Hayward H400FDN Pool Heater Review

Nobody likes swimming in a freezing cold swimming pool and there is a fair chance you are currently fed up with this exact situation. The next pain you may have experienced is trying to decide which pool heater is right for you and your pool. We have reviewed the most common pool heaters on the market today to help answer your questions and allow you to quickly and easily make your purchase decision today.

This review is a comprehensive analysis of the Hayward H400FDN Pool Heater.  We have investigated the most important and pressing questions prospective purchasers like yourself have come up against when looking to invest in a heater.

We deal with these questions and concerns in as much detail as possible to help you make an informed choice as to whether the Hayward H400 is the right heater for you. If you have any further questions please send then to us via the comments section at the bottom and we will do our utmost to help answer them.

Do You Really Need A Pool Heater?

Firstly, there are many reasons why you may wish to install a pool heater. It could be you prefer your pool that bit warmer during the summer months or simply that you wish to extend your pool use during the cooler weeks and months either side of summer.

Whatever your reason, it is all down to personal choice and budget. Yes, the budget is another key reason in itself because running a pool heater could cost a significant amount if you wish to use it regularly.

There are several tips and tricks you may wish to make use of to get the most value from your heater. If these interest you check out our top tips for pool heaters.

What Does the H400FDN Model Code Name Mean?

Here is the breakdown the H400FDN model code to explain exactly what each part means and also help you identify what features some other types of heater have used the same naming scheme:

H identifies the heater as part of the Hayward H-Series Pool Heater range.

400 defines the size of the heater in BTU. 400 shows the unit is rated at 400,000BTU. BTU is an acronym for British Thermal Unit and identifies the amount of energy required to raise the temperature of one pound water (in the case of pool heaters) by one degree.

FD identifies the unit as a Forced Draft Low NOx Heater

N identifies the unit is designed for a Natural Gas fuel source. You will find this is a P on models designed for Propane.

H-Series Sizing and Install Site

Is the Hayward H400FDN the correct size heater for your pool?

The H400 is one of seven sizes of H Series Pool Heater. It is aimed at large pools or those that wish to heat their pool or spa rapidly. As you will find out by reading our pool heater sizing guide the speed at which you can heat your pool is directly related to how powerful the heater is.

Do You Need a 400000 BTU Pool Heater?

The bigger the BTU the faster you can heat the water. Therefore, you may choose the H400 because of the surface area and/or the volume of water you have to heat . Alternately this heater may make sense because you have random times when it is possible make use of the pool. In these situations sat waiting what seems like forever waiting for the desired temperature and missing out on some spa action is simply frustrating. You want to be changed and in the spa or hot tub on impulse and this heater will deliver.

The H400 can raise the water temperature of a 300-gallon spa in under 15 minutes which is plenty enough time for you to go and get changed into your bathing suit. We therefore always recommend oversizing your heater if you can afford it.  The price is not massively more compared with the performance improvements – just $340 at the time of review.

What Are The Physical Dimensions of the Hayward H400FDN Heater?

If you are concerned about space restrictions for the installation, the physical size of the heater is 30 inches wide by 24 inches high (30 x 38 x 32 inches). As a safety precaution, the heater should always be installed a minimum of 5 feet away from the pool it is heating so check you have space for this.

Is The Hayward H-Series Pool Heater  Heater Suitable For Above Ground Pools and Spas?

Absolutely. The Hayward H Series can be used in any environment where you need to heat a pool or spa both in-ground and above ground.

Is The Hayward H-Series Pool Heater Heater Suitable For In-ground Pools?

Many users have chosen to heat their in-ground pool with an H-Series Poo Heater and found they work great. The H400 is one of the most powerful in the range so offers up plenty of power for the largest of pools and spas.

How efficient is the H400?

The H Series is up to 18% more efficient than other competing heaters of its class. It is an industry leading hydraulic design and Hayward have spared no expense to ensure this heater provides a top class service.

Is the H400 Environmentally Friendly?

The H Series range of pool heaters exceeds the requirements set out in the air quality for California and Texas, therefore, and therefore should be acceptable in any other Low NOx zone.

Pricing and Purchase Options

How Much Is the Hayward H400FDN?

At the time of writing this review, the price of the H400FDN places it in the $2000+ range. This, however, doesn’t include installation costs which could add approximately another $4-500 depending on your requirements.

Purchasing and installing the heater yourself would probably save you in the region of $1000 in comparison to paying a pool company to do it. We would, however, always recommend having a professional do the gas work because of the obvious risks. It doesn’t pay to skimp on safety here and the chances are it will also be law in your part of the country too.

Where Can You Buy The H400FDN?

Several online retailer and authorized dealers sell the Hayward H-Series heaters, including the H400FDN. Owing to the size and weight of the heater delivery costs could be high if delivery is not free or included in the price.

One way around this would be to utilize Amazon Prime and order from Amazon and make the most of the free delivery. This could save you even more compared to other online retailers so is worth factoring in when making price comparisons.

What Warranty Cover Is Provided?

Hayward provides a 1 Year Limited Warranty with the H400 and all their H-Series Heaters. You will be covered in the event of failure providing you have not invalidated the warranty. To ensure you don’t fall foul of the warranty issue below are some key factors you really need to ensure you understand:

  1. Flow Rate – Ensuring you can get the right amount of water through the heater
  2. Ensure you prime the pump prior to first use. Running the pump dry will most likely cause damage to the pump.
  3. Ensure a well-balanced chemistry of the water
  4. Install a bypass valve to allow unbalanced water to be diverted away from the pump until it is correctly balanced.
  5. Installation of a chlorinator is done downstream of the heater
  6. Not placing chlorine or bromine tablets directly into the skimmer
  7. The heater is designed for residential use only so don’t install into a commercial environment

 Installation and Delivery

The heater is delivered on average between 7-8 days. The package is very heavy so we recommend asking the delivery guy to drop the item to the exact location you need it. Also, as previously mentioned sign up to amazon prime to get free shipping could save you money if retailers are charging for delivery.  When it comes to listing the heater during install ensure you have at least two people for safe handling.

It is also worth noting the color key for the labels on the unit before you unbox it.  All the labels on the Natural Gas heaters in the H Series range are colored yellow.  The propane heaters are all a pink/purple color.

How Much Will It Cost To Install?

The installation will normally cost you in the region of $4-500 to get the heater connected up to the gas and water. This may increase if you have to install lots of extra pipework or want incorporate bypass valves or a multi-pool setup.

Is The Unit Handed?

The H400FDN can have the pipes installed to the left or right. This allows for configurable installation to suit your requirements. Be aware, however, it is quite an involved task to swap things around as you have to partially dismantle it to do so. It is not a trivial job even for an experienced plumber but and will take approx 1-1.5h to complete. This should be factored into your installation cost. If you wish to carry out this procedure the steps are fully covered in the Hayward H Series user manual.

Is It Easy To Install And Can I Install It Myself

The heater is not difficult to install for someone with basic DIY and plumbing skills. Doing so could save you around $1K so if you have the skills we would certainly recommend you doing it. It is still recommended that a professional is used to connect the heater to the gas main and tested for leaks.

A great guide that covers everything from unboxing to installing the heater can be found here:

Does The Unit Come With A Power Cord and Plug

No plug or cord is supplied. In addition to this, the unit should be hard wired into an isolated electric hookup. If you have to run this power out to the install site it is another install cost to include. Always ensure you follow all regulations and local codes with any electrical work.

What Gas Pressure Does The Unit Need?

The minimum gas pressure to operate the H400FDN is 10lbs. Any less than this and the unit will not be able to operate correctly. Please check with your gas engineer that your installation is set up to supply this amount fo pressure.

What Size Gas Connections and Piping Do You Need?

The connections on the heater are ¾ inch. If you intend on using ¾ inch pipe you will have a maximum distance of 20 feet from the outlet. Any further than this and we recommend you increase the pipe diameter.

1 Inch piping will allow you to cover up to 70 feet. Anything above this distance and you will need to go to 1 ¼ inch pipe which will be good for up to 200 feet.

Operation And Use

How Hot Can The You Heat The Water?

The maximum temp before the heater automatically shuts off is 104 degrees. This will give plenty of range to get your spa toasty hot. Make sure you always heat the spa with the cover on otherwise the heater will have to work extra hard to reach optimum temperature. The same applies to a pool and using a cover when the pool is not in use.

What Is The Ideal Temperature For Heating a Pool With The H400?

The ideal temperature for a heater is not really the issue. The heater is more than capable of heating the water to whatever level you desire within the operating range of the heater.

The normal water temperature range for a swimming pool is 78-82℉ . If you are having children in the pool then 80 degrees is the recommended minimum to keep it comfortable for them. If you have a larger pool and do a lot of lap swimming for fitness and exercise the lower end 78 degrees would be more suitable.

If you have a larger pool and do a lot of lap swimming for fitness and exercise the lower end 78 degrees would be more suitable or you may find yourself getting too hot.

What Is The Ideal Temperature For The H400 Heating a Spa or Hot Tub?

The normal range for a spa or hot tub is 100-102℉ but some people like to push the heater to its max of 104℉. Its is not recommended to allow children to use the spa but if they so then f 85℉ and 5-10 mins exposure are considered the maximum.

How Much Does It Cost To Run?

The cost of using the heater is down to many factors which can make it difficult to calculate an exact figure. Factors including average air temp, average wind, is the pool in direct sunlight, is a pool cover used, what is the surface area and probably most importantly what is the temperature increase you are normally faced with to heat the pool to your requirements.

Probably the best way to look at the cost is to take an average. It takes 4 therms (1 therm ber 100K BTU) to run the heater for 1 hour and natural gas will cost approximately $1 per therm depending on the current price of gas. You are therefore looking at $4 per hour to run the H400.

If you find at the number of minutes required to raise the temperature of your pool or spa using our pool heater sizing guide, you will be able to roughly estimate what it will cost each time you heat your pool up from cold.

Does The Heater Get Hot Whilst In Operation

The case top should not become too hot to touch whilst in operation. It may, however, be more of a risk to children so caution should be taken to ensure children are not allowed to play with the unit. You can place the heater inside an enclosure for added safety but when doing so you must ensure adequate airflow into the unit and sufficient venting of gasses outwards.

What Are The Disadvantages To The H400FDN?

Noise Levels

Some owners of the H400 have reported that the heater is louder than similar sized heaters such as the Pentair. However, most have also noted that the noise generated is not too loud and they don’t find a nuisance when in the hot tub or spa.

One way to help alleviate any noise would be to install the heater behind a wall or structure near to the pool. This way you get the benefit of any noise being deflected away but also the added benefit of sheltering the pool from cross winds. Reducing cross winds will really help prevent heat loss.

Always ensure you have adequate clearances as identified in the user guide and local laws when places the heater near structures. It is also very important to beware of any windows or ventilation areas on a property. It could be very easy to have poisonous gasses entering a property should this happen.

Water Chemistry: Beware of High pH Levels

Several owners have noted their heater was damaged when their water pH levels went too high for an extended time. Hayward clearly warns about the importance of maintaining a healthy water chemistry. Knowing this there is an added incentive to regularly testing the water to ensure the levels are correct.

An added measure would be to install a bypass valve to make it possible to take the heater out of the circuit until the levels have been rebalanced. These valves also make maintenance easier to we find them a no brainer to pool heater setup.

Good water chemistry is not only good for heaters but also good for the water quality and therefore users of the pool too.

Other Points to Be Mindful Of

Flow rates

One thing to look out for though is you have adequate flow rates.  Low flow rates may restrict the heater causing it to overheat. This could damage the unit and would also invalidate your warranty. It is definitely something you should check prior to using your heater for the first time.

Gas Supply Pressure

It is also imperative your gas supply is adequate. If you can’t supply the volume of gas the unit requires it may not be able to operate to it full potential.  Hayward stipulates a minimum of 10lb gas pressure to supply this unit.

Our Verdict

We find the H400 really appealing. Hayward is an established brand and is not likely to go anywhere in the medium or short term. You are getting years or refinements in the H-Series Heaters. These heaters have been around long enough to have enabled Hayward to remove any niggles. This means there is a very high probability of years of trouble free ownership.

The efficiency and power of the unit, whilst staying within regulation limits, make this heater suitable in California and Texas where strict controls are in place. They are priced competitively and available to purchase online to the general public rather than direct to the trade only.

At an average rate of approximately $4 per hour to run is a great saving over propane models where this could run to around $10 per hour. There is a lot more convenience to Natural Gas over propane too.

Additional savings can be made by self-purchasing and doing as much of the install work as possible. Pool companies will add their own markups on top of the purchase price as well as charge a premium for the one-stop-shop install. If you are handy or have good value tradesman at your disposal then savings of up to $1000 can be made handling it yourself.

So, if you have been looking at the Hayward H400FDN and like what you see then we feel there are very few disadvantages that can’t be easily overcome should you decide to purchase the unit. SO what are you waiting for? Go and pick up the H400 heater and be one step closer to a warm pool right now.

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