Help! My Air Source Heat Pump Is Not Heating My Hot Tub!

Air Source Heat Pump not heating your Hot Tub? Read on. In this article I will cover some of the possible causes for this and hopefully, by the end of this article you will be able to resolve the problem yourself – without paying for someone to come out to take a look at it. Quite often, it is something simple.

Air Source Heat Pump not heating your Hot Tub? Read on. In this article I will cover some of the possible causes for this and hopefully, by the end of this article you will be able to resolve the problem yourself – without paying for someone to come out to take a look at it. Quite often, it is something simple.

With the global energy crisis upon up, there has been a surge in popularity of Air Source Heat Pumps. However, unfortunately, as they are relatively new to this industry, there seems to be a lack of useful information. Even to the point that I have had people contact me that have had installers come out and install them to find they have been installed incorrectly.

I’m not saying I know everything, whilst I would like to think I do, yes, I’m that guy, I don’t. However, I do have quite a lot of experience with air source heat pumps and hot tubs so hopefully I can help you resolve the problem either on this blog or my YouTube Channel.

Air Source Heat Pump Is Not Heating My Hot Tub – not installed correctly.

The installation of an air source heat pump is not difficult. However, if you get it wrong, or your installer gets it wrong, then your air source heat pump will not heat your hot tub! Here are some key elements to the installation process.

Direction of flow

Air source heat pumps have a direction of flow. The water from the hot tub most enter into the “cold input” and must exit from the “hot output” and from there, must make its way back into your hot tub. Simple. Get the direction of flow wrong and you will have a E03 or Flow Error message on your air source heat pump.

How do you know what the direction of flow is. Easy. You need to trace back to the pump. The pump sucks water from the hot tub into the front of the pump and then returns water to the hot tub from the top or side of the pump. This gives you the direction of flow.

Therefore, if you air source is after the pump, the connection order should go “pump, pipe, cold input, hot output, back to jets in tub”. If you are connecting this before the pump, then it should go “hot tub, cold input, hot output, back to pump”

Get this order wrong and you will get a flow error.

Flow Error or Air Lock

This could firstly be because of the pipe order above so check that.

Next, it could be because of an air lock. If you have just installed your air source heat pump or just refilled it, then this could be the problem. Easy way to check, is your circulation pump running? If it is, then check if there is flow coming into the hot tub – you should see water movement. If not, then the chances are you have an air lock.

With your tub switched off at the breaker, to get rid of the air lock, first try loosening the unions at the air source heat pump until you get water there. You should hear air escape. Then, at the pump, do the same. Then, try you hot tub again, turn it on at the breaker. Check for flow and see if the flow error goes away.

If it doesn’t and you have a stubborn air lock, at the lowest point on the air source, with the tub turned off, undo the union and let a couple of buckets of water run out. This is usually enough to clear the air lock.

If all else fails, drain the tub, but then refill from the highest part of the system, either the filter or the top of the air source heat pump.

Air Source Heat Pump Is Not Heating My Hot Tub – bypass valve open

This is my favourite and easiest to fix “problem” for why an Air Source Heat Pump is either showing a flow error or is not heating your hot tub.

The bypass setup on an air source heat pump is there so you can reduce the pressure on the system if the pressure is too much inside of the air source. This can be due to a single pump system so the jet pump is too strong. In this scenario, the gate valve should be open to allow enough flow to the jets.

However, in a normal scenario, the gate valve should be fully closed. This then forces all the water into the air source heat pump. Remember, water always takes the route with least restriction so if the gate is open, it will bypass the heater and will not heat. This can cause a flow error on the heat pump, but usually, there is enough flow that it doesn’t and the water just doesn’t heat or doesn’t heat fast enough.

Trace the direction of water, make sure that ALL the water is going through the heat pump by having the bypass valve closed – job done! This is the easiest fix of all and believe it or not, this is the one that crops up the most when people call or email me.

Air Source Heat Pump Frozen up or too much ice

If it is cold outside, then the chances are you will see ice building up on the outside of the air source heat pump. This is normal.

This is because the heat pump extracts heat from the air outside and uses it to heat the hot tub water. In cold weather, the air can contain moisture that can freeze on the heat pump’s coils.

However, if there is a lot of ice on the heat pump, it could be a sign of a problem. This could be caused by a lack of proper insulation, a malfunctioning defrost system, or low refrigerant levels. The ice build up can prevent the heat pump from functioning properly

To prevent excessive ice build-up on an air source heat pump, make sure that you use the units manual defrost mode to periodically remove the ice. If there is too much ice on the unit, then the air source will struggle extracting warmth from the air as it has to pass over the ice first cooling it down, making the unit less efficient.

Air Source Heat Pump Is Not Heating My Hot Tub – too cold outside

The ambient temperature is important for an air source heat pump. The warmer it is outside, the easier it is for the heat pump to extract the warmth from the air. Drop to sub zero (late 20s F) and this is a whole new ball game.

If you r unit is only rated to say +5C and it is -5C outside, then the chances of your getting any meaningful heat out of the unit is low. Model to model it will vary and I have run my own unit which is only rated to zero in sub zero temperatures and it does work. However, this will vary so check what your air source is actually rated too as this might be your problem.

Hopefully, you have found something in this article that will help resolve the problem why your Air Source Heat Pump Is Not Heating your Hot Tub.

Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi

 

Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 1000 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi