]

11 hours ago, stegra said:

You normally need roughly equal pressure to both sides on these. Most specify that the pressure must be a minimum of 1 bar but I've seen a few where 0.5 bar is stated. In domestic situations this problem arises when there's low pressure with the hot side being gravity-fed and mains pressure on the cold. Fitting an inline pump in the hot feed normally resolves it but sometimes a cold header tank and dual pump might be needed.

Not sure how this relates to your system but getting the pressures approximately equal is important. It might be that there's too much resistance in the hot side thus reducing the pressure. These bar mixers don't like dirt in the water so be sure not to let them suck up any debris from a near empty tank and fit the filters on the inlets.

The modern low pressure ones work fine in my experience - we have vastly different pressures on H and CW supply but the Mira unit we have works perfectly.  They do not like frost though so if the OP's unit has been subjected to freezing temperatures it's a possible cause of the problem.

Alternatively, and assuming the hot and cold are connected correctly, I'd look up the manufacturers helpdesk number - I've had a couple of plumbing issues where I've had to do this and found them remarkably helpful.    

[jddevel]

A few years ago installed a couple of these "bar" showers in my properties for sale. Nothing but problems getting them right. Changed them for lever type i.e. Mira. More expensive but fit and forget. Incidentally they now have a limiter to prevent excessively high temperatures.

[sharpness]

7 hours ago, mrsmelly said:

I never have thermostatic valves they are an unecessary pain in the posterior. We have as always a plain instantly adjustable mixer tap. Hot and cold water are pumped into the back of it and a twiddle either way lets in more cold water straight from holding tank or more hot water from cauliflower. Infinately adjustable in an instant and nowt to go wrong.

That's OK for you &me but my 5yr old grandson who always washes his hands might get caught out, not something I would be willing to take a chance on.

Steve

[cuthound]

We have a thermostatic valve on the output of the calorifier. 

Two advantages,

one, there is no chance of anyone being scalded at any hot tap, 

two, the hot water in the calorifier goes a lot further.

[nicknorman]

We have a bar mixer shower that works perfectly. I'd strongly suspect hot and cold reversed as mentioned earlier.

[Neil Smith]

9 hours ago, sharpness said:

That's OK for you &me but my 5yr old grandson who always washes his hands might get caught out, not something I would be willing to take a chance on.

Steve

Why does he wash his hands in the shower and not the basin.

Neil

[frangar]

I fitted a Mira bar mixer for a friend in a house that refused to give a hot shower after a while.

When I phoned Mira I was given a checklist of things to try including hot/cold reversal. I was quite surprised they sent out a service engineer rather than a replacement unit....turns out that was a thermostat failure which the service chap said was quite rare. I was impressed with their customer service. 

[Neil2]

27 minutes ago, frangar said:

I fitted a Mira bar mixer for a friend in a house that refused to give a hot shower after a while.

When I phoned Mira I was given a checklist of things to try including hot/cold reversal. I was quite surprised they sent out a service engineer rather than a replacement unit....turns out that was a thermostat failure which the service chap said was quite rare. I was impressed with their customer service. 

I wouldn't rule that out either, I understand the OP's reluctance to conclude he has another duff unit but the last two items (a water pump and a gas cooker) I have bought for our boat both had manufacturing faults.  When something new doesn't work it's natural to assume you are doing something wrong but it seems to me something is going wrong with quality control these days.   These companies wouldn't have such sophisticated after sales set ups if the things worked perfectly out of the box every time.

[WotEver]

We have a service contract at home with British Gas. When our central heating developed a somewhat obscure fault the engineer diagnosed a faulty motorised valve. New valve duly fitted and the problem remained. It took three engineers and multiple calls to the boiler manufacturer, voltage readings and much head scratching to diagnose that the replacement valve had exactly the same fault from new as the old one. 

Very rare I'm sure, but it does happen. 

[mrsmelly]

11 hours ago, sharpness said:

That's OK for you &me but my 5yr old grandson who always washes his hands might get caught out, not something I would be willing to take a chance on.

Steve

I understand your concern. Problem is too much elf and safety can have the reverse to its desired effect by mollycoddling everyone no common sense attitude or ability is learnt. 

[nicknorman]

43 minutes ago, mrsmelly said:

I understand your concern. Problem is too much elf and safety can have the reverse to its desired effect by mollycoddling everyone no common sense attitude or ability is learnt. 

Eggzachary. Grandson has probably had "germs" drilled into him hence the washing obsession that will develop into OCD. Children need to learn that the world is a dangerous place and only they are responsible for their safety.

[Richard10002]

53 minutes ago, mrsmelly said:

I understand your concern. Problem is too much elf and safety can have the reverse to its desired effect by mollycoddling everyone no common sense attitude or ability is learnt. 

There was a simple mixer tap on our boat when we got it. For some reason, you could set up the mix to a nice temperature but it would keep changing during a shower - no idea why, but it did. From nice to scalding to freezing, and not easy to keep resetting it when carrying out in-shower activities.

Call me mollycoddled in my mid fifties, but I changed it for a spare thermostatic bar I had knocking around and it has worked fine since. 

[mrsmelly]

1 minute ago, Richard10002 said:

There was a simple mixer tap on our boat when we got it. For some reason, you could set up the mix to a nice temperature but it would keep changing during a shower - no idea why, but it did. From nice to scalding to freezing, and not easy to keep resetting it when carrying out in-shower activities.

Call me mollycoddled in my mid fifties, but I changed it for a spare thermostatic bar I had knocking around and it has worked fine since. 

I do think its less easy to sort this problem on a boat as there are too  many variables and mixtures of different systems delivering the combination of hot and cold water to the outlets. This boat has a large hot water tank ( cauliflower ) so water is fed directly from that and mixed with cold and doesnt alter one jot unless tap is moved. Problems do oft occur with thermo systems when trying to work in conjunction with say a morco for just one instance.

[Richard10002]

1 hour ago, mrsmelly said:

I do think its less easy to sort this problem on a boat as there are too  many variables and mixtures of different systems delivering the combination of hot and cold water to the outlets. This boat has a large hot water tank ( cauliflower ) so water is fed directly from that and mixed with cold and doesnt alter one jot unless tap is moved. Problems do oft occur with thermo systems when trying to work in conjunction with say a morco for just one instance.

My shower hot water is fed from a Rinnai Instant gas water heater. The cold comes direct from the tank via a Jabsco pump. If there are any variations in the supply of either, the thermostatic valve seems to take care of it fine.

[sharpness]

9 hours ago, nicknorman said:

Eggzachary. Grandson has probably had "germs" drilled into him hence the washing obsession that will develop into OCD. Children need to learn that the world is a dangerous place and only they are responsible for their safety.

No, not this one, its just that he's learnt that he should wash his hands after using the loo, not quite "a washing obsession that will develop into OCD" Going back to the original point I was making I think I misunderstood that mrsmelly was saying that there shouldn't be a thermostatic valve on the cauliflower output when he was in fact referring to the shower valve. I agree about children needing to learn the world is a dangerous place but until he has learnt, while he is with me, I am responsible for his safety.

[jddevel]

My suggestion to the answer regarding recurring faults in replacement new items. Check whether you can replace the item with one where none of the components were made in China!!!

[nicknorman]

3 hours ago, sharpness said:

No, not this one, its just that he's learnt that he should wash his hands after using the loo, not quite "a washing obsession that will develop into OCD" Going back to the original point I was making I think I misunderstood that mrsmelly was saying that there shouldn't be a thermostatic valve on the cauliflower output when he was in fact referring to the shower valve. I agree about children needing to learn the world is a dangerous place but until he has learnt, while he is with me, I am responsible for his safety.

How will he learn if you remove all dangers from his path? Ok I accept that it is trickier for the grandparent to teach recognition of danger / self preservation if the parents don't, my point is somewhat a generalisation on the nature of modern parenting.

Anyway, why does one need to wash hands after using the loo? I do so if I've got "stuff" on them. If I haven't (which is normally the case with #1s) then what exactly is one supposed to be washing off? There is more a case for washing hands BEFORE. For example, when having just been chopping some chillis / using chemicals.

[Boat&Bikes]

3 minutes ago, nicknorman said:

How will he learn if you remove all dangers from his path? Ok I accept that it is trickier for the grandparent to teach recognition of danger / self preservation if the parents don't, my point is somewhat a generalisation on the nature of modern parenting.

Anyway, why does one need to wash hands after using the loo? I do so if I've got "stuff" on them. If I haven't (which is normally the case with #1s) then what exactly is one supposed to be washing off? There is more a case for washing hands BEFORE. For example, when having just been chopping some chillis / using chemicals.

Ooh chillis then number ones... The pain!